Hymedesmia sp. 1

Pereira, Raquel, Larsson, Mats, Cárdenas, Paco & Thollesson, Mikael, 2025, Swedish marine demosponge fauna (Porifera: Demospongiae) sampled 80 years after Jägerskiöld’s inventory, European Journal of Taxonomy 983, pp. 1-64 : 39-41

Hymedesmia sp. 1

Fig. 18

Material examined

SWEDEN • 1 spec.; Slatbacken ; 59.0832° N, 11.2242° E; 19 m depth; 10 Nov. 2019; Mats Larsson leg. [MM-191110-1]; LAR-191110-PB100407–09; SCUBA; GenBank no.: OM415620 (28S D3-D5) .

Description

The specimen, of which a 5 mm fragment was collected, is thick encrusting and was found growing on a rock. The colour alive is saffron-yellow turning light greyish-white in ethanol. The surface presents high pore-sieves while oscules were not visible ( Fig. 18A ). The consistency of this specimen is extremely friable.

Skeleton

Unfortunately, due to the size and consistency of the fragment, it was not possible to do a section. The skeleton is composed of two size classes of acanthostyles both curved near the base: a) large acanthostyles with a poorly developed tyle and spines reach 2/3 of the shaft ( Fig. 18B ) measuring 354.9– 409.6 – 437.6± 47.43×4– 4.8 –6.0±1.10 µm (N=30), and b) small acanthostyles that are fully spined with spines more defined than for the large acanthostyles ( Fig. 18C ), measuring 134.7– 156.3 –291.6±3.16 ×3.2– 4.8 –9.6±1.41 µm (N=28). The ectosomal spicules are strongyles ( Fig. 18D ) measuring 179– 307.7 – 362.1± 37.11×1.4– 2.9 –4.3 ±0.71 (N =32). The microscleres are arcuated chelae, with a very wide and curved shaft and short alae ( Fig. 18E ): 20.6– 33.2 –64.2±12.99 µm (N =15).

Remarks

This specimen somewhat resembles Hymedesmia rathlinia Goodwin & Picton, 2009 . However, several characters distinguish it from this species: our specimen a) is light greyish white in ethanol rather than black or brown, b) it has no visible oscular papillae and c) it has chelae with a more curved shaft and shorter alae than what is presented for H. rathlinia . Therefore, we are inclined to conclude that our specimen is not conspecific with H. rathlinia . Also, our specimen lacks the polytyloted ectosomal spicules and the well-developed spines at the base of its large acanthostyles reported for Hymedesmia gustafsoni Alander, 1942 . Hence, we are disinclined to assign this specimen to that species.

Figures

Fig. 18. Hymedesmia sp. 1. GNM Porifera 1048 (LAR–191110-PB100407–09). A. Live specimen. B. Large acanthostyles ‘stitched’. C. Small acanthostyles. D. Tornotes/strongyles. E. Chelae.