Form: Thin sheets, up to 10cms across, but smaller typically.

Colour: Deep orange or red.

Smell: None.

Consistency: Soft.

Surface: Smooth, with subsurface exhalent canals visible. Densely covered with oval pore areas.

Apertures:

• Oscules may not be apparent. Pores in oval pore-sieve areas with smooth tissue between.

Contraction:

• Hard to determine because of thinness of sheets.

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Synonyms: Hymeniacidon jecusculum Bowerbank, 1866: 198

Internal characters

Skeleton: Hymedesmoid, with large primary acanthostyles and also smaller acanthostyles echinating the substrate. The rest of the skeleton consists of flexuous columns or fibres of many parallel tornotes, which fan out to run parallel with the surface. Arcuate isochelae reinforce the ectosome.

Spicules: Primary acanthostyles (a) measure 360-430 μm in length by ca. 7.5 μm in width. The head is thickly set with spines, whilst small, rather scattered, spines extend along the shaft but are much less frequent in the distal half. There is usually an abrupt curvature just above the head, the rest of the shaft being straight. The smaller acanthostyles (b) measure 120-140 μm in length by 5 μm in width. They are straight or very slightly curved, and conspicuously spined along the whole length. The spines on the head are fairly long, those on the shaft recurved. The tornotes (c) are slightly fusiform, thin, measuring 280-350 μm in length, by 5 μm in width. They are symmetrical, pointed at both ends. Microscleres are arcuate isochelae (d), ca. 20-26 μm in length.

Identity: External appearance is not particularly helpful, but the pore sieves and thin sheet may suggest a hymedesmid sponge. The spicule complement and sizes are distinct from the other Hymedesmia species in this Guide, but there are many other Hymedesmia species and the complex is currently ill-understood.

Distribution Map from NBN: Hymedesmia jecusculum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Hymedesmia jecusculum at iNaturalist World Species Observations database.

WoRMS: Hymedesmia jecusculum at World Register of Marine Species. Accepted name: Hymedesmia (Hymedesmia) jecusculum (Bowerbank, 1866). AphiaID: 133587.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Poecilosclerida; Hymedesmiidae; Hymedesmia

Voucher: BELUM : Mc1309. Loch Duich, Scotland