Caligus ariicolus Wilson, 1928

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 : 42-44

Caligus ariicolus Wilson, 1928

( Fig. 18 )

Material examined. 6♀♀, 2♂♂, 5 immature specimens, from Neoarius graeffei (Kner & Steindachner, 1867) (TC17597) 26 June 2016, QM Reg. No. W53055 ; 2♂♂ (TC17624) 27 June 2016; 15♀♀, 4♂♂ from N. graeffei (TC17881) 4 July 2016, NHMUK Reg. Nos 2017.213–222. 11♀♀, 2♂♂ from Netuma proxima (Ogilby, 1898) (TC18830) 0 1 August 2017, NHMUK Reg. Nos 2017.223–232.

Site on host. Roof of mouth, oral cavity.

Differential diagnosis. Cephalothorax dorsoventrally flattened with well-developed marginal membranes. Frontal plates with large lunules. Genital complex with short neck section anteriorly, about 1.4 times longer than wide ( Fig. 18A ), with weakly convex lateral margins, without posterolateral lobes; abdomen about 2.9 times longer than wide, and about 70% as long as genital complex. Proximal segment of antenna with large posterior process provided with marginal flange ( Fig. 18B ). Post-antennal process strongly recurved, with multisensillate papillae. Maxillule with narrow flange distally on lateral margin of posterior process. Maxilliped with smooth myxal margin ( Fig. 18C ). Sternal furca with divergent, flanged tines ( Fig. 18D ), slightly incurved at tip; small rounded accessory processes present either side of furca. Distal exopodal segment of leg 1 ( Fig. 18E ) without plumose setae on posterior margin but retaining 1 minute, naked vestigial seta on posterior margin; distal spine 1 longest; spines 2 and 3 each with accessory process; seta 4 just longer than spine 1, shorter than segment. Leg 2 outer spines on first and second exopodal segments aligned obliquely across ramus ( Fig. 18F ); proximal outer spine on third segment short, distal spine with marginal membrane bilaterally; outer margin of endopodal segment 2 ( Fig. 18G ) ornamented with large, long-tailed denticles. Leg 3 with 3-segmented exopod; bearing weakly curved spine on first segment, outer spine and inner seta on second, 3 spines and 4 setae on third segment; endopod 2-segmented; first segment with well developed velum and inner seta; compound distal segment with 6 plumose setae. Leg 4 uniramous, 3-segmented ( Fig. 18H ); first and second exopodal segments with I and IV spines, respectively; outer spine on first exopodal segment blade-like, extending nearly to tip of lateral spine on second segment. Mean body length of female 2.41 mm, range 2.27 to 2.58 mm (based on 10 specimens): mean length of male 1.89 mm, range 1.69 to 2.08 mm (based on 4 specimens).

Remarks. This poorly known species was considered as a valid member of the Caligus productus -group by Boxshall & El-Rashidy (2009) even though the original description ( Wilson, 1928) was inadequate by modern standards. The morphological description is supplemented here. The presence of a setal vestige on the posterior margin of the distal exopodal segment of leg 1 was overlooked by Wilson (1928) and, therefore, the key in Boxshall & El-Rashidy (2009) which uses this character, will need revision. Apart from the overall fit of the body tagmata proportions, the only distinctive character apparent in Wilson’s description that can be used to positively identify this species is the unusual blade-like shape of the outer spine on the first exopodal segment of leg 4 ( Fig. 17H ). The tip of this spine reaches beyond two-thirds of the length the lateral spine on the second segment and is blade-like, as figured by Wlison (1928: Fig. 9 ).

This species was originally described from material of both sexes obtained from the floor of the mouth of a marine catfish, Nemapteryx caelata (Valenciennes, 1840) (as Arius caelatus ) captured in the Menam Chao Phya at Paknam, Thailand ( Wilson, 1928). It was subsequently listed as occuring on a second ariid host Netuma thalassina (Rüppell, 1837) (as Arius thalassinus ) (Hirunraks et al., 1977) in Thai waters. The discovery of this species in Moreton Bay represents a major extension of its known geographical range. The host in Australia, Neoarius graeffei , is a new host record.

Figures

FIGURE 9. Anuretes plectorhynchi Yamaguti, 1936, female. A, habitus, dorsal; B, genital complex and abdomen, ventral; C, antenna, post-antennal process, maxillule and post-oral process, drawn in situ; D, sternal furca, interpodal bar of leg 1 and ventral processes; E,exopod of leg 2;F,exopod and endopod of leg 3, ventral view drawn in situ. Scalebars:0.5 mm on A, 200 µm on B, 100 µm on C–E, 50 µm on F.

FIGURE 17. Caligus alepicolus nom. nov., female. A, maxilliped; B, leg 1;, C, leg 2, with insets showing outer spine of exopodal segment 2, and proximal and distal outer spines on exopodal segment 3; D, leg 3; E, leg 4. Scale bars: 200 µm on A, D, E, 100 µm on B, C.

FIGURE 18. Caligus ariicolus Wilson, 1928, female. A, habitus, dorsal; B, antenna, post-antennal process and maxillule drawn insitu; C, maxilliped; D, sternal furca,showing adjacent accessory processes; E, leg 1; F,outer margin spines onexopod of leg 2;G, ornamentation on lateral margin of endopodal segments 1and 2of leg 2; H, leg 4. Scale bars:1.0mm on A, 200 µm on B, C, E, H, 100 µm on D, 50 µm on F, G.