The identity of Californian Philine auriformis

August 10, 1998
From: Bill Rudman

Realizing that there could be no satisfactory conclusion to the Californian Philine identity crisis until specimens from New Zealand could be re-examined, I searched through old material I had brought to Sydney many years ago and found 3 specimens of Philine auriformis, one of which was well enough preserved to re-examine the reproductive system. I have therefore compared two specimens from Bodega Bay directly with the New Zealand specimen and with dissection notes from material I examined years ago in New Zealand. Two very significant anatomical features were quickly apparent which suggest to me that Californian specimens are not Philine auriformis.


Comparison of Philine auriformis, from Stewart Is, New Zealand (LEFT), and specimens from Bodega Bay, California (RIGHT).
Shell height = 6mm. Gizzard plate length = 5mm (in both cases).

UPPER: Penis complex. (scale = 1mm)
in = incurrent sperm duct., ej = ejaculatory duct., pr = prostate gland.

LOWER: Whole radula. (scale = 1mm)

Fortunately I was able to compare specimens from California and New Zealand of the same size, as measured by the length of the shell (6mm in each case) and gizzard plate length (5mm in each case) which solved the potential problem of comparing sizes of preserved animals, possibly contracted to different degrees.

PENIS ANATOMY: Although the basic "plumbing" of the penial complex was the same, the proportional size of the prostate gland and ejaculatory duct are quite different. In the Californian species the ejaculatory duct is very short and the prostate gland forms a tightly tangled mass which sits betwen the straps of longitudinal muscle on the floor of the body cavity. In New Zealand animals the penial complex is much larger lying over the whole floor of the anterior part of the body cavity. The prostate gland forms a large mass of loosely coiled duct.

RADULA: There are no clear differences in shape of individual teeth between New Zealand and Californian specimens. However the radula and individual teeth of New Zealand specimens is only half the size of Californian animals of the same size.

These two species have been confused because we have so little information on the anatomy of the genus. In shell and gizzard plate size and shape they are very similar. In radular tooth shape they are very similar, and in penial plumbing they are also very similar. However the quite different tooth size and the proportional differences in the prostate gland and ejaculatory duct are real differences which need to be considered. ... Bill Rudman

Rudman, W.B., 1998 (Aug 10). Comment on The identity of Californian Philine auriformis by Bill Rudman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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