Pseudocoutierea acutidorsata Olthof & Becking & Fransen 2018, sp. nov

Autor: Olthof, Gabriël, Becking, Leontine E., Fransen, Charles H. J. M.
Rok vydání: 2018
Předmět:
ISSN: 0081-0282
DOI: 10.5281/zenodo.5971375
Popis: Pseudocoutierea acutidorsata sp. nov. (Figs. 1–6) Material examined. RMNH. CRUS.D.57272: 1 ovigorous female holotype, pocl. 2.0mm; RMNH. CRUS.D.57273: 5 ovigerous female paratypes (pocl. 1.95 to 2.45mm, eggs 0.5mm in width and 0.6mm in length), 2 small non-ovigerous female paratype s (pocl. 1.75 and 1.85mm): stn BON 3, Bonaire, 12°08'13"N, 068°17'09"W, depth 138m, 31.v.2013, dive with submersible Curasub, from octocoral Callogorgia gracilis (Milne Edwards & Haime, 1857) identified by Bastian T. Reijnen (31.vi.2013), collected by L.E. Becking and H.W.G. Meesters, sample nr BDR041. Comparative material. Pseudocoutierea antillensis Chace, 1972: RMNH. CRUS.D.51635, 19 specimens, Curaçao, Eastpoint, 12°02'25"N, 068°45'03"W, depth: 18.2 m, 18.vi.2005, from Pseudoplexaura flagellosa (Houttuyn, 1772), collected by N. Snijders G.127. ZMA: DE 103.525, 8 specimens from Curaçao, from a depth of around 30m, 14.xi.1975, from Eunicea cf. clavigera Bayer, 1961. Pseudocoutierea conchae Criales, 1981: ZMA DE 103.237, holotype, male, Colombia, 11°18'N, 74°10'W, depth 15m, 15.ii.1976, from Leptogorgia virgulata (Lamarck, 1815). Pseudocoutierea edentata Criales, 1981: ZMA DE 103.238, 1 juvenile holotype, Colombia, 11°18'N, 74°10'W, depth 18m, 17.iv.1977, from Leptogorgia virgulata (Lamarck, 1815); ZMA: DE 103.239, 1 ovigerous female, 6 non-ovigerous female paratypes, Colombia, 11°18'N, 74°10'W, 17.iv.1977, from Leptogorgia virgulata (Lamarck, 1815); RMNH.CRUS.D.51368, 1 ovigerous female, Fort Lauderdale, Florida, USA, depth 50m, on Elisella sp., spring 1975, collected by R. Guest. Pseudocoutierea elegans Holthuis, 1951: RMNH. CRUS.D.9194, 1 female paratype, south of White Friars, Guerrero, West Mexico, depth 45m, 2.iii.1934, rock, gorgonids, Allan Hancock Exp. 264–34. Don. U.S.N.M., reg. no. 90275, acc. no. 128938. Diagnosis. Body dorsoventrally depressed, wing-like expansions of rostrum quadrate with anteriorly sharp supra-ocular tooth. No hepatic protuberance, but with epigastric tooth in extension of rostrum. Third to fifth pleonal pleura with posterior tooth. Triangular spine on posterior margin of sixth pleonite. Scaphocerite 2.8 times as long as wide, outer border slightly concave. Mandible with four teeth on incisor process. Second maxilliped without exopod, epipod rounded and directed upwards, not reaching end of merus. Third to fifth pereiopod with well-developed meral swelling and infero-distal spine on propodus. Exopod of uropod with small moveable spine between blade and distolateral spine. Description. Carapace broad (Fig. 1A–C), slightly depressed. Sharp antennal tooth present on anterior margin of carapace with acuminate lobe just below, giving bifid appearance to antennal tooth in lateral view (Fig. 1A). Well-developed pterygostomial sinus present on anterior margin of carapace below antennal tooth (Fig. 1A). Short ridge from antennal tooth upwards on carapace terminating behind orbit (Fig. 1A). No hepatic protuberance or tooth present. Longitudinal groove running near lateral margin of carapace extending from pterygostomial sinus to near posterior margin of carapace. Rostrum long, unarmed, reaching beyond bifurcation of upper antennular flagellum (Fig 1B), round, curved slightly upwards distally (Fig. 1A), proximally on both sides expanded into supra-orbital eave with anteriorly sharp supra-ocular tooth (Fig. 1B, C). Expansions continue as small ridge downwards on carapace and terminate behind orbit close to end of ridge from antennal tooth (Fig. 1A). Rostrum continues as ridge on carapace; rostrum elevated above eyes (Fig. 1A), epigastric tooth present behind elevation above point where ridges from supraorbital eave and antennal tooth end (Fig. 1A). First two pleonal segments with pleura rounded. Third pleuron with small posteroventral tooth (Fig. 1A). Fourth and fifth pleura ending in sharp, slender point. Posterolateral angle of sixth pleonite sharply triangular (Fig. 1A); posteroventral angle small, acuminate. Sixth pleonite two times as long as fifth, 0.9 times as long as telson measured dorsally (without spines). Telson with two pairs of dorsolateral spines (about 0.05 times as long as telson), proximal pair at 0.56 of telson length, distal pair at 0.87 to 0.9 of telson length. Tip with three pairs of cuspidate setae, outer pair 0.31 times as long as intermediate pair, intermediate pair 0.20 times as long as telson, medial spines 0.74 times as long as intermediate pair (Fig. 1D, E). Eyestalks large, broad, cornea not much broader than eyestalks, small spine dorsally on eyestalk near cornea (Fig. 1B). Antennular peduncle with short stylocerite measuring about 0.4 of length of basal segment (without distolateral spine), distolateral spine well developed reaching to about end of intermediate segment, acute tooth present on ventral side near inner margin (Fig. 1F). Ultimate segment about 1.9 times as long as intermediate segment, intermediate segment 0.23 times as long as basal segment. Upper/outer antennular flagellum fused for three segments; short inner ramus two-segmented; longer outer ramus about as long as antennular peduncle. Scaphocerite overreaching antennular peduncle, about 2.8 times as long as wide, outer margin slightly concave, distolateral tooth not overreaching distal margin of lamina (Fig. 1G). Molar process of mandible with large blunt teeth and setal brushes; incisor process with 4 distal teeth (Fig. 2A). Maxillula with hook-like process on palp, hook directed upwards. Lower lacinia lost during dissection, upper lacinia with both plumose and simple spines (Fig. 2B). Maxilla with endite cleft, apical setae serrate on distal lobe, simple setae on proximal lobe, lobes subequal in length. Scaphognathite well developed, outer margin slightly convex. Palp distinct, without setae (Fig. 2C). First maxilliped without flagellum on caridean lobe; palp short; epipod well developed, bilobed. Outer margins of basal endite and caridean lobe slightly convex (Fig. 2D). Second maxilliped without exopod, epipod consisting of one rounded lobe directed upwards, not reaching meral segment (Fig. 2E). Third maxilliped without exopod, overreaching basicerite, without arthrobranch but with small knob there. Ultimate segment about as long as penultimate segment, antepenultimate segment more than twice as long as penultimate segment (Fig. 2F). First pereiopod reaching just beyond scaphocerite. Chela slender with fingers 0.5 times as long as palm. Carpus 0.9 times as long as chela and 0.9 times as long as merus (Fig. 3A, B). Cutting edge of chela entire, tips of fingers strongly hooked (Fig. 3C). Second pereiopods strongly unequal: major second pereiopod about 2.8 times as long as minor second pereiopod. Especially palm more robust in major second pereiopod (fig. 2F, G), being about 4.5 times as broad as palm of minor second pereiopod (fig. 3D) at broadest point. Major second pereiopod with merus reaching to about end of scaphocerite, with tubercles on surface of merus and propodus (Fig. 3F, G). Merus 1.3 times as long as ischium, 3.2 times as long as carpus. Carpus 0.2 times as long as palm, fingers 0.39 times as long as palm. Dactylus with small tooth on cutting edge, with indent in fixed finger to accommodate movement of dactylus (Fig. 3H). Minor second pereiopod with merus 2.8 times as long as ischium, 1.6 times as long as carpus (Fig. 3D). Carpus 0.6 times as long as palm, chela with long fingers (0,63 times as long as palm), no tubercles on merus or propodus. Cutting edge of fingers entire (Fig. 3E). Third pereiopod robust; merus slightly curved, about 1.8 times as long as ischium (Fig. 3I). Carpus about 0.4 times as long as merus; propodus curved, slightly longer than merus. Merus with swelling on distal part of flexor margin (Figs. 3I, 4E, F). Two small spines present in distoventral part of propodus together with several setae (Figs. 3J, 4B, C). Dactylus less than half as long as propodus, curved, with small decalcified protuberance in basal part of flexor margin (Fig. 4A). Suture visible between corpus and unguis of dactylus (Fig. 4D). Pleopods with endopod slightly shorter than exopod, second to fifth pleopods of female with appendix interna (Fig. 5A). Exopod of uropod with tiny moveable spine between distolateral tooth and blade (Fig. 1E). Special structures. Species of the genus Pseudocoutierea all possess a swelling (either triangular, or hook shaped in P. dotae only) on the merus of the third pereiopod and a protuberance on the flexor margin of the dactylus. d’Udekem d’Acoz (2000) first examined these protuberances in more detail for P. wirtzi. He found that the meral swelling had a decalcified part and hypothesized that under these swellings exocrine glands could be present which would possibly secrete through these decalcifications or via the setae beside it. To see if these decalcified parts were also present in the new species, the third pereiopod was photographed with a scanning electron microscope. No decalcifications were present and only some indents could be seen on the meral swelling (Fig. 4E, F). If an exocrine gland is present in the meral swelling of this species, it can only secrete through the setae present on the swelling. Another interesting structure on the third pereiopod is the decalcified part on the flexor border of the dactylus of the third pereiopod. That structure was also first described for this genus in P. wirtzi. We also made some photographs of the third pereiopod and found the exact same decalcified part (Fig. 4A). The epigastric tooth is a relatively new character for this genus that was first described for P. stephanieae by Ramos-Tafur & Lemaitre (2016). Although all eight currently reported specimens of P. acutidorsata sp. nov. possess the aforementioned tooth, there seems to be extensive variability in the exact form of this tooth. In some specimens the tooth is nothing more than a small knob while in other specimens it is elongated and almost rod-like (Fig. 5B). Etymology. This species is named after the epigastric tooth on the carapace which separates it from almost all other species of Pseudocoutierea. The name is derived from the latin acutus -sharp and dorsum -back, dorsata makes it an adjective suited for the feminine genus name. Habitat. Eight specimens were collected from a colony of Callogorgia gracilis (Milne Edwards & Haime, 1857) (Anthozoa, Alcyonacea) at a depth of 138 meters on the deep reef of Bonaire (Dutch Caribbean). No real-life colors were recorded for this shrimp before it was fixed in ethanol. The three last pereiopods were curved inwards as described by d’Udekem d’Acoz (2000) and we agree with his explanation of this position by the lifestyle of these shrimp. Remarks. Pseudocoutierea acutidorsata sp. nov. differs from most other species in the presence of an epigastric tooth which it shares with only the recently described P. stephanieae. It can be distinguished from P. stephanieae by the presence of a strong pterygostomial sinus (which is only very shallow in P. stephanieae) and the length and curvature of the rostrum. In P. acutidorsata sp. nov., the rostrum is curved upwards and reaches the bifurcation of the upper antennular flagellum, while in P. stephanieae the rostrum just reaches the end of the antennular peduncle and curves slightly downwards. Pseudocoutierea acutidorsata sp. nov. is closely related to the East-Pacific species P. elegans with which it shares a tiny moveable spine between the distolateral tooth and the blade of the exopod of the uropod, the absence of an exopodal flagellum on the caridean lobe of the first maxilliped and a long rostrum that distally curves up. De Grave (2007) and Ramos & Lemaitre (2016) used the placement of the dorsal tooth on the third pleonite (in midlength or distally) to distinguish P. elegans and P. conchae. This character seems only based on the drawing of the pleonal somites in the species description of P. conchae (Criales, 1981, Fig. 6C). Upon closer examination of the holotype of P. conchae, the tooth on the third pleonite was found to be in roughly the same place as the same tooth in other Pseudocoutierea species (Fig. 5C, D). The medial placement of the tooth seems to be an artifact in the drawing by Criales (1981) and should therefore not be considered as a valid deterministic character. Phylogenetic analysis. Characters and character states (Tables 1, 2) used are derived from the literature, material collected, and comparative material. The species Coutierea agassizi Coutière, 1901 was selected as the outgroup taxon. It resembles Pseudocoutierea in the presence of a pterygostomial sinus, the lack of an exopod on the maxillipeds (although an exopod is present on the second maxilliped in P. conchae and P. edentata), the presence of an orbital eave, a meral swelling on the third pereiopod and a strong lateral carina on the carapace near the ventral margin. Figure 6 shows the 50% majority rule consensus tree, which has the same topology as the strict consensus tree, of the genus Pseudocoutierea. The close relationship between P. acutidorsata sp. nov. and P. elegans is interesting as P. elegans is known from the East Pacific and is separated from the Caribbean P. acutidorsata sp. nov. by the Panama Isthmus. Pseudocoutierea stephanieae stands apart of most other species, partly because of the absence of a deep pterygostomial sinus which is present in all of the other species. P. dotae and P. wirtzi seem to be closely related which is in conformation with the remark by De Grave (2007) on their close affinity. The two species from Caribbean Colombia (P. conchae and P. edentata) also seem closely related. From this phylogenetic reconstruction it seems that the epigastric tooth and acute supra-orbital eaves evolved and got lost again independently several times. The variation in the latter character within Pseudocoutierea acutidorsata is in agreement with this observation.
Published as part of Olthof, Gabriël, Becking, Leontine E. & Fransen, Charles H. J. M., 2018, On a collection of deep-water shrimp (Crustacea, Decapoda) from the Dutch Caribbean, with the description of a new species of Pseudocoutierea, pp. 533-548 in Zootaxa 4415 (3) on pages 538-544, DOI: 10.11646/zootaxa.4415.3.7, http://zenodo.org/record/1242209
{"references":["Chace, F. A. (1972) The shrimps of the Smithsonian-Bredin Caribbean Expeditions with a summary of the West Indian shallowwater species (Crustacea: Decapoda: Natantia). Smithsonian Contributions to Zoology, 98, 1 - 179. https: // doi. org / 10.5479 / si. 00810282.98","Criales, M. M. (1981) Two new species of Pseudocoutierea (Decapoda Natantia, Palaemonidae) from the Colombian Caribbean. Crustaceana, 41 (2), 167 - 181. https: // doi. org / 10.1163 / 156854081 X 00219","De Grave, S. (2007) A new species of Pseudocoutierea Holthuis from the Caribbean coast of Panama (Crustacea, Decapoda, Palaemonidae), with a key to the genus. Zootaxa, 37 (1397), 29 - 37. https: // doi. org / 10.11646 / zootaxa. 1397.4"]}
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