Hymedesmia sp. 4

Fig. 21

Material examined

SWEDEN • 1 spec.; Yttre Vattenholmen; 58.8754° N, 11.1056° E; 27 m depth; 16 Nov. 2019; Mats Larsson leg. [MM-191116-2]; SCUBA; LAR-191116-PB160433, 35; GenBank no.: OM415632 (28S D3-D5); voucher: GNM Porifera 1049 .

Description

The specimen, of which a 5 mm fragment was collected, presents an encrusting morphology, growing on rock covered with coralline algae. The colour alive of the specimen is orangish-yellow presenting white dots that are possibly embryos (Fig. 21A). Its colour in ethanol is beige. The specimen does not present evident osculum, pore-sieves nor pores. The consistency is very fragile after being preserved in ethanol.

Skeleton

Skeleton composed of two size classes of acanthostyles: a) large acanthostyles with a small base, spines covering 1/3 of the length, some spines seem poorly formed by being extremely thin in the shaft, measuring 212.5– 239. 1 –270.4 ± 23.37 × 4.1– 6.7 –10.1 ± 2.7 µm (N = 5), b) small acanthostyles are fully spined (Fig. 21B) and have a well-developed tyle at base, measuring: 104.– 116.3– 138.2 ± 9.32 × 3.4– 5.3 –7.8 ± 1.60 µm (N = 11) (Fig. 20B). Additionally, the skeleton also presents a single class size of anisostrongyles measuring 124.2– 220.9 –287.5 ± 26.32 × 0.8– 1.8 –4.6 ± 0.66 µm (N =46) (Fig. 21C).

Remarks

The specimen examined presents a peculiar external morphology by lacking apparent structure on its surface. However, given the presence of several ‘white dots’, it is possible that the specimen is riddled with embryos and has lost its usual external morphology. The specimen does not present any nucleotide difference in the 28S D3-D5 sequences, when compared with other specimens identified as H. hibernica (Fig. 2). However, the lack of pore-sieves and the presence of small acanthostyles, thinner than what is reported for H. hibernica leads us to keep this specimen as Hymedesmia sp.