On Philine

[NOTE inserted Aug 5: The information here on penis structure is wrong. See correction . .. Bill Rudman.]

This is one of two species of Philine which have "invaded" California recently. They have been mistakenly identified with the New Zealand species Philine auriformis. A discussion on this is found elsewhere in the Sea Slug Forum.

This unidentified species which I have labelled SPECIES 2 has the following main characters:

Gizzard plates are all of similar spindle shape with distinctive pits on the outside face, as illustrated by Gosliner. These are similar to those found in Philine auriformis. The radular formula is 1.1.0.1.1 with a large inner tooth on each side of the midline, flanked by an outer reduced tooth as illustrated by Gosliner. The penial sac is relatively small and the prostate is a small blind sac partially embedded in the longitudinal foot musculature. It is similar to the penis of Philine falklandica (see Rudman, 1972b). The shell has a spiral beaded sculpture as illustrated by Gosliner.

The photos and drawing on the right are from specimens sent by Michelle Chow from Bodega Bay, California, July 1998.
UPPER LEFT: 2 shells, the larger being slightly damaged on the outer edge (Scale 10mm). UPPER RIGHT: Penis and prostate gland from animal 23mm long preserved (shell 13mm).
MIDDLE: Shell sculpture.
LOWER: Outer side of gizzard plates (Scale 10mm).
PHOTOS: Bill Rudman.

SPECIES 2 has similarities to Philine auriformis but its penial anatomy is quite different. I know of no published description of a species with this combination of characters. If Californian Species 1 (which I tentatively identify as Philine orientalis) is from Japan, then it is probable that Species 2 is as well. Unfortunately I know of no anatomical studies of other Japanese species except for one description by Habe (1950) of a species he identified as Philine argentata Gould, 1860 which has a radula and gizzard similar to Species 1 but a dentate upper margin to the shell like in Philine powelli Rudman, 1970.

Bill Rudman.