Thandarum hernandezi, Martinez, Mariano I. & Brogger, Martín I., 2012

Martinez, Mariano I. & Brogger, Martín I., 2012, Thandarum hernandezi, a new genus and new species of sea cucumber family Sclerodactylidae (Echinodermata: Holothuroidea: Dendrochirotida) from the Southwestern Atlantic Ocean, Zootaxa 3304, pp. 63-68 : 64-67

Thandarum hernandezi sp. nov.

( Figures 1 , 2 )

Type material. Holotype: 11.50 mm length, one individual and 4 slides with ossicles. Argentine Sea, “Mejillón II” Expedition (15 Sep. 2009), St. nº 24 (36°09,567’S; 55°53,649’W), 15 m. MACN-In nº 39256. Paratypes: Six individuals, 14.58 mm; 14.08 mm; 13.96 mm; 13.86 mm; 13.03 mm; and 10.40 mm. Same locality and date. MACN-In nº 39257/1-6.

Diagnosis. Body U shaped, up to 14.08 mm with double row of podia restricted to the ambulacra. Ossicles from body wall with buttons and 4 pillar tables. Tube feet with rods, end plate star-shaped. Introvert with rosettes and tentacles with rods.

Etymology. This species is dedicated to Dr. Domingo Andrés Hernández, for his contributions to the taxonomy of the Argentine Sea holothurians, and for being the starter of holothurians studies in Argentina. This epithet is use as a noun in apposition.

Description. (Based on the holotype) Body curved, skin usually soft; live color orange-pink, and white in preserved state; anus and tentacles up turned; 10 dendritic tentacles, 2 ventral smaller; body wall thin with double row of podia restricted to the radii; trivium and bivium complete with well developed podia ( Fig. 1 A–B); calcareous ring not tubular, radial and interradial plates joined only at the base, radials with posterior prolongations made up of a mosaic of 3–4 pieces; ratio of radial/interradial length approximately 1:3 ( Fig. 1 C). A single polian vesicle. Stone canal bifurcated; one madreporite with two kidneys shaped. Respiratory trees with multiple branches extending to the half part of the body. Gonads attached to the gonoduct at the middle part of the body, with multiple branches extended all over the coelom cavity. Ossicles in body wall of two types. Buttons typically 50–80 µm long with only 4 to multiple perforations ( Fig. 2 A) and 4 pillar tables, typically of 130 µm long and 260 µm across ( Fig. 2 B).

Tube feet with rods with 2 middle and 2 terminal holes; end plate star-shaped with multiple perforations typically 80–120 µm across ( Fig. 2 C). Introvert with rosettes 40-55 µm long and tentacles with rods typically 80–100 µm long with only 1 to multiple terminal perforations ( Fig. 2 D). No differences are observed between the holotype and paratypes.

Type locality. Off Buenos Aires (36°09.567’S, 55°53.649’W), Argentina.

Habitat. Sand.

Remarks. All the specimens collected are distinctive and have genus type characteristics. In comparison with Sclerothyone and Temparena species, Thandarum hernandezi gen. et sp. nov. presents 4 pillar tables. For Southwestern Atlantic waters, Pseudothyone belli has knobbed buttons with handle ( Ludwig 1887) not observed on T. hernandezi . Also from Brazil Cucumaria manoelina Tommasi 1971 has 4 pillar tables but no material was found of C. manoelina , the type is lost, for this reason comparisons were made with the original description from Tommasi (1971). The differences between the two species are in the number of rows of podia and the shape of the ossicles. In C. manoelina 5 lines of podia were described, while in Thandarum hernandezi gen. et sp. nov. a double row of podia were observed. The tegument buttons have some differences in the number of holes, more in C. manoelina than T. hernandezi . For the podia introvert and tentacles the rosettes and rods have differences in shape, the rosettes in C. manoelina are circular and oblong in T. hernandezi . The rods on T. hernandezi has more holes than in C. manoelina , also the holes in T. hernandezi are restricted to the ends. Also, C. manoelina has tables with more holes and a reduced diameter than the observed for Thandarum hernandezi gen. et sp. nov.

Figures

FIGURE 1. Holotype of Thandarum hernandezi gen. et sp. nov. A. Dorsal view; B. Ventral view; C. Calcareous ring shape. Scale bars: A and B = 1 mm.

FIGURE 2. Ossicles of Thandarum hernandezi gen. et sp. nov. A. Body wall buttons; B. Tables with four pillars from body wall; C. Rods from podia and star-shaped end plate; D. Rods from tentacles and rosettes from introvert. Scale bars: A, C and D = 50 μm, B = 100 μm.