Research Article |
Corresponding author: Luciana Martins ( martinsrluciana@gmail.com ) Academic editor: Rosana Rocha
© 2018 Luciana Martins, Marcos Tavares.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Martins L, Tavares M (2018) Ypsilothuria bitentaculata bitentaculata (Echinodermata: Holothuroidea) from the southwestern Atlantic, with comments on its morphology. Zoologia 35: 1-6. https://doi.org/10.3897/zoologia.35.e24573
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Ypsilothuria bitentaculata bitentaculata (Ludwig, 1893), previously known from several localities in the Pacific Ocean, is recorded herein for the first time from the southwestern Atlantic Ocean based on eight specimens caught off the coast of southeastern Brazil, between 505–511 m deep. Several morphological details are added to the description of Y. b. bitentaculata, including photographs of specimens and calcareous ring plates, as well as scanning electron microscope images of the ossicles from the body wall, oral and anal siphons and introvert. Additionally, Y. b. bitentaculata is compared to its congeners.
Sea cucumber, Dendrochirotida , Ypsilothuriidae , Brazil, deep-sea, REVIZEE
Historically, the southwestern Atlantic deep-water benthic fauna has been poorly sampled and poorly understood (
Likewise, only recently more progress has been made on the discovery of deep-sea holothuroids (e.g.
Among the recent efforts undertaken to explore Brazil’s deep-sea benthic habitats are a number of deep-water oceanographic investigations conducted in southeastern Brazil as part of the REVIZEE Program (Living Resources in the Exclusive Economic Zone) (
As currently understood, the genus Ypsilothuria comprises two species: Y. bitentaculata (Ludwig, 1893) and Y. talismani Perrier, 1886. These two species were questionably divided into five subspecies (
Here we present a detailed morphological description of the poorly known Y. b. bitentaculata, including color photographs of full specimens and of the calcareous ring plates, as well as scanning electron microscope images of the ossicles from the body wall, oral and anal siphons and introvert. Additionally, Y. b. bitentaculata is compared to its congeners.
Specimens of Ypsilothuria bitentaculata bitentaculata were collected from infaunal assemblages with the aid of a Van Veen grab and a rectangular dredge, sieved onboard through a 1 mm mesh. Measurements were obtained from ethanol fixed specimens and correspond to the maximum lengths of the smallest and the largest specimens, respectively. Holothuroid morphological techniques and terminology followed Rowe and Doty (
Abbreviations and acronyms: specimen (spm); Museu de Zoologia, Universidade de São Paulo (MZUSP); Muséum national d’Histoire naturelle, Paris (MNHN); National Museum of Natural History, Smithsonian Institution, Washington D.C. (USNM).
Sphaerothuria bitentaculata Ludwig, 1893:141, pl. XII, figs 16–17, pl. XIV, figs 5–14.
Sphaerothuria
talismani
–
Ypsilothuria
bitentaculata
–
Body strongly U-shapped. Tentacles crown of eight digitiform tentacles, the two lateral ones longest. Calcareous ring simple, radial and interradial plates deeply notched, without posterior projections. Plates of body wall forming a test, arched rods in tentacles. Knobbed plates in introvert.
Body strongly U-shaped (Fig.
Body wall tables with circular disc perforated, irregular in outline. Each disc consisting of a laminar stereom with holes ranging between 20 and 50 μm all over the disc plate (plate size between 500 and 1400 μm; Figs
MZUSP 1306, Brazil, REVIZEE, off coast of São Paulo, (25°43’S, 45°09’W), 13/Jan./1998, 511m, 6 spms. Ibidem, (24°20’S, 43°46’W), 9/Jan./1998, 505m, 2 spms.
MNHN-IE-2005 6332, Slides of the type [body wall tables] Pacific, (6°35’S, 81°44 W), 24/Feb./1891, 782m. MNHN 3693, Pacific, (34°6’S, 119°8’W), 1301m: 20 mm long [all originally labeled S. bitentaculata Ludwig, 1893]. USNM 15689, United States, northwestern Atlantic, Virginia, RV Albatross, stn 2723, (36°46’N, 73°09’W), 23/Oct./1886, 3082m: 10 spms 3–10 mm long [originally labeled Y. bitentaculata (Ludwig, 1893)].
Ypsilothuria b. bitentaculata has been regarded as a Pacific species (Oshima 1915,
Some authors have suggested that the morphological differences between the subspecies of Ypsilothuria are due to ontogeny only (
Recent observations are not consistent with Billet’s (1998) claim that the average size of the dermal plates varies with the size of the specimens. Specimens from the Indian Ocean with about 20 mm had two-spired dermal plates ranging between 1500 and 3000 μm (
Several authors (e.g.
Ypsilothuria t. talismani actually differs from Y. b. bitentaculata in the morphology of the lateral interradial plates of the calcareous ring, whose anterior ends are entire in Y. t. talismaniand deeply notched in Y. b. bitentaculata. Additionally, the tentacle rods are straight and have few perforations at the ends in Y. t. talismani (viz.
Ypsilothuria b. bitentaculata can be separated from Y. b. attenuata sensu
However, the differences between Y. b. bitentaculata and Y. b. attenuata sensu
Ypsilothuria b. bitentaculata and Y. b. virginiensis share similar shape of the calcareous ring (Figs
The specimens from the southwestern Atlantic (São Paulo, Brazil) are herein assigned to Y. b. bitentaculata on the account of the morphology of their tentacle rods and the size of the holes on their body wall plates.
Ypsilothuria bitentaculata bitentaculata (MZUSP 1306): (1) lateral view of the body; (2) detail of one of the two elongated lateral tentacles detail of the tentacle (white arrow); (3) dorsal view of a specimen preserved in ethanol (note oral and anal siphons, white and red arrows, respectively); (4) detail of the ossicles from the body wall (the red arrow indicates the spire); (5) calcareous ring. R, radial plate. IR, interradial plate. Scale bars: 1–3 = 5 mm, 4 = 1 mm, 5 = 0.5 mm.
SEM photomicrographs of the ossicles from Ypsilothuria bitentaculata bitentaculata (MZUSP 1306). (6–7) tables from body wall in dorsal and lateral views, respectively; (8) detail of the spire; (9) rod from tentacles; (10–11) knobbed plates from introvert (12–14); arched rods from anal and oral siphon. (15–16) plates from oral and anal siphons, respectively. Scale bars: 6 = 500 μm, 7–8 = 200 μm, 9–11 = 50 μm, 12–16 = 20 μm.
Outlines of the calcareous rings: (17) Ypsilothuria bitentaculata attenuata (after Heding, 1942); (18) Ypsilothuria bitentaculata bitentaculata (MZUSP 1306); (19) Ypsilothuria bitentaculata virginiensis (after Heding, 1942). Note in 18 radials and interradials narrow and the anterior end of both radials and interradials deeply notched. R, radial plate. IR, interradial plate.
We are grateful to Jon Norenburg (USNM) and Marc Eleaume (MNHN) for granting access to the collections under their responsibility and for providing working space to LM. Thanks also to Wagner Magalhães (University of Hawai’i at Mānoa) for his helpful comments on a first draft of the manuscript and to Lara Guimarães (MZUSP) for technical support with SEM images. LM thanks Fundação de Amparo à Pesquisa do Estado de São Paulo for providing financial support by way of a doctoral fellowship (FAPESP process number 201318202-9). MT thanks Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq process 301806/2010-1) and Petróleo Brasileiro S.A. (PETROBRAS process 4600224970) for supporting studies on the systematics of marine invertebrates. This manuscript greatly benefited from the comments of Y. Samyn and one anonymous reviewer.