Rapimenes, Ďuris, Zdenek & Horka, Ivona, 2017

Ďuris, Zdenek & Horka, Ivona, 2017, Towards a revision of the genus Periclimenes: resurrection of Ancylocaris Schenkel, 1902, and designation of three new genera (Crustacea, Decapoda, Palaemonidae), ZooKeys 646, pp. 25-44 : 33-35

Rapimenes gen. n.

Type species.

Periclimenes granulimanus Bruce, 1978, by present designation.

Included species.

Rapimenes brucei ( Ďuriš, 1990), comb. n.; Rapimenes granulimanus (Bruce, 1978), comb. n. (Fig. 3H); and Rapimenes laevimanus ( Ďuriš, 2010), comb. n. (Fig. 3G).

Material examined.

In addition to the type series ( Ďuriš 2010), the following specimens were subsequently examined: Rapimenes granulimanus - 6 spms, (MNHN-IU-2013-10931), 1 spm. (IU-2013-11097), 2 spms (IU-2013-11077), Papua Niugini Expedition 2012, Madang Lagoon, Papua New Guinea, Dec. 2012, coll. Z Ďuriš. - Rapimenes laevimanus - 3 spms (UO-Jp2012), Nago-city, Okinawa, Japan, 26°33,6'N, 127°57.6'E, 10 May 2012, depth 30 m, on sea pen cf. Stylatula sp. [ Pennatulacea ]; coll.: N Sirakawa & Y Yamada, lgt. R Minemizu.-1 spm. SW Taiwan, coll. C-W Lin (fcn 20130202-08).

Diagnosis.

Medium sized shrimps. Carapace smooth, with antennal and hepatic teeth; epigastric tooth lacking or, if present, clearly separated from them; hepatic tooth subequal and situated posteriorly of antennal tooth and slightly below. Rostrum slender, dorsal lamina bearing 6-10 teeth, ventral lamina obsolete, with 1-2 subterminal teeth. Inferior orbital angle produced, rounded. Pleon smooth, pleura posteroventrally rounded; telson slender, tapering distally, with 1-2 pairs of small dorsal spines and three pairs of posterior marginal spines. Ophthalmic somite without interocular process. Antennula and antenna normal, scaphocerite 3-4 times longer than broad. Eye with globular cornea and small accessory pigment spot, stalk distinctly longer than corneal diameter. Mandible without palp, incisor and molar processes stout. Maxillula with bilobed palp, upper and lower laciniae well developed. Maxilla with slender palp, well developed scaphognathite, distal (basal) endite bilobed; proximal (coxal) endite lacking. First maxilliped with simple palp, basal endite broad, coxal endite feebly demarcated, exopod well developed, caridean lobe normal, epipod distally bilobed. Second maxilliped with normal endopod and exopod, epipod small, simple, without podobranch. Third maxilliped with slender segments, ischiomerus and basis fused; exopod well developed, coxa with rounded lateral plate, single small arthrobranch present. Fourth thoracic sternites without special structures. First pereiopods slender, fingers narrow, simple, with dense tufts of long setae on sides, coxa with or without distoventral setose process, basis unarmed. Second pereiopods long and slender, distinctly unequal in length; major pereiopod overreaching scaphocerite by distal part of merus in adults; fingers simple, cutting edges entire or with 1-2 feebly developed teeth on proximal third of minor chela, and with 2-4 obtuse proximal teeth on major chela fingers; major pereiopod with palm 2.5-5 times longer than fingers. Ambulatory pereiopods slender, propodus with prehensile structure of long straight distoventral spines arranged to 2-5 pairs, spines longer than distal propodal depth; dactyli slender and curved, simple, or with distinct or minute distoventral tooth. Endopod of first male pleopod with angulate apex and distinct medial lobe; second male pleopod with appendix masculina with 3 terminal serrated setae and 2 lateral setae. Uropods normal; distolateral angle of exopod with small tooth and movable spine medially.

Etymology.

Combination of rapina, Latin for claw, to point on the prehensile structures on the ambulatory legs, and the name of the genus Periclimenes Costa, 1844, from which the new genus is separated; gender masculine.

Figures

(selected). Bruce (1978: figs 16-19), Ďuriš (1990: figs 1-2; 2010: figs 1-8).

Systematic position.

Based on the recent molecular phylogeny in Horká et al. (2016), the therein included two species of Rapimenes gen. n. are closely related to the genus Phycomenes Bruce, 2008, and to a pair of further Periclimenes spp., i.e. Periclimenes affinis , and Periclimenes kallisto , positioned near to Ancylocaris brevicarpalis comb. n. From Phycomenes , the species of the genus Rapimenes gen. n., can be easily distinguished by their larger size, distinctly unequal second pereiopods, prehensile ambulatory legs, and lack of a triangular process on the fourth thoracic sternum (see Bruce 2008b, Ďuriš 2010). Morphologically, the new genus (i.e. the previous " Periclimenes granulimanus group") is phylogenetically close to the " Periclimenes obscurus group", as already indicated by Eilbracht and Fransen (2015) who also listed the characters distinguishing all species of those two groups. Included in the " Periclimenes obscurus group" are some species which show distinct similarities to Rapimenes , such as Periclimenes macrorhynchia Eilbracht & Fransen, 2015, Periclimenes nomadophila Berggren, 1994, and Periclimenes tonga Bruce, 1988 (the latter synonymized with Periclimenes granulimanus by Marin 2012, but regarded as valid by Eilbracht and Fransen 2015), particularly in the shape and proportions of the pereiopods and rostrum. These species have biunguiculate walking dactyli, sternal thoracic ridges, and distinct setose coxal lobe on the first pereiopod, i.e. the characters typical for the " Periclimenes obscurus group". The ambulatory dactyli vary in Rapimenes spp. from simple to bearing a minute additional tooth; the latter is true for Rapimenes brucei , new comb., for which a coxal setose lobe also was reported ( Ďuriš 1990). It is thus possible that both species groups represent a common evolutionary clade which inner diversity is still to be resolved.

Distribution.

Madagascar; Maldive Islands; Indonesia; Vietnam and Taiwan, South China Sea; Japan; Heron Island, Great Barrier Reef, Australia.

Ecology.

The species of the present genus have been recorded as associated with antipatharians, hydroids, pennatularians, and scyphozoans ( Cnidaria) ( Bruce 1978, 1988, Ďuriš 1990, 2010, Minemizu 2013, Eilbracht and Fransen 2015).

Remarks.

The generic name Rapimenes was used as a nomen nudum by Marin (2009: 15) in reference to the then undescribed species Periclimenes laevimanus Ďuriš (2010), as " Rapimenes laevimanus Ďuriš & Petrusek (in press)". The name is herein validly reinstated for the genus, indeed now containing Rapimenes laevimanus .

Key to species identification of Rapimenes gen. n.

(modified from Ďuriš 2010).