Caligus praecinctorius Hayes, Justine & Boxshall, 2012, sp. nov.
Creators: name: Hayes, Polly
name: Justine, Jean-Lou
name: Boxshall, Geoffrey A.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Maxillopoda
Siphonostomatoida
Caligidae
Caligus
Caligus praecinctorius

description: Caligus praecinctorius sp. nov.
Type material: Holotype female, partly dissected in alcohol, reg. No. MNHN-IU- 2009-2252, on gills of Gymnocranius grandoculis Valenciennes, 1830 [JNC1620B] collected at depth of 13-20 m on 19 September 2005 near île Amédée, New Caledonia (22º 28.500’ S, 166º 28.000‘ E) by J.-L. Justine; 1 paratype female, Reg. No. BMNH. 2012.247, on gills of Gymnocranius euanus (Günther, 1879) [JNC3122] collected on 23 November 2009 at Récif Toombo, New Caledonia (22º 32.624’ S, 166º 29.113’ E) by J.-L. Justine; 1 paratype female, Reg. No. MNHN-IU- 2009-2253, on gills of Epinephelus fasciatus (Forsskål, 1775) [JNC 1258A] collected on 15 September 2009 near Récif Le Sournois, New Caledonia (22º 31.339’ S, 166º 26.538’ E) by J.-L. Justine.
Type locality: Near île Amédée, New Caledonia (22º 28’ 30” S, 166º 28’ 00” E), depth 13– 20m.
Type Host: Gymnocranius grandoculis Valenciennes, 1830
Microhabitat on host: gills
Additional Hosts: Gymnocranius euanus (Günther, 1879) and Epinephelus fasciatus (Forsskål, 1775).
Etymology: the species name derives from the Latin praecinctorius, meaning an apron, and refers to the exceptional breadth of the apron of leg 3 in this species.
Holotype adult female (Fig. 1 A) body length including caudal rami 2.20 mm; paratype lengths 1.97 and 2.12 mm; with a mean of 2.10 mm (based on 3 specimens). Egg strings uniseriate, short, 0.63 to 0.81 mm, with 5 to 8 eggs per string.
Cephalothorax subcircular with marked posterior sinuses; just wider than long (1.67 x 1.65 mm) and comprising about 74% of total body length. Free posterior margin of thoracic portion of dorsal cephalothoracic shield extending posterior to rear margins of lateral portions and abutting anterior margin of genital complex (Fig.
1B); scattered sensillae present on dorsal surface of thoracic portion. Ventral surface of cephalothorax with pair of minutely-ridged protuberances located either side of midline between intercoxal sclerite of first swimming leg and intercoxal sclerite of second leg (Fig. 1 D). Paired grooves extend transversely from deep T-shaped groove located either side of vestigial sternal furca (sf) (Fig. 1 D). Genital complex markedly wider than long (1.12 mm x 0.42 mm in midline, or x 0.59 mm to base of fifth leg); anterior margin straight, with rounded anterolateral margins leading to parallel lateral margins; posterolateral corners produced to form lobes bearing conspicuous, tapering fifth legs (Fig. 1 A–C); posterior margin of genital complex deeply concave. Dorsal surface of genital complex ornamented with scattered sensillae and pores as illustrated (Fig. 1 B). Abdomen 1-segmented, about 1.3 times wider than long (0.18 x 0.14 mm); carrying paired caudal rami on slightly oblique distal margin; anal slit terminal.
Caudal rami wider than long (Fig. 1 B): each ramus armed with 3 long plumose setae on distal margin, short hirsute seta at outer distal angle, slightly longer hirsute seta at inner distal angle and minute hirsute seta located on lateral margin.
Antennule typical for family: 2-segmented (Fig. 1 E); large proximal segment with 25 plumose setae along anteroventral margin and 2 setae located dorsally; distal segment bearing 12 elements (10 setae plus 2 aesthetascs) clustered around apex plus isolated seta on posterior margin. Antenna (a2) (Fig. 2 A) with posteriorly-directed broad spatulate process on proximal segment; middle segment subrectangular, tapering distally, unarmed; terminal segment forming strong, recurved claw armed with slender seta midway along anterior margin and with minute seta on raised knob located proximally on ventral surface. Post-antennal process (pap) (Fig. 2 A) forming blunt recurved claw; ornamented with 2 simple sensillae on basal part and with similar simple sensilla on adjacent ventral cephalic surface.
Mandible of typical stylet-like structure with 12 marginal teeth. Maxillule (mxl) (Fig. 2 A) comprising anterior papilla bearing 3 unequal, naked setae and simple, tine-like posterior process. Simple postmaxillulary process present (pmxlp) (Fig. 2 A). Maxilla 2-segmented (Fig. 2 B), comprising elongate syncoxa and basis: syncoxa with conspicuous tubular extension from pore at base; basis bearing subapical flabellum on anterior margin, terminating in 2 unequal claw-like elements (calamus and canna). Calamus more than twice as long as canna, both ornamented with strips of serrated membrane (on calamus strips arranged obliquely along surface). Maxilliped subchelate (Fig. 2 C); large proximal segment unarmed; distal subchela with short apical claw separated from proximal segmental part by incomplete suture; segmental part armed with distal seta, claw with stout seta. Sternal furca (sf) comprising two very short, slightly divergent tines, with bluntly rounded tips (Fig. 1 D) scarcely emergent from ventral cephalothoracic surface.
First swimming leg (Fig. 2 D) with characteristic structure for genus: comprising protopod consisting of incompletely separated coxa and basis, 2-segmented exopod and vestigial endopod represented by unarmed process on posterior margin of basis. Coxa unarmed, but fused to coxa of opposing leg by long, slender transverse intercoxal sclerite (interpodal bar). Basis with outer and inner plumose setae. Exopod directed laterally and forming main axis of leg; first exopodal segment elongate, more than 3.8 times longer than wide (measured along centre of segment), armed with small outer (anterior) spine and ornamented with row of setules along distal part of posterior margin; second segment armed with 3 long plumose setae along posterior margin and 4 distal margin elements (Fig. 2 D). Distal elements as follows: spine 1 (anteriormost) very short and naked; spines 2 and 3 each with long accessory process; seta 4 longer than spines 2 and 3, but shorter than segment.
Second leg (Fig. 3 A) biramous, with flattened protopodal segments and 3-segmented rami, as typical for genus. Coxae of leg pair joined by very broad, plate-like, intercoxal sclerite bearing marginal membrane posteriorly. Coxa with plumose seta and surface sensilla. Basis shorter than width of intercoxal sclerite; armed with outer plumose seta; ornamented with surface sensilla and marginal membrane posteriorly and anteriorly (latter reflexed back over dorsal surface of segment and not figured). Exopodal segments 1 and 2 each with large reflexed outer spines extending obliquely across ventral surface of ramus; segment 3 with 2 outer spines (proximal outer spine partly concealed by margin), 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. 3 B) extremely broad; rectangular intercoxal plate broader than limb itself; forming flattened apron closing posterior part of cephalothoracic sucker as typical for genus: apron ornamented with membrane along free posterior margin. Protopod flattened, bearing inner plumose seta at junction with intercoxal plate, and outer plumose seta usually concealed beneath exopod (visible in Fig. 3 B where exopod removed); ornamented with membrane along posterior margin medial to endopod and along lateral margin anterior to exopod; space between rami covered by flap-like velum ornamented with row of short setules along free margin. Exopod 3- segmented (Fig. 3 C); first segment with short, stout, outer claw directed over ventral surface of ramus; second segment with curved outer spine and inner plumose seta; third with 7 setal elements increasing in length from outermost to innermost. Endopod 2-segmented; first segment with inner plumose seta; second with 6 setal elements increasing in length from outermost to innermost.
Fourth leg (Fig. 3 D) 3-segmented, comprising long, slender, protopodal segment and 2-segmented exopod; oblique articulation separating exopodal segments not well defined on ventral surface. Protopodal segment armed with outer seta; first exopodal segment with slender outer spine; second exopodal segment armed with 3 unequal naked spines, each with pecten at base (Fig. 3 D).
Fifth legs located at posterolateral corners of genital complex; each comprising outer protopodal seta originating on dorso-lateral surface adjacent to robust tapering process, representing exopod, armed with 2 minute apical setae (Fig. 1 B). Sixth leg represented by unarmed plate closing off each genital opening.
Remarks: Two aspects of the body form of this species are unusual for Caligus: firstly the posteromedian lobe of the cephalothorax completely covers the fourth pedigerous somite in dorsal view, and secondly, the genital complex is 2.7 times wider than long (length measured along midline: 1.9 times wider than long if measured more laterally to the base of the fifth legs) and it has a concave posterior margin within which originates the small, onesegmented abdomen.
The posterior extent of the posteromedian lobe of the cephalothorax is reminiscent of the caligid genus Mappates Rangnekar, 1958, in which it conceals the fourth pedigerous somite in dorsal view. The lobe is not as extensive as in Mappates since it barely overlaps the anterior edge of the genital complex in the new species. Similarly the fourth pedigerous somite is concealed in ventral view by the apron of the third leg both in the new Caligus species and in Mappates. This character was regarded as a diagnostic character for the genus Mappates by Rangnekar (1958) although several authors have questioned the validity of this genus (e.g. Kabata, 1965). Some species of Anuretes Heller, 1865 also share this same character state. Heegaard (1962) established a new genus Caligulus based on C. longispinosus (Heegaard, 1962), in which the fourth pedigerous somite is concealed beneath a posterior extension of the posteromedian lobe of the cephalothorax. Caligulus was recognised as a synonym of Caligus by Prabha (1983). The new species and C. longispinosus are the only lunule-bearing caligids in which the posteromedian lobe of the cephalothorax completely conceals the fourth pedigerous somite in dorsal view.
No other species of Caligus has a genital complex that is 2.7 times wider than long (as measured along the midline) and has a posterior margin that is evenly concave between the prominent posterolateral corners bearing the robust fifth legs. The fifth legs are conical and largely fused to the genital complex at their bases. They are reminiscent of the strongly projecting fifth legs of the species of the nominal genus Dentigryps Wilson, 1905, which is now treated as a synonym of Lepeophtheirus von Nordmann, 1832 (see Hewitt, 1971; Kabata, 1979). The new species is the only representative of Caligus to exhibit such fifth legs.
Caligus praecinctorius sp. nov. was previously reported as Caligus sp. nov. from the host Epinephelus fasciatus in Justine et al. (2010a), and as Caligus sp. nov. from the hosts Gymnocranius grandoculis and Gymnocranius euanus in Justine et al. (2010b).
description: Published as part of Hayes, Polly, Justine, Jean-Lou & Boxshall, Geoffrey A., 2012, The genus Caligus Müller, 1785 (Copepoda: Siphonostomatoida): two new species from reef associated fishes in New Caledonia, and some nomenclatural problems resolved, pp. 21-39 in Zootaxa 3534 on pages 22-27, DOI: 10.5281/zenodo.210824