Caligodes laciniatus (Krøyer, 1863)

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 : 31-33

Caligodes laciniatus (Krøyer, 1863)

( Fig. 12 )

Material examined. 8♀♀ from Tylosurus gavialoides (Castlenau, 1873) (TC17113) 13 January 2016, QM Reg. No. W53049; 13♀♀ (TC17297) 19 January 2016, QM Reg. No. W53050; 1♀ (TC17114) 13 January 2016, 1♀ (TC17270) 19 January 2016, 6♀♀ (TC17282) 19 January 2016, 3♀♀ (TC17671) 28 June 2016, 5♀♀ (TC17826) 3 July 2016, NHMUK Reg. Nos 2017.192–201.

Site on host. Gills arches and floor of branchial cavity.

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes; frontal plates with lunules. Fourth pedigerous somite fused to slender anterior part of genital complex, forming elongate “neck” region ( Fig. 12A ). Genital complex elongate, about 2.2 times longer than wide; narrow anteriorly, broadest posteriorly, bearing very large, diverging posterolateral lobes armed with apical setae, representing fifth legs at tip ( Fig. 12B ). Abdomen elongate about 5 times longer than wide; slightly shorter than posterolateral lobes of genital complex, giving a trifid appearance to habitus in dorsal view. Caudal rami each with 6 setae. Antennule 2-segmented: armed with 25 setae on proximal segment. Antenna ( Fig. 12C ) with short blunt posterior process on proximal segment. Post-antennal process without tine, represented by multisensillate papillae on weakly defined surface sclerite ( Fig. 12C ). Anterior process of maxillule with 3 setae, posterior process corrugated ( Fig. 12D ). Maxilliped of female with myxal margin inflated proximally. Sternal furca small with divergent tapering tines; paired lateral processes present on ventral surface posterolateral to furca ( Fig. 12E ). Leg 1 with vestigial endopod: distal exopodal segment of leg 1 with 3 plumose setae on posterior margin; distal spine 1 longer and more robust than other spines; spines 2 and 3 reduced, without accessory processes; seta 4 smaller than spine 3. Leg 2 with second and third endopodal segments mostly fused, surface of distal endopodal segments ornamented with patches of small denticles: exopodal segments 2 and 3 fused but with vestige of suture marking plane of fusion ( Fig. 12F ); outer spine on exopodal segment 1 small and proximal 2 spines on compound distal segment small and slender, directed disto-laterally away from ramus. Leg 3 apron ornamented with patch of fine denticles on ventral surface; exopod 2-segmented ( Fig. 12G ) with large recurved spine on first segment; compound distal segment with total of 4 naked outer spines and 4 short plumose setae; endopod 2-segmented, first segment bearing inner plumose seta not forming expanded velum; second segment with 4 setae. Leg 4 uniramous, indistinctly 3-segmented; exopodal segments with I; III spines. Leg 5 represented by elongate lobes bearing 3 reduced seta at apex ( Fig. 12B ). Mean body length of adult female 5.59 mm, range 5.20 to 6.0 mm (based on 10 specimens).

Male unknown.

Remarks. This species was common on T. gavialoides in Moreton Bay, with a prevalence of about 57%. In their monographic survey of the copepod parasites of needlefishes ( Belonidae ), Cressey & Collette (1970) reported C. laciniatus from T. gavialoides (as Lhotskia gavialoides ) caught in Australian waters, but there is some confusion over the precise locality as in the main text of the taxonomic part (p. 378) they refer to “off northern Australia ” while in the summary of host material examined they refer only to “ New South Wales, Australia ” (p. 398). However, in the addendum (p. 430) they provide additional records of C. laciniatus from T. gavialoides in New South Wales, from Strongylura leirua (Bleeker, 1850) in the Gulf of Carpentaria and from Tylosurus crocodilus (Péron & Lesueur, 1821) in Queensland, the Torres Strait and the Gulf of Carpentaria. Caligodes laciniatus has an almost cosmopolitan distribution in warm temperate to tropical waters, occurring in the North and South Atlantic, North and South Pacific and Indian Oceans, and Cressey & Collette (1970) recorded it on seven host species within the family Belonidae .

The mean body length exhibited by ovigerous females from Moreton Bay was 5.59 mm, which is larger than the mean of 4.66 mm given for ovigerous females parasitic on T. gavialoides in the Indo-West Pacific by Cressey & Collette (1970). Dojiri & Ho (2013) commented that the large posterolateral processes on the genital complex of C. laciniatus may represent the fifth legs, citing Cressey & Collette (1970) who referred to these processes as the fifth legs. The presence of 3 setae on the tip of each process is strong evidence in support of the interpretation of Cressey & Collette (1970).

The validity of the genus Caligodes Heller, 1865 needs to be tested. According to Dojiri & Ho (2013) Caligodes can be differentiated from other members of the family by the combination of the long posterodorsal processes on the genital complex, the elongate abdomen, the enlarged spine 1 on the distal exopod segment of leg 1, the slender exopodal spines of leg 2, and the segmentation and armature of the rami of leg 4. Except for the long posterodorsal processes on the genital complex (here identified as fifth legs), none of these characters appears to be particularly robust as a generic level discriminant. Even the hyper-development of the fifth legs into long processes, taken alone, could be interpreted as a unique difference (i.e. an autapomorphy) that provides no information on relationships. There are major uncertainties concerning the validity of Caligodes , but it is treated as valid here pending a thorough revision of the caligid genera.

Figures

FIGURE12.Caligodes laciniatus (Krøyer,1863), female.A, habitus,dorsal; B, setal elements on tipsof fifthleg processes; C, antenna and vestigial post-antennal process, drawn in situ; D, maxillule; E, sternal furca and adjacent paired ventral processes; F, exopod of leg 2; G, rami of leg 3, drawn in situ. Scale bars: 1.0 mm on A, 50 µm on B, 100 µm on C–G.