Californian invader not P.auriformis

Some features of the anatomy of the Philine from California as described by Gosliner (1995) differed slightly from my studies of Philine auriformis. After receiving Michelle's photos of Californian Philine I asked her to send me some specimens as I was not entirely happy that the photos were of one species. I was also not sure whether it, or one of them, was really Philine auriformis. [NOTE added 5 August 1998: See correction re P. auriformis penis anatomy]

Rather than post all the emails that have passed between us over the last 2 weeks, I have now dissected some specimens that Michelle has sent me from Bodega Bay and there are definitely two species and neither of them is the New Zealand Philine auriformis. The description of the anatomy by Terry Gosliner (1995) refers either to a third species, or is a combination of parts of the anatomy of the two quite distinct species that Michelle has sent to me. I list the main anatomical features of the two species below. A comparison is made with two New Zealand species Philine auriformis and Philine angasi which are described in Rudman, 1970, 1972a, 1972b. Further images of each species can be found on separate pages for each species.

SPECIES 1. Gizzard plates relatively large. Two are mirror images of each other and the third, which is slightly smaller, is symmetrical in shape. The plates are flattened on the outside and have a pair of deep pin holes in the centre of the plate. The radular formula is 1.0.1, the teeth being large and hook-like with a denticulate inner edge. The penis has a long tangled tubular prostate gland filling much of the anterior body cavity beneath the foregut. The shell is smooth with no sign of sculpture. It has similarities to Philine angasi, in radula, gizzard plate and penis structure, but the shell is more constricted. One major difference is the relative size of the shell and gizzard plates, almost equal in length in Philine angasi, but in this species the larger plates are only about one half the length of the shell.

SPECIES 2. 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 reduced outer 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 animal described by Gosliner appears to have the shell and gizzard plates of Species 2 and the penis of Species 1. Since the penial complex in Species 2 is relatively small and partially hidden in the body musculature while in Species 1 the coils of the prostate gland are a prominent feature of the anterior body cavity it is easy to see how a mistake could be made if an investigator thought they were dealing with only one species.

Clearly neither species is Philine auriformis. Is it possible to identify them? Firstly there has been no published discussion on whether one or both these species is native to the West Coast of America rather than being introduced. To my knowledge three species have been described from that region, Philine bakeri Dall, 1919, Philine californica Willett, 1944 and Philine alba Mattox, 1958. We only have anatomical information for Philine alba which differs in having small gizzard plates, a radular formula of 2.1.0.1.2, and a quite different shaped shell. The other two species are only known from their shells, both of which are similar to Michelle's specimens. Macfarland (1966), publishes some photos of a Philine he identifies with Philine bakeri but gives no anatomical information.

Unfortunately there are many species of Philine described world-wide for which we have no anatomical information. In many cases, the fragile flattened shell is not enough to distinguish species. From the links on Terry Gosliner's webpage on the invasion in California it appears that many of the marine species are from Japan. Perhaps that is the most likely place to find the origin of these two species of Philine.

SPECIES 1 belongs to a group of species which includes Philine angasi, from New Zealand and southern Australia, and Philine aperta, from Europe, with two large mirror image gizzard plates and a third smaller plate. A third species in that group, Philine orientalis A. Adams, 1854, occurs in Japan and has been recently described from Hong Kong (Morton & Chiu, 1990). The shape of the teeth and the gizzard plates in that description are very similar to those of the Californian Species 1. A species, Philine kurodai Habe, 1946, which is now considered a synonym of Philine orientalis, has a smooth constricted shell just like the Californian animal. Although it would need a proper comparison with Japanese material, my guess is that Species 1 is probably Philine orientalis from Japan and China. If it is this species, Morton & Chiu (1990) has some interesting information on the feeding biology of it in Hong Kong.

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 Species 1 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.

Sorry I can't be more definite. Your next problem is separating the two species in the field so your biological and ecological studies make some sense. I'm afraid as you have the living animals you are going to have to sort out a method. Species 1 seems to have more solid muscular parapodia and so appears more diamond shaped, while Species 2 has thinner parapodia making the body more cylindrical in shape. As a guess I would say the upper photo you sent is of Species 2 and the lower one is of Species 1. A quick way with preserved specimens would be to slit the skin and look at the shell. The shell of Species 1 is basically smooth, with some growth lines, while the shell of Species 2 is sculptured with spiral rows of shallow oval pits .... Bill Rudman.

Dall, W.H., 1919. Description of new species of Mollusca from the North Pacific Ocean in the collection of the United States national Museum. Proceedings of the U.S. National Museum, 56(2295): 293-371.

Gosliner, 1995. Introduction and spread of Philine auriformis from New Zealand to San Francisco Bay and Bodega Harbour. Marine Biology. 122: 249-255.

Habe, T., 1950. Philinidae in Japan. In: Illustrated Catalogue of Japanese Shells (Ed. by T.Kuroda), 7: 48-52.

MacFarland, F.M., 1966. Studies of opisthobranchiate mollusks of the Pacific Coast of North America. Memoirs of the California Academy of Sciences, 6: 1-546.

Mattox, N.T., 1958. Studies on the Opisthobranchiata: 2. A new tectibranch of the genus Philine. Bulletin of the Southern Californian Academy of Sciences, 57: 98-104.

Morton, B. & Chiu, S.T., 1990. The diet, prey size and consumption of Philine orientalis (Opisthobranchia: Philinidae) in Hong Kong. Journal of Molluscan Studies, 56: 289-299.

Rudman, W.B., 1970. A revision of the genus Philine in New Zealand with descriptions of two new species (Gastropoda, Opisthobranchia). Journal of the Malacological Society of Australia 2(1): 23-34.

Rudman, W.B., 1972a. Structure and functioning of the gut in the Bullomorpha. (Opisthobranchia) Part 3. Philinidae. Journal of Natural History 6(4): 459-74.

Rudman, W.B., 1972b. The genus Philine (Opisthobranchia, Gastropoda). Proceedings of the Malacological Society of London, 40(3): 171-87.

Willett, G., 1944. New species of mollusks from Redondo, California. Bulletin of the Southern Californian Academy of Sciences, 43: 71-73.

Bill Rudman.