Amphiura (Amphiura) callida, 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 : 595-598

Amphiura (Amphiura) callida n. sp.

( Figs 2 ; 3 )

TYPE MATERIAL. — MD 55/ Brazil 1987, stn 60, BT 101, 22 o 58’S, 42 o 06’W, 50 m depth, 1. VI.1987, holotype d.d. 8 mm ( MNHN, EcOS20835).

TYPE LOCALITY. — South of Cabo Frio, Rio de Janeiro.

ETYMOLOGY. — From the Latin verb callere: hard skin; to allude to the robustness of the species.

MATERIAL EXAMINED. — MD 55/ Brazil 1987, stn 60, BT 100, 22 o 58’S, 42 o 06’W, 50 m depth, 1. VI.1987, holotype 33-45 mm, ( MNHN, EcOs22636), 28 paratypes, d.d. 4.0 to 10.0 mm ( USU.EO.III. 9.5.1147) et 31 paratypes, d.d. 3.0 to 10.0 mm ( MNHN, EcOs22637).

DIAGNOSIS. — Dorsal surface covered with imbricated scales with distinct primary plates. The oral shields are small in relation to the size of the disk. Robust, erect infradental papilla; the second oral papilla is narrow and pointed; the distal is the largest, leaf-shaped, erect, with an acute extremity. The dorsal spines are the smallest. Two tentacle scales: the internal scale is slightly larger and supported on the ventral arm plate, and the external is supported on the lateral arm plate.

DESCRIPTION

Disk

8 mm in diameter, sub-circular contour, slightly flattened dorsally, with slight interradial excavations. Dorsal surface covered with imbricated scales. Distinct primary plates, separated from each other, and slightly larger than the other disk scales. Proximally, in each interradius, there is a scale of the same size as the primary plates. The radial shields correspond to approximately a third of the disk radius, are semicircular in shape, longer than wide and completely separat- ed by a triangular wedge of scales. Two of the latter are relatively large, surrounded by smaller ones.

Tiny imbricated scales cover the oral surface of the interradii with their free margins orientated distally. These scales invade the interradii dorsally, where they become slightly bigger. The bursal slits are conspicuous, narrow and long, with a row of marginal scales.

The oral shields are small in relation to the size of the disk. They are longer than wide, have a proximal acute angle, and a blunt distal margin. The madreporite is slightly larger than the other oral shields. Sub-triangular adoral shields are joined on the interradial mid line. Jaws are short and erect. There are three papillae in each half jaw: the infradental is robust, erect and separated from the opposite one with which it forms a pair; the second is narrow and pointed; the distal one is the biggest, larger and erect with an acute extremity in the resemblance of a leaf.

Arms

45 mm long and 1.5 mm wide. The dorsal arm plates are contiguous, longer than wide and flabelliform. These plates are reduced in size in the first six segments nearest to the disk. The ventral arm plates are pentagonal, contiguous with slight lateral indentation; the first plate is very small with a concave proximal margin. The lateral arm plates are narrow, separated from each other, and support spines as long as the length of the segment. The dorsal spines are the smallest. The number of spines are distributed as follows on the first seven segments: 2, 3, 3, 4, 4, 5, 6, and 7 from the 8 th to the 11 th segment. The number of spines decreases to three distally. Spines are cylindrical with an blunt tip. In ventral view, proximally, the second spine from the bottom upwards has a curved extremity that turns inwards, hook-like. There are two tentacle scales: the internal is slightly larger and is supported on the ventral plate, and the external is supported on the lateral plate.

No variation is observed in the paratypes.

Ecology

A total of 61 individuals of Amphiura callida n. sp. were collected from a station subject to temperatures of 10 oC or less during upwelling in the spring and summer months. As this species was not sampled in the more typically tropical northern stations during the cruise, it could be that this area represents the northern limit of its range. This area has strong seasonality signals with a nutrient increase in spring and summer, and this has probably resulted in a more typically temperate faunal composition close to the island of Cabo Frio. The collection station had a sandy ooze substrate ( Albuquerque & Guille 1991) with a water temperature of 23 oC and salinity of 34. Amphiura callida n. sp. have hook-like spines on the second arm segment, which might be used for traction. According to Guille & Albuquerque (1990), the other ophiuran species in the vicinity of Cabo Frio were Amphilimna olivacea (Lyman, 1869) and Amphiura crassipes Ljungman, 1867 . Both species were found in high densities along with fewer numbers of Ophiothrix rathbuni Ludwig, 1882 , Nudamphiura carvalhoi Tommasi, 1965 , Amphiura complanata Ljungman, 1867 , and Ophiacantha cosmica Lyman, 1878 .

Figures

FIG. 2. — Amphiura (Amphiura) callida n. sp., holotype 8 mm disk diameter, 45 mm arm length; A, dorsal surface of the disk; B, oral surface of the disk.

FIG. 3. — Amphiura (Amphiura) callida. n. sp., holotype 8 mm disk diameter, 45 mm arm length; A, dorsal surface, primary plates away from each other in the radial areas of the disk, a scale approximately the same size as the primary plates in each interradius of the disk; B, detail of the arm spines; C, detail of the oral shields, distal oral papillae are larger, enlarged, erected, with an acute edge, leaf-like in shape. Scale bars: A, 1.5 mm; B, C, 0.1 mm.