JellyWeb: an interactive information system on Scyphozoa, Cubozoa and Staurozoa.

Identification of organisms is traditionally based on the use of "classic" identification keys, normally printed on paper. These keys have several drawbacks: they are mainly based on the systematics, requiring identification of orders, families and genera at first; they are written by experts for other experts, in a specific scientific jargon; they have a "frozen" structure (sequence of theses/antitheses); once published, they cannot be changed or updated without printing a new edition. Due to the use of computers, it is now possible to build new digital identification tools, which: 1) can be produced automatically, if the characters are stored in a database; 2) can be freed from the traditional systematics, giving priority to easy-to-observe characters, incl. those usually uncommon to the classical keys, such as ecology and distribution; 3) can be updated in real time once published on-line; 4) can be available on different media, and on mobile devices. An important feature of these new digital tools is their "collaborative" nature. They can be enriched by the contribution of several researchers, which can cooperate while maintaining rights and property of the resources and data they contribute to the system. JellyWeb, the information system on Scyphozoa, Cubozoa and Staurozoa has been developed in Trieste since 2010. The system was created with the aim of - potentially - becoming a starting point for a wide collaborative effort in developing a user-friendly worldwide digital identification system for jellyfishes.

Introduction

Since the Rio Earth Summit in 1992, access to biodiversity information has become a fundamental task. Biodiversity data are targeted by several efforts of digitalization and aggregation, most of which focus on primary biodiversity data, i.e. natural history collection specimens and field records. Some of these efforts produced wide global networks, e.g. the GBIF; Berendsohn et al. 2010, King et al. 2010), which, together with the BioCASE, Holetschek et al. 2012), is mobilizing ca. 600 millions of records. Primary biodiversity data are mostly used in modeling the distribution of the taxa, and in predicting the effect of climate changes and anthropic pressure on endangered or alien invasive taxa. Taxon related information (nomenclature, auto-ecology, etc.) become the focus of similar large scale efforts only in the last years (Martellos and Attorre 2012, Martellos 2014). The GBIF itself is starting to aggregate checklist data (GBIF 2010), while other efforts are focused on molecular data (Field et al. 2011, Holetschek et al. 2012, Wieczorek et al. 2012), and to ecological information (Fegraus et al. 2005). In the field of hydrobiology, some recent examples can be Fish-SPRICH (Brosse et al. 2013) and Fish-AMAZBOL (Carvajal-Vallejos et al. 2014). In the case of jellyfishes, online resources are however scarce, but some relevant exceptions (e.g., the Jellyfish Dataset Initiative, http://www.bco-dmo.org/dataset/526852).

(Global Biodiversity Information Facility

(Biodiversity Collection Access for Europe

Digital identification keys are a particular case in the world of biodiversity informatics. Since the development of the DELTA language (Dallwitz 1980), efforts aiming at creating online digital identification keys followed several approaches. The resulting products differ in usability, accessibility, size, etc. (Nimis and Martellos 2009, Hagedorn et al. 2010, Randlane et al. 2010, Martellos and Nimis 2015). With the development of FRIDA, Martellos 2010), the researchers of the Department of Life Sciences, University of Trieste, aimed at producing a simple but effective instrument for the development of digital identification keys in collaborative efforts. This led to the publication – in the framework of project , and of the EU projects KeyToNature (http://www.keytonature.eu), SiiT (http://ww.siit.eu) and CSMON-LIFE (LIFE13 ENV/IT/842, http://www.csmon-life.eu) – of ca. 600 different digital identification keys for several groups of organisms.

(FRiendly IDentificAtion

As far as , and are concerned, there are digital databases hosting taxonomic information, such as WoRMS (World Register of Marine Species, http://www.marinespecies.org/), as well as paper printed keys to genera (as an example, see Cornelius 1997; other keys are listed in Morandini et al., 2005). Few examples of digital resources are available in the web, often limited to specific geographic regions, as the Cubozoan and scyphozoan key of the Carolinian Biogeographic Province (Calder 2009), the key to the and of the South Atlantic Bight (Calder and King 2008), and, as far as the Mediterranean is concerned, the web site MeteoMeduse (Boero 2013, http://meteomeduse.focus.it/). The latter, however, is an example of citizen science observatory, and does not provide an identification key. To our knowledge, no comprehensive digital identification tools to species of these taxa exist.

By combining taxonomical, ecological, and morphological and anatomical features into an information system, we developed the so called JellyWeb, a simple tool which allow to researchers and laypersons to identify , and to the species level. This paper presents the results of this effort, available online at the URL http://dryades.units.it/jelly.

Methods

Data were collected from several sources in literature. The most relevant are Kramp (1961), WoRMS (http://www.marinespecies.org/), the Scyphozoan Wiki (http://thescyphozoan.ucmerced.edu/), and Mills (1999-). Further sources are listed in Balboni 2008, Benci 2008, Sarto 2009, Sola 2009, Coral 2012, Benci 2012, Savonitto 2012, Ukosich 2014. Other paper are under consideration, and will lead to adding to the database other species for several genera, such as (, , ), (), (), (, , , , and several other species), (, ), (, ), (), () ().

The information system is freely available online at the URL http://dryades.units.it/jelly. It organizes data collected in the last five years by the research unit headed by Massimo Avian, at the Dept. of Life Sciences of the University of Trieste. The researchers which contributed to the project agreed on distributing the data under a Creative Commons, share alike, by attribution 3.0 (CC 3.0 by-sa) license.

The software of the information system has been developed in PHP language. The data are stored in a MySQL database. The system is equipped with a multi-entry query interface (Hagedorn et al. 2010), which operates on both a taxonomic database, and a database of nine easily recognizable morphological characters (see below). The multi-entry interface allows complex queries, which can be a first step in the identification of an organism. The multi-entry query system returns lists of taxa, on which the identification process can continue by using a digital identification system. The latter has been developed by using the FRIDA (FRiendly IDentificAtion) package (Martellos 2010). It operates on a morpho-anatomical database, which hosts ca. 200 characters for several infra-generic taxa of , and (a revision of the content of the database due to recent taxonomic advancements is ongoing). The output of the digital identification system is a digital identification key to the remaining taxa, which can be used by an interactive interface, or printed out as a dichotomous, illustrated key. The whole key can also be exported in a stand-alone version for mobile devices (Nimis et al. 2012).

The query interfaces have been developed according to the results of several usability tests, conducted in the framework of projects KeyToNature and SiiT, as detailed in Martellos and Nimis (2015). The system is under continuous development, following users’ input.

Results

JellyWeb hosts several information pages and two query system. The home page (http://dryades.units.it/jelly) provides access to several sections: information, describing how the system works; survey area; query (detailed below); checklist, listing all taxa alphabetically by genus and species name, and providing access to their taxon pages; credits.

The query system is made of two parts.

Multi-entry interface (Fig. 1). The first interface of the query system provides the users with the opportunity of specifying a set of nine easily observable characters, and/or scientific name and family. The morphological characters are:

Figure 1.

Multi-entry interface. The multi-entry interface allows to combine the states of several morphologic and anatomic characters, together with taxonomic information, to query the database.

Jellyfish sessile / swimming;

Umbrella shaped like a cube or a box / not shaped like a cube or a box;

Tentacles present / absent;

Tentacles isolated / grouped in clusters;

Umbrella with a coronal groove / without a coronal groove;

Umbrella flat / not flat;

Oral arms absent / 4 / more than 4;

Jellyfish with filaments (oral arm appendages) / without filaments;

Jellyfish with scapulae / without scapulae.

For each character, an information popup window with images and text detailing the most relevat features is accessible by clicking on the question mark button. The result of a query is a list of taxa (Fig. 2). For each taxon an image is displayed (if available, see below). A link provides access to the taxon page (Fig. 3), which displays a description, as well as all the images available in the system, with credits and metadata, and other information (when available). Taxon pages can host a virtually unlimited amount of information and images, and/or provide access to external resources through HTML links.

Figure 2.

List of taxa. The result of a query made by using the multi-entry interface is an illustrated list of infra-generic taxa.

Figure 3.

Taxon page. A typical taxon page displays an image, a description, as well as all the other images available in the system, together with credits and metadata. Taxon pages can host a virtually unlimited amount of data, links and media.

Digital identification key. The results page of the multi-entry interface allows to generate an interactive identification key to remaining taxa. The key can be used through a simple single entry interface (Fig. 4, Hagedorn et al. 2010), or printed out as a textual, illustrated dichotomous key. At each step of the identification process users can list out the remaining taxa, or print an illustrated key. By clicking on a taxon name, the corresponding taxon page is shown (Fig. 3). Each key generated by this system is different from the others, since they contain a different number of infra-generic taxa. Normally, the lower the number of taxa is, the easier the resulting key. A key to all the taxa currently included in our databases can also be generated, and is provided below.

Figure 4.

Single entry digital identification key. The digital identification key to remaining taxa is generated from the results of the multy-entry query system. It is used through a single entry interface, and can be printed out as a textual, illustrated dichotomous key as well.

Dichotomous key to all taxa

This key was automatically generated by the system, and contains all the infra-generic taxa currently stored in our databases at the date October 30, 2015. When a taxon is added to the system the key automatically changes. Hence, the key an user will obtain in the future will be slightly – or completely – different. The keys are not the transposition of an existing paper printed key, but are automatically generated by the system from a database for morphological and anatomical characters by using the package FRIDA (Martellos 2010).

Discussion

Digital resources on biodiversity can be relevant not only to researchers, but also to laypeople, such as tourists or citizen scientists. The importance of involving citizens in understanding, monitoring and protecting biodiversity has been recently expressed by the European Commission, in the document “Establishing Horizon 2020” (EU Regulation no. 1291/2013). However, most of the biodiversity-related resources available in the Web – especially the ones dedicated to to “difficult” groups, such as jellyfish – are normally devoted almost exclusively to experts (Martellos and Nimis 2015). Exposing scientific information in a form which can be accessible to everybody – without losing its content and informative value – can be a true revolution. Many citizens, especially if already interested in nature and aware of environmental issues (e.g. the presence of invasive alien species), are potentially interested in similar resources. Hence digital resources can be used to involve a wider amount of citizens in scientific tasks, such as the collection of those “big data” which are nowadays fundamental to researchers. The examples of OPAL initiative in the British Isles (http://www.opalexplorenature.org; accessed 08 August 2015) or, in the field of jellyfish, of MeteoMedusa (Boero 2013, Boero et al. 2013), and JellyWatch (http://www.jellywatch.org/; accessed 08 August 2015) are demonstrating the effectiveness of a citizen science approach in collecting scientific data.

JellyWeb is based on morpho-anatomic and taxonomic data, collected and organized in ca. 10 years of research. The development of the portal (Martellos and Nimis 2015) was based upon the experience of the European project KeyToNature (mainly devoted to digital identification) and of the project (devoted to the pubblication of biodiversity data in the web). This is the first portal devoted to organisms other than vascular plants developed by the research unit of the Dept. of Life Science of the University of Trieste. During its development, a particular attention was paid to user interfaces, in order to provide high quality scientific information in the most straightforward way, and to make it useable by the wider audience as possible.

The multi-entry interface can be useful to both researchers (whom can simply type the name of a taxon to retrieve related information or generate an identification key), and laypeople (whom can use it to start the identification of a jellyfish they have just seen on the seashore). As a further help, interactive keys are enriched by images and drawings of the most relevant characters. Since digital keys are generated in real time, on the basis of the list of remaining organisms, each query produces a different identification key.

Since identification is nowadays often based on molecular analysis, the system has been developed to host molecular data as well. In fact, several attempts to revise the taxonomy of the various taxa like the on the basis of morphological observations integrated with genetic analysis are underway, highlighting several critical points, such as the recognition of cryptic species in the complex within the “traditional” species (Dawson and Jacobs 2001, Dawson and Martin 2001, Dawson 2003, Dawson et al. 2005, Ramšak et al. 2012), or even at higher taxonomic levels like the proposition of at least two new families within the PageBreak(Bayha and Dawson 2010, Straehler-Pohl et al. 2011). The integration of molecular information in a digital identification system by using the FRIDA software was studied by Bruni et al. (2012) for vascular plants.

Conclusion

JellyWeb is an accumulative system, which can potentially host all data on , and , and even extend its aim to other groups of the phylum . However, a research group alone can hardly complete such a challenging task. The research unit at the University of Trieste plans to maintain and enrich JellyWeb, but its growth could be faster, if other research groups join this effort. A researcher, or a research group, can contribute to the system by:

Fostering a taxon (such as a genus, or a family). This can be done by managing an instance of the FRIDA system. FRIDA allows to different authors to independently manage separate instances, while at the same time contributing to the same database of morphological ans anatomical data, hence, generating updated multi-authored keys to any subset of taxa in the whole system (for a complete description see Martellos 2010). All the digital keys which are generated by the system give credit to the authors of all the data. The keys and all the data and images in JellyWeb are always distributed under a Creative Commons share alike, by attribution 3.0 license (CC 3.0 by-sa).

Contributing to the image archive. High quality images of morphological and anatomical characters and of the whole organisms are probably the most relevant bottlenecks in the process of creating a portal such as JellyWeb. Especially when identifing a taxon, digital images are of capital relevance, both for choosing among the leads of each choice, and as visual census when an identification has been achieved. Several species of , and are known for one or few specimens, and, even when the taxa are well known, high quality images are, however, scarce. JellyWeb was developed to host a virtually unlimited number of images for each taxon. Each image is displayed with credits to the author(s) and owner(s), institution(s), other metadata, and license.

Producing descriptions. Another relevant bottleneck in developing digital identification keys and portals to one or more groups of organisms are their descriptions. While taxonomic descriptions can be found in books and papers, descriptions which could be actually useful to people other than researches are difficult to produce. In our experience, to be appreciated by a wider audience, they should mix different sources of information, from ecology to taxonomy, from distribution to human uses, relevance for economy, etymology of the name, etc. Hence, their production is not a simple cut and paste, but a relevant effort of analysis and synthesis.

Potential contributor can contact Massimo Avian (avian@units.it), to define the extent of their participation.

1	Medusa sessile	2
–	Medusa swimming	34
2 (1)	Medusa without aboral peduncle	Lucernariopsis vanhoeffeni (Browne, 1910)
–	Medusa with aboral peduncle	3
3 (2)	Medusa with sense organs: rhopalioids (anchors)	4
–	Medusa without sense organs	15
4 (3)	Coronal muscle divided	5
–	Coronal muscle unbroken	10
5 (4)	Calyx not conical	6
–	Calyx conical	7
6 (5)	Calyx quadro-pyramidal	Haliclystus borealis Uchida, 1933
–	Calyx pyramidal, octangular	Haliclystus salpinx Clark, 1863
7 (5)	Marginal anchors fairly large, egg-shaped	Haliclystus stejnegeri Kishinouye, 1899
–	Not as above	8
8 (7)	Marginal anchors very large, biscuit-shaped	Haliclystus antarcticus Pfeffer, 1889
–	Not as above	9
9 (8)	Marginal anchors kidney-shaped, with a short, cylindric stalk	Haliclystus auricula (Rathke, 1806)
–	Marginal anchors small, oval	Haliclystus kerguelensis Vanhöffen, 1908
10 (4)	Peduncle single-chambered	Manania hexaradiata (Broch, 1907)
–	Peduncle with 4 perradial chambers	11
11 (10)	Gonads not united by a transverse circumferential membrane (claustrum) which divide each of the 4 perradial stomach pouches into an outer and an inner space	Stenoscyphus inabai (Kishinouye, 1893)
–	Gonads united by a transverse circumferential membrane (claustrum) which divide each of the 4 perradial stomach pouches into an outer and an inner space	12
12 (11)	Calyx as long as wide	Manania gwilliami Larson & Fautin, 1989
–	Calyx longer than wide	13
13 (12)	Calyx with dark herringbone pattern	Manania distincta (Kishinouye, 1910)
–	Calyx without dark herringbone pattern	14
14 (13)	Arms twice as long as broad	Halimocyathus platypus Clark, 1863
–	Arms short	Manania handi Larson & Fautin, 1989
15 (3)	Peduncle with 4 perradial chambers	16
–	Peduncle single-chambered	22
16 (15)	Peduncle with muscle in the septa	17
–	Peduncle without muscle in the septa	18
17 (16)	On each arm about 9 tentacles	Depastrum cyathiforme (M. Sars, 1846)
–	On each arm about 25 tentacles	Depastromorpha africana Carlgren, 1935
18 (16)	Gonads united by a transverse circumferential membrane (claustrum) which divide each of the 4 perradial stomach pouches into an outer and an inner space	19
–	Gonads not united by a transverse circumferential membrane (claustrum) which divide each of the 4 perradial stomach pouches into an outer and an inner space	20
19 (18)	On each arm 60–80 tentacles	Craterolophus convolvulus (Johnston, 1835)
–	On each arm about 30 tentacles	Craterolophus macrocystis von Lendenfeld, 1884
20 (18)	Arms adradial	Kishinouyea nagatensis (Oka, 1897)
–	Arms interradial	21
21 (20)	Arms larger at base than Sasakiella tsingtaoensis	Sasakiella cruciformis Okubo, 1917
–	Arms narrower at base than Sasakiella cruciformis	Sasakiella tsingtaoensis Ling, 1937
22 (15)	Peduncle without muscle in the septa	Lucernariopsis campanulata (Lamouroux, 1815)
–	Peduncle with muscle in the septa	23
23 (22)	Marginal lobes (arms) faintly developed	24
–	Marginal lobes (arms) well developed	26
24 (23)	Tentacles reduced	Lipkea stephensoni Carlgren, 1933
–	Not as above	25
25 (24)	Tentacles not true	Lipkea ruspoliana Vogt, 1886
–	Tentacles rudimentary	Lipkea sturdzi (Antipa, 1893)
26 (23)	Tentacles up to 60 on each arm	27
–	Tentacles more than 60 on each arm	28
27 (26)	Subumbrellar margin with 4 perradial pigment spots	Stylocoronella riedli Salvini-Plawen, 1966
–	Subumbrellar margin without 4 perradial pigment spots	Stylocoronella variabilis Salvini-Plawen, 1987
28 (26)	Peduncle rudimentary	Lucernaria australis Vanhöffen, 1908
–	Peduncle true	29
29 (28)	Peduncle as long or longer than height of calyx	30
–	Peduncle shorter than height of calyx	31
30 (29)	Tentacles 100–140 on each arm	Lucernaria quadricornis O.F.Müller, 1776
–	Tentacles 700–850 on each arm	Lucernaria walteri (Antipa, 1892)
31 (29)	Tentacles 80 or less on each arm	Lucernaria infundibulum Haeckel, 1880
–	Tentacles more than 80 on each arm	32
32 (31)	Peduncle 1/3 as long as height of calyx	Lucernaria haeckeli (Antipa, 1892)
–	Not as above	33
33 (32)	Peduncle less than 1/3 of the height of calyx	Lucernaria bathyphila Haeckel, 1880
–	Peduncle about half as long as height of calyx	Lucernaria sainthilairei (Redikorzev, 1925)
34 (1)	Medusa with calix	Tesserantha connectens, Haeckel, 1880 – Warning: some authors debate on the validity of swimming Stauromedusae (see Rodriguez et al. 2011)
–	Medusa with umbrella	35
35 (34)	Exumbrella divided by a circular and deep coronal groove	36
–	Exumbrella not divided by a circular and deep coronal groove	64
36 (35)	Tentacles from 4 to 6	37
–	Tentacles 8 or more	42
37 (36)	Rhopalia 4	38
–	Rhopalia 6	39
38 (37)	Gonads almost equidistant	Pericolpa campana (Haeckel, 1880)
–	Gonads in 4 pairs	Pericolpa quadrigata Haeckel, 1880
39 (37)	Gonads 6	Atorella arcturi Bigelow, 1928
–	Not as above	40
40 (39)	Gonads 8	Atorella octogonus Mills, Larson & Young, 1987
–	Gonads 4	41
41 (40)	Gonads sac-like, swollen	Atorella subglobosa Vanhöffen, 1902
–	Gonads leaf-shaped	Atorella vanhoeffeni Bigelow, 1909
42 (36)	Rhopalia up to 6	43
–	Rhopalia more than 6	48
43 (42)	Rhopalia perradial, 4	44
–	Rhopalia interradial, 4	45
44 (43)	Coronal muscle divided	Paraphyllina intermedia Maas, 1903
–	Coronal muscle unbroken	Paraphyllina ransoni Russel, 1956
45 (43)	Marginal lappets 32	Nauphantopsis diomedeae Fewkes, 1885
–	Not as above	46
46 (45)	Gonads 4	Periphyllopsis galatheae Kramp, 1959
–	Gonads 8	47
47 (46)	Marginal lappets 16	Periphylla periphylla (Péron & Lesueur, 1809)
–	Marginal lappets 24	Periphyllopsis braueri Vanhöffen, 1902
48 (42)	Gonads 4 or 4 pairs	49
–	Gonads 8	53
49 (48)	Stomach pouches break up into numerous ragged-edged branches in the marginal lappets	50
–	Stomach pouches simple, radiating	51
50 (49)	Subumbrellar protuberances in 2 circles	Linuche aquila Mayer 1910
–	Subumbrellar protuberances in 3 circles	Linuche unguiculata (Schwartz, 1788)
51 (49)	Gonads bean-shaped	Palephyra indica Vanhöffen, 1902
–	Gonads crescent-shaped	52
52 (51)	Gonads with horns recurved	Palephyra antiqua Haeckel, 1880
–	Gonads consisting of 3 swellings	Palephyra pelagica Haeckel, 1880
53 (48)	Rhopalia > 8	54
–	Rhopalia 8 (Genus Nausithoe. The key refers to free-swimming stages only)	56
54 (53)	Gastric ostia with two pigmented spots	Atolla vanhoeffeni Russell, 1957
–	Gastric ostia without pigmented spots	55
55 (54)	Species with 20–24 tentacles	Atolla parva Russell, 1958
–	Species with usually 22, sometimes up to 32 tentacles	Atolla wyvillei Haeckel, 1880
56 (53)	Central disk with large pits	57
–	Central disk without pits	58
57 (56)	Central disk with radiating furrows	Nausithoe rubra Vanhöffen, 1902
–	Central disk without radiating furrows	Nausithoe atlantica Broch, 1914
58 (56)	Gonads very small	Nausithoe clausi Vanhöffen, 1892
–	Not as above	59
59 (58)	Gonads of normal dimensions	Nausithoe albatrossi (Maas, 1897)
–	Gonads large	60
60 (59)	Central disk not thick nor finely punctured	Nausithoe globifera Broch, 1914
–	Central disk thick, finely punctured	61
61 (60)	Central disk with radiating furrows	Nausithoe challengeri (Haeckel, 1880)
–	Central disk without radiating furrows	62
62 (61)	Medusa with chocolate brown or carmine gonads and blue gastric cirri	Nausithoe picta Agassis & Mayer, 1902
–	Medusa without chocolate brown or carmine gonads and blue gastric cirri	63
63 (62)	Gastric cirri not grouped in clusters	Nausithoe punctata (Kölliker, 1853)
–	Gastric cirri grouped in clusters	Nausithoe limpida Hartlaub, 1909
64 (35)	Opening of the subumbrellar cavity partly closed by an annular diaphragm (velarium)	65
–	Opening of the subumbrellar cavity not closed by an annular diaphragm (velarium)	88
65 (64)	Tentacles 8 or more	66
–	Tentacles from 4 to 6	76
66 (65)	Stomach pouches without diverticula	Tripedalia cystophora Conant, 1897
–	Stomach pouches with 8 diverticula	67
67 (66)	Gonads not four-leaved	Chirodectes maculatus (Cornelius, Fenner & Hore, 2005)
–	Gonads four-leaved	68
68 (67)	Medusa with nematocysts on bell	69
–	Medusa without nematocysts on bell	71
69 (68)	Each pedalium with more than 4 fingers and tentacles	Chiropsalmus quadrumanus Müller, 1859
–	Each pedalium with 4 or less fingers and tentacles	70
70 (69)	Each pedalium with 2 fingers and tentacles	Chiropsalmus zygonema Haeckel, 1880
–	Each pedalium with 3–4 fingers and tentacles	Chiropsalmus alipes Gershwin, 2006
71 (68)	Medusa with mesenteries poorly developed	Chiropsella bronzie Gershwin, 2006
–	Not as above	72
72 (71)	Gastric saccules are functioning gonads	Chironex fleckeri Southcott, 1956
–	Gastric saccules are not functioning gonads	73
73 (72)	Stomach pouches with 2 branched or feathered saccules	74
–	Stomach pouches with 2 unbranched saccules	75
74 (73)	Each pedalium with 9–11 fingers and tentacles	Chirodropus gorilla Haeckel, 1880
–	Each pedalium with 21 fingers and tentacles	Chirodropus palmatus Haeckel, 1880
75 (73)	Tentacles and fingers irregularly placed	Chiropsoides buitendijki (van der Horst, 1907)
–	Tentacles and fingers not irregularly placed	Chiropsoides quadrigatus (Haeckel, 1880)
76 (65)	Tentacles branched	Manokia stiasnyi Bigelow, 1938
–	Tentacles simple	77
77 (76)	Stomach with weakly developed mesenteries	78
–	Not as above	80
78 (77)	Sensory niches without well developed covering scale	Copula sivickisi Stiasny, 1926
–	Sensory niches with covering scale above	79
79 (78)	Velarial canals 3–4 per octant	Carybdea marsupialis (Linnaeus, 1758)
–	Velarial canals 2 per octant	Carybdea rastonii Haacke, 1886
80 (77)	Stomach without mesenteries	81
–	Stomach with well developed mesenteries	84
81 (80)	Exumbrella without nematocyst-warts	Alatina moseri (Mayer, 1906)
–	Exumbrella with nematocyst-warts	82
82 (81)	Velarial canals 3 per octant	Alatina rainensis Gershwin ,2005
–	Velarial canals 4–5 per octant	83
83 (82)	Medusa with 6 eyes per rhopalium	Alatina madraspartana Menon, 1930
–	Medusa with 1 eye per rhopalium	Alatina tetraptera (Haeckel, 1880)
84 (80)	Medusa with phacellae	Tamoya haplonema Müller, 1859
–	Medusa without phacellae	85
85 (84)	Velarial canals 1 per octant	Carukia shinju Gershwin, 2005
–	Not as above	86
86 (85)	Velarial canals 2 per octant	Carukia barnesi Southcott, 1966
–	Not as above	87
87 (86)	Velarial canals 4–5 per octant	Malo maxima Gershwin, 2005
–	Velarial canals more than 5 per octant	Gerongia rifkinae Gershwin & Alderslade, 2005
88 (64)	Medusa with a permanent primary mouth opening in adult specimens	89
–	Medusa without a permanent primary mouth opening in adult specimens	135
89 (88)	Medusa without tentacles	90
–	Medusa with tentacles	94
90 (89)	marginal lappets very shallow, or entirely lacking	91
–	marginal lappets evident	92
91 (90)	Exumbrella transparent white, sometimes with brown nuances on margins	Deepstaria enigmatica (Russel, 1967)
–	Exumbrella reddish-brown, with stomach margin lighter brown	Deepstaria reticulum (Lerson, Madin & Harbison, 1988)
92 (90)	Rhopalia from 24 to more than 50, one in every cleft between the lappets	Tiburonia granrojo (Matsumoto, Raskoff & Lindsay, 2003)
–	Not as above	93
93 (92)	Rhopalia 20	Stygiomedusa gigantea (Browne, 1910)
–	Rhopalia 8	Stellamedusa ventana (Raskoff & Matsumoto, 2004)
94 (89)	Medusa with ring-canal	95
–	Medusa without ring-canal	113
95 (94)	Tentacles arising from umbrella’s margin	96
–	Tentacles not arising from umbrella’s margin	104
96 (95)	Marginal lappets 48	Undosa undulata (Stiasny, 1935) – Warning: dubious species, some authors suggest it is a juvenile stage of Discomedusa lobata Claus 1877
–	Not as above	97
97 (96)	Marginal lappets 16	98
–	Not as above	99
98 (97)	Oral arms broad, egg-shaped	Ulmaris prototypus (Haeckel, 1880)
–	Oral arms narrow and pointed	Ulmaris snelliusi (Stiasny, 1935)
99 (97)	Marginal lappets 32	100
–	Marginal lappets 64	102
100 (99)	Tentacles 32 or 48	Discomedusa lobata (Claus, 1877)
–	Tentacles 24	101
101 (100)	Perradial canals branched	Discomedusa philippina (Mayer, 1910)
–	Perradial canals not branched	Floresca parthenia (Haeckel, 1880)
102 (99)	Tentacles 24	Parumbrosa polylobata (Kishinouye, 1910)
–	Tentacles 16	103
103 (102)	Anastomoses absent	Diplulmaris antarctica (Maas, 1908)
–	Anastomoses present	Diplulmaris malayensis (Stiasny, 1935)
104 (95)	Tentacles arising from subumbrella	105
–	Tentacles arising from exumbrella	107
105 (104)	Gonads 8	Poralia rufescens (Vanhöffen, 1902)
–	Gonads 4	106
106 (105)	Rhopalia 8	Sthenonia albida (Eschscholtz, 1829)
–	Rhopalia 16	Phacellophora camtschatica (Brandt, 1835)
107 (104)	Oral arms bifurcated	Aurosa furcata (Haeckel, 1880)
–	Oral arms not bifurcated	108
108 (107)	Marginal lappets 16	Aurelia labiata (Chamisso & Eysenhardt, 1821)
–	Marginal lappets 8	109
109 (108)	Oral arms short, thick and curved, much folded, extending laterally against subumbrellar surface	Aurelia limbata (Brandt, 1835)
–	Not as above	110
110 (109)	Oral arms linear, thick and stiff, with densely crenulated margins, as long as bell’s radius	Aurelia aurita (Linnaeus, 1758)
–	Not as above	111
111 (110)	Oral arms narrow and thin, with slightly folded margins only in proximal part	Aurelia solida (Browne, 1905)
–	Oral arms long and broad, curtain-like, with densely crenulated margins	112
112 (111)	Adradial canals not branched	Aurelia maldivensis (Bigelow, 1904)
–	Adradial canals branched	Aurelia colpata (Brandt, 1838)
113 (94)	Tentacles arising from the subumbrella at some distance from the margin	114
–	Tentacles arising from the exumbrellar margin	122
114 (113)	Tentacles not arranged in tufts	Drymonema dalmatinum (Haeckel, 1880)
–	Tentacles arranged in tufts	115
115 (114)	Medusa without radial muscolature in the subumbrella	116
–	Medusa with radial muscolature in the subumbrella	118
116 (115)	Medusa with few broad canals in the lappets	Desmonema gaudichaudi (Lesson, 1830)
–	Medusa with numerous narrow canals in the lappets	117
117 (116)	Tentacles not ribbon-like	Desmonema chierchianum (Vanhöffen, 1888)
–	Tentacles ribbon-like	Desmonema glaciale (Larson, 1986)
118 (115)	Rhopalar and tentacular stomach pouches completely separated	119
–	Rhopalar and tentacular stomach pouches connected by anastomoses	120
119 (118)	Peripheral canals without, or with few anastomoses	Cyanea capillata (Linnaeus, 1758)
–	Peripheral canals with numerous anastomoses	Cyanea purpurea (Kishinouye, 1910)
120 (118)	Peripheral canals with numerous anastomoses	Cyanea nozakii (Kishinouye, 1891)
–	Peripheral canals without, or with few anastomoses	121
121 (120)	Radial muscles originating from the outer side of coronal muscle	Cyanea buitendijki (Stiasny, 1919)
–	Radial muscles originating from the middle of coronal muscle	Cyanea mjobergi (Stiasny, 1921)
122 (113)	Stomach pouches 32	123
–	Stomach pouches 16	124
123 (122)	Subgenital pits heart-shaped	Sanderia malayensis (Goette, 1886)
–	Subgenital pits horseshoe-shaped	Sanderia pampinosus (Gershwin & Zeidler, 2008)
124 (122)	Marginal lappets 16	125
–	Not as above	126
125 (124)	Nematocyst warts about as long as wide	Pelagia noctiluca (Forsskål, 1775)
–	Nematocyst warts highly protrusive, more long than wide	Pelagia flaveola (Eschscholtz, 1829)
126 (124)	Marginal lappets 48	127
–	Marginal lappets 32	129
127 (126)	Tentacles all alike	Chrysaora fulgida (Reynaud, 1830)
–	Tentacles different in length	128
128 (127)	Tentacles usually 5 per octant, 1 central primary, 2 lateral secondary about half in length, 2 tertiary, between former two types, about 1/4 as long as the median	Chrysaora lactea (Eschscholtz, 1829)
–	Tentacles 5 per octant, 3 primary arising from deep cleft between tentacular lappets and 2 lateral and shorter secondary, arising from subumbrellar side of rhopalar lappets	Chrysaora quinquecirrha (Desor, 1848)
129 (126)	Tentacles 8	Chrysaora colorata (Russel, 1964)
–	Tentacles 24	130
130 (129)	Exumbrella yellowish-brown or reddish-yellow with 32-rayed chestnut-brown star	Chrysaora fusescens (Brandt, 1835)
–	Not as above	131
131 (130)	Exumbrella reddish-brown or purplish-pink with 16 broad, darker radial bands and numerous light spots	Chrysaora plocamia (Lesson, 1830)
–	Not as above	132
132 (131)	Oral arms extremely large with frilly margins, hardly coiled to form a dense mass	Chrysaora achlyos (Martin, Gershwin, Burnett, Cargo & Bloom, 1997)
–	Oral arms linear, with broad frilly margins, more or less coiled around central body	133
133 (132)	Exumbrella golden-brown, with darker margins, sometimes with 16-32 lighter radial stripes	Chrysaora fuscescens (Brandt, 1835)
–	Not as above	134
134 (133)	Stomach pouches all-alike	Chrysaora hysoscella (Linnaeus, 1766)
–	Stomach pouches unequal, tentacular ones slightly broader proximally and distally than rhopalar ones	Chrysaora melanaster (Brandt, 1838)
135 (88)	Umbrella with papillar knobs	136
–	Umbrella without papillar knobs	138
136 (135)	Oral arms without filaments	Lobonemoides sewelli Rao, 1931
–	Oral arms with filaments	137
137 (136)	Intracircular anastomosing network in communication with the inter-rhopalar canals	Lobonema smithii Mayer, 1910
–	Intracircular anastomosing network not in communication with the inter-rhopalar canals	Lobonemoides robustus Stiasny, 1920
138 (135)	Oral arms dichotomous	139
–	Oral arms three-winged	159
139 (138)	Medusa with 4 completely separated subgenital cavities	140
–	Medusa with 4 not completely separated subgenital cavities	147
140 (139)	Oral arms 3/4 the lenght of bell radius	Cassiopea frondosa (Pallas, 1774)
–	Not as above	141
141 (140)	Oral arms cylindrical, slender, somewhat longer than bell radius	Cassiopea ornata Haeckel, 1880
–	Not as above	142
142 (141)	Oral arms very large, flat, with 6-8 short, wide-spreading main branches	Cassiopea depressa Haeckel, 1880
–	Not as above	143
143 (142)	Oral arms 1 1/4 times the lenght of bell radius, triangular in cross-section, aboral surface broad and flat, with 10–15 alternate primary branches	Cassiopea xamachana Bigelow, 1892
–	Not as above	144
144 (143)	Oral arms wide, flat, with 4–6 flat, short tree-shaped side branches	Cassiopea andromeda (Forskål, 1775)
–	Not as above	145
145 (144)	Oral arms with numerous small lateral branches in their proximal portion	Cassiopea medusa Light, 1914
–	Oral arms cylindrical, 1 1/2 times as long as bell radius, branched tree-like	146
146 (145)	Species with numerous large club-shaped vesicles	Cassiopea mertensi Brandt, 1838
–	Species without ribbon-like filaments	Cassiopea ndrosia Agassiz & Mayer, 1899
147 (139)	Oral arms without filaments	148
–	Oral arms with filaments	150
148 (147)	Exumbrella without a central rised dome	Marivagia stellata (Galil & Gershwin, 2010)
–	Exumbrella with a central rised dome	149
149 (148)	More than 1 cupolar warts	Netrostoma dumokuroa (Agassiz & Mayer, 1899)
–	1 cupolar wart	Netrostoma nuda (Gershwin & Zeidler, 2008)
150 (147)	In each octant 3 radial canals	151
–	In each octant more than 3 radial canals	153
151 (150)	Between the mouths two kinds of appendages	Netrostoma coerulescens Maas, 1903
–	Between the mouths numerous appendages	152
152 (151)	Exumbrella with a central rised dome	Netrostoma setouchianum (Kishinouye, 1902)
–	Exumbrella without a central rised dome	Cephea octostyla (Forskål, 1775)
153 (150)	Exumbrella without a central rised dome	Polyrhiza vesiculosa (Agassiz, 1862)
–	Exumbrella with a central rised dome	154
154 (153)	Medusa with warts on the central portion of the exumbrella	155
–	Medusa without warts on the central portion of the exumbrella	156
155 (154)	Radial canals 5–6 per ottante	Cephea cephea (Forskål, 1775)
–	Radial canals 7 per ottante	Cephea coerulea Vanhöffen, 1902
156 (154)	In each octant 4–6 radial canals	Cotylorhiza erythraea Stiasny, 1920
–	Not as above	157
157 (156)	In each octant 7–9 radial canals	Cotylorhiza tuberculata (Macri, 1778)
–	In each octant more than 11 radial canals	158
158 (157)	Radial canals 11–13 per ottante	Cotylorhiza ambulacrata Haeckel, 1880
–	Radial canals 16–17 per ottante	Cotylorhiza pacifica (Mayer, 1915)
159 (138)	Oral arms triangular	160
–	Oral arms not triangular	162
160 (159)	Oral arms terminate in a short, oval knob	Thysanostoma loriferum (Ehrenberg, 1835)
–	Not as above	161
161 (160)	Oral arms terminate in a long, tapering filament	Thysanostoma flagellatum (Haeckel, 1880)
–	Oral arms without a terminal portion	Thysanostoma thysanura Haeckel, 1880
162 (159)	Oral arms not pyramidal	163
–	Oral arms pyramidal	181
163 (162)	Oral arms broad	164
–	Oral arms of normal width	169
164 (163)	Oral arms without filaments	165
–	Oral arms with filaments	166
165 (164)	Oral arms without terminal clubs	Lychnorhiza malayensis Stiasny, 1920
–	Oral arms with terminal clubs	Pseudorhiza aurosa von Lendenfeld, 1882
166 (164)	Oral arms with terminal clubs	167
–	Oral arms without terminal clubs	168
167 (166)	Medusa without a single filament at the distal end of one of the oral arms	Anomalorhiza shawi Light, 1921
–	Medusa with a single filament at the distal end of one of the oral arms	Pseudorhiza haeckeli Haacke, 1884
168 (166)	In each octant 8 velar lappets	Lychnorhiza arubae Stiasny, 1920
–	In each octant 4 velar lappets	Lychnorhiza lucerna Haeckel, 1880
169 (163)	Oral arms coalesced throughout their entire length	170
–	Oral arms coalesced in proximal portion only	171
170 (169)	Velar lappets about 14 in each octant	Stomolophus meleagris Agassiz, 1862
–	Velar lappets about 24 in each octant	Stomolophus fritillaria Haeckel, 1880
171 (169)	Oral arms with filaments	172
–	Oral arms without filaments	175
172 (171)	Umbrella more than 100 cm wide	Nemopilema nomurai (Kishinouye, 1922)
–	Umbrella less than 100 cm wide	173
173 (172)	Velar lappets 14–20 in each octant	Rhopilema esculentum Kishinouye, 1891
–	Velar lappets 8 in each octant	174
174 (173)	Exumbrella with sharply conical warts	Rhopilema hispidum (Vanhöffen, 1888)
–	Exumbrella with blunt tuberculation	Rhopilema nomadica Galil, Spanier & Ferguson, 1990
175 (171)	Oral arms with clubs	176
–	Oral arms without clubs	177
176 (175)	Velar lappets 14–20 in each octant	Rhopilema rhopalophorum Haeckel, 1880
–	Velar lappets 6 in each octant	Rhopilema verrilli (Fewkes, 1887)
177 (175)	Oral arms without terminal clubs	178
–	Oral arms with terminal clubs	179
178 (177)	Umbrella ca. 150 mm wide; marginal lobes rectagular in shape	Eupilema scapulare Haeckel, 1880
–	Umbrella ca. 400 mm wide; marginal lobes triangular in shape	Eupilema inexpectata (Pages, Gili & Bouillon, 1992)
179 (177)	Proximal portion of oral arms considerably longer than distal portion	Rhizostoma luteum (Quoy & Gaimard, 1827)
–	Proximal portion of oral arms about as long as distal portion	180
180 (179)	Taxon present in the Mediterranean and in the Atlantic Ocean	Rhizostoma pulmo (Macri, 1778)
–	Taxon present in the North Sea only	Rhizostoma octopus (Macri, 1778)
181 (162)	Oral arms shorter than usual	182
–	Oral arms of normal lenght	195
182 (181)	Oral arms without terminal appendages	183
–	Oral arms with terminal appendages	184
183 (182)	Medusa with rhopalar canals with anastomoses throughout thier length	Mastigietta palmipes (Haeckel, 1880)
–	Medusa with perradial rhopalar canals without anastomoses, interradial canals with anastomoses	Versuriga anadyomene (Maas, 1903)
184 (182)	Intracircular mesh-work of canals never communicating with the rhopalar canals	185
–	Intracircular mesh-work of canals usually communicating with the rhopalar canals	187
185 (184)	Terminal appendages nearly as long as the oral arms	Phyllorhiza pacifica (Light, 1921)
–	Terminal appendages very long, with distal expansion	186
186 (185)	Oral filaments without a triple heart-shaped knob; bell diameter far larger than 25 cm	Phyllorhiza punctata (von Lendenfeld, 1884)
–	Oral filaments with a triple heart-shaped knob; bell of ca. 25 cm of diameter	Phyllorhiza peronlesueuri (Goy, 1990)
187 (184)	Mouth arms twice as long as disk radius	188
–	Not as above	189
188 (187)	In each octant more than 10 canal-roots	Mastigias pantherinus Haeckel, 1880
–	In each octant up to 10 canal-roots	Mastigias siderea Chun, 1896
189 (187)	Mouth arms shorter than disk radius	190
–	Mouth arms long as disk radius	192
190 (189)	In each octant more than 10 canal-roots	Mastigias ocellatus (Modeer, 1791)
–	In each octant up to 10 canal-roots	191
191 (190)	Vaulted bell, thin at margin but very thick at apex	Mastigias gracilis (Vanhöffen, 1888)
–	Doubtful species, flat and hat-shaped bell, average size unknown	Mastigias roseus (Reynaud, 1830)
192 (189)	In each octant up to 10 canal-roots	193
–	In each octant more than 10 canal-roots	194
193 (192)	Umbrella not flat	Mastigias papua (Lesson, 1830)
–	Umbrella flat, disk-shaped	Phyllorhiza luzoni Mayer, 1915
194 (192)	Perradial rhopalar canals not bottle-shaped	Mastigias albipunctatus Stiasny, 1920
–	Perradial rhopalar canals bottle-shaped	Mastigias andersoni Stiasny, 1926
195 (181)	Oral arms with filaments	196
–	Oral arms without filaments	199
196 (195)	Intracircular anastomosing network not in communication with the rhopalar canals	197
–	Intracircular anastomosing network in communication with the rhopalar canals	198
197 (196)	Distal three-winged portion of oral arms about twice as long as proximal simple portion	Crambione bartschi (Mayer, 1910)
–	Distal three-winged portion of oral arms as long as proximal simple portion	Crambione mastigophora Maas, 1903
198 (196)	Oral arms narrow with short filaments	Acromitus flagellatus (Maas, 1903)
–	Oral arms thick and broad with long filaments	Acromitus maculosus Light, 1914
199 (195)	Oral arms with terminal clubs	200
–	Oral arms without terminal clubs	202
200 (199)	In each octant 10 velar lappets	Leptobrachia leptopus (Chamisso & Eysenhardt, 1821)
–	Not as above	201
201 (200)	In each octant 16 velar lappets	Crambionella orsini (Vanhoffen, 1888)
–	In each octant 12 velar lappets	Crambionella stuhlmanni (Chun, 1896)
202 (199)	Intracircular anastomosing network not in communication with the rhopalar canals	203
–	Intracircular anastomosing network in communication with the rhopalar canals	204
203 (202)	In each octant 4 cleft velar lappets	Acromitoides purpurus (Mayer, 1910)
–	In each octant at least 5 cleft velar lappets	Acromitoides stiphropterus (Schultze, 1897)
204 (202)	Distal three-winged portion of oral arms 1/6 as long as proximal simple portion	Catostylus mosaicus (Quoy & Gaimard, 1824)
–	Not as above	205
205 (204)	Distal three-winged portion of oral arms 6 times as long as proximal simple portion	Catostylus perezi Ranson, 1945
–	Not as above	206
206 (205)	Distal three-winged portion of oral arms 5 times as long as proximal simple portion	Catostylus viridescens (Chun, 1896)
–	Not as above	207
207 (206)	Distal three-winged portion of oral arms half as long as proximal simple portion	Catostylus tripterus (Haeckel, 1880)
–	Not as above	208
208 (207)	Distal three-winged portion of oral arms as long as proximal simple portion	Catostylus ornatellus (Vanhöffen, 1888)
–	Distal three-winged portion of oral arms 2–4 times as long as proximal simple portion	209
209 (208)	Oral arms 2/3 the length of bell diameter	Catostylus townsendi Mayer, 1915
–	Not as above	210
210 (209)	Oral arms 1–1,5 times the length of bell radius	Catostylus cruciatus (Lesson, 1830)
–	Oral arms as long as bell diameter	Catostylus tagi (Haeckel, 1869)