Dercitus Dercitus bucklandi lusitanicus, Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010

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 : 12-13

Dercitus Dercitus bucklandi lusitanicus ssp.n. Figs 4 A–E 5f-jTable 1

Dercitus bucklandi ; Ferrer-Hernandez 1918: 17; Rodriguez Babio and Gondar 1978: 34; Acuña et al. 1984 (in Solórzano 1991: 21); Templado et al. 1986: 96 (table); Xavier and Van Soest 2007: 1646.

Material examined.

Holotype ZMA Por. 21810, Portugal, Gorringe Bank, Gettysburg Peak, 31-38 m, coll. J. Xavier, 2006 (cf. Xavier and Van Soest 2007, Figs 4 A–E).

Additional specimens. Xavier collection, field nr. B05.09.36, Portugal, Berlengas Archipelago, Lagosteira, 7 m, 16 –IX– 2005, coll. J.R.B.T. Xavier.

Xavier collection, field nr. B05.09.59, Portugal, Berlengas Archipelago, Lagosteira, 6-7 m, 16 –IX– 2005, coll. J. Cristobo.

Xavier collection, Portugal, field nr. B05.09.98, Berlengas Archipelago, Lagosteira, 6 m, 18 –IX– 2005, coll. J.R.B.T. Xavier.

Xavier collection, field nr. B05.09.267, Portugal, Berlengas Archipelago, Gruta do Carreiro Maldito, 6-8 m, IX– 2005, coll. A. Cunha.

Xavier collection, Portugal, field nr. A03/73, Arabida, Ponta da Passagem, 7 m, 16 –VII– 2003, coll. J.R.B.T. Xavier.

Description

(Fig. 4A). Alive blackish outside and greyish inside (in alcohol chocolate brown throughout). Shape massively encrusting, flat with smooth surface, no apparent oscules; inhalant openings in sieve plates. Consistency cheesy, slightly compressible. A representative size of preserved specimens is 5 ×4× 0.7 cm.

Skeleton: a layer of microscleres overlying a loose mass of calthrops megascleres. Spicular density appears lower than in the specimens from the British Isles.

Spicules: calthrops, toxas, sanidasters.

Calthrops (Fig. 4B), relatively uniform in size, cladi of irregular outline with endings irregularly stair-stepped and/or malformed, occasionally one or more cladi lacking; 58 –108.3– 165 × 5 –14.6– 27 µm, cladome 110 –159.3– 240 µm.

Toxa-like microscleres (Figs 4 C–D), symmetrical, smooth, but slightly undulate / polytylote, with a shallow curve and evenly pointed; 37 –51.3–69× 0.5 –0.7– 1.5 µm.

Sanidasters (Fig. 4E), rather uniform in size and shape, spines relatively long and thin, occasionally with a somewhat irregular shape; 16 –19.3– 24 × 0.5 –2.4– 6 µm (including spines).

Habitat.

Encrusting, typically bridging crevices and gaps in the substrate, sublittoral down to 6-38 m.

Distribution.

Portuguese main coast, Berlengas Islands, Gorringe Seamount. Furthermore, there are reports from the north coast of Spain (Ferrer-Hernandez, 1918; Babio & Gondar, 1978 (not seen); Acuña et al. 1984 (not seen). There is also a record from the Alboran Sea (Western Mediterranean) by Templado et al. 1986.

Remarks.

The spicule measurements of the present specimens are generally significantly smaller than those provided by most previous authors (Table 1), which is especially clear in the sizes of the toxiform microscleres: 51-111 × 1.5-3 µm in the subspecies bucklandi, 42-69 × 0.5-1.5 µm in the samples of the new subspecies, compared in Fig. 5: with bucklandi bucklandi toxas in Figs 5 a–e and bucklandi lusitanicus ssp.n. toxas in Figs 5 f–j. Possibly, the southern samples may be distinguished at the species level from the northern samples, but in view of the fact that there is an overall strong similarity with Dercitus bucklandi , we prefer to recognize only subspecies.

The toxa–like microscleres of Dercitus bucklandi s.l. are unique in the Astrophorida . They have been called ‘toxa’ because of the similarity in shape to similar microscleres in microcionid and mycalid Poecilosclerida. However, the resemblance is probably superficial and it is unlikely that these are homologous spicule types. There are subtle differences mostly only clearly visible in SEM images, such as the tendency to become apically swollen, and an overall faint ‘polytyly’ (Fig. 4D), and - at least in the Bowerbank type material of the nominal subspecies - the not infrequent presence of peculiar side branches or single long spines near the curved part in the middle. Possibly, this indicates that the microsclere derives from an end to end fusion of two incipient smooth microxeas - a more likely assumption than Topsent’s (1895) suggestion that the toxas are modified asters -, but firm proof for this hypothesis is wanting. Smooth microxeas are relatively common in several ancorinid genera.