Philine auriformis Suter, 1909
Philine auriformis is a sea-slug with an internal shell known as a bubble-shell. It has a well-developed head-shield, roughly quadrangular, comprising about 2/3 of the body length. Narrow parapodia extend from the foot, but do not meet in the midline of the body. The anterior end of the head shield is slightly indented. The posterior end of the body is rounded when the gills are extended and squarish when the gills are partially contracted. The posterior shield is short and roughly quadrangular, ending in two posterior lobes. Three spindle-shaped gizzard plates are visible through the dorsal and ventral surfaces of the body. There are two paired gizzard plates, roughly diamond-shaped. The shell occupies most of the body cavity immediately ventral to the dorsal portion of the posterior shield. The shell is broad, shallowly curved, with a short and narrow columella. The protoconch is tightly coiled and consists of three whorls. The surface of the shell is finely dotted. The buccal organ is large and muscular with the radular sac forming a postero-ventral lobe. The gizzard contains three similar calcareous spindle-shaped plates, which are convex on the ventral surface. Adult slugs are 15-30 mm in length. The body is translucent white to yellowish white. The shell is visible through the posterior tissue of the dorsal shield. Hancock's organs (i.e. paired chemosensory organs situated between the foot and the head-shield) are reddish brown and consist of 12 simple folds. Description based on Willan et al. (1984), Gosliner (1995), Behrens (2004), Gosliner and Williams (in Carlton 2007), and Price et al. (2011).
When exotic Philine sp. invaded California waters, there was much confusion about their identity. William Rudman (Rudman 1998) doubted the identification of P. auriformis, and one or more additional species were suspected. At one time, four species of introduced Philine: P. aperta, P. japonica, P. orientalis, and P. auriformis were listed for California waters (Behrens 2004). A recent molecular analysis has reduced the crowd to two, P. auriformis and P. orientalis (Krug et al. 2012).
Philine aperta Linneaus 1767 is native to the Atlantic coast of South Africa. This slug was erroneously reported to be present on the California coast (Behrens 2004; Krug et al. 2012). It was also lumped with the European species, P. quadripartita in the 20th century, and given a range from Britain to South Africa, but the two species are now treated as separate (Price et al. 2011).
Philine orientalis, native to the Northwest Pacific, is introduced and established on the California Coast in San Francisco, Tomales, and Bodega Bays (Price et al. 2011; Krug et al. 2012).