(Bowerbank, 1858)
Species Overview
Iophon hyndmani (Bowerbank, 1858) is an irregularly branching or encrusting soft sponge with a pale yellow colour. The surface is iregularly wrinkeled and folded. It occurs typically in sheltered waters and often encrusts shells and other sessile organisms. It differs from the sympatric I . nigricans in becoming dark in preservation and in the possession of a second, smaller category of acanthostyles.
Taxonomic Description
Colour: Pale yellow, purple only when preserved. The colour change in alcohol to brown is distinctive. Paper labels are stained brown.
Shape, size, surface and consistency: (Iophon hyndmani MCS2) (Iophon hyndmani MCS3) (Iophon hyndmani MCS4) Branching-repent form, developed from a thin sheet or cushion. Branches dividing and anastomosing, typically 2-5 cm high, 3-4 mm in diameter. Surface wrinkeled or thrown into folds. Oscules small, scattered, not obvious. Consistency moderately soft, branches have no axial skeletal structure and apparently only develop fully in fairly sheltered conditions. Friable and not easy to section. No contraction. No smell, at least not strong.
Spicules: (Iophon hyndmani V spics) Megascleres : The ectosomal spicules are very thin tylotes, with barely swollen ends which bear crowns of a few spines: ca. 135-200 x 2 µm. Spicules of the main skeleton are acanthostyles, which are smooth in the distal (i.e. further from the base) half, typically 200-250 x 8 µm, but may range up to 320 µm. The echinating acanthostyles are entirely spined: 80-175 by 8 µm. Microscleres are spurred palmate anisochelae (Iophon hyndmani chela): 13-20 µm, and bipocilles (bipocilla) with saucer shaped ends: 9-15 µm long.
Skeleton: Ectosomal tylotes are arranged vertically or tangentially. Choanosomal skeleton is a plumoreticulation of loose, multispicular fibres, with echinating spicules. Spongin is scarce.
Ecology: On shells such as Modiolus modiolus , Chlamys varia , and Chlamys opercularis , on rocks, in localities sheltered from wave action, with no or slight tidal currents. On hydroids, other sponges, coralline algae, nullipores, fucoids, etc.
Distribution: Norway; British Isles; France; Mediterranean.
Etymology: Named after the collector of the type specimen, Mr G.C. Hyndman of Strangford Lough, N Ireland.
Type specimen information: The type is in the Natural History Museum, London: BNMH 1930.7.3.319 (dry) + 2 slides unregistered (Bk. 649 and 650). Orkney or Hebrides? (Halichondria hyndmani). MCS voucher: BELUM Mc138, Strangford Lough, N-Ireland.
Remarks
This description is based on voucher material collected from Strangford Lough in 1980 (the original type specimen was collected from Strangford Lough by Hyndman). The species may be difficult to identify with confidence when encrusting, but when well developed the characteristic branching combined with the colour are fairly distinctive. Many authors in the past regarded Bowerbank's (1866) Iophon spinulentum (as Microciona spinulenta) as a separate species; however, its characters fall within the variability of I . hyndmani ; the same applies to Bowerbank's (Gray's) Menyllus ingalli (as Halichondria ) and its synonym Halichondria scandens (Halichondria ingalli scandens).
A common sympatric species is I . nigricans , which is similar in growth form, though more squat with thicker bases and branches. That species turns a dark colour when taken out of the water. The two can be readily distinguished microscopically because I . nigricans has no special category of small echinating acanthostyles
Source: Ackers et al., 1985, 1992 (editors B.E. Picton, S.M. Stone, R. Earl and D. Moss).