Dercitus Stoeba plicatus (Schmidt, 1868)

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 : 15-18

Dercitus Stoeba plicatus (Schmidt, 1868) Figs 6 C–F

Corticium plicatum Schmidt 1868: 2, pl. III fig. 11.

Calcabrina plicata ; Sollas 1888: 281.

Dercitus plicata ; Lendenfeld 1894: 17, pl. II fig. 10, l. III fig. 43.

Dercitus plicatus ; Topsent 1895: 531, pl. XXII figs 6-10; Babiç 1922: 286, fig. V-1; Lévi and Vacelet 1958: 231, Figs 10-11; Pulitzer-Finali 1972: 345; Pulitzer-Finali 1983: 467; Templado et al. 1986: 96 (table); Pansini 1987: 157; Van Soest 1993: 210 (table).

Material examined.

Holotype MNHN DT 3635, labeled " Corticium plicatum Schmidt 1868 no. 96" (there is also a slide - not examined - with Schmidt’s handwriting, bearing the date 1868); schizotype BMNH 1868.3.2.1. (slide), labeled " Corticium plicatum Schmidt, 1868, Calcabrina plicata , Algiers 1868".

Additional specimen ZMA Por. 15101a, Banyuls, ‘coralligène’, 42.4833°N; 3.138°E, 10 m, coll. S. Groot, 10 August 1981.

Description.

The wet holotype (Fig. 6C) consists of two pieces, one small brownish mass of 2 × 2 cm, the actual specimen, and a larger limestone mass covered with bryozoans which does not appear to contain any additional sponge material but is presumed to be part of the substratum on which the sponge grew. The holotype is slightly fleshy, and in cross section consists of an outer layer of sanidasters overlying a dense confused mass of calthrops. Later descriptions (e.g. Topsent 1895) diagnose this species as encrusting and insinuating between stones and calcareous algae. Colour white, interior yellowish. Consistency firm, collagenous. Surface smooth with single oscules elevated into small conical papillae. Numerous large cells with inclusions (70 µm).

Spiculation of the holotype (Figs 6E-F, Table 2): Calthrops, dichocalthrops, sanidasters.

Calthrops (Fig. 6E) are dominating the megasclere complement, in a wide size range, but not divisible in size classes, most are regular four-claded equal-length spicules, a few three-claded occur and occasionally cladi are a bit crooked, cladi 41 –101.0– 188 × 3 –14.7– 29 µm, cladomes 57 –154.4– 252 µm.

Dichocalthrops (Fig. 6E), relatively rare, only a dozen were encountered in the spicule slide made from the holotype, invariably smaller than the biggest calthrops; infrequent incipient dichocalthrops, were encountered, with only two or one of the cladi bifid. Size of protocladi 20 –22.4– 28 × 4 –5.6– 8 µm, deuterocladi 15 –28.0– 36 × 2 –3.6– 6 µm, rhabds 28 –45.6– 57 × 3 –5.6– 9 µm, and cladomes 67 –86.8– 105 µm.

Sanidasters (Fig. 6F) are slightly fusiform and profusedly spined, relatively uniform in shape and size, 11 –14.9– 19 × 1 –1.65– 2 µm.

Additionally, we observed some oxeas of uniform size, approximately 150 × 3-4 µm, assumed to be foreign to the sponge.

Description of the BMNH Schmidt’s type slide (Fig. 6D, Table 2). The spicules (calthrops, dichocalthrops and sanidasters) are dissociated, but even in that condition it can be concluded that the slide is almost certainly taken from the holotype as the frequencies of occurrence and the sizes of the spicules are very similar to those of the holotype. Calthrops dominate the megascleres (Fig. 6C); most are regular, but occasionally some are three-claded or rarely two-claded. Endings of the cladi may occasionally be abruptly bent, bifid, indicating incipient dichocalthrops. They occur in a large size range, cladi 36-183 × 4-28 µm, cladomes 62-258 µm, almost identical in range to the spicules measured from the holotype. Dichocalthrops rare, as the slide contained only four measurable dichocalthrops, protocladi 15-21 × 3.5-10 µm, deuterocladi 21-33 × 3-8 µm, rhabds 73-95 µm, cladomes 36-45 µm. Sanidasters 11-18 × 1-2.5 µm.

The only non-type specimen available to us, ZMA Por. 15101 from Banyuls has spiculation closely similar to the type material (Table 2). Only the sanidasters appear on average slightly longer and more robust.

Habitat.

Encrusting and insinuating in crevices, large depth range down to 100 m.

Distribution.

Originally reported from Algeria. Elsewhere reported with certainty from Banyuls, Naples and the Adriatic. Possibly some of the records from the adjacent North Atlantic ( Lévi and Vacelet 1958; Boury-Esnault and Lopes 1985) also refer to the present species, but see below.

Remarks.

Spicule dimensions of reported specimens are presented in Table 2. Sollas (1888), Lendenfeld (1894) and Pulitzer-Finali (1972) give unusually small calthrops (cladi 60-80 µm). Sollas (1888) and Lendenfeld (1894) additionally give very small sanidasters (8.3 and 6-7 µm). Topsent (1895) gives spicule data for this species as follows: calthrops with cladi 170-200 µm; dichocalthrops with similar sized cladi, with rabd thickness 25-30 µm; sanidasters 12-15 × 2-3 µm. Pulitzer-Finali (1983) reports this species from various Western Mediterranean localities and depths 1-100 m. Colours reported were white, pink, violet and brown. Both calthrops (cladi 40-200 µm) and dichocalthrops (cladome 60-210 µm) were present in variable quantities. Sanidasters varied between 10 and 20 µm. Pansini (1987) reports white specimen s from the Alboran Sea lacking dichotriaenes, but provided no further data. It is possible this record concerns Dercitus (Stoeba) senegalensis sp. n. (see below).

Dercitus (Stoeba) plicatus is apparently quite variable and this may have led to widespread reports of the species from various East Atlantic localities, but also from Malaysia ( Sollas 1902), Gulf of Mannar ( Thomas 1970), Maldives ( Calcinai et al. 2000), and Fiji ( Tendal 1969).

We believe alleged records of this species outside the Mediterranean (Table 2) need to be reviewed critically on the basis of reexamination of the specimens. We have done so for material available to us from West African and Fijian localities (see below). In these specimens we found important differences with Mediterranean Dercitus (Stoeba) plicatus , which led us to assign them to three new species. It is likely that further records from e.g. Indo-West Pacific localities which we could not verify are part of a complex of Dercitus plicatus -like sister species distributed over most of the warmer parts of the oceans.

Several species of Dercitus (Stoeba) were synonymized with the present species by various authors, including the type species Dercitus (Stoeba) simplex . In most cases these synonymies are not accepted by us.