Caligus bonito Wilson, 1905

Boxshall, Geoff, 2018, The sea lice (Copepoda: Caligidae) of Moreton Bay (Queensland, Australia), with descriptions of thirteen new species, Zootaxa 4398 (1), pp. 1-172: 48-50

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Caligus bonito Wilson, 1905


Caligus bonito Wilson, 1905  

( Figs. 21 View FIGURE 21 , 22 View FIGURE 22 )

Syn: Caligus kuroshio Shiino, 1959  

Material examined. 20♀, 9♂♂ from Euthynnus affinis (Cantor, 1849)   (TC18121), 21 November 2016; 10♀♀, 4♂♂ QM Reg. No. W53058; 10♀♀, 5♂♂ NHMUK Reg. Nos 2017.237–246.

Site on host. Gill cavity.

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes; frontal plates with lunules. Genital complex 1.04 times longer than wide (measured along dorsal midline) with small posterolateral lobes ( Fig. 21A View FIGURE 21 ); abdomen elongate, about 3.8 times longer than wide and longer than genital complex. Antenna with small, blunt posterior process ( Fig. 21B View FIGURE 21 ). Post-antennal process with weakly-curved tine; associated papillae each bisensillate. Posterior process of maxillule slender ( Fig. 21B View FIGURE 21 ). Maxilla with smooth distal margin on brachium ( Fig. 21C View FIGURE 21 ). Maxilliped of female with slight expansion on myxal margin ( Fig. 21D View FIGURE 21 ). Sternal furca with slender, diverging tines without lateral flanges ( Fig. 21E View FIGURE 21 ). Distal exopodal segment of leg 1 ( Fig. 21F View FIGURE 21 ) with 3 plumose setae on posterior margin, basal setules on margin of plumose setae nearest apex unusually stout; distal spine 1 simple, longer than spines 2 and 3, each armed with accessory process; seta 4 about twice as long as spines and about as long as segment, ornamented with setule row on one side and marginal membrane on other. Leg 2 with strong denticles along outer margins of endopodal segments 1 and 2 ( Fig. 21G View FIGURE 21 ); endopodal segment 3 ornamented with 2 shallow membranous ridges on ventral surface; outer spines on exopodal segments 1 and 2 lying obliquely across axis of ramus ( Fig. 21H View FIGURE 21 ); proximal outer spine on segment 3 tiny, much shorter than distal spine. Leg 3 with 3-segmented exopod; first exopodal segment ( Fig. 22A View FIGURE 22 ) bearing small slightly curved outer spine, lacking inner seta; second segment with outer spine and inner seta; third segment with 3 naked spines, plus 4 plumose setae; distal endopodal segment with swollen lateral margin. Leg 4 uniramous, 3-segmented ( Fig. 22B View FIGURE 22 ); first and second exopodal segments with I and IV spines, respectively. Mean body length of female 4.80 mm, range 4.46 to 5.31 mm (based on 10 specimens).

Male ( Fig. 22C View FIGURE 22 ) with cephalothorax as in female. Genital complex slender with linear margins, about 1.7 times longer than wide. Abdomen 2-segmented; first segment just shorter than second; including caudal rami, about 3.4 times longer than wide and longer than genital complex. Fifth legs located ventrally near posterior corners of genital complex, not visible in dorsal view. Post-antennal process ( Fig. 22D View FIGURE 22 ) more strongly recurved than in female; associated papillae bisensillate. Maxilliped ( Fig. 22E View FIGURE 22 ) with 3 small processes along myxal margin, middle process largest with bifid apex. Mean body length of male 4.91 mm, range 4.31 to 5.27 mm (based on 5 specimens).

Remarks. The distinctive features of C. bonito   , within the C. bonito   -group, are its long genital complex and long abdomen combined with the presence of stout denticles along the outer margins of endopodal segments 1 and 2 of leg 2, plus the unusually stout basal setules on the margin nearest the limb apex of the 3 plumose setae on the posterior margin of the distal exopodal segment of leg 1. Interestingly, Ho & Lin (2004) noted the existence of two forms of C. bonito in Taiwanese   waters. Lin & Ho (2001) initially reported C. bonito   from Katsuwonus pelamis (Linnaeus, 1758)   and Euthynnus affinis   , and their redescription of the female showed an abdomen about 3.7 times longer than wide and shorter than the cephalothorax, a sternal furca with tapering, slightly curved tines that lacked marginal flanges, bisensillate papillae on the post-antennal process, and seta 4 on the distal exopodal segment of leg 1 is much longer than the segment. In their subsequent study of C. bonito   from Sarda orientalis (Temminck & Schlegel, 1844) Ho & Lin (2004)   illustrated another form characterized by an abdomen that is about 4.0 times longer than wide and markedly longer than the cephalothorax, a sternal furca with divergent linear tines that have marginal flanges, multi-sensillate papillae on the post-antennal process, and seta 4 on the distal exopodal segment of leg 1 is only just longer than the segment. There are other minor   differences, for example, the posterior process on the female antenna is much larger in the latter form (from S. orientalis   ).

The Moreton Bay material can be attributed to typical C. bonito   as described by Wilson (1905), Kabata (1979) and Pillai (1985), all of which show females with the abdomen shorter than the cephalothorax. The detail provided by Pillai (1985) confirms the presence of other relevant character states, such as the tapering tines without marginal flanges on the sternal furca, the bisensillate papillae on the post-antennal process, and a seta 4 on the distal exopodal segment of leg 1 that is much longer than the segment. The Moreton Bay sample shares these character states with the material described by Lin & Ho (2001). The status of the second, atypical, form (from S. orientalis   ) described by Ho & Lin (2004) needs to be re-assessed as it may represent a distinct species.

Although it has been reported from at least 24 different hosts (Ho & Lin, 2004), C. bonito   is typically a parasite of scombrids of the tribes Sardini   and Thunnini   (Cressey & Cressey, 1980) and of dolphinfish ( Coryphaenidae   ) (Burnett-Herkes, 1974; Carbonell et al., 1999; Hutson et al., 2011), and it has a broad distribution in low to middle latitudes in all oceans (Cressey et al., 1983: Fig. 10 View FIGURE 10 ). Caligus bonito   has previously been reported from Queensland on Euthynnus alletteratus (Rafinesque, 1810)   as C. kuroshio (Kabata, 1965b)   , from New South Wales on Sarda australis (Cressey & Cressey, 1980)   and from southeastern Australia on Arripis truttacea (Cuvier, 1829)   , A. trutta (Forster, 1801)   and Coryphaena hippurus Linnaeus, 1758   (Catalano & Hutson, 2010; Hutson et al., 2011). The material collected in Moreton Bay was found on Euthynnus affinis   , a previously known host of C. bonito (Cressey & Cressey, 1980)   .