Hymedesmia hibernica Stephens, 1916


Family : Hymedesmiidae

Form: A thin encrusting sponge with large pore sieves, which is slightly translucent in appearance. Forms small patches typically less than 5 cm in maximum diameter.

Colour: Yellow

Internal characters

Skeleton: Basal layer of acanthostyles, in which the smaller category are more abundant, and in which acanthostyles are spread evenly but fairly sparsely, with some space in between them. The ascending columns of anisostrongyles are 58 spicules thick. The sponge is 500800μm thick.

Spicules: Large acanthostyles: 250325 μm by 512 μm. These acanthostyles have a slightly tylote head, which is more obvious in thinner specimens, and are spined on the head and up to half of the way up the shaft, although with much smaller spines. The head spines are often strongly curved up towards the shaft. Small acanthostyles: 110130 μm by 1012 μm, These are entirely spined with large recurved spines on the shaft, which become progressively sparser towards the tip. The head is not tylote, but is marked by denser spines that are often curved up towards the shaft. Ectosomal spicules: 200250 μm by 24 μm, with thin anisostrongyles. One end is usually thicker than the other, and neither end is tylote. No microscleres.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: Several species of Hymedesmia have similar appearance and identifications of this species would require examination of the spicules.

Editors: Claire Goodwin & Bernard Picton.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland