Caligus turbidus, 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 : 129-133

Caligus turbidus sp. nov.

( Figs. 60–62 )

Type material. Holotype ♀ and 3♀♀ paratypes from Tripodichthys angustifrons (Hollard, 1854) (TC17072) 13 January 2016, QM Reg. Nos Holotype ♀ W53114, 3 ♀♀ paratypes W53115; 1♀ paratype (TC17024) 12 January 2016, 1♂ paratype (TC17080) 13 January 2016, QM Reg. No. W53116, 3♀♀, 1 immature ♀ paratypes (TC 17335) 20 January 2016, QM Reg. No. W53117; 8♀♀ paratypes (TC17096) 13 January 2016, 3♀♀ paratypes (TC17927) 5 July 2016, NHMUK Reg. Nos 2017.323–333.

Type Host. Tripodichthys angustifrons (Hollard, 1854) .

Site on host. Roof of mouth and surface of tongue.

Etymology. The name of the new species is derived from the Latin, turbidus , meaning unclear.

Description. Adult female ( Fig. 60A ) body length 2.76 mm, including caudal rami; range 2.54 to 2.92 mm (based on 11 specimens). Dorsal cephalothoracic shield subcircular; comprising about 35 % of total body length. Free margin of thoracic portion of dorsal cephalothoracic shield extending posteriorly beyond rear margins of lateral portions. Lunules present ventrally on frontal plates. Fourth pedigerous somite separated from genital complex by narrow constriction. Genital complex with anterior section defined by constriction, main part of complex narrow anteriorly, becoming wider posteriorly; about 1.5 times longer than wide; with linear lateral margins and rounded corners ( Fig. 60A ); fifth legs located ventrally close to posterolateral corners. Genital complex about 2.0 times longer than abdomen; genital complex and abdomen combined about 1.4 times longer than cephalothorax. Abdomen 2-segmented, about 1.3 times longer than wide. Anal somite ( Fig. 61A ) carrying paired caudal rami distally; anal slit terminal; ornamented with patches of minute spinules ventrally near origin of caudal rami. Caudal rami with parallel sides, just longer than 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 long plumose setae on distal margin.

Antennule ( Fig. 60B ) 2-segmented; large proximal segment with 25 plumose setae arrayed along anteroventral surface and 2 setae located dorsally; short distal segment bearing 12 elements (10 setae plus 2 aesthetascs) around apex, plus isolated seta on posterior margin. Antenna ( Fig. 60C ) comprising long proximal segment bearing broad, posteriorly-directed spinous process with marginal flanges; middle segment subrectangular, unarmed but with dorsal adhesion pad; terminal segment forming recurved claw bearing accessory spine proximally, and armed with slender distal seta. Post-antennal process ( Fig. 60C ) with well-developed curved tine; ornamented with 2 bisensillate papillae on basal part and single bisensillate papilla on adjacent ventral cephalothoracic surface. Small tapering process present between base of antenna and post-antennal process.

Mandible of typical stylet-like structure, with 12 marginal teeth. Maxillule ( Fig. 60C ) comprising large anterior papilla bearing 1 large and 2 small naked setae and posterior, tapering process with blunt tip. Maxilla 2- segmented ( Fig. 60D ), comprising unarmed syncoxa and basis: basis bearing rounded membranous subapical flabellum on anterior margin, and terminating in 2 subequal claw-like elements (calamus and canna). Calamus longer than canna, ornamented with strips of serrated membrane arranged obliquely around surface; canna ornamented with strips of serrated membrane. Maxilliped subchelate ( Fig. 60E ); proximal segment unarmed, with 4 ridges proximally on posterolateral surface; distal subchela with apical claw; short, slender seta present on concave margin.

Sternal furca ( Fig. 60F ) with incurved tines, with wide gape; small knob-like accessory processes present either side of furca.

First swimming leg pair ( Fig. 60G ) joined by slender intercoxal sclerite; sympod with inner and outer plumose setae derived from basis; sympod ornamented with extensive patch of spinules; endopod represented by rounded process on posterior margin of basis. Exopod 2-segmented, directed laterally and forming main axis of leg; first segment robust, about 2.6 times longer than wide and armed with small outer (anterior) spine and ornamented with row of setules along posterior margin; second segment short, lacking well developed plumose setae on posterior margin but with interruptions in thickness of cuticle and 1 minute setal vestige (arrowed in Fig. 60G ), oblique distal margin with 4 elements as follows: spine 1 (anterior-most) longest with marginal membrane distally; spines 2 and 3 progressively smaller, each with accessory process; seta 4 plumose, about as long as spine 1, shorter than segment.

Second leg ( Fig. 61B ) biramous, with flattened protopodal segments and 3-segmented rami. Coxae of leg pair joined by intercoxal sclerite bearing extensive marginal membrane posteriorly. Coxa with plumose seta and surface sensilla. Basis armed with outer naked seta; ornamented with long surface sensilla, marginal membrane posteriorly, and flap of membrane anteriorly, reflexed back over dorsal surface of segment. Exopodal segment 1 with inner plumose seta and large outer spine extending obliquely across surface of ramus, ornamented with flap of membrane anteriorly, reflexed back over dorsal surface of segment; exopodal segment 2 with outer spine directed obliquely across surface of ramus plus inner plumose seta; segment 3 with 2 outer spines (proximal spine slender and naked, distal spine with extensive membrane bilaterally); 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 margin of endopodal segment 1 ornamented with setules distally, segment 2 margin with stout tapering spinules.

Third leg pair ( Fig. 61C ) forming flattened plate closing posterior part of cephalothoracic sucker as typical for genus. Protopodal part flattened joined by plate-like, intercoxal sclerite (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; apron ornamented with circular patch of small spinules medially; sensillae located adjacent to inner coxal seta and adjacent to origin of endopod. Exopod 3- segmented; first segment armed with stout outer claw directed over ventral surface of ramus, without inner seta; second segment with outer spine and inner plumose seta; distal segment with 3 spiniform elements on outer margin and 5 plumose setae on distal and inner margins; outer margins of segments 2 and 3 ornamented with slender setules. Endopod 2-segmented; first segment expanded laterally to form flap-like velum closing off space between rami; velum ornamented with row of fine setules along free margin; bearing inner plumose seta; compound distal segment with 6 setal elements increasing in length from outermost to innermost.

Fourth leg 3-segmented ( Fig. 61D ), comprising protopodal segment and 2-segmented exopod: protopodal segment armed with plumose seta distally and ornamented with 2 sensillae; first exopodal segment armed with outer spine extending beyond tip of lateral margin spine on distal segment; compound distal segment armed with short spine on lateral margin and 3 unequal spines on oblique distal margin; apical spine about 25% longer than middle spine, about 45% longer than outer spine; all spines with well-developed pecten at base.

Fifth legs located ventrally near posterolateral corner of genital complex ( Fig. 61E ); comprising plumose seta on anterior papilla and 2 plumose setae on posterior papilla representing exopod.

Male body length 1.95 mm, including caudal rami. Cephalothorax as in female, dorsoventrally flattened and with prominent frontal plates bearing large lunules ( Fig. 62A ). Genital complex with slightly convex lateral margins; about 1.5 times longer than abdomen. Abdomen 2-segmented, first somite just longer than wide; anal somite longer than preceeding somite, carrying paired caudal rami distally; anal slit terminal. Caudal rami with parallel sides, longer than wide. Each ramus armed with short plumose seta at inner distal angle, slightly longer seta at outer distal angle, small seta located just ventral to outer distal seta, and 3 long, plumose setae on distal margin.

Antennule, mandible, maxillule and maxilla as in female. Antenna modified ( Fig. 62B ); first segment elongate; second segment reflexed, elongate, bearing corrugated adhesion pads proximally and distally; distal segment forming short powerful claw, armed with 2 setae proximally. Post-antennal process ( Fig. 62C ) more highly curved than female. Maxilliped ( Fig. 62D ) with pointed myxal process on proximal segment (syncoxa) directly opposing tip of claw.

Legs 1 to 4 as in female.

Leg 5 located on ventral surface, just anterior to rounded posterodistal corner of genital complex; comprising protopodal seta and 2 plumose setae on papilla derived from exopod. Leg 6 forming operculum, closing off genital opening, armed with naked seta.

Remarks. This species belongs to the Caligus productus -group characterized by the loss of 2 of the 3 plumose setae, and strong reduction or loss of the third, from the posterior margin of the distal exopodal segment of leg 1. The key to species of the C. productus -group provided by Boxshall & El-Rashidy (2009) already requires amendment because of the presence of a setal vestige on the posterior margin of the distal exopodal segment of leg 1 of C. ariicolus that was overlooked by Wilson (1928) (see above). Given the difficulty in observing such minute setal vestiges using light microscopy, it is clear that the use of this character in an identification key is problematic.

The new species is most similar to C. schlegeli even in fine scale ornamentation such as the presence of sensillae on the protopodal and first exopodal segments of leg 4 ( Fig. 53E ), the bisensillate papillae associated with the post-antennal process, and the ornamentation of the exopodal spines of leg 2. However, these two species can be distinguished by the more robust spine of the first exopodal segment of leg 3 in the new species and by the armature of leg 4. Leg 4 is more robust in the new species ( Fig. 61D ) than in C. schlegeli ( Fig. 53E ) and the outer spine on the first exopodal segment extends beyong the tip of the small lateral spine on the distal segment, whereas in the latter species it barely reaches the mid-point of the lateral spine. In addition, the post-antennal process of the female is larger and more highly recurved in C. schlegeli than in C. turbidus sp. nov.

In Moreton Bay, the new species, with a mean female body length of 2.76 mm (range 2.54 to 2.92 mm), is smaller than C. schlegeli , mean body length 3.14 (range 2.82 to 3.42 mm).

Figures

FIGURE 53. Caligus schlegeli Ho & Lin, 2003, female. A, habitus, dorsal; B, antenna, post-antennal process and maxillule drawn in situ; C, exopod of leg 1, ventral; D, outer margin spines on exopod of leg 2; E, exopod of leg 3; F, leg 4. Scale bars: 1.0 mm on A, 100 µm on B, C, F, 50 µm on D, E.

FIGURE 60. Caligus turbidus sp. nov., paratype female. A, habitus, dorsal; B, antennule; C, antenna, post-antennal process and maxillule drawn in situ; D, maxilla; E, maxilliped; F, sternalfurca;G, leg 1with minute vestige of seta arrowed.Scale bars: 1.0 mm on A, 100 µm on C–G, 50 µm on B.

FIGURE 61. Caligus turbidus sp. nov., paratype female. A, anal somite and caudal rami, ventral view showing spinule patches; B,leg 2; C, leg 3; D, leg 4; E, leg 5. Scale bars 100 µm on A–D, 50 µm on E.

FIGURE62. Caligus turbidus sp. nov., paratype male.A, habitus, dorsal; B,antenna; C, post-antennal process; D, maxilliped. Scale bars 0.5 mm on A, 50 µm on B, C, 100 µmon D.