A new pontoniine shrimp from Tahiti, French Polynesia (Crustacea, Decapoda, Palaemonidae) Author Bruce, A. J. text Zoosystema 2004 26 2 279 289 journal article 10.5281/zenodo.10113003 1638-9387 10113003 Epipontonia tahitiensis n. sp. ( Figs 1-4 ) HOLOTYPE . — French Polynesia . Tahiti, stn S(?) 11, 1982, coll. O. Odinetz , 1 ovig. ( MNHN Na. 15021). ETYMOLOGY. — Named after the locality of discovery: Tahiti. DIAGNOSIS. — Rostral dentition 6/1, supraorbital or paraorbital spines absent, incisor process of mandible well developed with numerous small teeth, second maxilliped with epipod, second pereiopods similar, unequal, third ambulatory dactyl biunguiculate, corpus and unguis ventrally denticulate. DESCRIPTION Small sized pontoniine shrimp of subcylindrical body form, in general closely resembling previously described species of the genus. Rostrum ( Fig. 1B ) compressed, about 0.44 of CL, 7 times longer than deep, slightly depressed, reaching to level of distal segment of antennular peduncle, with six small acute dorsal teeth, with one to three interdental setae, ventral border straight, non-setose, with single small preterminal ventral tooth. Carapace ( Fig. 1A ) smooth, glabrous, without epigastric, supraorbital and hepatic spines, orbit feebly developed, antennal spine well developed, submarginal, overlying small inferior orbital angle, anteroventral margin of branchiostegite produced, rounded. Abdomen without special features, pleura round- ed, sixth segment ( Fig. 1I ) strongly depressed, with small posterolateral process with acute upper tooth, ventrolateral process broadly expanded, posterolaterally acute. Telson ( Fig. 1J ) about 1.8 times sixth segment length, 0.55 of CL, 2 times longer than width, lateral margins convex, convergent, with two pairs of large submarginal dorsal spines ( Fig. 1L ), about 0.2 of telson length, at 0.2 and 0.5 of telson length, posterior margin ( Fig. 1K ) rounded, without median process, lateral spines small, 0.5 of dorsal spine length, intermediate spines robust, about 0.25 of telson length, submedian spines long, slender, non-setulose, slightly shorter than intermediate spines. Antennule ( Fig. 1C ) with proximal segment ( Fig. 1D ) with medial length 1.7 times longer than width, medial margin straight, non-setose, lateral margin feebly concave, with large acute distolateral lobe reaching beyond level of proximal dorsal margin of second segment, stylocerite broad, acute, reaching to about 0.45 of segment length, statocyst well developed, without statolith, ventromedial border with small acute tooth at about 0.5 of length; intermediate and distal segments short, subequal, combined equal to about 0.5 of proximal segment length; upper flagellum biramous, proximal three segments of rami fused, shorter free ramus with one segment, longer with five segments, with six groups of paired aesthetascs, each with a small black pigment spot ( Fig. 1E ) at about 0.2 of length; lower flagellum short with nine segments. FIG. 1. — Epipontonia tahitiensis n. sp. , ovigerous holotype (MNHN Na. 15021); A , carapace and rostrum; B , rostrum; C , antennule; D , same, proximal peduncular segment; E , same, aesthetasc; F , antenna; G , same, scaphocerite; H , eye; I , sixth abdominal somite, lateral; J , telson; K , same, posterior marginal spines; L , same, dorsal spine; M , uropod. Scale bars: A, C, F, H-J, M, 0.5 mm; B, D, G, K, L, 0.2 mm; E, 0.1 mm. Antenna ( Fig. 1F ) with basicerite robust, with long acute distolateral tooth, ischiocerite and merocerite short; carpocerite about 3.4 times longer than central width, reaching to about 0.6 of lamellar length of scaphocerite; flagellum short; scaphocerite ( Fig. 1G ) well developed, reaching to level of end of antennular peduncle, lamella about 2.5 times longer than width, anterior margin broadly convex, lateral margin sublinear with strong acute distolateral tooth, about 0.3 of lamella length, far exceeding lamellar margin. Eye ( Fig. 1H ) with oblique globular cornea, without accessory pigment spot; stalk about as long as wide, tapering slightly distally. Mandible ( Fig. 2A ) slender, without palp; incisor process ( Fig. 4B ) distally convex, with 12 small acute teeth, of decreasing size proximally; molar process ( Fig. 4C ) subcylindrical, distally truncate, with large acute tooth ventrally, dorsally carinate with upper and lower simple spines. Maxillula ( Fig. 2B ) normal, with bilobed palp ( Fig. 4D ), upper lobe small, lower lobe elongate, with small simple seta distally; upper lacinia broad, with 10 short stout serrulate spines and simple setae distally; lower lacinia short, subcylindrical, with numerous setae distally and ventrally. Maxilla ( Fig. 2C ) with elongate palp, with distal seta, with few short proximolateral setae; basal endite bilobed, lobes short, broad, each with about 14 simple setae distally, coxal endite obsolete, medial margin convex; scaphognathite broad, 2.5 times longer than central width. First maxilliped ( Fig. 2D ) with subcylindrical non-setose palp, basal and coxal endites fused, broad, medial margin straight with numerous slender simple setae, exopod with well developed small caridean lobe, slender flagellum, with four plumose terminal setae, with small feebly bilobed epipod laterally. Second maxilliped ( Fig. 2E ) of normal form, dactylar segment narrow, with numerous slender spiniform setae medially; exopod normal with four plumose terminal setae, coxa produced medially, with two slender setae; with small rounded epipod laterally, without podobranch. Third maxilliped ( Fig. 2F ) with endopod normal, ischiomerus and basis feebly separated, combined segment about 4.2 times longer than central width, tapering slightly distally, sparsely provided with slender simple setae medially, intermediate segment about half of combined antepenultimate segment length, subcylindrical, 3.3 times longer than width, medial margin with few robust spiniform setae; terminal segment about 0.66 of preterminal segment length, tapering distally, 3 times longer than proximal width, with long spiniform seta distally, subequal to segment length, with proximoventral serrulations, medial margin with numerous spiniform setae; exopod normal, with slender flagellum with four plumose terminal setae; coxa not medially produced, with rounded epipod laterally, without arthrobranch. Paragnaths ( Fig. 2G ) rounded, simple, deeply divided. First pereiopod ( Fig. 3A ) normal, extending beyond rostrum by distal third of merus, chela ( Fig. 3B ) with palm 3 times longer than deep, sub-oval in section, distal two thirds slightly tapering, fingers ( Fig. 4E ) 0.4 of palm length, sparsely setose, dactylus 4 times longer than proximal depth, subspatulate laterally, cutting edge entire, tips ( Fig. 4F ) bidentate, teeth simple, fixed finger similar; carpus 1.25 times chela length, 6.5 times longer than distal width, subcylindrical; merus 0.95 of carpal length, 5 times longer than central width; ischium subequal to chela length; basis and coxa normal, coxa with small setose medial process. Second pereiopods similar, unequal. Major second pereiopod ( Fig. 3C ) with chela ( Fig. 3E ) about 1.3 of CL, palm compressed curved dorsally ( Fig. 3D ), generally smooth, with small acute denticles along ventral margin, glabrous, 1.7 times longer than central depth, dactylus ( Fig. 4G ) about 0.4 of palm length, 2.7 times longer than deep, dorsal margin strongly convex, tip broadly acute, cutting edge sharp, entire, feebly convex, fixed finger similar, slightly shorter, stout broad acute tip, cutting edge deeply channeled, medial and lateral edges concave, entire; carpus about 0.35 of palm length, broadly expanded distally, smooth, unarmed; merus 0.45 of palm length, 2.1 times longer than central width, slightly expanded centrally, ventral margin with four small acute teeth, ischium subequal to meral length, 2.6 times longer than distal width, tapering proximally, ventral margin unarmed; basis and coxa without special features. Minor second pereiopod with chela ( Fig. 3F ) subequal to CL, 0.7 of major chela length, palm 1.9 times longer than deep, compressed, ventral border with numerous small acute denticles and long simple setae, fingers ( Fig. 4H ) about 0.47 of palm length, dactylus 2.3 times longer than central depth; proximal segments as in major chela, slightly smaller. FIG. 2. — Epipontonia tahitiensis n. sp. , ovigerous holotype (MNHN Na. 15021); A , mandible; B , maxillula; C , maxilla; D , first maxilliped; E , second maxilliped; F , third maxilliped; G , paragnaths. Scale bar: 0.2 mm. FIG. 3. — Epipontonia tahitiensis n. sp. , ovigerous holotype (MNHN Na. 15021); A , first pereiopod; B , same, chela; C , major second pereiopod; D , same, lateral; E , same, chela; F , minor second pereiopod, chela; G , third pereiopod; H , same, dactyl and propod; I , fourth pereiopod, dactyl and propod; J , fifth pereiopod, dactyl and chela. Scale bars: A, E-G, 0.5 mm; B, H-J, 0.2 mm; C, D, 1.0 mm. FIG. 4. — Epipontonia tahitiensis n. sp. , ovigerous holotype (MNHN Na. 15021); A , antennal spine, inferior orbital angle and anterolateral branchiostegite, ventrolateral aspect; B , mandible, incisor process; C , same, molar process; D , maxillula, palp; E , first pereiopod, fingers; F , same, tips of fingers, lateral; G , major second pereiopod, fingers; H , minor second pereiopod, fingers; I , third pereiopod, distal propod and dactyl; J , fourth pereiopod, distal propod and dactyl; K , fifth pereiopod, distal propod and dactyl; L , uropod, distolateral exopod. Scale bars: A, G, H, L, 0.2 mm; B-F, I-K, 0.1 mm. Third pereiopod ( Fig. 3G ) normal, dactyl ( Fig. 4I ) compressed, unguis distinctly demarcat- ed, 3 times longer than oblique basal width, with single small spinule proximodorsally, curved, ventral border concave with three small acute denticles; corpus twice as long as proximal depth, with pairs of sensory setae distally, biunguiculate with large acute distoventral tooth, ventral margin slightly concave with four smaller acute teeth; propod ( Fig. 3H ) about 0.43 of CL, subuniform, compressed, about 5 times longer than wide, with single stout distoventral spine, subsequal to basal width of corpus, five similar equally spaced ventral spines and single smaller proximal ventral spine; carpus 0.66 of propod length, unarmed; ischium 1.16 of propod length, 3.4 times longer than wide, unarmed; ischium 0.77 of propod length, unarmed; basis and coxa without special features. Fourth pereiopod similar to third pereiopod; dactyl ( Fig. 4J ) distally damaged(?), unguis without dorsal spinule, not clearly demarcated, otherwise similar, corpus biunguiculate with single small acute distoventral tooth only; propod ( Fig. 3I ) about 0.9 of third propod length, 5.4 times longer than deep, with single more slender distoventral spine, four ventral spines of diminishing size proximally; other segments without special features. Fifth pereiopod similar to third pereiopod; dactyl ( Fig. 4K ) with clearly demarcated unguis without dorsal spinule, ventral margin with three denticles; corpus biunguiculate, with very small acute distoventral tooth only; propod ( Fig. 3J ) 1.06 of third propod length, 6.7 times longer than proximal depth, without spines, with numerous slen- der distoventral setae; other segments without special features. Uropod ( Fig. 1M ) with protopodite posterolaterally unarmed; exopod 0.9 of telson length, 2.2 times longer than broad, lateral margin nonsetose, convex proximally, distally straight, with strong distolateral tooth ( Fig. 4L ), with robust spine medially, diaeresis obsolete; endopod subequal to exopod length, 2.4 times longer than width. Ova normal, 13. Measurements (in mm) Total body length, c. 5.9; postorbital carapace length, 1.45; carapace and rostrum, 2.2; major second pereiopod, chela, 1.9; minor second pereiopod, chela, 1.4; length of ovum, 0.5. Coloration and host No data. Systematic position Epipontonia tahitiensis n. sp. is not closely relat- ed to the three previously described species of the genus, differing from all three in possessing an unreduced mandibular incisor process and an epipod on the second maxilliped, although the mandible of E. hainanensis Li, 1999 has not yet been illustrated in detail. In all other features it conforms closely to the generic description. REMARKS Epipontonia tahitiensis n. sp. is completely without the remarkably ornate first pereiopod finger tips found in E. anceps Bruce, 1983 . In this species the finger tips are provided with long slender serrulate terminal spines flanked by denticulate medial and lateral expansions. These are also lacking in E. anceps and E. hainanensis .