Hymedesmia undefined-1

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.