Four species of Caligus Müller, 1785 (Copepoda, Siphonostomatoida, Caligidae) parasitic on marine fishes of Taiwan Author Ho, Ju-Shey Author Lin, Ching-Long Author Chang, Wen-Been text Journal of Natural History 2007 2007-03-26 41 5 - 8 401 417 http://dx.doi.org/10.1080/00222930701203853 journal article 10.1080/00222930701203853 1464-5262 4582139 Caligus arii Bassett-Smith, 1898 ( Figures 1 , 2 ) Material examined One adult ♀ on body surface of Trichiurus lepturus Linnaeus collected on 14 June 2004 at Dong-shi Fishing Port of Chiayi County . Female Body ( Figure 1A ) 5.82 long, excluding setae on caudal ramus. Cephalothoracic shield subcircular, 2.12 long and 2.02 wide, excluding lateral, hyaline membrane. Fourth pediger distinctly wider than long, 0.22X0.54. Genital complex, 1.86X1.18, bottle-shaped, with posterolateral corners slightly protruded posteriorly. Abdomen ( Figure 1A ) with two unequal segments, proximal segment longer than wide 1.66X0.42, and anal segment wider than long but measuring only 146X 348 mm . Caudal ramus ( Figure 2E ) attaching to posterolateral surface of anal segment, distinctly wider than long, 28X 64 mm ; armed with three short and three long setae. Egg sac not seen. Antennule ( Figure 1B ) two-segmented; proximal segment carrying on anterodistal surface 25 setose and two naked setae (on dorsal side), distal segment short, about 2.42 times as long as wide, with one subterminal seta on posterior margin and 11 setae plus two aesthetascs on distal margin. Antenna ( Figure 1C , with broken tip) three-segmented; proximal segment smallest, with spatula-like process on posteromedial corner; second segment subrectangular and unarmed; distal segment long, curved claw bearing two setae, one proximal and other one close to medial region. Postantennal process lacking, except two usual, setule-bearing papillae. Mandible ( Figure 1D ) with four sections; bearing 12 teeth on medial margin of distal blade. Maxillule ( Figure 1C ) comprising stout dentiform process and basal papilla with two short and one long setae. Maxilla ( Figure 1E ) two-segmented; proximal segment (lacertus) unarmed; slender distal segment (brachium) carrying subterminal, hyaline membrane on outer edge, terminal calamus slightly longer than subterminal canna. Maxilliped ( Figure 1F ) three-segmented; proximal segment (corpus) unarmed, twice as long as next two segments combined (subchela); middle (shaft) segment armed distally with a pinnate seta and in middle region small, blunt element; distal (claw) segment sharply pointed and slightly bent. Box of sternal furca ( Figure 1G ) subsquare, carrying two tines with truncate tip. Figure 1. Caligus arii Bassett-Smith , adult female. (A) Habitus, dorsal; (B) antennule; (C) antenna, postantennal process, and maxillule; (D) mandible; (E) maxilla; (F) maxilliped; (G) sternal furca. Armature on rami of legs 1–4 as follows (Roman numerals indicating spines and Arabic numerals, setae): Exopod Endopod Leg 1 1-0; III,1,3 (Vestigial) Leg 2 I-1; I-1; II,I,5 0–1; 0–2; 6 Leg 3 I-1; I-1; III,5 0–1; 6 Leg 4 I-0; I-0; III ( Absent) Figure 2. Caligus arii Bassett-Smith , adult female. (A) Leg 1, with tip shown in ventral view (upper insertion) and dorsal view (lower insertion); (B) leg 2; (C) leg 3; (D) leg 4; (E) left half of anal somite and caudal ramus, ventral. Leg 1 ( Figure 2A ) protopod with long, plumose, outer seta and another small, plumose, inner seta in addition to a patch of spinules on ventral surface; vestigial endopod fringed with setules around distal region; first segment of exopod with row of setules on posterior edge and short spiniform seta at outer distal corner; outer three of four terminal elements on last segment of exopod with sharply pointed, slender tip and hyaline membrane on posterior margin, middle two elements with long accessory process and element four with a small, spiniform seta. Leg 2 ( Figure 2B ) coxa small, with large plumose inner seta on posterior edge and setule-bearing papilla on ventral surface; basis with simple, outer seta and medial papilla bearing long setule; both outer and medial edges of protopod fringed with large marginal membrane; similar membrane on outer margin of elongated, proximal segment of exopod; basal segment of endopod with small distolateral membrane, but terminal two segments bearing rows of setules on outer surface. Leg 3 ( Figure 2C ) protopod (apron) with short, outer and long, inner seta; large marginal membrane on outer edge and another marginal membrane on posterior edge of basis inner to velum; setule-bearing papilla on basis near both ends of this posterior membrane; and a patch of spinules on lateral edge of ventral surface of protopod. Leg 4 ( Figure 2D ) protopod with small, plumose, outer seta; pectens on three exopodal segments at insertion of each of five outer spines. Leg 5 (inserted drawing in Figure 1A ) represented by three small, plumose setae on a protuberance located on posterolateral margin of genital complex. Remarks his is the first record of C. arii from a host other than a marine catfish. However, we consider the carrier of our C. arii , a largehead hairtail, Trichiurus lepturus Linnaeus , to be a fortuitous host, because we have examined in the past 10 years no fewer than 1000 T. lepturus , and only one female C. arii has been recovered from them. Nevertheless, our specimen from Taiwan fits very well with the description of the syntype (reg. no. is 98.12.2.9, in the Natural History Museum, London) given by Pillai (1969) . The characteristic features of the present species are: (1) two-segmented, long abdomen with tiny anal segment; (2) minute caudal ramus attaching subterminally to anal segment; (3) absence of postantennal process; (4) maxilliped with slender corpus; and (5) reduced proximal segment and spine on leg 3 exopod. If Kirtisinghe’s (1964) proposal to move Barnard’s (1955) ‘‘ Caligus arii B-S.’’ to Caligus dakari van Beneden, 1892 is correct, then, C. arii is so far known only from Ceylon ( Bassett-Smith 1898 ) and India ( Pillai 1963 ). This means that the present report is the first record of C. arii outside of the Indian Ocean.