Amphiodia habilis, Albuquerque & Campos-Creasey & Guille, 2001

Albuquerque, Maria da Natividade, Campos-Creasey, Lúcia S. & Guille, Alain, 2001, Two new species of Amphiuridae (Echinodermata, Ophiuroidea) from the southeastern coast of Brazil, Zoosystema 23 (3), pp. 591-604 : 599

Amphiodia habilis n. sp.

( Figs 4 ; 5 )

TYPE MATERIAL. — MD 55/ Brazil 1987, stn 52, CB 90, 19 o 33’S, 39 o 34’W, 34 m depth, 29. V.1987, holotype d.d. 3.5 mm ( MNHN, EcOs22638).

TYPE LOCALITY. — Opening of the Rio Doce.

ETYMOLOGY. — From the Latin verb habere, translat- ed as habilis : to have, in allusion to the spirit of the cruise MD55.

MATERIAL EXAMINED. — MD 55/ Brazil 1987, stn 52, BT 90, 19 o 33’S, 39 o 34’W, 34 m depth, 29. V.1987, holotype d.d. 3.5 mm ( MNHN, 22638) and 1 paratype ( USU.EO.III. 9.2.1149), without disk.

DIAGNOSIS. — Disk with inflated circular contour, slightly flattened, dorsally covered by large scales, and ventrally with small imbricated scales, forming a clear border at the edge of the disk. In each jaw, the oral plates protrude ventrally at their point of contact. Three oral papillae,the most distal on adjacent jaws almost sealing the oral opening. Dorsal and ventral arm spines are slightly larger, flattened, blunt, and approximately the same size as the segment itself. The middle spine is smallest, sub-cylindrical and blunt. Two tentacle scales.

DESCRIPTION

Disk

Thick, circular contour, slightly flattened dorsally, measuring 3.5 mm in diameter and 1.09 mm in height. Dorsal surface covered by large scales. A rosette of large primary plates is conspicuous; the central plate is pentagonal, and the radial plates are larger and irregular in shape. From the centre of the disk to its border, on each interradius, there is a row of scales larger than the ones surrounding the radial shields, the most distal scale is semicircular with the round border towards the centre of the disk. The radial shields are contiguous, wide, slightly smaller than half of the disk radius, and slightly longer than wider.

Smaller imbricated scales forming a distinct bor- der at the edge of the disk cover the ventral interradii. Bursal slits are conspicuous.

Oral shields are longer than wide, and almost lozenge-shaped. Adoral shields are triangular, contiguous proximally at the interradial mid line, enclosing the oral shield. In each jaw, the oral plates protrude ventrally at their point of contact. The oral tentacle scale is not present. There are three oral papillae: the paired infradentals are robust and separated by a slight gap; the intermediate papilla is narrower than the distal one. The most distal papillae on adjacent jaws almost seal the oral opening.

Arms

20 mm long. Dorsal plates are contiguous, subrectangular, and slightly wider than longer. The lateral edges of the dorsal arm plates are rounded, the distal edge is concave. Ventral arm plates are contiguous, the most proximal being smallest, and the others as long as wide, almost square within slightly excavated distal border. The lateral arm plates are inconspicuous dorsally. There are two spines on the first segment, the ventral one being flattened laterally, blunt, and the dorsal one blunt and subcylindrical in shape. There are three spines on the other arm segments: the dorsal and ventral arm spines are slightly bigger, flattened laterally, blunt, and approximately the same size as the segment itself. The middle spine is smaller, subcylindrical and blunt. There are two equal in size, semi-circular tentacle scales: the internal articulates on the ventral arm plate, and the external tentacle scale on the lateral arm plate.

ECOLOGY

Two specimens of Amphiodia habilis n. sp. were collected near the Rio Doce outlet. Ophiurid diversity in this area is low. The locality has a strong fresh water flow from the river that is reflected by the presence of characteristic ophiuroid fauna ( Guille & Albuquerque 1990): notably the populations of three abundant species, Ophiocnida loveni (Ljungman, 1866) , Amphiodia atra (Stimpson, 1852) and Hemipholis elongata ( Say, 1825) . The water temperature and salinity were respectively 25.5 oC and 36 at the time of the sample, reflecting the tropical conditions of the environment ( Esteves et al. 1987). Nonetheless, this station probably receives large quantities of river discharge and fine particles, evidenced by the substrate composed of organic rich black ooze ( Albuquerque & Guille 1991).

Figures

FIG. 4. — Amphiodia habilis n. sp., holotype 3.5 mm disk diameter,20 mm arm length; A, dorsal surface of the disk; B, oral surface of the disk.

FIG. 5. — Amphiodia habilis n. sp., holotype 3.5 mm disk diameter, 20 mm arm length; A, dorsal surface; B, detail of the arm spines; C, oral surface, detail of the oral shields and arm spines, the distal oral papillae of the half jaw touch the neighbouring ones almost closing the oral opening. Scale bars: A, C, 1.0 mm; B, 0.5 mm.