Proc. malac. Soc. Lend. (1972) 40, 171. THE GENUS PHILINE (OPISTHOBRANCHIA, GASTROPODA) Downloaded from https://academic.oup.com/mollus/article/40/3/171/1087467 by guest on 27 September 2021 W. B. RUDMAN Department of Zoology, University of Auckland, Auckland, New Zealand INTRODUCTION An earlier study of Philine angasi and Philine auriformis, from New Zealand (Rudman, 1972), showed some interesting variations in the structure of the foregut. Specimens of P. falklandica and P. gibba, from Antarctica, were subsequently studied and with P. quadrata and P. powelli these species exhibit an interesting range of development within the genus. EXTERNAL FEATURES AND MANTLE CAVITY The external features of the animal, and structure of the mantle cavity are similar in all species studied. Published information shows these features are constant throughout the genus (Franz and Clark, 1969; Horikoshi, 1967; Mattox, 1958; Sars, 1878; Vayssiere, 1885). The following description is based on Philine auriformis Suter, 1909; for illustrations of P. auriformis, P. angasi and P. powelli, see Rudman (1970). The animal is elongate and the head shield is approximately two-thirds the length of the body. The posterior edge of the head shield sometimes has a median indentation and a thin median line, free of cilia, runs the length of the shield. The posterior or mantle shield, approximately one-third of the body-length, arises from under the head shield and extends some distance beyond the foot. There is usually a median notch on the posterior edge of this shield. The shell is internal and, as in the Aglajidae, there is a narrow ciliated duct running from the shell cavity to open in the left posterior quarter of the mantle shield. A small glandular pocket is situated on the posterior end of the mantle shield below the median notch of the notum (Figs. 4c, d, 5); it consists of a central ciliated pouch which is surrounded by a radially arranged group of gland cells. Most of the gland cells are clustered just below the epithelium with a few cells scattered more deeply. The granular cytoplasm of the cells stains brown in Weigert's iron haematoxylin and van Gieson and blue in Mallory and Heidenhain. This is the 'fossette glandulaire' of Pelseneer (1894). On each side of the mouth are two light brown patches. These patches, which are innervated, are considered to be sensory (Brown, 1934). Large glands, lying above and below the buccal bulb, open above and below the mouth. The granular cytoplasm of these gland cells stains light blue in Mallory and Heidenhain and light grey in Weigert and van Gieson. 172 PROCEEDINGS OF THE MALAGOLOGICAL SOCIETY At the posterior end of the mantle shield, the sides fold down and under, forming a posterior border to the mantle cavity (Fig. 5). The spiralling raphae, at the posterior end of the cavity, run dorso-ventrally. At the anterior end, on the right side of the body, is the genital opening; from this the external seminal groove runs forward to the opening of the penial sac on the right hand side of the head. The simple plicate gill is relatively small and is attached to the roof of the mantle cavity. Just behind it is a short length of intestine, the anus opening alongside the lower raphe. The Downloaded from https://academic.oup.com/mollus/article/40/3/171/1087467 by guest on 27 September 2021 ciliation of the raphae draws water down both sides of the body, over the gill and out posteriorly. The foot is relatively short ending approximately half way down the mantle shield. The parapodia enclose the sides of the body and fold over the edges of the dorsum. ALIMENTARY CANAL The species studied show a wide variety in the structure of the alimentary canal, and each species will be discussed separately. A full account of the structure and functioning of the gut of P. angasi and P. auriformis has been published separately (Rudman, 1972). Philine quadrata (Wood, 1839) The buccal bulb is relatively large being between one-third and one-half the length of the anterior body cavity. There are four pairs of extrinsic muscles. Two large lateral protractors run from the posterior end of each side of the buccal bulb to the body wall at the side of the mouth. There are also two pairs of anterior muscles, one attached mid-dorsally, the other mid-ventrally. The salivary glands, opening on each side of the oesophageal opening, are approximately as long as the buccal bulb. The radular formula is 2.1.0.1.2, the inner row of teeth being typically philinid in shape, the inner edge denticulate, while the outer two teeth on each side are much smaller and are similar in shape to those of P. gibba (Fig. 2a). The radula of P. quadrata has been illustrated by Sars (1878, Table 12, Fig. 7). The specimens I studied possessed neither gizzard nor crop. However, both Sars (1878) and Marcus and Marcus (1969) described a small crop, and the latter stated that the epithelium is thrown into small folds. The rest of the gut is similar to that of Philine auriformis and P. angasi. In one specimen food remains were found in the stomach. These consisted of two conical sand tubes, open only at the wide end. These were tentatively identified as the test of a spirotrich protozoan of the genus Tintinnopsis Stein (Kudo, 1960). Philine falklandica Powell, 1954 The buccal bulb is large, filling most_of the anterior body cavity (Figs, la, b, 2c). It has four pairs of extrinsic muscles; the numbering is identical to that used for Philine angasi and P. auriformis described in an earlier study (Rudman, 1972). A muscle (P.M.2) arises on each side, just below the oesophageal opening, and runs forward to the body wall at the side of the mouth; another pair of long muscles RUDMAN: PHILINE 173 Downloaded from https://academic.oup.com/mollus/article/40/3/171/1087467 by guest on 27 September 2021 P.M. 2 S.G.- CR. G. OES. (W FIG. I. (a) Philine falklandica, foregut, X 10; (b) Philine falklandka, gizzard plates, x 20; (c) Philine gibba, foregut, X 13. B.G., buccal ganglion; CR., crop; G., gizzard; OES., oesophagus; P.M., protractor muscle; S.G., salivary gland. (P.M.3) arises below the former and each is inserted in the body wall below and to the side of the mouth. The other two pairs arise at the anterior end of the buccal bulb and run out to the body wall, one dorsally (P.M.I) and one ventrally (P.M.6). The large pair of muscles (P.M.4, 5), acting as retractors in P. angasi and dilators in P. auriformis, are not present in this species. The radular formula is 2.1.1.1.2. The central tooth, in each row, is a very small, semi-circular, raised plate. The inner lateral tooth of each side is large and has very insignificant serrations along the inner edge, while the outer two rows are small and hook-shaped. This radula is similar to that 174 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY Downloaded from https://academic.oup.com/mollus/article/40/3/171/1087467 by guest on 27 September 2021 R.S. (c) RM.3 P.M.6 FIG. 2. (a) Philine gibba, radula, x 100; (b) Phitine gibba, buccal bulb and gizzard, x 20; (c) Philine falklandica, buccal bulb, X 10; D.M., dilator muscles; P.M., protractor muscle; R. M., retractor muscle; R.S., radular sac. of P. gibba (Fig. 2a) and the occurrence of a central tooth is obviously primitive. The oesophagus enlarges to form a thin-walled crop followed at the posterior end by a small gizzard containing three brown chitinous plates (Fig. lb). For the size of the animal, the gizzard plates are extremely small; in one specimen with a shell measuring 16'5 X 11 mm the gizzard plates were 1-5 mm long and in another specimen with a shell 15 X 10 mm, the plates were 1-2 mm long. This can be com- r RUDMAN: PH1LINE 175 pared with both P. angasi and P. auriformis in which the plates are between half and two-thirds the length of the shell. The rest of the alimentary canal is typical of the genus. Philine gibba Strebel, 1908 The buccal bulb is relatively much smaller in size than that of the preceding Downloaded from https://academic.oup.com/mollus/article/40/3/171/1087467 by guest on 27 September 2021 species and the proportion of buccal bulb to gizzard is as in P. angasi. The extrinsic musculature is similar to that of P. falklandica but there is a pair of dilator muscles (Fig. 2b, D.M.) running out, one from each side of the oesophageal opening. There is also a pair of long thin muscles (R.M.) attached to the anterior end of the buccal bulb which run back to the body wall behind the buccal bulb (Fig. 2b). The radula is similar to that of P. falklandica but the inner edge of the large lateral teeth is slightly denticulate. The gizzard is large containing three large, oval chitinous plates. In a specimen with a shell 9 mm long, the gizzard plates were 3 mm long. There is no oesophageal crop. Philine powelli Rudman, 1970 The structure of the foregut is very similar to that described for P. auriformis (see Rudman, 1972). However, the large lateral muscles which act as dilators in that species are longer in P. powelli, joining the body wall some distance behind the buccal bulb, and acting as retractor muscles.