Rynkatorpa felderi, Pawson, David L. & Vance, Doris J., 2005

Pawson, David L. & Vance, Doris J., 2005, Rynkatorpa felderi, new species, from a bathyal hydrocarbon seep in the northern Gulf of Mexico (Echinodermata: Holothuroidea: Apodida), Zootaxa 1050, pp. 15-20 : 17-19

Rynkatorpa felderi new species

Figures 1 , 2 A–G.

Diagnosis: Tentacles with two pairs of terminal digits. Body wall ossicles anchors, anchor plates and accessory rods. Anchor stock unbranched. Perforations in anchor plates smooth, lacking denticulation. Accessory rods of uniform diameter, lacking central thickening.

Material Examined: HOLOTYPE, National Museum of Natural History, Smithsonian Institution, Catalogue No. 1080258, one specimen, northern Gulf of Mexico, off Louisiana, near hydrocarbon seep “Brine Pool”, 3 July 2003, R/V Pelican, 27º43.41’N, 91º16.76’W, 620 meters, 0.25 m ² box core, 1620 hrs., soft sulfurous mud with brownish surface showing a petroleum sheen, containing bacterially precipitated calcium carbonate nodules and evidence of thalassinidean shrimp burrows, pore water salinity 44 parts per thousand, collected by D. Felder and associates. PARATYPE, National Museum of Natural History, Smithsonian Institution, Catalogue No. 1080259, 1 specimen, Northeast Gulf of Mexico, 29º13.4’N, 87º00’W, 12 July 1967, 752 meters, dredge, collected by W.E. Pequegnat. From Texas A&M collections, donated by M. Wicksten.

Description: Holotype ( Figure 1 ) 80 mm in length, diameter approximately 7 mm, specimen mostly relaxed, tentacles extended ( Figure 1 ), a contracted area about 14 mm long lying 18 mm posterior to oral field. Color in alcohol uniform light maroon to brown. Oral field with extended tentacles 5 mm in diameter. Tentacles 12, each approximately 2.60 mm long, terminating in two pairs of gently tapering, bluntly pointed, digits; each digit approximately 530 µm long. Specimen slightly sticky to touch, especially near posterior end, due to presence of numerous anchor ossicles.

Body wall with numerous anchors and anchor plates, all of approximately the same size in anterior, posterior, and mid­body regions. Anchors ( Figure 2 A) symmetrical, arms with 4–8 teeth; stock unbranched but finely toothed. Anchors in mid­body of average length 355 m (note: n=10; average sizes are calculated from necessarily small sample sizes of ossicles); posterior anchors of similar size, 356 m long. Anchor plates ( Figure 2 C) approximately rectangular, with rudimentary bridge for support of anchor. Perforations few, of variable size, but near center of plate 2–4 perforations larger than others. Plates at mid­body of average length average 211 m, at posterior 229 m.

Curved accessory rods ( Figure 2 B), smooth, with enlarged, slightly branched ends, of average length 119 m, present in skin overlying radial longitudinal muscles, especially near mid­body and the posterior region. Radial longitudinal muscles contain no military granules. Tentacle digits contain curved rods ( Figure 2 D) of greatly variable size (averaging 142 m in length) with enlarged ends. Tentacle stems with short, straight to curved rods ( Figure 2 E) with more or less rounded ends, average length 55 m.

Paratype 62 mm in length, contracted, variegated light brown in alcohol. Anchors ( Figure 2 G) and anchor plates ( Figure 2 F) essentially similar to those of Holotype, except that they are larger (anchors 495 m long, plates 321 m long). Anchor plates apparently more fully developed, with more numerous perforations, but bridge remains rudimentary.

Distribution: Northern and Northeastern Gulf of Mexico, 620–752 meters. Of the two records of this species, the Holotype is certainly from near a hydrocarbon seep, the Paratype from an area where seeps occur.

Etymology: It is a pleasure to name this species for our friend and colleague Dr. Darryl Felder of the University of Louisiana, Lafayette, who has contributed so much to our knowledge of the marine fauna of the Gulf of Mexico.

Remarks: The anchors and anchor plates of this distinctive new species superficially resemble those of R. hickmani Rowe & Pawson from Tasmania, but in this latter species the anchors and plates are considerably smaller, and the accessory rods differ in having central swellings. R. challengeri (Théel) , from near Fiji, has anchors and plates of the same order of size as R. felderi , but the plates have fewer perforations, and accessory rods are apparently absent.

Figures

FIGURE 1. Holotype of Rynkatorpa felderi new species. Left, whole animal, total length 80 mm. Right, oral field, showing 12 tentacles each with 2 pairs of terminal digits.

FIGURE 2. Rynkatorpa felderi new species. Holotype: A, Anchors from mid­body. B, accessory rods from body wall overlying radial muscles, mid­body. C, anchor plates from mid­body. D, Rods from tentacle digits. E, rods from tentacle stem. Paratype: F, anchor plates from mid­body. G, anchor from mid­body. All scale lines are 50 µm long.