Mexorchestia carpenteri carpenteri, Wildish, David J. & Lecroy, Sara E., 2014

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 : 562-568

Mexorchestia carpenteri carpenteri n. sp. and subsp.

(Figures 3–6)

Tethorchestia species B: Bousfield, 1984, pp. 204–205, tab. 6. “ Tethorchestia ” sp. B: LeCroy, 2011, pp. 757–758, fig. 590.

Type material. Holotype: Male, 11.5 mm; Tiger Tail Beach, Marco Island, Florida, U.S.A.; 25° 56.7′ N, 81° 44.6′ W; D.J. Wildish; 23 February 2004; bare sand above high water line; USNM 1218141. Slide material from holotype, USNM 1218141. Allotype: Ovigerous female, 8 mm, same data as holotype; USNM 1218142. Slide material from allotype, USNM 1218142. Paratypes: 9 males, 5 females, 1 juvenile; same data as holotype; 10 March 2007; USNM 1218143. 1 male, 6 females; same data as holotype; 28 February 2004; CMNC-2012-0020. 2 males; 2 females; same data as holotype; 29 February 2004; USNM 1218144. 13 males, 18 females, 4 juveniles; Tiger Tail Beach, Marco Island, Florida; S.E. LeCroy; 15 July 2006; among fiddler crab burrows and Halodule detritus on edge of inlet behind dunes, slightly muddy sand flat; GCRL 0 6521.

Type locality. Tiger Tail Beach, Marco Island, Florida, U.S.A. (25°56.7′ N, 81°44.6′W). General habitat: a saltmarsh behind the main beach facing the Gulf of Mexico, with a brackish pool subject to tidal changes. Parts of the marsh were being re-colonized by mangroves, marsh grass and saltwort, Batis maritima . Hoppers were found on bare, white sand above the recent HW line in association with the fiddler crab, Uca pugilator . The fresh, moist digging pellets around the crab holes were coloured green/brown, suggesting microalgal growth. The hoppers sheltered under the damp digging wastes and did not burrow. Little wrack was present during sampling by DJW and it is possible that the hoppers were feeding on the microalgae within the digging pellets.

Other material examined. 2 males, 6 females, 9 juveniles; Indian River Lagoon at Route 406, Merritt Island, Titusville, Florida; 28°37.61′ N, 80°47.35′ W; S. Kent; October 2009; in Syringodium wrack on sand/shell beach; GCRL 0 6522. 12 males, 15 females, 10 juveniles; John U. Lloyd Beach, Ft. Lauderdale, Florida, U.S.A.; 24°50.78′ N, 80°44.67′ W; S.E. LeCroy; 12 July 2006; under Sargassum drift on sand beach just above high tide line; GCRL 0 6523. 9 males, 8 females; Spanish Harbor Key, Florida, U.S.A., R.W. Heard; 11 October 2004; among beach wrack; ARC 79187. 6 males, 5 females, 7 juveniles; Anne’s Beach, Lower Matacumbe Key, Florida; S.E. LeCroy; 14 October 2004; under Thalassia and Syringodium wrack on a sandy substrate; ARC 79188. 1 male; Goodland Bay Bridge, Florida, U.S.A.; 25°56.001'N, 81°38.985'; D.J. Wildish; 11 March 2007; with Tethorchestia antillensis under mangrove litter on sandy beach; USNM 1218145. 2 males, 3 females; near Cedar Key, Florida, U.S.A.; 29° 0 8.143' N 83° 0 2.705' W; D.J. Wildish; 18 March 2007; among 6 individuals of Platorchestia platensis in eelgrass wrack on a sand beach, near fiddler crab holes, saltwort and mangrove leaves absent; USNM 1218149. 1 male; Lower Suwanee saltmarsh, Florida, U.S.A.; 29°12.409' N, 83° 0 4.099' W; D.J. Wildish; 18 March 2007; among 5 individuals of O rchestia grillus under woody marsh grass (black needle rush, marsh, cord and saltgrass) wrack on a sandy upper shore, with fiddler crab holes and saltwort; USNM 1218148. 2 males, 1 female; Shired Island beach, Florida, U.S.A.; 29°23.661′ N, 83°12.158′ W; D.J. Wildish; 16 March 2007; with Orchestia grillus under recent, copious wrack consisting mainly of red and green macroalgae, fiddler crab holes and creeping stolons of saltwort present on upper beach; USNM 1218146. 58 (all life history stages); Hagen’s Cove, Florida, U.S.A.; 29°46.267' N, 83°34.753' W; D.J. Wildish; 17 March 2007; under marine wrack (mainly eelgrass) on a sandy upper beach, near fiddler crab holes and with saltwort, but no mangrove, present; USNM 1218147. 3 males, 3 females, 2 juveniles; North Beach, Perdido Key, Florida, U.S.A.; S.E. LeCroy; 14 July 1993; ARC 79189. 5 males, 9 females, 6 juveniles; Riviera Beach, Texas, U.S. A; 27°17.20' N, 97°10.19' W; S.E. LeCroy; 2 May1999; under wrack principally consisting of Halodule ; ARC 79190. 4 males, 11 females, 5 juveniles; Port Mansfield, Texas, U.S.A.; 26°34.13' N, 97°25.73'W; S.E. LeCroy; 1 May 1999; from Syringodium wrack; ARC 79191. 7 males, 5 females, 4 juveniles; South Padre Island, Texas, U.S.A.; 26° 0 4.69' N, 97°10.19' W; S.E. LeCroy 30 May 1999; ARC 79192.

Maximum body length (N = 222): males 14 mm, females 9 mm.

Diagnosis. Small talitrids (<14 mm). Antenna 2, flagellum with 13–18 articles in adult males; ovigerous female antenna 2 with 11–13 articles, oostegite 2 with 17–35 marginal setae; telson, each lobe with 1 distal dorsolateral robust seta; dorsal pigment pattern in both sexes diamond-shaped on cephalon (may be absent), linear, quadrate or diamond-shaped on mid-line of pleon (always present).

Description. Based on male holotype, 11.5 mm.

Cephalon (Fig. 3): Deeper than long; eyes round, with less than one diameter between them when viewed dorsally. Antenna 1 short, not or little exceeding the junction between peduncle articles 4 and 5 of antenna 2; flagellum 6-articulate. Antenna 2 short, reaching only to second peraeon segment, peduncle slightly incrassate; flagellum 18-articulate, slightly longer than peduncle, each article with two groups of bristles, within each group, some bristles directed forward, some laterally.

Mouthparts (Fig.3): Upper lip sub-ovate, 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 3–5-dentate incisor, 2–3-dentate lacinia mobilis. Maxilla 1, inner plate narrow, with 2–3 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 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 3–4 robust 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 2–3 robust setae.

Peraeon: Gnathopod 1 ( Fig. 4 ), coxa shield-shaped, with slender setae along ventral margin; basis long, expanded distally, with small robust setae on anterior and posterior margins; ischium and merus, strong robust setae present on posterior margins; carpus and propodus subequal in length, 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 ( Fig. 4 ), coxa quadrate, with small robust setae on ventral margin; basis long, abruptly expanded posteroproximally; propodus and dactylus enlarged, 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 robust setae on ventral margin, small notch present on anterodorsal corner, robust setae and small notches repeated on peraeopods 4–5 ( Fig.4 ); coxal gill sac-like. Similar notches on peraeopods 3–5 were absent in males from other populations of the same species. Peraeopod 4 ( Fig.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 ( Fig. 4 ), 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; propodus with long, fine “comb” setae present in 4 clumps near distal tip, setae approximately half length of dactylus ( Fig. 4 , maximum length = 248 microns), first clump of small setae directed anteroventrally, second clump of long setae directed ventrally, third clump of short setae at posterodistal tip of propodus directed posteroventrally, fourth clump of a few small comb setae near distal group of robust setae on posterior margin of the propodus.

Pleon: Pleopods slightly reduced, inner ramus slightly longer than outer, both rami slightly shorter than peduncle, peduncle of each pleopod with pair of hooked coupling robust setae on inner margin, fine marginal hairs present on outer margin; rami of 8–9 articles, each bearing pair of long, plumose setae. Pleopod 1 bears 6 simple robust setae along inner mid-line of peduncle, with only two each in pleopods 2–3.

Urosome: Uropod 1, peduncle, inner and outer margins with 7 robust setae each; inner ramus approximately one-half length of peduncle, with 2 terminal and 2 marginal robust setae; outer ramus approximately three-quarters length of peduncle, with 4 terminal robust setae, without marginal robust setae. In all other specimens examined the inner and outer rami were subequal in length so the holotype inner ramus length is an artefact. Distolateral robust seta absent. Uropod 2, peduncle with two rows of robust setae, one row with 2 larger distal setae, plus 4 smaller setae, the second with 3 stout marginal robust setae; rami approximately equal in length, slightly shorter than peduncle, with 4–5 terminal and 3 marginal robust setae; inner ramus with 2 robust setae on lateral surface. Uropod 3 small, peduncle slightly longer than ramus, armed with 4 long and 2 short robust setae distally; ramus with 5 subequal terminal and 3 marginal robust setae. Telson (Fig. 3) heart-shaped, with mid-dorsal groove forming a notch distally; each lobe with 4 apical robust setae, 1 distal dorsolateral robust seta, 4 proximal dorsolateral robust setae (one is missing from right lobe).

Allotype: with similar body colouration and epidermal pigment markings as the holotype.

Sexually dimorphic differences include: Antenna 2, peduncle not quite as thick or long as in male; flagellum 12-articulate. Gnathopod 1 ( Fig. 4 ) without rounded posterior lobes on carpus and propodus; dactylus longer than palm. Gnathopod 2 ( Fig. 4 ) basis widest medially, expanded anteriorly in deep, smooth convex curve; carpus and propodus with rounded posterior marginal lobe, with fine palmate setae; propodus and dactylus not enlarged. Oostegite on gnathopod 2 spatulate, exceeding length of the basis, with 22 long, thin, simple marginal setae; FIGURE 3. M. c. carpenteri n. subsp. Habitus drawing of male, 12 mm, Hagen’s Cove, Fl. Mouthparts and telson of male holotype, 11.5 mm body length, Tiger Tail Beach, Fl. (USNM 1218141). Uropods from ovigerous female allotype, 8.0mm from Tiger tail Beach (USNM 1218142). Scale bars all 37.5µ, except LL = 18.8µ, T = 225µ and uropods = 500µ.

oostegites on peraeopods 3–5 are successively smaller, with setal numbers of 19, 16 and 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.4 ), propodus length approximately 6 times width, clusters of propodal “comb” setae absent.

Etymology. The species name commemorates the marriage of Clare Wildish and Jamie Carpenter at Marco Island on 4th March, 2004. Pronunciation: car pent air ii.

Epidermal pigment patterns. The general body colour of live animals from the type locality was pale white, similar to the sand on which they live, with epidermal pigment markings which were bright red in colour. The markings occurred both on the dorsal and lateral parts of the body, but only the former are illustrated here ( Fig.5 ). Dorsal pigment patterns (DPP) of M. c. carpenteri n. subsp. from Tiger Tail Beach samples were found to be highly variable, with DPPs ranging from relatively heavily pigmented ( Fig. 5 A) to nearly absent ( Fig. 5 D). Individuals showing various stages of loss of DPP were present at the type locality as shown in Fig.5 . Even in the individuals with the most reduced DPP, mid-line blotches of epidermal pigment were present on the pleon ( Fig. 5 D). There was no evidence of sexual dimorphism in DPPs; similar patterns were present in both sexes.

In addition to Tiger Tail beach material, we examined the DPP’s of five different populations of M. c. carpenteri n. subsp., distant from the type locality, all of which occupied the same ecotope (supralittoral wrack) and differed from individuals at the type locality (see below). All of these populations had essentially similar DPPs and examples are shown in Fig. 6 . The supralittoral wrack samples showed little intra-population variation and were more heavily pigmented than the most pigmented individuals from Tiger Tail Beach. A characteristic feature was the presence in the last peraeon segment of a U or W shape made by the epidermal pigments (incomplete in Fig. 5 A–D).

Distribution. Northwestern Atlantic: Titusville to Ft. Lauderdale, Florida. Gulf of Mexico: Lower Florida Keys to South Padre Island, Texas.

Figures

FIGURE 4. M. c. carpenteri n. subsp. Appendages of male holotype, 11.5 mm, Tiger Tail Beach, Fl (USNM 1218141), except Gn 1 F, Gn 2 F from ovigerous female allotype, 8 mm, from same locality (USNM 1218142). Scale bars = 500 Μ, except magnification of tip of P 7 = 100 Μ.

FIGURE 5. M. c. carpenteri n. subsp. Representative polymorphic dorsal epidermal pigment patterns from Tiger Tail Beach, Fl specimens (BL not measured). A: male 2004, B: male 2007, C: male 2007, and D: male 2007.

FIGURE 6. M. c. carpenteri n. subsp. Representative dorsal epidermal pigment patterns of specimens from various locations in Florida in 2007. A: female, 8 mm, Cedar Key; B: female, 8 mm, Hagen’s Cove; C: male, Lower Suwanee marsh; D: female, John U. Lloyd Park, Ft. Lauderdale. (BL not measured if not given).