Dercitus Stoeba reptans Desqueyroux-Faundez & Van Soest, 1997

Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010, Skeletons in confusion: a review of astrophorid sponges with (dicho-) calthrops as structural megascleres (Porifera, Demospongiae, Astrophorida), ZooKeys 68, pp. 1-88 : 27

Dercitus Stoeba reptans Desqueyroux-Faundez & Van Soest, 1997

Dercitus reptans Desqueyroux-Faúndez and Van Soest 1997: 402, Figs 50-52.

Material examined.

Holotype USNM 43170, Galapagos Islands, Albemarle Island, 0-3 m, 0.25°S; 91.4833°W, coll. Anton Bruun Cruise 16-66139, 25 May 1966 (slides and fragments of the holotype are present in MHNG, nr. 18963). Paratype ZMA Por. 11215, three fragments from the same locality.

Description

(from Desqueyroux-Faúndez and Van Soest 1997). Creeping branches encrusting corals. Surface micronulose, no oscules, whitish pink (preserved condition).

Skeleton: thick ectosomal crust of microscleres. Choanosomal skeleton confused mass of megascleres.

Spicules: calthrops, dichocalthrops, sanidasters. Some spicule types are remeasured to provide additional data and to correct a remarkable error in the original description.

Calthrops robust, variable in size, cladi 344 –484– 648 (remeasured 39-648) x 16 –27– 50 µm (remeasured 6-50 µm) (cladome up to 670 µm, remeasured 60-680 µm). The smaller calthrops category reported here is rare.

Dichocalthrops, or short-shafted dichotriaenes, small, cladome 156 –164– 170 µm (remeasured 141 –154.5– 180 µm), individual cladi up to 90 × 8-9 µm (remeasured: protocladi 27 –33.8– 36 × 9 –10.4– 12 µm; deuterocladi 35 –47.2– 69 × 6 –8.2– 11 µm; rhabds 57 –74.5– 106 × 9 –11.0– 12 µm).

Sanidasters: short and slim, with blunt apices. Remarkably, they were quoted to be 15-74 × 2-8 µm in size, but this is an obvious error. Remeasured they appear to be highly uniform in size and shape: 9 –12.8– 16 × 1 –1.9– 2.5 µm, which is also in accordance with the size and shape of the figured sanidaster (fig. 52).

Habitat.

Shallow water.

Distribution.

Only known from the Galapagos Islands.

Remarks.

By its large calthrops this species stands out among Dercitus species with a complement of small dichocalthrops. None of the extant species are morphologically close.