Caligus upenei, 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 : 133-136

Caligus upenei sp. nov.

( Figs. 63 , 64 )

Type material. Holotype ♀ from Upeneus tragula Richardson, 1846 (TC17214) 18 January 2016, QM Reg. No. W53118.

Type Host. Upeneus tragula Richardson, 1846 .

Site on host. Unknown (in head wash).

Etymology. The name of the new species refers to the generic name of the host.

Description. Adult female ( Fig. 63A ) mean body length including caudal rami 2.45 mm. Cephalothorax subcircular; maximum width about 1.44 mm, maximum length 1.51 mm; comprising about 62% of total body length. Free margin of thoracic portion of dorsal cephalothoracic shield extending posteriorly just beyond rear margins of lateral portions. Lunules present ventrally on frontal plates. Genital complex 1.4 times wider than long; with rounded convex lateral margins and rounded corners bearing fifth legs ( Fig. 63B ). Genital complex about 5.2 times longer than abdomen. Abdomen 1-segmented, wider than long; carrying paired caudal rami distally; anal slit terminal. Caudal rami about as long as wide, measured at midpoints of margins. Each ramus armed with short hirsute seta at inner distal angle, slightly longer hirsute seta at outer distal angle, minute hirsute seta located just ventral to outer distal seta, and 3 plumose setae on distal margin.

Antennule ( Fig. 63C ) 2-segmented; proximal segment with 25 plumose setae along anteroventral margin and 2 setae located dorsally; distal segment bearing 12 elements (10 setae plus 2 aesthetascs) around apex, plus isolated seta on posterior margin. Antenna ( Fig. 63D ) comprising proximal segment with posteriorly-directed spinous process; middle segment subrectangular, tapering slightly distally, unarmed; terminal segment forming short recurved claw bearing short spinous element on swelling proximally, and armed with slender distal seta on anterior margin. Post-antennal process ( Fig. 63E ) well-developed, curved, ornamented with 2 unisensillate papillae on basal part; single unisensillate papilla on adjacent ventral cephalothoracic surface.

Mandible of typical stylet-like structure, with 12 marginal teeth. Maxillule ( Fig. 63F ) comprising anterior papilla bearing 3 unequal, naked setae and posterior tine-like process. Maxilla 2-segmented ( Fig. 63G ), comprising elongate syncoxa and basis: syncoxa unarmed; basis bearing subapical membranous flabellum on anterior margin, and terminating in 2 claw-like elements (calamus and canna). Calamus longer than canna, ornamented with strips of serrated membrane arranged obliquely around surface; canna with linear strips of serrated membrane. Maxilliped subchelate ( Fig. 63H ); slender proximal segment unarmed, with spinous process located proximally on posterior surface; tubular membranous structures (possibly filamentous epibionts) present, originating on posterior surface; distal subchela with small apical claw separated from proximal segmental part by incomplete suture; segmental part and claw each armed with 1 seta.

Sternal furca ( Fig. 63I ) with divergent tines, each with linear sides and blunt tip.

First swimming leg pair ( Fig. 64A ) with sympods joined by slender intercoxal sclerite; sympod with inner and outer plumose setae (derived from basis); endopod represented by unarmed process on posterior margin of basis. Exopod 2-segmented; directed laterally and forming main axis of leg; first segment robust, about 2.05 times longer than maximum width (near base) and armed with small outer (anterior) spine and ornamented with setule row along mid-section of posterior margin; second segment armed with 3 long plumose setae along posterior margin and 4 distal elements. Distal elements as follows: spine 1 (anterior-most) simple, shortest; spines 2 and 3 equal in length, both lacking accessory process; seta 4 about twice length of spines 2 and 3, and shorter than segment.

Second leg ( Fig. 64B ) biramous, with flattened protopodal segments and 3-segmented rami. Coxae of leg pair joined by plate-like intercoxal sclerite bearing marginal membrane posteriorly. Coxa with plumose seta and surface sensilla. Basis armed with outer naked seta; ornamented with surface sensilla, marginal membrane posteriorly, and flap of membrane anteriorly, reflexed back over dorsal surface of segment. Exopodal segment 1 with large reflexed outer spine extending obliquely across ventral surface of ramus and inner plumose seta, ornamented with flap of membrane anteriorly reflexed back over dosal surface of ramus; segment 2 with outer spine extending obliquely across ventral surface of ramus and inner plumose seta; segment 3 with 2 outer spines (proximal spine small), apical spine with marginal membrane laterally and pinnules medially, and 5 inner plumose setae. Endopodal segments 1 and 2 armed with 1 and 2 inner plumose setae respectively; segment 3 with 6 plumose setae; outer margins of all endopodal segments ornamented with fine setules.

Third leg pair ( Fig. 64C ) forming flattened plate closing posterior part of cephalothoracic sucker, as typical for genus. Protopodal part flattened joined by plate-like, intercoxal sclerite forming apron, ornamented with marginal membrane posteriorly and along lateral margin anterior to exopod; bearing inner plumose seta at junction with intercoxal sclerite, and outer plumose seta dorsal to base of exopod; sensillae located adjacent to inner coxal seta and adjacent to origin of endopod; space between rami covered by flap-like velum ornamented with row of fine setules along free margin. Exopod 3-segmented; first segment armed with short, weakly curved, outer claw directed over ventral surface of ramus; second segment with slender outer spine and inner plumose seta; third with 7 setal elements (3 outer spiniform elements and 4 inner plumose setae); outer margins of segments 2 and 3 ornamented with rows of slender setules. Endopod 2-segmented; first segment with inner plumose seta; second with 6 setal elements increasing in length from outermost to innermost.

Fourth leg ( Fig. 64D ) 3-segmented, comprising slender protopodal segment and 2-segmented exopod with exopodal segments separated by oblique articulation: protopodal segment armed with outer seta; first exopodal segment just shorter than second, armed with slender outer spine not reaching distal tip of ramus; second segment armed with 3 unequal spines along distal margin, each with pecten at base; spines increasing in length from outer to inner.

Fifth leg located posterolaterally on genital complex, represented by plumose, outer protopodal seta originating on anterior papilla and 2 unequal plumose setae on small inner papilla representing exopod ( Fig. 63B ).

Remarks. This species shares a 3-segmented leg 4 with a 2-segmented exopod bearing I, III spines with 65 other species of Caligus . However, it does not share all aspects of the armature of the distal exopodal segment of leg 1 characteristic for the C. macarovi -group (as discussed above in the remarks section for Caligus hyporhamphi sp. nov.): spine 1 is less than half as long as spines 2 and 3 whereas spines 1, 2 and 3 are subequal in members of the core C. macarovi -group. Comparisons are restricted here to those 19 species exhibiting a 3-segmented leg 4 with a 2-segmented exopod bearing I, III spines in combination with a broad genital complex in the female ( Table 7). Broad is defined here as having a L: W ratio between 0.6:1 and 0.8:1. Included in this list are three species, C. punctatus , C. orientalis and C. oviceps , which are common and widely distributed in the Indo-Pacific, but all three have a genital complex that is about 2.3 to 2.4 times longer than the abdomen, compared to 5.2 times longer in the new species.

Few of the species listed in Table 7 have such a short abdomen relative to the genital complex. Only four of these species have a genital complex that is 3.0 or more times longer than the abdomen: C. calotomi , C. sclerotinosus , C. flexispina and C. sicarius . Comparisons with these species follow. Caligus calotomi was redescribed by Lin & Ho (2007) who showed that the distal exopodal segment of leg 1 carries only three setal elements rather than the typical four, and it seems probable that spine 1 is the missing element. Spines 2 and 3 both lack an accessory process. In C. calotomi the two exopodal segments of leg 4 are unequal, the proximal is markedly shorter than the distal, whereas, in the new species these segments are subequal.

Lewis (1964a) described C. flexispina from Acanthurus triostegus (Linnaeus, 1758) (as Acanthurus triostegus sandvicensis Streets ) caught off Hawaii. The presence of accessory processes on spines 2 and 3 of the distal exopodal segment of leg 1 was not noted. There are numerous small differences: the papillae on the post-antennal process are bisensillate in C. flexispina but unisensillate in the new species, the distal margin of the maxilla is smooth in the former but spinulate in the latter, and the 2 setae on the exopodal papilla of leg 5 in the female are equal in C. flexispina but in the new species the inner seta is nearly 3.0 times longer than the outer. The outer spine on the first exopodal segment of leg 3 is pointed in C. flexispina but blunt in the new species, and the outer spines on segments 2 and 3 increase in length distally in the former but are all similar in length in the latter ( Fig. 64C ).

Caligus sclerotinosus is redescribed herein and can be distinguished from the new species by its prominent fifth legs, visible in dorsal views of the genital complex ( Fig. 54A ), and by the broad spatulate tines of the sternal furca ( Fig. 54E ).

Caligus sicarius was found in Moreton Bay and is redescribed in the present account. It can be readily distinguished from the new species by the extremely unusual leg 4 (see Figs. 57B , 58E ) and by the possession of wedge-shaped tines on sternal furca plus accessory processes adjacent to the furca ( Fig. 58A ).

Caligus callyodoni Prabha & Pillai, 1986 was not included in Table 7 because it has a L: W ratio of 0.88:1 for the genital complex, however, in other respects its general habitus closely resembles that of the new species. It is known as a parasite of parrotfish of the genus Scarus Forsskål, 1775 from India ( Prabha & Pillai, 1986) to Taiwan ( Lin & Ho, 2007). These species share the possession of a small (about half as long as spine 2) spine 1 on the distal exopodal segment of leg 1 and both have unisensillate papillae on the post-antennal process, but there are numerous differences. The post-antennal process is short and straight in C. callyodoni but curved in the new species, the distal margin of the maxilla is smooth in the former but spinulate in the latter, and the tines of the sternal furca are parallel in C. callyodoni compared to strongly divergent in the new species. There are sufficient differences to justify the establishment of a new species to accommodate the material from Upeneus tragula .

The new species was found in Moreton Bay on a single occasion. The tubular membranous structures present on the syncoxa of the maxilliped ( Fig. 63H ) are possibly filamentous epibionts.

These poorly described species are included but many morphological details are lacking.

Figures

FIGURE 57. Caligus sicarius Kabata, 1984, female. A, habitus, dorsal; B, fourth pedigerous somite, genital complex and abdomen, ventral;C, left corner of genital complex showing leg 5, ventral; D, antennule; E, antenna,post-antennal process and maxillule drawn in situ; F, maxilliped.Scale bars:500 µm on A, B,100 µm on C–D, 200 µm on E–F.

FIGURE 58. Caligus sicarius Kabata, 1984, female. A, sternal furca and accessory processes, ventral view in situ; B, leg 1, with inset showing setationelements of distal margin; C, leg 2; D, leg 3, ventral; E, exopod of leg 4. Scale bars:200 µm on A– D, 100 µm on E.

FIGURE 63. Caligus upeneisp. nov., holotype female. A, habitus, dorsal; B, left corner of genital complex showing fifth leg, ventral; C, antennule; D, antenna; E, post-antennal process; F, maxillule; G, tipof maxilla; H, maxilliped; I, sternal furca. Scale bars:0.5 mm on A, 100 µm on B–H, 50 µm on I.

FIGURE 64. Caligus upenei sp. nov., holotype female. A, leg 1, ventral; B, leg 2, ventral; C, leg 3, ventral; D, leg 4. Scale bars:100 µm on A, 200 µm on B–D.

FIGURE54.Caligus sclerotinosus Roubal, Armitage& Rohde, 1983, female.A, habitus, dorsal; B, antenna and post-antennal process drawn in situ; C, maxillule and postoral process drawn in situ; D, tip of maxilla; E, sternal furca;F, exopod of leg 2; G, exopod of leg 3; H, leg 4. Scale bars:1.0 mm on A, 200 µmon B,C, H, 50 µm on D, E, 100 µm on F, G.