Isodictya kerguelenensis Ridley & Dendy 1886

Isodictya kerguelenensis (Ridley & Dendy, 1886)

(Fig. 15, Tab. 11)

Isodictya kerguelenensis (Ridley & Dendy, 1886): Lévi 1956: 27, text-fig. 2, 3. Koltun 1964: 44, pl. 8, figs. 11, 12, 1976: 175. Vacelet & Arnaud, 1972: 16. Desqueyroux-Faúndez 1989: 113, pl. 3, figs. 11a–b, pl. 9, fig. 52. Barthel et al. 1990: 122. Cuartas 1992: 75, text-figs. 5, 6, 62. Ríos et al. 2004: 114, fig. 12.

Synonymy:

Desmacidon kerguelenensis (Ridley & Dendy, 1886): Topsent 1908: 24.

Desmacidon (Homoeodictya) kerguelenensis (Ridley & Dendy, 1886): Ridley & Dendy 1887: 110, pl. 23, figs. 3, 3a–c, pl. 24, fig. 3.

Desmacidon kerguelenensis var. antarctica Kirkpatrick, 1908: 37, pl. 19, fig. 1, pl. 23, fig. 1.

Desmacidon kerguelenensis var. cactoides Kirkpatrick, 1908: 38, pl. 19, fig. 2, pl. 23, fig. 2

Homoeodictya antarctica (Kirkpatrick, 1908): Topsent 1917: 67–68.

Homoeodictya kerguelenensis Ridley & Dendy, 1886: 346. Topsent 1917: 67. Burton 1932: 283.

Homoeodictya kerguelenensis var. simillima Hentschel, 1914: 80, pl. 6, fig. 7. Burton 1932: 285, pl. 51, fig. 4.

Isodictya antarctica (Kirkpatrick, 1908): Koltun 1964: 44, pl. 8, figs. 17, 18, 1976: 175. Desqueyroux 1972: 51. Vacelet & Arnaud 1972: 16, figs. 3, 4. Barthel et al. 1990: 122.

Isodictya cactoides (Kirkpatrick, 1908): Burton 1929: 424, 1934: 20.

Platychalina cactoides (Kirkpatrick, 1908): Burton 1938: 9.

Platychalina kerguelenensis (Kirkpatrick, 1908): Burton 1938: 9.

Material. 3 fragments, probably parts of one specimen from station 016-1 (SMF 11805, 11856, 11857), 488.7 m, 70° 35.35' S, 9° 2.31' W, 17.12.2007.

Description. Samples (Fig. 15 A) poorly preserved, determination mainly based on spicule characters.

Spiculation (Tab. 11): Principal spicules oxeas (Fig. 15 B–C) with slender pointed ends, very slightly kinked in the middle, about 660 µm long and 22 µm wide. Microscleres very characteristic palmate isochelae (Fig. 15 D–E). Lateral alae completely coalesced with shaft, aggravating differentiation. Middle alae free and fully formed; each bearing one rounded extension on the inner falx, which almost reaches the shaft. Chelae about 26 µm long.

Remarks. From the holotype, Ridley and Dendy (1887) reported oxeas of 350 µm in length, with no indication of the number of spicules measured. In a recent report on newly sampled material from the Antarctic, Ríos et al. (2004) gave values for the length of oxeas 130–650 µm. These are quite similar to the values of our new sponges, which show just a little tendency to a larger oxea growth. The smallest of the spicules reported by Ríos et al. (2004) are very likely to be juvenile spicules, similar to the ones we reported from I. doryphora (see above). Both studies present the same very characteristic palmate isochelae in similar sizes. The species was previously found in rather shallow, near-shore waters: Ridley and Dendy (1887): 45–72 m; Ríos et al. (2004): 15– 56 m. Our new material was sampled at a deeper station in about 488 m depth. Still, this station can be considered situated on the lower Antarctic shelf, which is within the distribution range of the species.