Two new species of Acanthobothrium in Narcine entemedor (Rajiformes: Narcinidae) from the northwest coast of Guanacaste Peninsula, Costa Rica.

This paper describes 2 new species of Acanthobothrium collected in Narcine entemedor from Cuajiniquil, Guanacaste Province, Costa Rica (10 degrees 57'N, 85 degrees 42'W). Acanthobothrium franus n. sp. averages 27 mm long, composed of 110 proglottides, has bothridial hooks 344-469 microns long, and 24-56 testes per proglottis. This new species resembles Acanthobothrium colombianum, Acanthobothrium coquimbensis. Acanthobothrium dujardini, Acanthobothrium lineatum, Acanthobothrium lintoni, and Acanthobothrium paulum. The new species differs from these 6 species by having a relatively shorter cirrus sac length not reaching the middle region of the proglottis. Additionally, A. franus differs from these species by having longer bothridia (627-1,408 microns vs. 299-391 microns for A. colombianum, 312-480 microns for A. coquimbensis, 240-560 microns for A. dujardini, 275-624 microns for A. lineatum, 389-720 microns for A. lintoni, and 300-880 microns for A. paulum), and larger bothridial hooks (344-469 microns vs. 175-193 microns, 120-192 microns, 180-210 microns, 118-216 microns, 108-230 microns, and 104-229 microns, respectively). Acanthobothrium inbiorium n. sp. averages 59 mm long, composed of 198 proglottides, has bothridial hooks 95-120 microns long, and possesses 44-73 testes per proglottis. Among species of Acanthobothrium, the new species resembles Acanthobothrium electricolum, Acanthobothrium dasybati, Acanthobothrium dighaensis, Acanthobothrium icelandicum, Acanthobothrium indicum, Acanthobothrium microcephalum, and Acanthobothrium wedli. The new species closely, resembles A. dasybati, but differs from that species in average strobila length and number of proglottides (58 microns long and 198 proglottides in A. inbiorium vs. 20 and 80 in A. dasybati, respectively). The new species can be distinguished from A. electricolum by having a wider scolex (450-900 microns vs. 189-252 microns), from A. dighaensis by having a narrower scolex (450-900 vs. 1,050-1,429), and from A. indicum by average strobilar length and number of proglottides (58 mm and 198 for A. inbiorium vs. 25 mm and 145 for A. indicum). Finally, A. inbiorium differs from A. icelandicum by having a shorter cirrus sac (122-285 for A. inbiorium vs. 380-410 for A. icelandicum), and A. microcephalum and A. wedli by having longer bothridia (an average of 603 microns vs. 447 microns for A. microcephalum and 350 microns for A. wedli), and fewer testes per proglottis (44-73 vs. 105-115 and 80-100, respectively). Morphological similarities suggest that some components of the eastern Pacific fauna of Acanthobothrium might share historical associations with the Caribbean and the western Pacific/Indian Ocean fauna.