Abasia platyrostris Pillai, 1963

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 : 11

Abasia platyrostris Pillai, 1963

( Fig. 1 )

Material examined. 1♀ from Saurida undosquamis (Richardson, 1848) (TC17620) 26 June 2016; 1♀, 1♂ from (TC17625) 27 June 2016, NHMUK Reg. Nos 2017.173–175; 6♀♀ from (TC17850) 0 4 July 2016. QM Reg. No. W53040.

Site on host. all females were attached to the membrane running along the groove in the upper jaw, just the inside tooth row; the male was found on the gills.

Differential diagnosis. Body tripartite, comprising cephalothorax, genital complex and abdomen ( Fig. 1A ). Cephalothorax with ventrally-folded lateral margins. Frontal plates reduced, carried on anteriorly-projecting rostral region; lunules well developed ( Fig. 1B ). Fourth pedigerous somite free. Genital complex widest part of body and 1.2 times wider than long; dorsal surface ornamented with fingerprint-like rows of minute nodules ( Fig. 1C ). Abdomen 2-segmented; first free somite much broader than second and with posterolateral lobes overlapping small anal somite ( Fig. 1A ). Antennule with 23 setae on proximal segment, distalmost setae strongly spinulate ( Fig. 1B ). Antenna subchelate but reduced in size ( Fig. 1D ), lacking posterior process on proximal segment. Post-antennal process vestigial, represented by unisensillate papillae ( Fig. 1D ). Mandible stylet-like with 12 marginal teeth subapically. Maxillule with 3 well developed, hirsute setae on anterior papilla ( Fig. 1D ); posterior process absent. Maxilla with robust calamus and canna. Maxilliped subchelate, with smooth myxal margin. Sternal furca absent. Leg 1 lacking plumose setae on posterior margin of distal exopodal segment; spines on distal margin without accessory processes. Leg 2 with 3-segmented rami; outer spines on exopodal segments 1 and 2 directed obliquely across surface of ramus; endopodal segment 1 ornamented with crescent of spinules distally; segment 2 with row of stout spinules along outer margin. Leg 3 ( Fig. 1E ) with reduced apron ornamented with spinules laterally and rosette of larger denticles medially; exopod 2-segmented; first segment with small outer spine, lacking inner seta; compound distal segment armed with 3 outer spines and 3 inner plumose setae, all derived from incorporated third exopodal segment: endopod 2-segmented, first segment with reduced velum and armed with inner seta, second segment with 2 apical setae. Leg 4 uniramous, 3-segmented; first and second exopodal segments with I and III spines, respectively ( Fig. 1F ). Mean body length of adult female 2.95 mm, range 2.77 to 3.07 mm (based on 4 specimens).

Body length of adult male 1.54 mm.

Remarks. Abasia platyrostris was described by Pillai (1963) based on material collected from the buccal cavity of the lizardfish Saurida tumbil (Bloch, 1795) and Synodus indicus (Day, 1873) caught off Trivandrum, India. It was subsequently reported from Australia by Kazachenko (1975a) who found it on Saurida tumbil and S. undosquamis caught off the northwestern coast. Cressey & Cressey (1979) also reported A. platyrostris from the latter host in the Arabian Sea, as well as from Synodus ulae Schultz, 1953, taken off Honolulu, Hawaii. This record from Moreton Bay is the first from Queensland, and from the east coast of Australia.

Key features of both sexes were described by Pillai (1963, 1985) and Cressey & Cressey (1979) provided supplementary morphological details on the female as well as an identification key to females of the six species known in the genus at the time. No further species have been added since 1979. Within the genus, the 2-segmented state of both rami of leg 3 is a unique feature of A. platyrostris .

Figures

FIGURE 1. Abasia platyrostris Pillai, 1963, female. A, habitus, dorsal; B, right frontal plate with lunule, and antennule, ventral; C. detail of surface ornamentation of genital complex; D, antenna, vesitigial post-antennal process and anterior papilla of maxillule, drawn in situ; E, leg 3, ventral; F, leg 4. Scale bars: 0.5 mm on A, 100 µm on B,C, E, F, 50 µm on D.