Tethorchestia antillensis Bousfield, 1984

Wildish, David J. & Lecroy, Sara E., 2014, Mexorchestia: a new genus of talitrid amphipod (Crustacea, Amphipoda, Talitridae) from the Gulf of Mexico and Caribbean Sea, with the description of a new species and two new subspecies, Zootaxa 3856 (4), pp. 555-577 : 558-561

Tethorchestia antillensis Bousfield, 1984 .

(Figures 1, 2)

Tethorchestia antillensis Bousfield, 1984 , p. 205. — Ciavatti, 1989, pp. 139–140, figs. 12–14. — Bousfield & Poinar, 1995, pp. 751–753, fig. 3. — Varela et al., 2003, p. 74. —LeCroy, 2011, p. 759, fig. 589.

Material examined. 7 males, 9 females; Goodland Bay Bridge, Florida; 25° 56.001′ N, 81° 38.985′ W; D.J. Wildish; 11 March 2007; under mangrove litter on a sandy beach; CMNC-2012-0019. 3 males, 9 females; south of Hob Horse Cove, Indian River, Florida; E.L. Bousfield; 19 February 1963; CMNC-1983-0973 (slide mounts of male and female specimens were prepared from this material and are deposited at the CMN).

Diagnosis. Moderately large talitrids (10–18 mm); antenna 2, flagellum subequal to or shorter than peduncle articles 3-5; female gnathopod 1, palm slightly oblique; peraeopods 3–7, articles with stout marginal robust setae; peraeopod 7, basis subrectangular, slightly broader than those of peraeopods 5–6, propodus slender, length approximately 6 (female) to 7 (male) times width; uropod 2, inner ramus with 1-2 robust setae on lateral surface; telson with more than 12 dorsal and marginal robust setae; dorsal pigment pattern lacking on anterior body.

Description. Based on adult male.

Cephalon (Fig. 1): Deeper than long; eyes round, with less than one diameter between them when viewed dorsally. Antenna 1 short, slightly exceeding the junction between peduncle articles 4 and 5 of antenna 2; flagellum 5-articulate. Antenna 2 short, reaching to third peraeon segment, peduncle not incrassate; flagellum 24-articulate, slightly longer than peduncle, each article with two groups of bristles, within each group, some bristles directed forward, some laterally.

Mouthparts (Fig. 2): Upper lip subovate, apex with fine setae. Lower lip with lateral lobes slightly divergent, minute setae present in inner cleft and on anterior surface. Left mandible with 4–5-dentate lacinia mobilis, strong molar process. Right mandible with 5-dentate incisor, 3–dentate lacinia mobilis. Maxilla 1, inner plate narrow, with 2 terminal plumose slender setae, long fine setae on inner margin; outer plate with vestigial 2-articulate palp on outer margin, very short fine setae on inner margin, apical robust setae curved, serrated near tip. Maxilla 2, both plates subequal in size; inner plate with single strong plumose slender seta at midpoint of inner margin, short robust setae lining distal half of margin; outer plate with two types of short and long robust setae apically, with fine setae proximally on outer margin. Maxilliped, inner plates with 3 stout robust setae apically, 2 groups of 4–6 slender setae on medial face, inner margin lined with plumose slender setae; outer plates rounded distally, with distal and distomedial robust and slender setae; palps robust, 4-articulate, distolateral margin of articles 1–2 with 1–3 robust setae.

Peraeon (Fig. 1): Gnathopod 1, coxa shield-shaped, with slender setae along ventral margin; basis long, slightly expanded distally, with small robust setae on anterior and posterior margins; ischium and merus, robust setae present on posterior margins; carpus slightly longer than propodus, with robust setae on all surfaces, posterodistal margins of each article broadened into rounded lobes, with many minute palmate setae and many long thin robust setae of various sizes; dactylus strong, shorter than palm. Gnathopod 2, coxa quadrate, with small robust setae on ventral margin; basis long, abruptly expanded posteroproximally; propodus and dactylus enlarged, FIGURE 1. T. antillensis . Male, 15.3 mm from Goodland Bay, Fl., collected 9 July 2006. Habitus, limb parts and telson. Scale bars all 500µ, except tips of P7 and maxilliped, where it is 100µ.

FIGURE 2. T. antillensis . Female 13.0 mm from Goodland Bay, Fl., collected 9 July 2006. Head, mouthparts and peraeopods. Scale bars all 500µ, except tip of P7 and mouthparts where it is 100µ.

dactylus drawn out into a long, fine tip which fits in a groove on the propodus, inner margin with fine robust setae. Peraeopods 3–7 short, peraeopods 6–7 longer than peraeopods 3–5, peraeopod 7 slightly longer than peraeopod 6, all peraeopods cuspidactylate. Peraeopod 3, coxa quadrate, with small robust setae on ventral margin, small notch present on anterodorsal corner; coxal gill sac-like. Peraeopod 4 shorter than peraeopod 3, coxa similar to that of peraeopod 3; dactylus with notch on inner surface (described by Bousfield and Poinar (1995) as a “pinched unguis”). Peraeopod 5, coxa dorsoventrally compressed, bilobed ventrally, anterior lobe largest; basis oval, slightly smaller robust setae on posterior margin than on anterior margin, larger robust setae on both margins of remaining articles. Peraeopod 6, coxa reduced, bilobed, anterior lobe small; basis and distal articles as in peraeopod 5, but longer. Peraeopod 7, coxa very small, bilobed, anterior lobe almost absent; basis subquadrate, posterior margin weakly serrate, robust seta at point of each serration; strong marginal robust setation on other articles; propodus slender, length approximately 7 times width, with long, fine “comb” setae present in 5–6 clumps near distal tip, setae approximately half length of dactylus, first 3–4 clumps of long setae directed anteroventrally, fifth clump of long setae directed ventrally, sixth clump of short setae at posterodistal tip of propodus directed posteroventrally.

Pleon (Fig. 1): Pleopods slightly reduced, inner ramus slightly longer than outer, both rami slightly shorter than peduncle, peduncle of each pleopod with pair of robust hooked coupling setae on inner margin, fine marginal hairs present on outer margin; rami of 6–9 articles, each bearing pair of long, plumose setae. Pleopod 1 bears 2–5 simple robust setae along inner mid-line of peduncle, with only 0–2 each in pleopods 2–3.

Urosome (Fig. 1): Uropod 1, peduncle, inner and outer margins with 6–8 robust setae each; inner ramus slightly shorter than peduncle, with 2–3 terminal and 4–5 marginal robust setae; outer ramus slightly shorter than peduncle, with 2–3 terminal robust setae, without marginal robust setae, distolateral robust seta present. Uropod 2, peduncle with two rows of robust setae, inner row with 2 larger distal setae, plus 3–4 smaller setae, the outer with 3 stout marginal robust setae; rami approximately equal in length, slightly shorter than peduncle, with 3–5 terminal and 2–3 marginal robust setae; inner ramus with 1–2 robust setae on lateral surface. Uropod 3 small, peduncle longer than ramus, armed with 4 robust setae distally; ramus with 5 subequal terminal and 3 marginal robust setae. Telson heart-shaped, with mid-dorsal groove forming a notch distally; each lobe with 4 apical robust setae, 2 distal dorsolateral robust seta, 4 proximal dorsolateral robust setae.

Sexually dimorphic differences include: Antenna 2 (Fig. 2), peduncle not quite as thick or long as in male; flagellum 16-20-articulate. Gnathopod 1 (Fig. 2) parachelate, without rounded posterior lobes on carpus and propodus; palm slightly oblique; dactylus longer than palm. Gnathopod 2, basis inverted pyriform, expanded proximally, anterior margin narrowing distally; carpus and propodus with rounded posterior marginal lobe, with fine palmate setae; propodus and dactylus not enlarged, dactylus minute. Oostegite on gnathopod 2 strap-like, exceeding length of the basis, with 23–27 long, thin, simple marginal setae; oostegites on peraeopods 3–5 are successively smaller, with setal numbers of 20–23, 18 and 8-10 respectively; peraeopod 5 oostegites are smallest, approximately equal in length to basis. Peraeopods 3–5 lack notch on anterodorsal corner of coxa. Peraeopod 7 (Fig. 2) clusters of long propodal “comb” setae absent, propodus length approximately 6 times width.

Epidermal pigment patterns. Dorsal pigmentation is difficult to see against the orange/brown background colour and it appears to be absent on the cephalon and the first 3 peraeon segments. Pigment patterns on the following peraeon and pleosome segments are as figured in Wildish & Martell (2013). In peraeon segments 4 and 5, there is one bar of pigment; in segments 6 and 7, the same but with two "eyes" without pigment. A similar pattern is seen in the first pleon segment, but in segments 2–3 there are two separate bars of solid pigment in each segment.

Distribution. Bahamas; central east coast of Florida; Florida Keys to Marco Island; Cuba; Yucatan; Guadeloupe and the Lesser Antilles ( Bousfield, 1984; Ciavatti, 1989; Bousfield & Poinar, 1995; Varela et al., 2003; LeCroy, 2011).

Remarks. Our samples agree well with the description provided by Bousfield (1984), and the description and figures of Ciavatti (1989) and Bousfield & Poinar (1995). The maximum body length from our two samples (N = 28) was 14 mm (female) to 15 mm (male).