Philine punctata (J. Adams, 1800)

PDF available at www.researchgate.net/publication/351091121_Philine_puncta…

Current taxonomy: World Register of Marine Species www.marinespecies.org/aphia.php?p=taxdetails&id=140758
Synonyms:Colpodaspis punctata (J. Adams, 1800); Bullaea alata Forbes, 1844; Ossiania alata (Forbes 1844); Philine pusilla M. Sars, 1859.
GLOSSARY below.

Shell Description ( 01 Philine punctata)
The shell is up to 2.8 mm high (longest dimension) (Ohnheiser & Malaquias, 2013). It is thin, fragile, nearly transparent and glossy white with spiral rows of impressed, unconnected dots. The spire is very small with narrow, deep, channelled sutures. It does not protrude beyond the encompassing body whorl. The large aperture is nearly as long as the height of the shell. It occupies two thirds of the apertural view of the shell.

Body Description
The body is up to 5 mm long. All surfaces are smooth and there are no tentacles. The anterior half of the dorsum is a shovel-like cephalic shield ( 02 Philine punctata). The posterior half of the dorsum consists of a translucent mantle enclosing an interior shell ( 03 Philine punctata). The posterior of the mantle is an open sleeve ( 04 Philine punctata) within which the shell can be seen through a thin membrane, and the gill in the mantle cavity is sometimes visible.
The extended sole is an oblong with rounded corners and a slight waist ( 05 Philine punctata). It has similar, but less intense, brown stippling to that on the dorsum. The foot has parapodial lobes extending up the flanks of the animal (02 Philine punctata & 03 Philine punctata). Its mouth and a small part of the head are visible ventrally ( 04 Philine punctata ). The radula has about 12 transverse rows of teeth ( caption 06 Philine punctata).
The epithelium is translucent yellowish, densely covered by brown or reddish brown stipple, apart from the whitish anterior edge of the cephalic shield and foot ( 03 Philine punctata ), and a transverse pale band on the mantle ( 06 Philine punctata). The summit of the band is sometimes eroded, exposing a portion of the shell which may be abraded at the same location ( 07 Philine punctata).

Key identification features
1) General colour of body is brown with distinct pale transverse band on mantle ( 06 Philine punctata).
2) Shell has spiral rows of separate impressed dots (occasionally a few fused) ( 01 Philine punctata).

Similar species
Philine spp.
1) Other British and Irish Philine spp. have paler bodies.
2) Shells of P. quadrata, P. scabra and P. catena have spirals of sculpture spots, but they are linked as chains. Shell of P. pruinosa has reticulate sculpture of spiral and longitudinal striae with slightly raised dots where they intersect.

Runcina coronata (Quatrefages, 1844)
1) Has brown body, often with yellow marks on rear of head and rear of mantle, and a medial black band on the foot protruding from the rear ( 08 Philine punctata). No parapodial lobes, and cephalic shield is fused to the mantle.
2) Has no internal shell.

Ecology and behaviour
Sublittorally it is found on silty sand, and on shells and stones covered in Bugula (polyzoan). It occurs littorally at low water spring tides among encrusting organisms and sediment on the sides of large rocks standing on silty sand, on silty gravel under rocks, and on small stones covered in marine growths. Its diet is unknown.
Spawn is deposited as a string of about 200 ova wrapped like a ball of wool within a spherical, transparent, colourless, gelatinous capsule with diameter of about 1.5 mm ( 09 Philine punctata. The capsule is attached to the substrate by a gelatinous stalk. Individual egg cases are transparent colourless showing the whitish embryos with a distinct pitchy spot. The embryos rotate slowly within the ova.

Distribution and status
P. punctata is found from southern Norway to the Mediterranean; GBIF map www.gbif.org/species/2291549 . It is widespread and not uncommon in Britain, but the small live animal is easily overlooked. Many British records are of dead shells found in shell sand; UK distribution map, NBN, species.nbnatlas.org/species/NHMSYS0021056057

References and links
Ohnheiser, L.T, and Malaquias M. 2013. Systematic revision of the gastropod family Philinidae (Mollusca: Cephalaspidea) in the north-east Atlantic Ocean with emphasis on the Scandinavian Peninsula. Zoological Journal of the Linnean Society, 167 (2): 273–326
www.researchgate.net/publication/260190461_Systematic_rev…

Smith, I.F. 2011. Images of live Philine punctata. Mollusc World 26:3

Thompson, T.E. 1976. Biology of opisthobranch molluscs 1. London, Ray Society.

Current taxonomy: World Register of Marine Species www.marinespecies.org/aphia.php?p=taxdetails&id=140758

Glossary
aperture = mouth of gastropod shell; outlet for head and foot.
cephalic shield = shovel-like feature covering front part of philinid sea slugs.
epithelium = tissue forming outer layer of body surface and lining the alimentary canal and other hollow structures.

height = (of gastropod shells, as in most publications) distance from apex of spire to base of aperture but, as difficult to measure on Philine, the longest linear dimension is used in this account.

LWS = low water spring tide, two periods of a few days each month when tide falls lowest.

mantle = sheet of tissue covering visceral mass of molluscs. Secretes shell of shelled species, and forms part or all of dorsal body surface (notum) of those without shells.

parapodial lobes = flaps of the parapodium (fleshy structure used in locomotion) which extend up the sides of some sea slugs.

radula = chitinous ribbon of teeth; extended on odontophore to rasp food.
suture = groove or line where whorls of gastropod shell adjoin, or joint line on other items, such as egg capsules.