Aplysilla sulfurea Schulze, 1878

Aplysilla sulfurea Schulze, 1878 View in CoL

Fig. 6 View Fig

Aplysilla sulfurea Schulze, 1878: 405–416 View in CoL , pl. XXIII– XXIV figs 15, 19–30.

Aplysilla sulphurea View in CoL – Alander 1942: 18.

Material examined (3 specimens)

SWEDEN • 1 spec.; Saltbacken ; 59.0832° N, 11.2242° E; 30 m depth; 24 Apr. 2018; Mats Larsson leg. [MM-180424-1]; SCUBA; LAR-180424-4596; voucher: GNM Porifera 991 GoogleMaps • 1 spec.; Lunneviken ; 59.0546° N, 11.1690° E; 30 m depth; 18 Sep. 2018; Mats Larsson leg. [MM-180916-1]; SCUBA; LAR-180918-7202, 7205; voucher: GNM Porifera 992 GoogleMaps • 1 spec.; Yttre Vattenholmen ; 58.8754° N, 11.1056° E; 30 m depth; 16 Nov. 2019; Mats Larsson leg. [MM-191116-1]; SCUBA; LAR-191116-PB160463–64, 66; voucher: GNM Porifera 993 GoogleMaps .

Description

The specimens have a thick encrusting morphology. The living specimens had a yellow sulphur colour, turning to dark purple when fixed in ethanol. The surface is conulose ( Fig. 6A View Fig ). In some specimens (in situ and while expanded) it is possible to observe a network of membranous polygonal areas heavily pierced by multiple ostia, enabling to see the inside of the sponge. The oscula are spread, often on oscular chimneys, and with translucent membranous rims.

Skeleton

The skeleton is composed of dendritic fibres (i.e., the fibres might ramify but never coalesce) attached to a spongin basal plate, clear of debris ( Fig. 6B View Fig ). The fibres have a distinct core, darker, that occupies 80–90% of the total thickness of the fibre. Fibres are thicker at the base becoming thinner toward the tip.

Ecology and distribution

Specimens of this species have been reported worldwide. However, most reports are in the Atlantic, North Sea and Mediterranean (GBIF.org 2021) from the littoral zone (under rocks or in crevices) to 230 m ( Ackers et al. 2007). The type locality is in the Adriatic Sea.

Remarks

The species of the genus Aplysilla can be discriminated by the colour as it seems to be a stable feature in the genus ( Bergquist 1980). However, a few specimens identified as A. sulfurea have been reported with a pale yellow colour as opposed to the typical bright/sulphurous yellow. All specimens we examined had a bright yellow colour.

The distinction between species relies primarily on external features, such as colour and conule size. These features are difficult to observe in preserved, or damaged specimens, which could explain the low number of described species. The microscopic features that distinguish the species are: the fibre pigmentation, and fibre ramifications, which can be easily overlooked, or dependent on the size of the sponge.