Leptalpheus marginalis Anker, 2011, sp. nov.
Creators: name: Anker, Arthur
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alpheidae
Leptalpheus
Leptalpheus marginalis

description: Leptalpheus marginalis sp. nov.
Figs. 1, 2
Type material. Holotype: male (cl 4.0 mm), USNM 1155316, Colombia, Caribbean coast, Ciénaga Porto Nao, Colcar sta. B-6B, 10°10'N 75°40'W, low tide, yabby pump, 19.07.1991. Paratypes: 1 male (cl 4.2 mm), USNM 1155317, same collection data; 1 male (cl 4.0 mm), USNM 1155318, Colombia, Caribbean coast, Ciénaga Porto Nao, Colcar sta. B-6A, 10°10'N 75°40'W, low tide, yabby pump, 18.07.1991.
Description. Frontal margin of carapace broadly rounded, without rostral projection; small orbital crests present near anterolateral margin, one in front of each eye (Fig. 1 A–C). Telson widest in proximal third, distally tapering; dorsal surface with two pairs of strong spiniform setae inserted in deep pits at some distance from lateral margin; posterior margin rounded, with two pairs of spiniform setae at posterolateral angles, lateral less stout and much shorter than mesial (Fig. 1 D).
Eyestalks with anteromesial margin bluntly projecting (Fig. 1 C). Antennular peduncles moderately stout, flattened dorsoventrally; stylocerite appressed, not reaching distal margin of first article; ventromesial carina with strong tooth bearing sharp distal point and concave anterior margin; second article almost twice as long as broad; lateral flagellum with secondary ramus short, stump-like (Fig. 1 A, B, E, F). Antenna with stout basicerite bearing strong distoventral tooth; scaphocerite ovate, with small, subacute distolateral tooth reaching slightly beyond anterior margin of blade; carpocerite stout, reaching well beyond scaphocerite and slightly beyond end of antennular peduncle; flagellum with proximal articles armed with short processes dorsomesially (Fig. 1 B, G, H). Mouthparts typical for genus. Third maxilliped with lateral plate on coxa extremely produced, sword-shaped, reaching far beyond arthrobranch, subacute distally (Fig. 1 I).
Major cheliped relatively slender; ischium with large, subacute, distal process on mesial face; merus somewhat twisted, depressed ventrally, ventrolateral, ventromesial and dorsal margins with small tubercles; carpus cupshaped, depressed and with two blunt processes ventrally; chela slender, with palm somewhat excavated and bearing numerous small, rounded tubercles ventrally, especially on margins of ventral depression and close to pollex; fingers about one third of palm length, twisted laterally, curved, not gaping when closed, cutting edge armed with seven-eight, more or less rounded teeth, largest rugose distally; adhesive disks absent (Fig. 2 A–E). Minor cheliped with ischium unarmed; merus slender, ventrally flattened, with smooth margins; carpus small, cup-shaped, chela slender, simple, with fingers slightly longer than palm, tips crossing distally; finger cutting edges with some rugosities or minute teeth (Fig. 2 F, G).
Second pereiopod with merus as long as carpus; carpus five-articulated, with article ratio approximately equal to 3: 1: 1: 1: 2.2 (Fig. 1 J). Third and fourth pereiopods similar; third pereiopod fairly slender, compressed; ischium unarmed; merus around 4.5 times as long as wide; carpus about half length of merus, with distoventral spiniform seta; propodus with three spiniform setae along ventral margin; dactylus about 0.4 length of propodus, conical, moderately slender, acute distally (Fig. 1 K). Fifth pereiopod slender, not compressed; propodus with three rows of setae distolaterally.
Male second pleopod with appendix masculina by far exceeding appendix interna, with at least three stiff setae on apex (Fig. 1 L). Uropod with lateral lobe of protopod ending in two broadly rounded teeth; exopod with slightly truncate distal margin; diaeresis straight laterally, deeply incised and with large tooth near mesial margin (Fig. 1 M).
Size. The type specimens range from 4.0 to 4.2 mm cl.
Colour in life. Not recorded.
Etymology. From Latin marginalis (marginal), referring to the orbital crests positioned at the anterolateral margin; used as an adjective.
Type locality. Colombia, Caribbean coast, Ciénaga Porto Nao (near Cartagena).
Distribution. Western Atlantic: presently known only from the type locality on the Caribbean coast of Colombia.
Ecology. No collection data other than yabby (suction) pump and low tide.
Remarks. Leptalpheus marginalis sp. nov. is distinguishable from all the other described species of Leptalpheus by the fingers of the major chela not gaping when closed (as in L. forceps, L. mexicanus), without a distal hiatus (as in L forceps), and with cutting edges armed with similar-sized subtriangular teeth (vs. armed only proximally in L. forceps, or with a very different armature in L. mexicanus, L. felderi, L. pierrenoeli, L. axianassae); the carapace with two orbital crests situated near the anterolateral margin, in front of the eyes (vs. without crests in L.
forceps, L. mexicanus, L. pierrenoeli, L. axianassae, or with crests situated more posteriorly, right above the eyes, in L. felderi); the lateral plate on coxa of the third maxilliped extremely produced dorsally, almost as long as antepenultimate article (feature shared only with L. cf. forceps, cf. Anker 2008, fig. 4D); and the antennal flagellum with the proximal dozen or so articles armed with short, sometimes spiny processes (usually one per article) on dorsomesial margin (absent in L. forceps, L. mexicanus, L. pierrenoeli, L. felderi, L. axianassae).
description: Published as part of Anker, Arthur, 2011, Six new species and three new records of infaunal alpheid shrimps from the genera Leptalpheus Williams, 1965 and Fenneralpheus Felder & Manning, 1986 (Crustacea, Decapoda), pp. 1-38 in Zootaxa 3041 on pages 4-5, DOI: 10.5281/zenodo.278802