Tapholeon tenuis Gheerardyn and Fiers, 2007

Gheerardyn, Hendrik, Fiers, Frank, Vincx, Magda & Troch, Marleen De, 2007, Revision of the genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida, Laophontidae), Journal of Natural History 41 (37 - 40), pp. 2479-2510 : 2499-2504

Tapholeon tenuis Gheerardyn and Fiers sp. nov.

( Figures 10–12 )

Type locality Western Indian Ocean, Kenyan coast, Wasini Island (4 ° 409S, 39 ° 239E), red (terrigenous?)

sediment, water depth 3–4 m.

Material

From type locality: one female holotype dissected on four slides ( COP 4737 a–d); one male allotype on one slide ( COP 4738 ) ; two female and three male paratypes dissected on slides ( COP 4739–4743 ) , and numerous female and male paratypes preserved in 70% alcohol ( COP 4744 ) ; collected 28 February 2002 by M. Raes.

From Western Indian Ocean : different locations along Kenyan coast [Diani Beach (4 ° 189S, 39 ° 359E), Kisite Island (4 ° 409S, 39 ° 229E)], coral sand, water depth from less than 0.5 m to 6 m, three female and four male paratypes ( COP 4745 ) and seven female and 16 male paratypes ( COP 4746 ) preserved in 70% alcohol; collected February 2002 by M. Raes .

Etymology

The specific name tenuis (Latin meaning slender) refers to the slender body shape.

Description of female Total body length 354–413 Mm (n 510; average5386 Mm; measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 90 Mm.

Rostrum ( Figure 10A ) broad triangular; fused to cephalothorax.

Habitus ( Figure 10A, B ) elongate and slender; slightly dorso-ventrally depressed; with distinct convex curvature in lateral aspect. Genital double-somite and following urosomite slightly extended laterally. Second and third urosomite fused to form genital doublesomite. Integument of cephalothorax with pattern of relatively large pits; regularly ornamented with small sensilla. Pleurotergites of prosomites and urosomites and dorsal surface of anal somite with irregular pattern of very small denticles. Posterodorsal margin of cephalothorax smooth, of all free somites strongly serrate. Posterodorsal margins of cephalothorax and free somites (except second urosomite) clothed with slender hairs, all bearing number of sensilla (not in penultimate urosomite). Anal operculum convex with slightly serrate margin, not protruding.

Ventral surface ( Figure 10C ) of genital double-somite smooth. Copulatory pore minute, situated in middle of anterior somite. Ventral surface of following two somites each bearing two rows of very small spinules. Genital double-somite and following two urosomites laterally with spinules. Anal somite smooth ventrally, laterally with few spinules. Ventral surface of caudal rami smooth, with some spinules laterally and two spinular rows apically. Posteroventral margins of genital double-somite and of following urosomites bearing row of spinules.

Caudal rami ( Figure 11H ) flattened; slightly longer than broad; meeting each other along inner margin. Dorsal surface strongly concave beyond implantation of seta VII. Dorsal surface covered with small denticles; inner margin bearing spinules along proximal half. Distal inner corner rounded and strongly serrate. Seta I, II, and III inserted in distal fourth of outer margin, seta VII near middle of ramus. Seta IV and V not fused, both pinnate and short; all other setae naked. Seta I rudimentary.

Antennule ( Figure 11A ) six-segmented. First segment with spinules along anterior margin. Second segment bearing small blunt process along posterior margin, and spinules along anterior and posterior margins. Third segment with spinules along posterior margin. Majority of setae long and slender; second segment with strong, armed spine inserted near posterior margin; ultimate segment bearing two stout setae. Armature formula as in type species.

Antenna ( Figure 11F ): allobasis with one minute abexopodal seta. Exp unisegmented and small, bearing three short bipinnate setae and one long plumose seta. Armature of endopod as in type species.

Mouthparts as in type species.

Maxilliped ( Figure 11E ): syncoxa with one pinnate seta and a row of spinules. Basis with few spinules along outer margin. Endopod claw-shaped, distally pinnate, with short naked seta at base.

P1 ( Figure 12A ): exopod two-segmented; exp-2 bearing four setae. Enp-1 three times as long as exp.

P2–P4 ( Figure 12B, C, D ) with three-segmented exopods and two-segmented endopods. Exp-1 and exp-2 equal in length; exp-3 slightly longer. Segments of endopods and exopods with pattern of spinules as figured. Setal formula in Table I.

P5 ( Figure 12E ) with separate exopod and baseoendopod. Margins of rami furnished with spinules, surface smooth. Baseoendopod reaching slightly beyond middle of exopod; bearing one apical and three lateral setae. Exopod ovate; 2.5 times as long as wide; bearing five plumose setae.

P6 vestige ( Figure 10C ) bearing one seta.

Description of male Total body length 320–394 Mm (n 510; average5356 Mm; measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 76 Mm.

Habitus as in female; except for fully separated second and third urosomites and lack of lateral extensions in second to fourth urosomites ( Figure 11G ). Ventral surface of third urosomite with several short rows of strong spinules.

Antennule ( Figure 11B, C ) eight-segmented; sub-chirocer. Shape of first and second segment as in female. Setae on ultimate segment all slender, i.e. without any stout setae as in female. Armature formula: 1-[1], 2-[9], 3-[7], 4-[2], 5-[10(?)+(1+ae)], 6-[0], 7-[1], 8-[8+acrothek]. Apical acrothek consisting of small aesthetasc fused basally to two setae.

Antenna, mouthparts, and P1–P4 as in female.

P5 ( Figure 11D ): endopodal lobe of P5 obsolete; without seta. Exopod small; about as long as wide; bearing three plumose setae. Inner margin and anterior surface with spinules.

P6 vestiges ( Figure 11G ) asymmetrical; each bearing one plumose, strong inner and one naked outer seta.

Variability

Some male and female paratypes have a right or left P2 enp with an aberrant setal formula (0.120), the opposite side consistently having a normal setal formula. Two female paratypes were found with an aberrant right and left P2 enp (0.120). One female paratype bears an aberrant P3 enp (0.120) on the left side; one other female paratype has an aberrant P3 exp (0.1.123) on the left side.

Differential diagnosis

The present species bears three outer spines on the ultimate segments of the exopods of P2–P4 and bears four, four and three setae on the second endopodal segments of P2–P4, respectively.

Distribution

Different locations along the Kenyan coast (present study).

Figures

Figure 10. Tapholeon tenuis Gheerardyn and Fiers sp. nov. (A) Female habitus, dorsal; (B) female habitus, lateral; (C) female urosome (copulatory pore arrowed), ventral. Scale bars in Mm.

Figure 11. Tapholeon tenuis Gheerardyn and Fiers sp. nov. (A) Female antennule, dorsal; (B) male antennule (armature of segments III, IV, and V omitted), dorsal; (C) male antennule (segments III, IV, and V), ventral; (D) male P5, anterior; (E) female maxilliped; (F) female antenna; (G) male second and third urosomite, ventral; (H) female anal somite and caudal rami, dorsal. Scale bars in Mm.

Figure 12. Tapholeon tenuis Gheerardyn and Fiers sp. nov. (A) Female P1, anterior; (B) female P2, anterior; (C) female P3, anterior; (D) female P4, anterior; (E) female P5, anterior. Scale bar in Mm.