Periclimenes rincewindi, Grave, Sammy De, 2014

Grave, Sammy De, 2014, A new species of crinoid-associated Periclimenes from Honduras (Crustacea: Decapoda: Palaemonidae), Zootaxa 3793 (5), pp. 587-594 : 588-593

Periclimenes rincewindi sp. nov.

(Figs. 1–4)

Periclimenes cf meyeri .— Humann et al., 2013: 109 (photo, Bay Islands, Honduras) Periclimenes sp.— Charteris, 2012: 177 (photo, Roatan, Honduras)

Material examined. Holotype, ovigerous female (pocl 3.0 mm), Sandy Bay, Roatán Island, Islas de la Bahia, Honduras, 18 m depth, on Analcidometra armata , leg. M. Charteris, Febr. 2010, OUMNH.ZC.2014-01-004; paratype, male (pocl 1.6 mm), Flower Bay, Roatán Island, Islas de la Bahia, Honduras, 10 m depth, on Analcidometra armata , leg. M. Charteris, Jan. 2010, OUMNH.ZC.2014-01-005.

Etymology. Rincewind is a fictional wizard in several Discworld novels by Terry Pratchett, who is well known for his ability to blend in with any situation, despite his penchant for colourful clothing. Used as a noun in the genitive case.

Description. Rostrum nearly horizontal (Figs. 1A–B, E), reaching to midlength of distal segment of antennular peduncle; dorsal margin armed with 10 teeth in holotype female, 6 in male paratype, posterior tooth placed at level of orbital margin or slightly posterior to it; ventral margin armed with four teeth in distal half in holotype female, two in paratype male; midrib equidistant from dorsal and ventral margin of rostrum proximally. Antennal tooth distinct, reaching to distal angle of orbital margin, subequal in size to hepatic tooth (Fig. 1A).

Pleura of third and fourth abdominal somites distally rounded (Fig. 1C), fifth bluntly angular; third somite with somewhat distinct dorso-distal cap; sixth somite with posterolateral margin produced into polygonal lobe (Fig. 1D), posteromedial margin produced into distinct tooth.

Telson slightly longer than sixth somite (Fig. 1C); with two pairs of dorsal spines (Fig. 3A), proximal pair at about 0.6 of telson length, distal pair at 0.9 (Fig. 3A); distal margin with two pairs of spines and one (mesial) pair of stout, plumose setae (Fig. 3B), intermediate pair longest, about 4.0 times as long as lateral ones; terminal process between mesial setae present.

Eyes with cornea slightly narrower than and about half as long as eyestalk; ocellus distinct (Fig. 1F).

Antennular peduncle (Fig. 1H) with slender and sharp stylocerite, falling short of mid-length of basal segment; distolateral margin of basal segment produced into 3 broad teeth, two lateral-most ones more narrow (Fig. 1I); distal segment 1.5 times as long as penultimate; lateral antennular flagellum with branches fused for 5-6 segments, free part of shorter branch consisting of 2-3 segments, distinctly shorter than fused segment.

Antennal scale (Fig. 1G) reaching to distal margin of distal segment of antennular peduncle, approx. 2.5 times as long as broad; lateral margin straight, distal tooth falling far short of distal margin of blade, distal margin anteromesially produced; basal segment of antennal peduncle with sharp lateral tooth.

FIGURE 1. Periclimenes rincewindi n. sp. A, carapace, frontal margin, lateral; B, same, dorsal; C, pleon; D, sixth somite; E, rostrum, lateral; F, eye, dorso-lateral; G, antenna; H, antennule; I, same, distolateral angle of basal segment; J, mandible. Holotype (A–D, G–I), paratype (E–F, J). Scale bar indicates 0.5 mm (F), 0.75 mm (C–B), 1 mm (A), 1.5 mm (D–E, G–H) or 2.5 mm (I–J).

FIGURE 2. Periclimenes rincewindi n. sp., holotype. A, first pereiopod, B, same, chela; C, major second pereiopod; D, same, chela; E, same, distal; F, minor second pereiopod, G, same, chela; H, same, distal; I, third pereiopod, J, same, dactylus; K, fourth pereiopod; L, same, dactylus; M, fifth pereiopod, same, dactylus. Scale bar indicates 2 mm (A, C–D, F–G, I, K, M), 1 mm (E, H) or 0.5 mm (B, J, L, N).

Mandible (Fig. 1J) with widely separated incisor and molar process; molar process of usual type for genus; incisor process narrow, distally armed with 4 teeth.

First pereiopod (Figs. 2A–B) just overreaching antennal scale by tip of fingers; fingers unarmed, subequal in length to palm; carpus approx. twice as long as chela and subequal in length to merus. Second pereiopods subequal and similar in size and shape. Major cheliped (Figs. 2C–E) overreaching antennal scale by two-thirds of carpus; fingers not ornamented, cutting edges non-denticulate, tips simple; carpus two-thirds in length of chela and of equal length to merus; ischium slightly shorter than merus. Minor cheliped (Figs. 2F–H) more slender and slightly shorter than major cheliped, reaching to mid-length of major cheliped palm; fingers not ornamented, cutting edges non-denticulate, tips simple; carpus subequal in length of chela and of equal length to merus; ischium slightly shorter than merus.

Third (Figs. 2I –J) and fourth (Figs. 2K–L) pereiopod similar in size and structure; dactyli unguiculate, unguis poorly demarcated; propodus about almost six time as long as dactylus, distal margin of flexor margin unarmed, distolateral margin armed with pair of slender spines; carpus two-thirds as long as propodus, unarmed; merus subequal to propodus. Fifth pereiopod (Figs. 2M–N) slender, similar to fourth in proportions; setal brush poorly developed, consisting of single row of 3-4 comb-like setae.

Uropods (Figs. 3C–D) typical for genus, slightly over-reaching telson; exopod somewhat broader than endopod, transverse suture distinct, disto-lateral tooth and associated spine well developed, spine twice as long as tooth.

First pleopod of male with endopod entire, not bilobate. Second pleopod of male (Fig. 3E) with appendices masculina and interna on endopod; appendix masculina slightly shorter than interna (Fig. 3F), provided with four subdistal/distal serrulate setae.

Color in life. Carapace semi-transparent with scattered red to dark red spots; anterior to eyestalks background colour white to light pink, incl. rostrum; lower margin of carapace with series of large red to dark red spots. Abdomen semi-transparent up to and including fifth somite; dorsal margin with broad orange to pink stripe, with scattered red to dark red spots; lower margin with series of darker spots, positioned above white to pinkish pleopods. Sixth somite pink background colour with single, large red spot dorsally near articulation with telson; telson and uropods similar. Pereiopods orange to pink in background colour, with single, large spot at joints.

FIGURE 4. Periclimenes rincewindi n. sp. A, holotype, in situ; B–C, non-collected specimen, in situ; D, non-collected specimen, on host.

Remarks. In general morphology, P. rincewindi sp. nov. appears closely related to the other three crinoid dwelling species of the genus in the western Atlantic, P. crinoidalis , P. meyeri and P. bowmani , sharing a similar ornamentation of the distolateral angle of the basal segment of the antennular peduncle, as well as similar chelipeds. The new species differs from P. bowmani in that the third abdominal somite is posteriorly produced into a low hump or cap (a feature it shares with the other two species), the feebly developed chelipeds, differences in the molar structure of the mandible, as well as the proportions of the carpus of the first pereiopod. The new species differs from P. meyeri primarily by the different structure of the mandibular incisor process, being flared in P. meyeri and not flared in P. rincewindi sp. nov. Further differences are the absence of a minute tubercle on the dactyls of the ambulatory pereiopods (vs. present in P. meyeri ) and the carpus of the first pereiopod being twice as long as the chela (vs. carpus being only slightly longer in P. meyeri ).

Morphologically, the new species is most closely related to P. crinoidalis , a known symbiont of Nemaster grandis , sharing a similar rostral morphology, presence of a posterodorsal hump on third abdominal somite, a very similar ornamentation of the distolateral angle of the basal segment of the antennular peduncle, similar incisor process and weakly developed chelae. Both species can be distinguished on the basis of the following characteristics: 1) carpus of first pereiopod twice as long as chela in P. r i n ce w i n di vs. at most 1.2 times as long in P. crinoidalis ; 2) denticle on carpus of ambulatory pereiopods absent in P. rincewindi vs. minute, but always present in P. crinoidalis ; 3) terminal process on telson present in P. rincewindi vs. absent in P. crinoidalis and 4) pleuron of fifth somite bluntly angular in P. rincewindi vs. rounded in P. crinoidalis . A further difference may lie in the number of ventral rostral teeth, with Chace (1969) indicating only a single, often inconspicuous subapical tooth is present in most specimens, with however three being distinct in larger females. The holotype specimen of P. rincewindi (of similar size to adult P. crinoidalis ) harbours four ventral teeth, whilst the paratype male has two. This character will need to be confirmed in more material, before its utility can be confirmed.

Both species also differ in their host preference, as P. crinoidalis appears to exclusively associate with Nemaster grandis (see Chace, 1969; Criales, 1984) whilst the new species has only been recorded from Analcidometra armata .

The colour pattern of P. rincewindi is very distinctive and will likely prove a useful identification aid in the field and be fully species specific. However a comparison with P. crinoidalis can currently not be made, as colour photos in several guide books (e.g. Humann et al., 2013) of P. crinoidalis appear to refer to the related P. bowmani , which is exclusively known from Davidaster rubiginosa (see Criales, 1984).

Ecology. All known individuals were inhabiting Analcidometra armata (Pourtalès) (Crinoidea: Colobometridae ) in water depths of 10- 18 m.

Distribution. Currently only known from the type locality, Roatán Island, Islas de la Bahia, Honduras. As the host species is however, relatively widespread, if rare, across the wider Caribbean, it is anticipated that P. rincewindi will prove to be more widespread.