Strianassa lerayi Anker 2020, sp. nov.
Creators: name: Anker, Arthur
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Laomediidae
Strianassa
Strianassa lerayi

description: Strianassa lerayi sp. nov.
Figs. 1–6
Type material. Holotype: male (cl 5.4 mm), FLMNH UF 53414, Panama, Pacific coast, Coiba Archipelago, Canales de Afuera, Isla Afuerita, small bay on north-eastern side of island, 7°42’17.3”N– 81°38’06.3”W, shallow subtidal flat with rocks, corals and rubble, depth: 0.5–1 m at low tide, snorkeling, under large rock, leg. A. Anker, 23 February 2019 [fcn PAN-254].
Description. Body weakly calcified, with relatively thin integument. Carapace somewhat elongate, subcylindrical, slightly compressed laterally, smooth, with erect setae of various length, latter more numerous on dorsal surface; cervical groove deep, crescent-shaped in dorsal view; linea thalassinica almost straight, running entire length of carapace from post-ocular margin to posterolateral margin; anterolateral margin feebly produced anteriorly, with deep notch; pterygosmial margin broadly rounded; pterygostomial and branchiostegial margins fringed with setae (Figs. 1, 2D).
Rostrum broadly rounded-triangular, as long as wide at base, not tapering distally; apex with strong, subtriangular, distinctly up-turned tooth; lateral margins armed with two or three strong, widely spaced, distally rounded, anteriorly directed, somewhat up-turned teeth, all positioned in distal half of rostrum; dorsal surface with one middorsal and two lateral shallow depressions, and with numerous, blunt or subacute, usually more or less anteriorly directed teeth, their disposition as following: two short submedian longitudinal rows of two or three teeth on each side of median depression; small field of four more irregularly placed teeth posterior to submedian teeth; two more lateral and more posterior teeth at imaginary carapace-rostrum limit (apparently present only on left side); row of three teeth on low crest situated near proximolateral margin, adjacent to deep notch of anterolateral margin of carapace; ventral surface of rostrum unarmed (Fig. 2 A–C).
Pleon smooth; dorsal surface with scattered setae of various length; first pleuron short, ventrally produced into blunt lobe, latter furnished with setae; second to fifth pleura with ventral margins broadly rounded, with blunt rounded distoventral angle, fringed with some stiff setae locally; sixth pleonite with blunt distolateral lobe (Fig. 1). Telson broad, slightly constricted proximally, smoothly tapering posteriorly, about 1.3 times as long as wide at base; posterior margin broadly rounded; dorsal surface and all margins unarmed (Fig. 2E).
Eyes fully concealed in dorsal view, visible in lateral view; eyestalk distally somewhat produced, with small blunt tubercle subdistally; cornea relatively small compared to eyestalk, in lateral-subterminal position, with moderate pigmentation (Fig. 2 A–C).
Antennular peduncle with third article elongate, subcylindrical, slender, falling short of half-length of fourth article of antenna; ventral flagellum slender, distinctly shorter than much stouter dorsal flagellum, latter with two single and three pairs of sensorial setae (aesthetascs) distally (Fig. 2A, B). Antenna with robust basicerite bearing rounded distoventral lobe; scale (= scaphocerite, acicle) short, relatively broad at base, tapering distally, simple, tip not reaching 0.2 length of fourth article of antennal peduncle; fourth article of antennal peduncle elongate, subcylindrical, much stouter than third article and antennular peduncle (Fig. 2A, B).
Mouthparts typical for family. Mandible with palp subdivided into three articles, distal-most longest, densely furnished with setae on dorsal surface; incisor process square-shaped, with medium-sized distal teeth; molar process partly fused with incisor process, with two blunt cusps (Fig. 3A). Maxillule with broad, proximal (coxal) endite and smaller, rounded distal (basial) endite; palp (endopod) with two articles (Fig. 3B). Maxilla with proximal (coxal) endite subdivided by deep cleft into much larger proximal lobe and small distal lobe; distal (basial) endite subdivided by deep cleft into smaller proximal lobe and larger distal lobe; palp (endopod) entire; scaphognathite large, its ventral margin with seven or so elongate setae extending posteriorly into branchial chamber (Fig. 3C). First maxilliped with stout, square-shaped proximal (coxal) endite; distal (basial) endite moderately developed; endopod widening distally, with trace of subdivision (barely distinct line); exopod reaching beyond endopod, composed of three articles, most proximal one much longer and broader than two distal ones; epipod relatively small; single arthrobranch moderately developed (Fig. 3D). Second maxilliped with endopod composed of four articles, proximal article integrating basis, ischium and merus; exopod reaching far beyond endopod, composed of three articles, most proximal one much longer and broader than two distal ones; epipod with elongate, curved, posterior process, podobranch hypertrophied; two arthrobranchs present (Fig. 3E).
Third maxilliped pediform, relatively slender; ischium slightly shorter than merus, with well-developed crista dentata consisting of 16 teeth, including two small, well-spaced proximal teeth, distal-most tooth largest; merus with two small spaced teeth on distal third of ventral margin; carpus slightly curved, about half-length of merus, with dense field of setae on dorsal surface; propodus as long as merus, broadened; dactylus about 0.6 times as long as propodus, distally tapering; all endopodal articles with long fine setae, especially along ventral margin; exopod short, entire, overreaching half-length of ischium; epipodal complex with cluster of five setobranchs near its base, one rod-shaped mastigobranch, large bipartite epipod with proximal, marginally toothed lamella and distal, slender, setose lobe, latter with two subdivisions, and well-developed podobranch; two arthrobranchs present (Fig. 3 F–H).
First pereiopods (chelipeds) stout, somewhat unequal in length and asymmetrical in shape, i.e. dissimilar in size and proportions of meri, carpi and chelae, and with slightly different dentition on finger cutting edges (Fig. 4, see also Fig. 6). Major cheliped robust; ischium with four well-spaced teeth along ventral margin, distal-most strongest; merus markedly inflated, with strongly convex dorsal and ventral surfaces; ventromesial margin with two widely spaced, sharp teeth, one near proximal margin and one at about 0.6 of merus length; carpus somewhat cup-shaped, with more protruding ventral portion; ventrolateral surface with several blunt tubercles; chela somewhat compressed laterally, somewhat rectangular in shape; palm about 1.5 times as long as high, both mesial and lateral surfaces covered with granules and rugosities, especially dorsally and closer to ventral margin; fingers about 0.6 length of palm, very stout, pollex and dactylus subequal; cutting edge of pollex with one larger tooth at about 0.4 length and some irregularly shaped, lower teeth in distal half; dactylus with blunt, longitudinal, parallel-running ridges and row of blunt tubercles proximally on mesial surface, cutting edge with low blunt teeth or rugosities (Fig. 4A, B). Minor cheliped noticeably shorter and less robust than major cheliped; ischium and merus with armature very similar to that of major cheliped; ischium with five well-spaced teeth along ventral margin, distal-most strongest, and minute ventrolateral tubercle proximally; carpus much smaller than that of major cheliped, less protruding ventrally, lateral and ventrolateral surfaces with blunt tubercles; chela noticeably compressed laterally, somewhat rectangular in shape; palm about 1.7 times as long as high, both mesial and lateral surfaces covered with granules and rugosities, especially dorsally and closer to ventral margin; fingers about 0.8 length of palm, moderately stout, pollex and dactylus subequal, crossing distally; cutting edge of pollex with two larger teeth at about 0.3 and 0.7 of pollex length, respectively, and some irregularly shaped, lower teeth between them; dactylus with blunt, longitudinal, parallel-running ridges, cutting edge almost straight, with one small tooth at about 0.7 of dactylar length (Fig. 4 C–E).
Second pereiopod relatively stout; ischium with minute bumps marking insertions of setae; merus, carpus and propodus smooth, with numerous long flexible setae along ventral margin; carpus about 0.3 length of merus and half as long as propodus; dactylus about 0.6 length of propodus, with crenulated ventral margin (Fig. 5A). Third pereiopod moderately slender; ischium, merus and carpus smooth, with few setae; carpus slightly less than halflength of merus and about 0.7 length of propodus; propodus with distoventral brush of stiff setae; dactylus about 0.8 length of propodus, dorsal margin with row of stout corneous spines or spiniform setae, increasing in size distally, distoventral margin slightly expanded, with comb-like row of minute setae (Fig. 5B, C). Fourth pereiopod generally similar to third pereiopod, somewhat more slender; epipodal complex with podobranch (Fig. 5D, E). Fifth pereiopod noticeably slenderer than third and fourth pereiopods, subchelate; ischium, merus and carpus smooth; ischium shorter than that of fourth pereiopod; carpus about 0.6 length of merus and 0.8 length of propodus; propodus ending in short blunt tooth, latter partly concealed by thick stiff setae extending from about 0.4 of propodus length to distal margin; dactylus subspatulate, somewhat twisted and excavated mesially, with comb-like row of minute setae subdistally (Fig. 5F, G).
First pleopod absent in male (Fig. 1). Second to fifth pleopods similar, biramous, with unarmed protopods, with narrow exopod and endopod, without further distinguishing features (Fig. 1). Uropod with broadly ovate exopod and endopod; protopod with two rounded lobes; exopod without transverse suture (diaeresis); dorsal surface of exopod with several, posteriorly directed, acute or subacute teeth, viz. five teeth in distolateral field, at some distance from lateral margin, and six teeth aligned in transverse-oblique row running almost parallel to distal margin, mesial-most teeth of this row distinctly exceeding distal margin; lateral margin of exopod with four posteriorly directed, subacute teeth increasing in size towards posterior, and stout distolateral spiniform seta adjacent to distal-most tooth of lateral margin; endopod almost as long as exopod, slightly narrower; dorsal surface with longitudinal median ridge armed with row of five posteriorly directed, subacute teeth, most-distal tooth not reaching distal margin; lateral margin with small blunt tooth at about mid-length (Fig. 2H).
Gill/exopod formula as given for genus.
Colouration. Overall whitish, most of carapace, pleon, tail fan and most appendages (e.g. antennules, antennae, ambulatory pereiopods, pleopods) covered with orange-brown, difficult to detach, thin crust of mixed organic and inorganic (possibly containing iron) origin (Fig. 6). Similar type of crust of orange-brown or dark-brown colour was reported in some species of Axianassa (Anker 2010; Anker & Pachelle 2016; Komai & Fujita 2019).
Etymology. The new species is named after the author’s friend and colleague, Dr. Matthieu Leray, for his invitation to participate in the highly successful expedition to the Coiba Archipelago in February 2019, during which three new genera and one new species of decapod crustaceans were collected and described (Anker 2020 a, 2020b, 2020c; present study).
Ecology. The holotype of S. lerayi sp. nov. was collected on a shallow subtidal flat situated near a narrow channel between a larger island and smaller rocky islands (Fig. 7), about 5 m from a steeply descending rocky shore, at a depth of about 0.5–1 m at low (incoming) tide. The entire subtidal flat was affected by a strong cold current coming from the open ocean through several breaches between large rocky outcrops. The bottom was composed of sand, silt-mud (patchy), fragmented corals, larger pieces of coral rubble and coral rocks, as well as some living corals (e.g. small colonies of Pocillopora). The specimen was found in a slightly muddier area, under a very large rock.
Distribution. Presently known only from the type locality in the Coiba Archipelago, Pacific coast of Panama.
Remarks. See discussion under the genus.
description: Published as part of Anker, Arthur, 2020, Strianassa lerayi gen. et sp. nov., a new laomediid mud-shrimp from the eastern Pacific, with new records of Axianassa ngochoae Anker, 2010 and Heteroaxianassa heardi (Anker, 2011) in the western Pacific (Malacostraca: Decapoda: Gebiidea), pp. 523-539 in Zootaxa 4820 (3) on pages 526-531, DOI: 10.11646/zootaxa.4820.3.6, http://zenodo.org/record/4398178