A checklist of helminth parasites of Elasmobranchii in Mexico.

A comprehensive and updated summary of the literature and unpublished records contained in scientific collections on the helminth parasites of the elasmobranchs from Mexico is herein presented for the first time. At present, the helminth fauna associated with Elasmobranchii recorded in Mexico is composed of 132 (110 named species and 22 not assigned to species), which belong to 70 genera included in 27 families (plus 4 incertae sedis families of cestodes). These data represent 7.2% of the worldwide species richness. Platyhelminthes is the most widely represented, with 128 taxa: 94 of cestodes, 22 of monogeneans and 12 of trematodes; Nematoda and Annelida: Hirudinea are represented by only 2 taxa each. These records come from 54 localities, pertaining to 15 states; Baja California Sur (17 sampled localities) and Baja California (10), are the states with the highest species richness: 72 and 54 species, respectively. Up to now, 48 elasmobranch species have been recorded as hosts of helminths in Mexico; so, approximately 82% of sharks and 67% of rays distributed in Mexican waters lack helminthological studies. The present list provides the host, distribution (with geographical coordinates), site of infection, accession number in scientific collections, and references for the parasites. A host-parasite list is also provided.

Introduction

According to Eschmeyer and Fong (2015), 1338 species of elasmobranchs have been described worldwide (768 rays and 570 sharks). However, Naylor et al. (2012), based on the fact that since 2005 more than 130 new species have been described, considered that more species remain to be discovered. According to these authors, this increase is a result of reassessment of geographic variation; some of the increase represents recognition of subtle morphological variants among congeneric forms that nevertheless exhibit substantial molecular sequence divergence (cryptic species). In Mexico, this group is represented by 204 known species (95 rays and 109 sharks) (Del Moral-Flores and Pérez-Ponce de León 2013) (Table 1); this richness constitutes 15% of the living species in the world. Nonetheless, most of the species recorded in Mexican waters also have been found in international waters, and many of them are cosmopolitan (Espinoza-Pérez et al. 2004).

Table 1.

Species of reported from Mexico and richness of associated helminths (modified from Del Moral-Flores and Pérez-Ponce de León 2013).

Subclass	Order	Family	Genera	Species	Sampled species	Helminth recorded
Selachii	Hexanchiformes	Chlamydoselachidae	1	1	0	0
		Hexanchidae	3	4	1	1
		Echinorhinidae	1	1	0	0
		Squalidae	2	4	0	0
		Centrophoridae	1	4	0	0
	Squaliformes	Etmopteridae	2	8	0	0
		Somniosidae	3	3	0	0
		Oxynotidae	1	1	0	0
		Dalatiidae	4	5	0	0
	Squatiniformes	Squatinidae	1	4	1	2
	Heterodontiformes	Heterodontidae	1	2	2	7
		Ginglymostomatidae	1	1	1	3
	Orectolobiformes	Rhicodontidae	1	1	0	0
		Odontaspididae	2	3	0	0
		Pseudocarcharhiidae	1	1	0	0
		Megachasmidae	1	1	0	0
	Lamniformes	Alopidae	1	4	2	6
		Cetorhinidae	1	1	0	0
		Lamnidae	3	4	0	0
		Scyliorhinidae	6	15	0	0
		Triakidae	3	11	5	9
	Carcharhiniformes	Carcharhinidae	7	25	5	19
		Sphyrnidae	1	6	3	5
TOTALS*	7	23	48	109	20	52
Batoidea	Torpediniformes	Torpedinidae	1	2	0	0
		Narcinidae	2	4	2	5
	Pristiformes	Pristidae	1	3	0	0
		Rhinobatidae	2	10	5	10
	Rhinobatiformes	Platyrhinidae	1	1	0	0
		Arhynchobatidae	2	4	0	0
	Rajiformes	Rajidae	9	29	2	2
		Anacanthobatidae	2	4	1	1
		Urotrygonidae	2	10	5	27
		Dasyatidae	3	9	5	26
		Gymnuridae	1	4	0	0
	Myliobatiformes	Myliobatidae	3	8	8	38
		Rhinopteridae	1	2	0	0
		Mobulidae	2	6	0	0
TOTALS*	5	14	32	95	28	108

The totals in the table are greater than in the text because some species infect 2 or more host species (sharks and/or rays).

Elasmobranchs (sharks, skates and rays) are host to a great variety of parasites in nature, particularly helminths. Up to now, more than 1500 helminth species have been recorded in association with these hosts worldwide; cestodes represent the most diverse group, with approximately 1133 species, followed by monogeneans with 226, nematodes with 83, digeneans with 50-60, leeches with 23, and aspidogastreans with 2 (Caira et al. 2012). In addition, 4 species of acanthocephalans have been found only in elasmobranchs (Weaver and Smales 2014). In Mexico, the first record of a helminth parasitizing an elasmobranch was made by Caballero y Caballero (1945), who described the digenean (=) from the body cavity of an undetermined shark in the Pacific slope of this country. Since then, a great amount of information has been generated, most of it in the last 2 decades, particularly in the Gulf of California. The main goal of this checklist is to compile and discuss all these data and to establish some patterns of richness, geographical distribution and host spectrum.

Methods

This checklist contains information updated until December, 2015, and comes from two different sources: 1) retrospective bibliographical search, using different databases such as CAB Abstracts, Biological Abstracts, and Zoological Record; 2) Search in databases of national [, Instituto de Biología, UNAM, Mexico City, Mexico] and international [, University of Nebraska-Lincoln, USA; , Smithsonian Institution, Washington, D.C., USA, formerly , Beltsville, Maryland, USA] parasite collections.

Colección Nacional de Helmintos

Harold W. Manter Laboratory of Parasitology

National Museum of Natural History

United States National Parasite Collection

The checklist is divided into two sections; the first includes a parasite-host list, presented in phylogenetic order, starting with the phylum (, PageBreakPageBreak and ), and followed by the phyla and (). Each phylum contains families, genera, and species in alphabetical order. The nomenclature and classification for each metazoan group is based on the following references: (Gibson et al. 2002; Jones et al. 2005; Bray et al. 2008), (Boeger and Kritsky 1993), (Caira et al. 2014b), (Anderson et al. 1974–1983; Gibbons 2010), and (Sawyer 1986; Davies 1991). The information for each helminth species includes species name, authority, and site of infection. We use “NA” when some data are not available in the original source. Next, we present species distributions, referring to states of the Mexican Republic (in caps) where the record was made as well as the specific locality name, followed by the species of host and the bibliographic references related to records. For specimens deposited in a collection, acronyms are as follows:

BMNH

The British Museum (Natural History) Collection at the Natural History Museum, London, UK

CNHE

Colección Nacional de Helmintos, Instituto de Biología, UNAM, Mexico City, México

CPMHN-UABCS

Colección Parasitológica del Museo de Historia Natural de la Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico

ECOPA

El Colegio de la Frontera Sur, Chetumal, Quintana Roo, Mexico

HWML

Harold W. Manter Laboratory of Parasitology, University of Nebraska-Lincoln, Nebraska, United States

IPCAS

Institute of Parasitology, Academy of Sciences of the Czech Republic, Česke Budějovice, Czech Republic

LRP

Lawrence R. Penner Collection, Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs CT, USA

MNHG-INV or PLAT

Museum of Natural History, Geneva, Switzerland

SBMNH

Santa Barbara Museum of Natural History, Santa Barbara, California, United States

TINRO

Pacific Fisheries Research Center, Vladivostok, Russian Federation

UCLA

Helminthological Collection, Zoology Department, University of California at Los Angeles

USNPC

Accession numbers used in this work correspond to those given by United States National Parasite Collection, Beltsville, Maryland, USA, which was recently transferred to the , Smithsonian Institution, Washington, D.C., USA

National Museum of Natural History

The name of the , , and of the new species described from elasmobranchs recorded in Mexico are indicated with abbreviations of these words in superscript.

type locality

type host

original reference

The host-parasite list is ordered alphabetically by families of elasmobranchs; each family includes the scientific name of the host and the authority name. Then, the sciPageBreakentific names of the species of helminths are listed in alphabetical order, indicating in parentheses the parasite group to which they belong. The scientific names of elasmobranchs were updated following Froese and Pauly (2014); higher levels of classification follow Del Moral-Flores and Pérez-Ponce de León (2013).

Results

To date, 48 species of elasmobranchs (20 sharks and 28 rays) have been recorded as host of 132 taxa of helminths (110 named species and 22 not assigned to species); these parasite species belong to 70 genera included in 27 families (plus 4 families of cestodes that are incertae sedis). is represented by 128 taxa: 94 taxa of cestodes, 22 taxa of monogeneans and 12 taxa of trematodes; for both and () only 2 species have been recorded. The 54 sampled sites for helminths are located in 15 states; Baja California Sur (17 localities) and Baja California (10), are the states with the highest species richness (72 and 54, respectively) (Fig. 1). Up to now, no helminths parasitizing elasmobranchs from Mexican waters have been PageBreakreported from the states of Michoacán and Tabasco; for Chiapas, Colima, Tamaulipas and Yucatán, only one record each has been reported. Below, we present the checklist of helminth parasites recorded in elasmobranch species caught in Mexico, which summarizes the current knowledge on this group in the country.

Figure 1.

Map of Mexico showing the localities that have been sampled for elasmobranchs as hosts of helminth species.

Parasite-host list

Site of infection. Intestine.

Locality. BAJA CALIFORNIA SUR: Bahía Magdalena: (see Arai 1962).

Specimens in collections. UCLA.

Site of infection. Body cavity, stomach.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: , , , (see Curran and Overstreet 2000).

Specimens in collections. CNHE (3852).

Site of infection. Intestine.

Locality. BAJA CALIFORNIA SUR: El Comitán: (see Villarreal-Lizárraga 1995).

Specimens in collections. CPMHN-UABCS (20).

Site of infection. Pericardial and body cavities.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Curran et al. 2003). BAJA CALIFORNIA SUR: Loreto: (see Curran et al. 2003). NA: Golfo de California: , , , , , , , , (see Curran et al. 2013)

Specimens in collections. CNHE (4499); HWML (16702); SBMNH (345780).

Site of infection. Body cavity.

Locality. BAJA CALIFORNIA SUR: Bahía de La Paz: (see Curran et al. 2009).

Specimens in collections. CNHE (6198).

Site of infection. Body cavity.

Locality. BAJA CALIFORNIA SUR: Loreto : (see Curran et al. 2009 ).

Specimens in collections. CNHE (6199); HWML (48889); SBMNH (423115).

Site of infection. Body cavity.

Locality. BAJA CALIFORNIA: Isla San Esteban: sp. (see Curran et al. 2009). BAJA CALIFORNIA SUR: Bahía de Santa Inés: , , (see Markell 1956). NA: Golfo de California: , , , , (see Curran et al. 2009)

Specimens in collections. CNHE (6200); HWML (48890); SBMNH (423116); USNPC (49354).

Notes. The specimens of Bahía de Santa Inés were identified as , but this species is a synonym of according to Curran et al. (2009).

Site of infection. Body cavity.

Locality. COLIMA: Manzanillo : “Tiburón no determinado” (see Caballero y Caballero 1945). JALISCO: Puerto Vallarta: “” (CNHE); NAPageBreakYARIT: Punta Mita: “Tiburón no determinado” (see Bravo-Hollis 1954); San Blás: (see Lamothe-Argumedo 1969). SINALOA: Mazatlán: (see Winter 1959).

Specimens in collections. CNHE (921, 1069, 1111, 1585, 3246).

Notes. The original description of this species was made under the name (Caballero y Caballero 1945); later, this species was transferred to by Markell (1953). This act was accepted by Sogandares-Bernal (1959) and Curran et al. (2009) but rejected by Caballero y Caballero et al. (1956) and Winter (1959). Lamothe-Argumedo (1969) erected to accommodate this species, but this genus was considered a synonym of (Curran et al. 2009). Pigulevski (1953) divided the genus in 2 subgenera, including the species of described by Caballero y Caballero (1945) in . Currently, this trematode species is accepted as (see Campbell 2008).

Site of infection. Stomach.

Locality. BAJA CALIFORNIA SUR: Las Barrancas: (see Méndez 2005).

No specimens in collections.

Site of infection. Stomach.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Curran and Overstreet 2000); Puertecitos: (see Curran and Overstreet 2000).

Specimens in collections. CNHE (3853-4).

Site of infection. Buccal cavity, cloaca, gills.

Locality. BAJA CALIFORNIA SUR: Boca de Álamo: , (see Curran and Overstreet 2000); Puntarena, San Isidro: (see Cur). SINALOA: Bahía Santa María: (see Curran and Overstreet 2000).

Specimens in collections. CNHE (3855); HWML (15263, 15265).

Site of infection. Gills.

Locality. BAJA CALIFORNIA SUR: Puntarena: (see Curran and Overstreet 2000); Santa María: (see Curran and Overstreet 2000).

Specimens in collections. CNHE (3850); HWML (15261).

Site of infection. Skin.

Locality. CAMPECHE: Estuario Champotón: (see Pulido-Flores and Monks 2005).

Specimens in collections. CNHE (4370).

Site of infection. Gills, skin.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Bullard et al. 2004); Isla San Esteban: , , sp. (see Bullard et al. 2004). SONORA: Bahía de Guaymas: (see Caballero y Caballero and Bravo-Hollis 1962).

Specimens in collections. CNHE (34-5); USNPC (94826-8).

Notes. This species was described as (Caballero y Caballero and Bravo-Hollis 1962) and transferred to by Bullard et al. (2004).

Site of infection. Skin.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Bullard et al. 2004 ). BAJA CALIFORNIA SUR: Santa Rosalía: (see Bullard et al. 2004).

Specimens in collections. CNHE (5021-2); USNPC (94829-34).

Site of infection. Skin.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Bullard et al. 2004). BAJA CALIFORNIA SUR: Bahía de La Paz: (see Bullard et al. 2004).

Specimens in collections. CNHE (5023-4); USNPC (94835-9).

Site of infection. Gills.

Locality. SINALOA: Mazatlán: (see Escorcia-Ignacio et al. 2015).

Specimens in collections. CNHE (9361).

Site of infection. Gills.

Locality. SONORA: Bahía de Guaymas: (see Caballero y Caballero and Bravo-Hollis 1961).

Specimens in collections. CNHE (86-7).

Site of infection. Gills.

Locality. SINALOA: Mazatlán: (see Bravo-Hollis 1970).

Specimens in collections. CNHE (153-4).

Site of infection. Gills.

Locality. SINALOA: Mazatlán: (see Bravo-Hollis 1969).

Specimens in collection. CNHE (178).

Notes. Based on the morphology of the posterior hooks of the haptor, Neifar et al. (2002) considered that this material is composed of 2 different monocotylideans.

Site of infection. Body cavity.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Bullard and Overstreet 2000).

Specimens in collections. CNHE (3907).

Site of infection. Cloaca, rectum.

Locality. CAMPECHE: Bancos de Campeche: , (see Chisholm et al. 1997).

No specimens in collections.

Site of infection. Cloaca, rectum.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: , (see Bullard and Overstreet 2000); Bahía de San Francisquito: (see Bullard and Overstreet 2000); Puertecitos: (see Bullard and Overstreet 2000). BAJA CALIFORNIA SUR: Santa Rosalía: , (see Bullard and Overstreet 2000).

Specimens in collections. CNHE (3908-9); HWML (15365-6); USNPC (89777-8).

Site of infection. Gills.

Locality. GUERRERO: Acapulco: (see Carbajal-Violante 2012).

Specimens in collections. CNHE (8287-8).

Site of infection. Gills.

Locality. CAMPECHE: Ciudad del Carmen: (CNHE); Estuario Champotón: (see Pulido-Flores and Monks 2005). QUINTANA ROO: Holbox: (see Pulido-Flores and Monks 2005).

Specimens in collections. CNHE (327, 4368).

Notes. Specimens from Ciudad del Carmen were identified as Hargis, but this species was considered a synonym of by Chisholm and Whittington (1998).

Site of infection. Gills.

Locality. GUERRERO: Acapulco: (Pulido-Flores et al. 2015).

Specimens in collections. CNHE (9558-9); HWML (75364-7).

Site of infection. Skin.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Isla Rasa: “Mantarraya gris” (see Bravo-Hollis 1969) .

Specimens in collections. CNHE (149-50).

Notes. Valid species according to Chisholm et al. (2004).

Site of infection. Skin.

Locality. GOLFO DE MEXICO (Mexico): , (see Fehlauer-Ale and Littlewood 2011). QUINTANA ROO: Blanquizal, Holbox: (see Pulido-Flores and Monks 2005); El Paso de los Cedros (Cozumel), Ixmapuit (Isla Contoy), Xcalak: (see Pulido-Flores and Monks 2005). YUCATÁN: Ría Lagartos: (see Pulido-Flores and Monks 2005).

Specimens in collections. CNHE (4362-3, 4366-7); ECOPA (001); USNPC (90353).

Notes. Valid species accordig to Chisholm et al. (2004).

Site of infection. Gills.

Locality. CAMPECHE: Ciudad del Carmen: (see Pulido-Flores and Monks 2008). QUINTANA ROO: Isla Contoy: (see Pulido-Flores and Monks 2008).

Specimens in collections. CNHE (6067-8); HWML (48817); CHE (P00056).

Site of infection. Gills.

Locality. GUERRERO: Acapulco: (see Carbajal-Violante 2012).

No specimens in collections.

Site of infection. Gills.

Locality. BAJA CALIFORNIA SUR: Bahía Almejas: (see Gómez del Prado-Rosas and Euzet 1997).

No specimens in collections.

Notes. This material was recorded as n. gen., n. sp., but its description was not published, so that name is a nomen nudum.

Site of infection. Gills.

Locality. BAJA CALIFORNIA SUR: Bahía Almejas: (see Gómez del Prado-Rosas and Euzet 1999).

No specimens in collections.

Site of infection. Gills.

Locality. SINALOA: Mazatlán: (see Bravo-Hollis 1969).

Specimens in collections. CNHE (151-2).

Site of infection. Gills.

Locality. BAJA CALIFORNIA SUR: Bahía Almejas: (see Gómez del Prado-Rosas and Euzet 1999 ).

Specimens in collections. BM(NH) (1997.1.28.1); CNHE (2975-6); CPMHN-UABCS (54); MNHN (547HF Tk80); USNPC (87037).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Puertecitos: (see Ruhnke and Seaman 2009); Bahía de Los Ángeles: (see Ruhnke et al. 2015). BAJA CALIFORNIA SUR: Puntarena: (see Ruhnke and Seaman 2009).

Specimens in collections. CNHE (6234-5); USNPC (100993).

Notes. This species was identified as n. sp. 2. in Olson et al.’s (1999) phylogenetic analysis.

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco (Bahía Cholla): (see Ruhnke 1994 ).

Specimens in collections. HWML (37095); USNPC (83437).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Puertecitos: (see Ruhnke and Seaman 2009). BAJA CALIFORNIA SUR: Bahía de La Paz: (see Ruhnke and Seaman 2009).

Specimens in collections. CNHE (6232-3); USNPC (100995).

Notes. This species was identified as n. sp. 1. in the Olson et al.’s (1999) phylogenetic analysis.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Ruhnke and Seaman 2009); Isla San Esteban: (see Caira et al. 2001). BAJA CALIFORNIA SUR: Bahía de La Paz, Loreto, Puntarena, San José del Cabo: (see Ruhnke and Seaman 2009).

Specimens in collections. CNHE (6230-1); LRP (4232); USNPC (100998-9, 101000).

Notes. Specimens from Isla San Esteban, identified as by Caira et al. (2001), were re-identified as by Ruhnke and Seaman (2009).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Caira et al. 2005).

Specimens in collections. CNHE (5300).

Site of infection. Spiral valve.

Locality. VERACRUZ: Playa Chachalacas: (see Méndez and Dorantes 2013).

Specimens in collections. CNHE (6860).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Santa Rosalía: (see Caira et al. 1999), (see Healy et al. 2009).

Specimens in collections. LRP (4217).

Notes. This material was recorded as sp., but according to Euzet (1994), this genus is a synomym of .

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Tyler and Caira 1999 ); Puertecitos: , (see Tyler and Caira 1999). BAJA CALIFORNIA SUR: Loreto: (see Tyler and Caira 1999); Puntarena: PageBreak (see Tyler and Caira 1999); Santa Rosalía: , (see Tyler and Caira 1999).

Specimens in collections. CNHE (3340-1); HWML (33910-11); USNPC (88217-19).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de San Francisquito: , (see Tyler 2001); Isla San Esteban: (see Tyler 2001). BAJA CALIFORNIA SUR: Puntarena: (see Tyler 2001).

Specimens in collections. CNHE (3916-9).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: , (see Tyler and Caira 1999); Puertecitos: (see Tyler and Caira 1999). BAJA CALIFORNIA SUR: Loreto: , (see Tyler and Caira 1999); Santa Rosalía: (see Tyler and Caira 1999).

Specimens in collections. CNHE (3343-5); HWML (33912-14); USNPC (88220-21).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Tyler 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Tyler 2001).

Specimens in collections. CNHE (3920-22).

Site of infection. Spiral valve.

Locality. GUERRERO: Bahía de Acapulco: sp. (see Zaragoza-Tapia et al. 2013).

Specimens in collections. CNHE (8513-4); HWML (49850-3).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de San Quintín: (see Heinz and Dailey 1974).

Specimens in collections. USNPC (072672).

Notes. The original denomination of this species was , but it was transferred to the genus by Beveridge et al. (2004).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Duszynski 2005).

Specimens in collections. USNPC (92215).

Notes. Notes. Published as sp. in Friggens and Brown (2005). The original denomination of this species was , but it was transferred to the genus by Schaeffner (2014).

Site of infection. Gall bladder.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: sp. (see Campbell and Beveridge 2006a); Puntarena: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5452); USNPC (97899, 9700).

Site of infection. Spiral valve.

Locality. VERACRUZ: Playa de Chachalacas: (see Mendez and Dorantes 2013).

Specimens in collections. CNHE (6169).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5466-7).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz, Puntarena: (see Campbell and Beveridge 2006a): Loreto, Santa Rosalía: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5465-6); LRP (3961); USNPC (97908-9).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: , (see Campbell and Beveridge 2006a); Loreto: , (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5460); LRP (3948); USNPC (97904-6).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Brown 2005).

No specimens in collections.

Site of infection. Nephridial system.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5458); USNPC (97902).

Site of infection. Cloaca.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5456).

Site of infection. Nephridial system.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2006a).

Specimens in collections. CNHE (5454); USNPC (97901).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Toth et al. 1992).

Specimens in collections. BMNH (1991.10.30.1-3); USNPC (082186).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2007); Loreto: (see Campbell and Beveridge 2007); San José del Cabo: (see Campbell and Beveridge 2007).

Specimens in collections. USNPC (97925-7).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: (see Campbell and Beveridge 2007).

Specimens in collections. CNHE (5472).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Campbell and Beveridge 2007). BAJA CALIFORNIA SUR: Loreto: (see Campbell and Beveridge 2007).

Specimens in collections. USNPC (97923-4).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Brown 2005).

Specimens in collections. USNPC (92211, 92216).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Duszynski 2005).

Specimens in collections. USNPC (92218-9).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Campbell and Beveridge 2006b). BAJA CALIFORNIA SUR: Bahía de la Paz: (see Campbell and Beveridge 2006b); San José del Cabo: (see Campbell and Beveridge 2006b)

Specimens in collections. CNHE (5468); USNPC (97915-6).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: , (see Campbell and Beveridge 2006b). BAJA CALIFORNIA SUR: Santa Rosalía: , (see Campbell and Beveridge 2006b); San José del Cabo: (see Campbell and Beveridge 2006b).

Specimens in collections. CNHE (5470); USNPC (97917, 97921-2).

Site of infection. Spiral valve.

Locality. VERACRUZ: Playa Chachalacas: (see Méndez and Dorantes 2013).

Specimens in collections. CNHE (6867).

Site of infection. Spiral valve.

Locality. SONORA: Laguna de Agiabampo: (see Cruz-Reyes 1977).

Specimens in collections. CNHE (479-80).

Notes. According to Palm (2004), this material is a synonym of . However, the poor condition of the type material re-examined during the present study precludes any conclusion about the taxonomic status of this species.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: NA: (see Heinz and Dailey 1974).

No specimens in collections.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa María, Santa Rosalía: (see Caira et al. 2014a).

Specimens in collections. CNHE (8941-4).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Olson and Caira 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Olson and Caira 2001). OAXACA: Golfo de Tehuantepec: (see Kurochkin and Slankis 1973).

Specimens in collections. BMNH (2000.3.7.8.10); CNHE (4051); TINRO (72020).

Notes. This species was described as a member of the genus , but Euzet (1994) considered as a synonym of .

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Olson and Caira 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Olson and Caira 2001). OAXACA: Golfo de Tehuantepec: (see Kurochkin and Slankis 1973).

Specimens in collections. CNHE (4050); TINRO (72012).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: (see Olson and Caira 2001).

Specimens in collections. CNHE (4052-3).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Olson and Caira 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Caira et al. 2014a).

Specimens in collections. CNHE (4054-55); LRP (8321).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: (see Jensen 2001).

Specimens in collections. CNHE (4188); HWML (16374); USNPC (91208).

Notes. This species appears as n. sp. in Caira et al. (1999) and Caira et al. (2001).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Punta Arena: (see Jensen 2001).

Specimens in collections. CNHE (4186); HWML (16376); USNPC (91212).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Punta Arena: (see Jensen 2001).

Specimens in collections. CNHE (4184); HWML (16377); USNPC (91213).

Notes. This taxon appears as New genus 3 n. sp., in the phylogenetic analysis done by Caira et al. (2001).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: (see Jensen 2001).

Specimens in collections. CNHE (4179); HWML (16375); USNPC (91209).

Notes. was referred to as New genus 2 n. sp. in the phylogenetic analysis done by Caira et al. (2001).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Punta Arena: (see Jensen 2001).

Specimens in collections. CNHE (4182); HWML (16378); USNPC (91214).

Notes. This species was referred to as New genus 4 n. sp. in the phylogenetic analysis done by Caira et al. (2001).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Caira et al. 1999). GUERRERO: Bahía de Acapulco: (see Carbajal-Violante 2012).

Specimens in collections. CNHE (8295-8296).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de San Quintín: (see Appy and Dailey 1973).

Specimens in collections. USNPC (72567-8).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Puertecitos: (see Goshroy and Caira 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Goshroy and Caira 2001).

Specimens in collections. CNHE (4045-6); LRP (2060–2062); USNPC (90466-8).

Site of infection. Spiral valve.

Locality. JALISCO: Bahía de Chamela: (see Monks et al. 1996).

Specimens in collections. CNHE (2670-1); HWML; MNHG INV.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Goshroy and Caira 2001).

Specimens in collections. CNHE (4043-4); HWML (15549-51); LRP (2051-4); USNPC (90463-5).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Isla San Esteban: (see Caira and Burge 2001). BAJA CALIFORNIA SUR: Punta Arena: (see Caira and Burge 2001).

Specimens in collections. CNHE (4169-70); LRP (2097-2101); USNPC (90837-9).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Loreto, Punta Arena: (see Caira and Burge 2001).

Specimens in collections. CNHE (4171-2); LRP (2012-3); USNPC (90840-1).

Site of infection. Spiral valve.

Locality. Sonora: Puerto Peñasco: (see Friggens and Brown 2005).

No specimens in collections.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Caira et al. 1999). SONORA: Puerto Peñasco: (see Friggens and Brown 2005).

Specimens in collections. CNHE (4171-2); LRP (2012-3); USNPC (90840-1).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Caira and Zahner 2001).

Specimens in collections. CNHE (4175-6); LRP (2105-6); USNPC (90843).

Notes. Caira et al. (2001) recorded this species as n. sp. 1.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Goshroy and Caira 2001).

Specimens in collections. CNHE (4043-4); HWML (15552); LRP (2055-6); USNPC (90461).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Loreto, Punta Arena: (see Caira and Burge 2001).

Specimens in collections. CNHE (4173-4); LRP (2014); USNPC (90842).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: Santa Rosalía: (see Caira and Zahner 2001).

Specimens in collections. CNHE (4177-78); LRP (2107); USNPC (90844).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles, Puertecitos: (see Goshroy and Caira 2001). BAJA CALIFORNIA SUR: Loreto: (see Goshroy and Caira 2001).

Specimens in collections. CNHE (4040-1); HWML (15548); LRP (2057-9); USNPC (90462).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Caira et al. 2001), Puertecitos: (see Caira et al. 2001). BAJA CALIFORNIA SUR: Santa Rosalía: (see Caira et al. 2001). NA: NA: (see Healy et al. 2009). SONORA: Puerto Peñasco: (see Friggens and Brown 2005).

No specimens in collections.

No specimens in collections

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Goshroy and Caira 2001). BAJA CALIFORNIA SUR: San José del Cabo: (see Goshroy and Caira 2001).

Specimens in collections. CNHE (4048); USNPC (90439).

Notes. This material probably represents a new species as it differs from both and (see Goshroy and Caira 2001).

Site of infection. Intestine.

Locality. BAJA CALIFORNIA: Ensenada: (HWML).

Specimens in collections. HWML (31324).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Caira et al. 2001). NA: Golfo de México (Mexico): (see Caira et al. 2001). VERACRUZ: Playa Chachalacas: (see Mendez and Dorantes 2013).

Specimens in collections. CNHE (6866).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Healy 2003).

Specimens in collections. CNHE (4727-9); LRP (3213-3215); USNPC (92236).

Site of infection. Intestine, spiral valve, stomach.

Locality. BAJA CALIFORNIA SUR: Bahía de La Paz, San Isidro: (see Healy 2003); Las Barrancas, Punta Abreojos, Punta Belcher: (see Méndez 2005).

Specimens in collections. CNHE (4730).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Caira et al. 1999).

Specimens in collections. CSMNH.

Notes. Caira et al. (1999) identified this material as , but according to Healy (2003) these specimens represent an undescribed species.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: , (see Healy 2003). BAJA CALIFORNIA SUR: San José del Cabo: (see Healy 2003).

Specimens in collections. CNHE (4731-3).

Site of infection. Intestine, stomach.

Locality. BAJA CALIFORNIA SUR: Punta Abreojos, Punta Belcher: (see Méndez 2005).

No specimens in collections.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: San José del Cabo: (see Schaeffner and Beveridge 2013). VERACRUZ: Playa Chachalacas: (see Méndez and Dorantes 2005).

Specimens in collections. CNHE (6863-3).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Caira et al. 1999).

No specimens in collections.

Site of infection. Spiral valve.

Locality. VERACRUZ: Playa Chachalacas: (see Méndez and Dorantes 2013).

Specimens in collections. CNHE (6864-5).

Notes. This material was recorded as sp. 1 and sp. 2.

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Church and Schmidt 1990).

Specimens in collections. USNPC (81051-2).

Notes. The accession number published by Church and Schmidt (1990) is wrong.

Site of infection. Intestine, spiral valve, stomach.

Locality. BAJA CALIFORNIA SUR: Las Barrancas, Punta Abreojos, Punta Belcher: (see Méndez 2005). GUERRERO: Bahía de Acapulco: (see Carbajal-Violante 2012). SONORA: Puerto Peñasco: (see Friggens and Brown 2005, Church and Schmidt 1990).

Specimens in collections. CNHE (8291-2); USNPC (81053).

Notes. The accession number published by Church and Schmidt (1990) is wrong.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Campbell and Beveridge 1997).

Specimens in collections. CNHE (3142); USNPC (85472).

Site of infection. Spiral valve.

Locality. GUERRERO: Bahía de Acapulco: (Monks et al. 2015 ). SINALOA: Mazatlán: (Monks et al. 2015).

Specimens in collections. CNHE (8293-4; 9725-7); HWML (75091-104); MNGH-PLAT (90513-5).

Notes. This species appears as sp. in Carbajal-Violante (2012). According to Ruhnke et al. (2015) the genus is clearly a candidate for membership in the ; a molecular analysis will be necessary to assign it to family level.

Site of infection. Spiral valve.

Locality. CAMPECHE: Ciudad del Carmen: (see Pulido-Flores and Monks 2014).

Specimens in collections. CNHE (8838).

Notes. The inclusion of this cestode species in follows Appeltans et al. (2012).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco (Bahía Cholla): (see Friggens and Duszynski 2005).

Specimens in collections. USNPC (92213-4).

Notes. Published as sp. in Friggens and Brown (2005).

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Duszynski 2005).

Specimens in collections. USNPC (92212).

Notes. Published as sp. in Friggens and Brown (2005).

Site of infection. Spiral valve.

Locality. NA: NA: (see Healy et al. 2009).

No specimens in collections.

Notes. Species identification requires verification according to Healy et al. (2009).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Healy et al. 2009). BAJA CALIFORNIA SUR: Loreto: (see Caira et al. 1999); San José del Cabo: (see Healy et al. 2009).

Specimens in collections. LRP (3893, 3896).

Notes. The records of Healy et al. (2009) of and were made as sp.5 and sp.6, respectively.

Site of infection. Spiral valve.

Locality. SONORA: Puerto Peñasco: (see Friggens and Brown 2005).

Specimens in collections. USNPC (92202-5).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: San José del Cabo: (see Healy et al. 2009).

Specimens in collections. LRP (3895).

Notes. This record appears as n. sp. in Healy et al. (2009).

Site of infection. Spiral valve.

Locality. GUERRERO: Bahía de Acapulco: (see Carbajal-Violante 2012).

Specimens in collections. CNHE (8297-8).

Site of infection. Stomach.

Locality. GUERRERO: Bahía de Acapulco: (see Carbajal-Violante 2012).

Specimens in collections. CNHE (8299-8300).

Poche, 1926

Site of infection. Spiral valve, stomach.

Locality. BAJA CALIFORNIA: Playa María: (see Heinz and Dailey 1974). SONORA: Bahía de San Carlos: (see Heinz and Dailey 1974).

Specimens in collections. USNPC (72675).

Site of infection. Stomach.

Locality. BAJA CALIFORNIA SUR: Las Barrancas: (see Méndez 2005).

No specimens in collections.

“

Site of infection. Intestine, stomach.

Locality. BAJA CALIFORNIA SUR: Punta Abreojos, Punta Belcher, Las Barrancas: (see Méndez 2005).

No specimens in collections.

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Healy et al. 2009).

Specimens in collections. LRP (3910).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Healy et al. 2009).

Specimens in collections. LRP (3012).

Notes. According to Healy et al. (2009) this material represents an undescribed species; recorded as n. sp. 1 in Caira et al. (1999) and Caira et al. (2001).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de los Ángeles, Puertecitos: (see Ruhnke et al. 2000). BAJA CALIFORNIA SUR: Santa Rosalía: (see Ruhnke et al. 2000).

Specimens in collections. CNHE (3846-7); HWML (15275,15276); USNPC (89726-7).

Notes. This species was reported as n. sp. 1 in the phylogenetic analysis done by Olson et al. (1999).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de los Ángeles, Puertecitos: (see Ruhnke et al. 2000).

Specimens in collections. CNHE (3848); HWML (15277, 15278); USNPC (89728-9).

Notes. This species was reported as n. sp. 2 in the phylogenetic analysis done by Olson et al. (1999).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: San José del Cabo: (see Caira and Euzet 2001).

Specimens in collections. CNHE (4191).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA SUR: San José del Cabo: (see Caira and Euzet 2001).

Specimens in collections. CNHE (4190).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía de Los Ángeles: (see Nasin et al 1997); Puertecitos: (see Caira 1985). BAJA CALIFORNIA SUR: San José del Cabo, Santa Rosalía: (see Nasin et al. 1997).

Specimens in collections. CNHE (3071); USNPC (78600, 87127).

Notes. This species was described as and recently transferred to by Bernot et al. (2015). Type host of was determined by Caira (1985) as “unidentified shark of the family ”; its accurate specific identity was established by Nasin et al. (1997).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Puertecitos: (see Caira 1985, Nasin et al. 1997). BAJA CALIFORNIA SUR: Santa Rosalía: (see Nasin et al. 1997).

Specimens in collections. CNHE (3068-70); HWML (22537).

Notes. Specimens from Puertecitos were identified by Caira (1985) as Euzet, 1954 and re-identified by Nasin et al. (1997) as . This species was recently transferred to by Bernot et al. (2015).

Site of infection. Spiral valve.

Locality. CHIAPAS: Laguna Mar Muerto: (see Hoberg et al. 1998).

Specimens in collections. CNHE (2642).

Site of infection. Spiral valve.

Locality. BAJA CALIFORNIA: Bahía San Francisquito, Isla Ángel de la Guarda (Puerto Refugio): (see Milleman 1963); Bahía San Felipe: (see Milleman 1963). BAJA CALIFORNIA SUR: Laguna Ojo de Liebre (Guerrero Negro), Punta Abreojos: (see Gómez del Prado-Rosas 1984).

Specimens in collections. CNHE (2289); USNPC (57448, 57450-2).

Site of infection. Skin.

Locality. BAJA CALIFORNIA: Isla San Esteban: (CNHE).

Specimens in collections. CNHE (4027).

Notes. This specimen was deposited at the CNHE by Steve Curran as the holotype of the new species , but their description was not published.

Site of infection. Skin.

Locality. TAMAULIPAS: Matamoros: (CNHE). VERACRUZ: Isla de Sacrificios: Elasmobranquio no determinado (CNHE).

Specimens in collections. CNHE (1640, 5572).

Host-parasite list

Selachii

(C)

(C)

(C)

(C)

(T)

Lowe

(C)

(C)

(C)

Günther

(M)

(Müller & Henle)

(C)

(C)

(C)

gen. sp. (C)

sp. (C)

(C)

sp. (C)

sp. (C)

sp. (C)

Müller & Henle

(T)

(Poey)

(C)

(Linnaeus)

sp. (C)

(T)

sp. (C)

(T)

sp. (C)

(C)

(C)

(Bonnaterre)

(C)

(C)

(H)

(Girard)

(C)

(C)

(C)

sp. (C)

(N)

(C)

(T)

Taylor & Castro-Aguirre

(T)

(Péron)

(C)

(Griffith & Smith)

(M)

(C)

(Rüppell)

sp. (C)

sp. (C)

(C)

(C)

Ayres

(T)

(C)

(Linnaeus)

(T)

Gill

(M)

(T)

(Gill)

(C)

(C)

sp. (C)

(T)

Jordan & Gilbert

(C)

(T)

(T)

(C)

Undetermined shark

(T)

Undetermined

(T)

(H)

Bigelow & Schroeder

(M)

Hildebrand & Schroeder

(M)

(C)

(Garman)

(C)

(C)

(C)

(C)

sp. (C)

(T)

(C)

(M)

(C)

(T)

(T)

(C)

sp. (C)

(C)

(Garman)

(C)

sp. (C)

(T)

(C)

(C)

(M)

(M)

(C)

(T)

(C)

(C)

(C)

sp. (C)

sp. (C)

Beebe & Tee-Van

(N)

Euphrasen

(M)

(Müller & Henle)

(C)

(C)

(C)

(C)

(C)

(C)

(C)

(T)

Notarbartolo-di-Sciara

(T)

(C)

(C)

(C)

(Lloyd)

(C)

(C)

(C)

(C)

(T)

(T)

Gill

(C)

(T)

(C)

sp. (C)

sp. (C)

(C)

(C)

(N)

(C)

(T)

Applegate & Fitch

(T)

(C)

(T)

(C)

(Mitchill)

(M)

(M)

(C)

Evermann & Jenkins

gen. sp. (M)

(M)

(C)

(C)

(C)

sp. (M)

gen. sp. (M)

sp. (C)

(C)

sp. (C)

(C)

sp. (C)

(Jordan & Gilbert)

(C)

(C)

(C)

(T)

Jordan & Starks

(T)

(T)

Bigelow & Schroeder

(M)

Chirichigno

sp. (C)

Jordan & Gilbert

(M)

(M)

Garman

gen. sp. (T)

Günther

(C)

(T)

Ayres

(T)

(C)

(M)

(Jordan & Gilbert)

(T)

gen. sp. (H)

(C)

(M)

Osburn & Nichols

(M)

(C)

Cuvier

(M)

sp.

(M)

(T)

Cooper

(C)

(C)

sp. (C)

(T)

(C)

(M)

(C)

(C)

(M)

(C)

sp. (C)

(C)

(C)

sp. (C)

(C)

(C)

(C)

(C)

(C)

(Garman)

sp. (C)

(T)

(C)

(M)

(C)

(M)

(C)

(T)

(T)

sp. (C)

(C)

(C)

“Mantarraya gris”

(M)

Discussion

To date, 132 helminth taxa (110 named species and 22 taxa not assigned to species) have been reported as parasites of elasmobranch species in Mexico. Seventy-three of these taxa are represented by holotypes from Mexican waters. All of these taxa have been collected in the adult stage (132). Thus, the richness of helminth species parasitizing elasmobranchs distributed in Mexican waters represents 7.2% of the worldwide species richness for this group (see Caira et al. 2012).

The 132 taxa parasitize 48 taxa of elasmobranchs (4 of them not assigned to species), within 15 families; (8 species) and (6) being the families with the highest number of species sampled, due to the fact that100% and 60% respectively of the species of these two families recorded in Mexico, have been studied for helminths. In addition, helminths have been reported from 9 of the 12 orders of elasmobranchs in Mexican waters; no records are available for , (Selachii) or (). Fifteen of the 23 families of sharks have not been reported as hosts of helminths, as well as half of the families of rays. From the 204 known species of elasmobranchs recorded in Mexican waters, only 26% of them have been studied for helminths; thus, only 18.3% and 32.6% of shark and ray species, respectively, have been examined for, and found to host, helminths (Table 1). This value is similar to that found by Randhawa and Poulin (2010), who established that only 317 species (26%) of this globally distributed group of hosts have been examined for intestinal parasites (specifically tapeworms).

The species of elasmobranchs with the higher parasite species richness are (with 19 taxa), (14) and (13). However, 8 shark and 9 ray species have been recorded only once as hosting helminths. In total, is parasitized by 109 taxa of helminths and Selachii by 52, of which 56% and 61%, respectively, are cestode species. The mean value of species harbored by a host is 2.8 for sharks and 3.8 for rays; these traits are in accordance with the findings reported by Randhawa and Poulin (2010), who noted that, on average, batoids harbor significantly more species of tapeworms than sharks.

and () are the species with the broadest host spectrum; the former species is associated with 11 species of rays PageBreakPageBreakfrom three localities, and the latter has been found in 7 species of rays and one shark from three localities. Higher host specificity was shown by cestodes; 62 of the 76 nominal species of this group were specialists for a particular species of elasmobranch. These results are in accordance with Caira and Jensen (2014) who noted that the majority of tapeworm species are extremely host-specific, exhibiting species-specific (i.e., oioxenous) associations with their hosts. However, more conclusive results can be obtained only by increasing the sampling of this group of vertebrates on both coasts of Mexico, through comprehensive studies in which complete necropsies of elasmobranchs are conducted, avoiding partial analysis of a particular site of infection or organ system, which is a common trait of the research in this field according to Caira et al. (2012).

had the widest geographic distribution, being found in 7 localities; this monogenean is followed by , and , which are distributed in 5 localities each, as well as and , recorded in 4 locations each. is the most specious genus, as it is represented by 14 species parasitizing 6 species of elasmobranchs.

Along with the increase in the number of species described worldwide, the number of helminth species parasitizing sharks and rays recorded in Mexico has increased in the past 2 decades, after slow growth from 1945, when Caballero y Caballero (1945) described the first species associated with this group of hosts (). Between 1945 and 1994, only 20 species were reported in this group of hosts in the country. From 1995 to the present, this number increased more than 400%, rising to 107 species (Figure 2). According to Caira and Jensen (2014), approximately 250 species were erected over the past 2 decades; 36 of them were collected from elasmobranchs inhabiting Mexican waters.

Figure 2.

Cumulative curve of helminth species recorded in Mexico over 70 years of research.

The helminthological record of elasmobranchs distributed in Mexico is asymmetrically constituted in terms of the helminth groups represented, the hosts studied and the geographical distribution of the sampling sites. Cestodes are the most widely represented group, with 76 named species and 18 not assigned to species. The main reasons that explain this asymmetry can be summarized in two points: 1) the great diversity of cestodes associated with elasmobranchs, as nine of the 19 orders included in this Class infect this group of hosts, and eight are even exclusive parasites of them (Caira et al. 2014b); cestodes are by far the most diverse group of metazoan parasites of elasmobranchs, representing more than half of the described species for this host group (Caira et al. 2012); 2) the particular interest of a research team lead by Janine N. Caira from the University of Connecticut to inventory the fauna of tapeworm parasites of sharks and rays distributed in the Gulf of California, through the project “A systematic survey of the metazoan parasites of elasmobranchs from the Sea of Cortez” between 1993 and 1994. As a result of this project, more than 45 species of cestode were recorded in this area of Mexico, 36 of which were described as new species. The most intensively studied host group is , with 32% of the species in the country harboring at least 1 species of helminth; on the other hand, only 18% of the species of sharks caught in Mexico have been reported as hosting helminths. To determine if this could represent a bias in sampling and not a reflection of the real richness of the helminths in the different PageBreakgroups of hosts, more sampling efforts are necessary. Likewise, the specific richness of helminths is concentrated in two states, i.e., Baja California Sur (69 helminth species reported to date) and Baja California (54), both located in the Gulf of California, up to now, the most intensively sampled region of Mexico.

In addition to the 132 helminth taxa recorded so far in elasmobranchs inhabiting Mexican waters, another 8 taxa of helminths were found in this group of hosts: 2 acanthocephalans, sp. (Méndez 2005) and (Monks et al. 2009), and 6 nematodes, , sp. (Méndez 2005), sp., sp., sp. (Pérez-Ponce de León et al. 1999), and (Moravec et al. 1998). However, their presence in elasmobranchs is considered accidental; elasmobranchs can be infected through 2 ways: 1) ingestion of prey acting as intermediate hosts for almost completely developed larvae and 2) ingestion of definitive hosts constituting an accidental, probably postcyclic transmission (Moravec et al. 1998; Anderson 2000; Weaver and Smales 2014).

In spite of the great amount of information generated in the last 20 years, new records of the helminth fauna of in Mexico remain scarce and fragmentary. To date, 81.7% of sharks and 67.4% of rays distributed in Mexican waters lack helminthological studies. Completing the helminthological inventory for this group of vertebrates is a major challenge, as recent estimates establish the number of species to be described associated with these hosts at approximately 3600, considering only the tapeworms (Randhawa and Poulin 2010). Only through efforts such as the one conducted by Caira and collaborators in the Gulf of California will a comprehensive understanding of these host-parasite associations be achieved.

Table 2.

Sampled localities for elasmobranchs as hosts of helminths in Mexico.

Baja California	N	W
1) Bahía de Los Ángeles†	28°54'31"	113°29'47"
2) Bahía San Felipe	28°42'00"	112°35'00"
3) Bahía San Francisquito	29°45'05"	114°18'36"
4) Bahía de San Quintín	30°27'09"	115°56'54"
5) Ensenada	31°51'14"	116°37'45"
6) Isla Ángel de la Guarda (Puerto Refugio)	29°26'26"	113°34'25"
7) Isla Rasa	28°49'01"	112°58'25"
8) Isla San Esteban	28°41'39"	112°31'30"
9) Playa María	31°52'18"	116°39'31"
10) Puertecitos	30°20'59"	114°38'27"
Baja California Sur
11) Bahía Almejas	24°31'00"	111°39'50"
12) Bahía de La Paz	24°14'30"	110°28'08"
13) Bahía de Santa Inés	27°02'55"	111°58'37"
14) Bahía Magdalena	25°20'00"	112°05'00"
15) Boca de Álamo	23°53'51"	109°48'12"
16) El Comitán	24°08'00"	110°25'00"
17) Isla Magdalena	24°15'00"	111°30'00"
18) Laguna Guerrero Negro (Ojo de Liebre)	27°51'21"	114°14'28"
19) Las Barrancas	26°00'30"	112°12'17"
20) Loreto	26°01'00"	111°19'50"
21) Punta Abreojos	26°27'45"	112°43'48"
22) Punta Arena	24°04'00"	109°50'00"
23) Punta Belcher	25°20'00"	112°05'00"
24) San Isidro	23°53'00"	109°47'00"
25) San José del Cabo	23°04'49"	109°40'49"
26) Santa María	27°24'53"	112°18'17"
27) Santa Rosalía	27°20'04"	112°15'35"
Campeche
28) Bancos de Campeche	19°53'03"	90°31'43"
29) Ciudad del Carmen	19°51'33"	90°31'35"
30) Estuario Champotón	19°20'56"	90°41'18"
Chiapas
31) Laguna Mar Muerto (El Paredón)	15°59'00"	94°00'00"
Colima
32) Manzanillo	19°04'54"	104°19'31"
Guerrero
33) Bahía de Acapulco	16°49'21"	99°52'55"
Jalisco
34) Bahía de Chamela	19°33'15"	105°06'45"
35) Puerto Vallarta	20°35'48"	105°15'00"
Nayarit
36) Punta Mita	20°46'38"	105°30'46"
37) San Blás	21°32'00"	105°17'22"
Oaxaca
38) Golfo de Tehuantepec	15°45'26"	96°07'21"
Quintana Roo
39) Blanquizal	18°16'03"	87°54'12"
40) Holbox	21°34'05"	86°14'32"
41) Isla Contoy	20° 48'25"	86° 47'15"
42) Isla Cozumel	20°24'10"	86°55'40"
43) Xcalak	18°19'32"	87°44'49"
Sinaloa
44) Bahía Santa María	25°02'38"	108°05'14"
45) Mazatlán	23°14'03"	106°27'40"
Sonora
46) Bahía de Guaymas	27°54'45"	110°52'41"
47) Bahía de San Carlos	27°56'36"	111°03'44"
48) Laguna de Agiabampo	26°21'54"	109°13'05"
49) Puerto Peñasco	31°18'33"	113°31'30"
50) Puerto Peñasco (Bahía Cholla)	31°20'00"	113°36'45"
Tamaulipas
51) Matamoros	25°52'00"	97°30'00"
Veracruz
52) Isla de Sacrificios	19°10'32"	96°05'50"
53) Playa Chachalacas	19°22'00"	96°22'00"
Yucatán
54) Ría Lagartos	21°36'08"	88°08'51"

These numbers correspond with the position of localities on Figure 1.