Caligus macoloricola, Hayes, Polly, Justine, Jean-Lou & Boxshall, Geoffrey A., 2012

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, Zootaxa 3534, pp. 21-39 : 27-31

Caligus macoloricola sp. nov.

Type material: Holotype female, partly dissected in alcohol, MNHN-IU- 2009-2254, and 4 paratype females (1 intact female paratype MNHN-IU- 2009-2255, 2 intact and 1 incomplete female paratypes BMNH 2012.244-246): all collected on 16 January 2006 by J.-L. Justine from gills of a single specimen of Macolor niger [JNC 1716B – Fork Length 560 mm, Weight 3200 gm].

Type locality: Passe de Dumbéa, New Caledonia.

Type Host: Macolor niger (Forsskål, 1775)

Microhabitat on host: gills

Etymology: the species name is based on the generic name of the host Macolor and - icola meaning inhabitant.

Holotype adult female ( Fig. 4 A) body length including caudal rami 3.54 mm; paratypes ranging from 3.52 to 3.64 mm; female mean body length 3.58 mm (based on 4 specimens). Egg strings uniseriate, 2.11 to 2.20 mm long, each containing 26– 33 eggs. Cephalothorax subcircular with marked posterior sinuses; just wider than long (1.97 x 1.90 mm) and comprising about 54% of total body length. Free margin of thoracic portion of dorsal cephalothoracic shield extending posterior to rear margins of lateral portions. Genital complex about 1.5 times wider than long (1.46 x 0.99 mm); with strongly convex, rounded lateral margins and no trace of posterolateral lobes ( Fig. 4 A). Abdomen 1-segmented; as long as wide (0.44 x 0.44 mm); carrying paired caudal rami on slightly oblique distal margin; anal slit terminal.

Caudal rami ( Fig. 4 B) with parallel sides, 1.05 times longer than wide, measured at midpoints of margins ( Fig. 1 B). 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 setae on distal margin (2 long and plumose; middle seta reduced, non-plumose). Inner margin of ramus naked.

Antennule ( Fig. 4 C) 2-segmented; large proximal segment with 25 plumose setae along anteroventral margin and 2 setae located dorsally; distal segment bearing 13 elements (12 setae plus 1 aesthetasc) around apex, plus isolated seta on posterior margin. Antenna (a2) ( Fig. 4 D) comprising proximal segment with posteriorly-directed narrow, tapering, spinous process; middle segment subrectangular, tapering slightly distally, unarmed; terminal segment forming strong, recurved claw armed with slender seta on anterior margin. Post-antennal process (pap) ( Fig. 4 D) vestigial, with short, blunt process; ornamented with 2 tiny sensillae on basal part and with similar bifid sensilla on adjacent ventral cephalic surface.

Mandible ( Fig. 4 E) of typical stylet-like structure, with 12 marginal teeth. Maxillule (mxl) ( Fig. 4 D) comprising anterior papilla bearing 3 unequal, naked setae and simple, posterior, tine-like process. Maxilla 2- segmented ( Fig. 4 F), comprising elongate syncoxa and basis: syncoxa unarmed; basis bearing subapical flabellum on anterior margin, terminating in 2 unequal claw-like elements (calamus and canna). Calamus about twice as long as canna, both ornamented with strips of serrated membrane arranged obliquely along surface. Maxilliped subchelate ( Fig. 4 G); large proximal segment unarmed; distal subchela with apical claw separated from proximal segmental part by incomplete suture; segmental part armed with 1 seta. Sternal furca ( Fig. 4 H) with long, slightly divergent tines, each with bluntly rounded tip.

First swimming leg ( Fig. 5 A) with unarmed coxa; coxae of leg pair joined by slender intercoxal sclerite (interpodal bar); basis with inner and outer plumose setae; exopod 2-segmented; endopod represented by unarmed process on posterior margin of basis. Exopod directed laterally and forming main axis of leg; first segment robust, about 2.8 times longer than wide and armed with small outer (anterior) spine; second segment armed with 3 long plumose setae along posterior margin and 4 distal elements ( Fig. 5 A). Distal elements as follows: spine 1 (anteriormost) well developed, simple, longer than spines 2 and 3; latter each with accessory process; seta 4 about twice as long as spine 1, and about equal in length to segment.

Second leg ( Fig. 5 B) biramous, with flattened protopodal segments and 3-segmented rami. Coxae of leg pair joined by narrow, 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 membrane anteriorly reflexed over dorsal surface of segment. 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-most spine minute; distal spine with bilateral membrane), 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 first and second endopodal segments ornamented with fine setules.

Third leg pair ( Fig. 5 C) forming flattened plate closing posterior part of cephalothoracic sucker as typical for genus. Leg pair joined by narrow, plate-like, intercoxal sclerite (apron) bearing marginal membrane posteriorly. Protopodal part flattened, bearing inner plumose seta at junction with intercoxal plate, and outer plumose seta near base of exopod; sensilla located adjacent to inner coxal seta; 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; first segment with large, 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). Endopod 2- segmented; first segment with inner plumose seta; second with 6 setal elements increasing in length from outermost to innermost.

Fourth leg ( Fig. 5 D) 3-segmented, comprising large protopodal segment and 2-segmented exopod with exopodal segments separated by oblique articulation: protopodal segment armed with outer seta; first exopodal segment with outer spine with pecten at base; second segment armed with 3 unequal naked spines along distal margin and outer margin spine, each with pecten at base ( Fig. 5 D).

Fifth leg located posterolaterally on genital complex, represented by outer protopodal seta originating on somite surface and 2 setae on small inner papilla representing exopod ( Fig. 5 E). Sixth leg represented by unarmed plate closing off genital opening.

Remarks: There are only 5 species of Caligus characterised by the possession of a 3-segmented fourth leg carrying 4 spines (three distal and one lateral) on the distal segment, in combination with a reduced or vestigial post-antennal process. These are C. afurcatus Wilson, 1913 , C. asymmetricus , C. dactylopteni Uma Devi & Shyamasundari, 1981 , C. enormis Wilson, 1913 and C. phipsoni Bassett-Smith, 1898 . Only one of these species, C. dactylopteni , shares a genital complex that is wider than long with the new species.

The new species differs from C. dactylopteni in several characters: it lacks the large myxal process present on the female maxilliped of C. dactylopteni , and it differs in the arrangement of the setal elements on the distal margin of the second exopodal segment of leg 1. In C. dactylopteni spine 1 is small and located subdistally on the anterior margin, spines 2 and 3 lack accessory processes, and seta 4 is about the same length as spines 2 and 3. In contrast in the new species, spine 1 is located at the antero-distal corner of the segment and is larger than spines 2 and 3, both of which carry accessory processes, and seta 4 is much longer than the longest of the spines. These differences support the establishment of a new species to accommodate this material. This species was reported as an unnamed Caligus sp. nov. from the host Macolor niger in Justine et al. (2012).

Figures

FIGURE 1. Caligus praecinctorius sp. nov., holotype female. A. body, dorsal view; B. posterior margin of thoracic zone of cephalothoracic shield, genital complex, abdomen and caudal rami (with fine pinnules on caudal setae omitted), dorsal view; C. fourth pedigerous somite, genital complex and abdomen, ventral view with left fourth leg omitted; D. vestigial sternal furca (sf), intercoxal sclerite of first (ic 1) and second legs (ic 2) and associated structures, in situ, ventral view; E. antennule. Scalebars: A = 1 mm, B, C = 500 μm, D, E = 100 μm.

FIGURE 4. Caligus macoloricola sp. nov., holotype female. A. body, dorsal view; B. caudal ramus, dorsal view; C. antennule; D. antenna, post-antennal process and maxillule, in situ, ventral view; E. mandible; F. maxilla; G. maxilliped; H. sternal furca. Scale-bars: A = 1 mm, B – E, H = 100 μm, F = 200 μm, G = 400 μm.

FIGURE 5. Caligus macoloricola sp. nov., holotype female. A. leg 1, ventral view; B. leg 2, ventral view; C. leg 3, ventral view; D. leg 4; E. Leg 5, in situ. Scale-bars: A = 100 μm, B – D = 200 μm, E = 50 μm.