Botryllophilus longicaudatus, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 80-84

Botryllophilus longicaudatus sp. nov.

( Figs. 48-50 )

Type material. Holotype ♀ (MNHN-IU-2018-1969, dissected and mounted on a slide) from Sẚgẚllẚna sp.; Juan de Fuca , MUA 88, Juan de Nova Is., Mozambique Channel, Laboute coll., 02 February 1996.

Etymology. The name is a combination of Latin lçngus (=long) and cauda (=tail), referring to the relatively long abdomen of the new species.

Description of female. Body ( Fig. 48A ) consisting of swollen anterior part and elongate posterior part, with thick exoskeleton; body length 1.45 mm. Anterior part of body expanded dorsally and laterally, with slightly depressed cephalosome and 3 dorsolateral constrictions, without division between fourth and fifth pedigerous somites. Leg 5 positioned laterally. Posterior part of body ( Fig. 48B ) as long as anterior part; consisting of genital and 4 abdominal somites. Genital somite 148×255 μm; genital apertures large, located dorsally. Four abdominal somites 138×175, 154×157, 151×138, and 200×126 μm, respectively. Caudal ramus ( Fig. 48C ) short, 51×46 μm, armed with 4 claws and 2 small setae; inner largest claw 92 μm long, much longer than ramus; 2 outer distal claws comprising blunt straight claw (60 μm long) tipped with 1 small setule, and strongly curved short claw (41 μm long).

Rostrum absent. Antennule ( Fig. 48D ) 187 μm long, not expanded, 5-segmented; articulation between 2 termi- nal segments incomplete, expressed only on one surface; armature formula 7, 5, 3, 4, and 8; first to third segments with 5, 3, and 1 large setae, respectively. Antenna ( Fig. 48E, F ) slender, 4-segmented; coxa, basis, and first endopodal segment unarmed: second endopodal segment of left antenna about 4.3 times longer than wide (82×19 μm), armed with 2 inner and 4 distal, attenuate setae. Second endopodal segment of right antenna ( Fig. 48F ) longer than that of left antenna, 115×18 μm; armed with longer, naked proximal seta and 5 shorter, spiniform setae ornamented with spinules distally.

Labrum ( Fig. 48G ) with broad posteromedian lobe bearing setules along posterior margin. Mandible ( Fig. 48H ) consisting of coxa and palp; medial margin of coxal gnathobase with bifurcate distal tooth and 4 or 5 smaller, blunt teeth; palp with semicircular tubercle on middle of medial margin and armed with 9 setae arranged as 3, 2, 2, and 2. Maxillule ( Fig. 48I ) consisting of precoxa and palp; precoxa with 6 distinct setae on arthrite; palp divisible into coxa, basis, and endopod; coxa with small, knob-like epipodite tipped with minute vestigial seta; basis with 2 medial and 3 outer setae and 1 tubercle-like distal process; endopod wider than long, incompletely articulated from basis, armed with 3 setae on distal margin. Maxilla ( Fig. 48J ) indistinctly 2-segmented with 3 setae on first segment and 6 setae on second, mediodistal seta strong, claw-like. Maxilliped ( Fig. 49A ) 4-segmented; syncoxa with 2 small setae on medial margin and blunt tubercle at mediodistal corner; basis with 1 small seta; first endopodal segment small, unarmed; second segment with 2 minute setae and 1 inner distal, dentiform process; terminal claw as long as second endopodal segment, bearing small subterminal denticle.

Legs 1-4 ( Figs. 49 B-G, 50A, B) biramous and asymmetrical, with unsegmented exopods and incompletely 2- segmented endopods (endopod of right leg 3 missing); coxa unarmed; basis with outer seta, but unornamented. First endopodal segment of all swimming legs bearing short seta; second endopodal segment of right leg 2 with 3 spines and 4 setae; endopods of legs 1 and 4 armed with setae only. Some of setae on endopods of legs 1 and 2 pinnate, other setae naked. Numbers of spines (Roman numerals) and setae (Arabic numerals) on right and left legs 1-4 as follows:

Leg 5 ( Fig. 49H ) small, not extending beyond anterior border of genital somite, about 1.4 times longer than wide (117×86 μm) with rounded distal margin; armed with 3 thin shorter setae and 1 large distal seta, longer than leg 5. Leg 6 ( Fig. 49I ) represented by 1 spinule and 1 spiniform process on genital operculum. Five small papillae present near leg 6.

Male. Unknown.

Remarks. In having the same combination of armature elements on legs 1, 2 and 4 and on the exopod of right leg 3 (the endopod of right leg 3 is missing in the single available specimen of B. lçngẚcaudatus sp. nov.), B. lçngẚcaudatus sp. nov. is comparable only with B. spẚnulçsus Ooishi, 2012. The latter species lives in association with an ascidian of the genus Synçẚcum in Madagascar ( Ooishi, 2012). The main differences that serve to distinguish between B. lçngẚcaudatus sp. nov. and B. spẚnulçsus are: (1) the anterior part of the body is swollen (cf. narrow in B. spẚnulçsus); (2) leg 5 is stout (cf. elongate in B. spẚnulçsus); (3) the first segment of the antennule is armed with 5 large and 2 small setae (cf. 2 large and 6 small setae in B. spẚnulçsus); (4) the second endopodal segment of right leg 2 is armed with 3 spines and 4 setae (cf. 3 naked and 4 pinnate setae in B. spẚnulçsus).

Figures

FIG. 48. Bçtryllçphẚlus lçngẚcaudatus sp. nov., female. A, habitus, left; B, posterior part of body, dorsal; C, caudal ramus; D, antennule; E, left antenna; F, endopod of right antenna; G, labrum; H, mandible; I, maxillule; J, maxilla. Scale bars:A, 0.2 mm; B, 0.1 mm; C-H, 0.05 mm; I, J, 0.02 mm.

FIG. 49. Bçtryllçphẚlus lçngẚcaudatus sp. nov., female. A, maxilliped; B, right leg 1; C, left leg 1; D, right leg 2; E, left leg 2; F, exopod of right leg 3; G, left leg 3; H, leg 5; I, genital aperture. Scale bars: A, H, 0.05 mm; B-G, 0.02 mm.

FIG. 50. Bçtryllçphẚlus lçngẚcaudatus sp. nov., female. A, right leg 4; B, left leg 4. Scale bars: 0.02 mm.