Philine indistincta
Shell description
The thin shell is internal and transparent. The shell is cylindrical with an elongate oval shape when viewed from above. The top of the shell (apex) is blunted, while the opening of the shell is wide and the outer edge is wavy (scalloped). The shell is not umbilicated. The surface is covered by a pattern consisting of round to oval pits that are fused to form chain-like lines. The size of the shell varies between 4.2–5.7 mm.
Animal description
The body is white and the tissue covering the shell (mantle) is thick, but the pattern of the shell is visible through it. The head shield is indented and a middle groove is present. There are side extensions of the foot (parapodial lobes). This species is externally undistinguishable from its sister species Philine scabra, however they have different internal anatomy.
Anatomy
The radula consists of 14–18 rows of teeth with one outer lateral tooth and one inner lateral tooth on each side. The central (rachidian) tooth is absent. The outer lateral teeth are straight to curved with rounded tips and a broad base. The inner lateral teeth are curved with flattened tips and a broad base, the inner edge is denticulate. The salivary glands are much longer than the part of the foregut containing the radula (buccal mass). The gizzard is elongate and surrounded by muscle fibres, which are densest at the middle. The gizzard plates are identical, elongate and spindle-shaped, on the front they are amber in colour, and on the back the plates are lighter in colour with a transparent margin. On the back of the plates we also find two longitudinal slits. Regarding the male reproductive system there is an obvious separation between the long and thick prostate and the elongate sack-shaped penis chamber. The latter has thick walls and a large empty bulb, narrowing slightly towards the genital opening. The prostate becomes thinner towards the penis chamber. The penis is hook-shaped and the upper part is warty.
Ecology
Found between 18 and 20 m on mud-like soft bottom. Foraminiferans and one bivalve were found inside the digestive tract.
Geographical distribution
Only known from Norway where it occurs from Silavågen (66°19.20′N), Ålesund, Florø, and Bergen.
Ventral view of shell (SEM), scale bar = 1 mm.
Dorsal view of shell. H = 4.5 mm
Sculpture on dorsal surface of shell (SEM), scale bar = 100 µm.
Dorsal view of complete animal, scale bar = 1 mm.
Right lateral view of complete animal, scale bar = 1 mm.
Detail of radula (SEM), scale bar = 20 µm.
Gizzard (automontage picture), scalebar = 0.5 mm.
Ventral view of gizzard plate (SEM), scalebar = 200 µm.
Male reproductive system, scale bar = 250 μm. Abbreviations: pc: penis chamber, pr: prostate, b: bulb.
References
Ohnheiser LT og Malaquias MAE (2013). Systematic revision of the gastropod family Philinidae (Mollusca: Cephalaspidea) in the northeast Atlantic Ocean with emphasis on the Scandinavian peninsula. Zoological Journal of the Linnean Society 167(2): 273-326. DOI: 10.1111/zoj.12000.