Caligus elasmobranchi, Boxshall, 2018

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 : 60-62

Caligus elasmobranchi sp. nov.

( Fig. 27 )

Syn. Caligus dasyaticus: Pillai, 1968 , p. 9–11, figs. 1A– K. Pillai, 1985, p. 280–282, Figs. 88A–K.

Type material. 7♀♀, 3♂♂ from Himantura uarnak (Gmelin, 1789) (TC17112) 13 January 2016, Holotype ♀ QM Reg. No. W53065, 4 paratype ♀♀ and 2 paratype ♂♂ QM Reg. No. W53066; 2 paratype ♀♀ and 1 paratype ♂, NHMUK Reg. Nos 2017.267–268.

Additional non-type material. 2 late chalimus from Aetobatus ocellatus (Kuhl, 1823) (TC17287) 19 January 2016; 2♀♀, 1♂, 12 immatures from Dasyatis fluviorum Ogilby, 1908 (TC17360) 21 January 2016, NHMUK Reg. Nos 2017.269–271; 2 immature ♀♀, from Himantura toshi Whitley, 1939 (TC17189) 15 January 2016; 5♀♀, 3♂♂ and 22 immature stages from Pastinachus atrus (MacLeay, 1883) (TC17166) 15 January 2016, QM Reg. No. W53067.

Site on host. Upper and lower body surfaces.

Etymology. The species name refers to the wide range of elasmobranchs that have been recorded as hosts of this copepod.

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes; frontal plates with small lunules. Genital complex about 1.1 to 1.3 times longer than wide ( Fig. 27A ); abdomen 1- segmented, about 2.0 to 2.1 times longer than wide; genital complex dimensions variable (see Table 3), ranging from shorter than to 1.3 times longer than abdomen. Antenna without posterior process on proximal segment; middle segment short ( Fig. 27B ). Post-antennal process with slender, strongly curved tine without marginal flange; associated papillae multisensillate. Posterior process of maxillule slender and slightly curved outwards ( Fig. 27B ). Maxilliped of female slender, with smooth myxal margin. Sternal furca with long divergent tines ( Fig. 27C ). Distal exopodal segment of leg 1 with 3 plumose setae on posterior margin; distal spine 1 just longer than other spines ( Fig. 27D ), with blunt tip and marginal membrane on one side; spines 2 and 3 each with accessory process and rounded tip ornamented with membrane; seta 4 naked, markedly shorter than spines 2 and 3. Leg 2 ornamented with setules along lateral margins of endopodal segments 1 to 3; outer spines on exopodal segments 1 and 2 ( Fig. 27E ) small and aligned with long axis of ramus, not reflexed. Leg 3 apron without conspicuous ornamentation: exopod 3-segmented ( Fig. 27F ); with straight outer spine and plumose inner seta on first segment; second and third segments incompletely separated, armed with total of 4 spines and 5 setae. Leg 4 extremely long, reaching almost to base of caudal rami ( Fig. 27A ); exopod 2-segmented; first exopodal segment with slightly curved outer spine and large pecten; compound distal segment with 1 medium length and 2 short apical spines, distal segment ornamented with modified pecten on margin and numerous surface sensillae ( Fig. 27G ). Mean body length of female 5.46 mm, range 4.85 to 6.18 mm (based on 6 specimens). Mean body length of male 7.03 mm, range 6.60 to 7.30 mm (based on 7 specimens).

Remarks. Both sexes of this species were described in detail by Pillai (1968, 1985) under the name C. dasyaticus . Pillai’s material, four females and 1 male, came from the gills of Pristis sp. caught near Trivandrum, India and is not conspecific with C. dasyaticus of Rangnekar (1957), as previously noted by Ho et al. (2007). These species are closely related and share numerous character states including the unusual marginal membrane near the apex of the distal segment of leg 4. However, as noted above, C. elasmobranchi sp. nov. can be distinguished from C. dasyaticus by the length of leg 4, which is shorter than the genital complex in the former, but extends almost to the base of the caudal rami in the latter.

The material of this species exhibited unusual size variation ( Table 3). The measurements given in the diagnosis are based on a sample of 6 complete females, five of which were ovigerous, plus a detached genital complex plus abdomen which retained its egg sacs. These had a mean body length of 5.46 mm. However, the sample contained another ovigerous female which was 10.34 mm in length, almost twice as long as the others, and its abdomen more than twice as long as wide. Its dimensions are given in Table 3, but it was excluded from the calculations of the mean. In other respects, this large female displayed all the morphological characteristics of C. elasmobranchi sp. nov., as described by Pillai (1968, 1985, under the name C. dasyaticus ). At 7.0 mm, the body length of female given by Pillai (1968, 1985) is intermediate between the typical and the large females in the current sample ( Table 3). Only a single female of this size was found, but this size disparity in a single locality and on the same host, deserves further study.

In Moreton Bay, four of the hosts, Dasyatis fluviorum, Himantura toshi , H. uarnak and Pastinachus atrus are members of the family Dasyatidae while Aetobatus ocellatus is in the Myliobatidae . The only previously known host of C. elasmobranchi sp. nov. is an unidentified species of Pristis (family Pristidae ) from India ( Pillai, 1968).

Figures

FIGURE 27. Caligus elasmobranchi sp. nov., female. A, habitus, dorsal; B, antenna, post-antennal process and maxillule drawn in situ; C, sternal furca; D, distal margin of exopod of leg 1; E, outer margin spines on exopod of leg 2; F, exopod of leg 3; G, distal part of exopodal segments of leg 4.Scale bars:1.0 mm onA, 200 µm on B,F, G, 250 µm on C, 100 µm on D, E.