Philinopsis coronata, Gosliner, 2011

Gosliner, Terrence, 2011, Six new species of aglajid opisthobranch mollusks from the tropical Indo-Pacific, Zootaxa 2751 (1), pp. 1-24 : 7-9

Philinopsis coronata n. sp.

( Figures 1C , 2B , 5 , 6 )

Material examined. Holotype: CASIZ 1822887 , dissected, 12 m depth, Mainit Bubbles , Mabini, Batangas Province, Luzon, Philippines, 13.686025°S, 120.895167° E, 23 May 2010, P. Paleracio.

Geographical distribution. Known only from the Philippines (present study).

Etymology. The name “coronata” comes from the Latin corona, meaning crown. This refers to the ring of rounded tubercles at the apex of the penis, which resemble a crown.

Natural history. This species is found in the same habitat and at the same locality as the preceding species on coral rubble in 15 m depth. Little else is known about its biology.

Description. External morphology. The living specimen was 28 mm in length and 7 mm wide. The general body color of the living animal ( Fig. 1C ) is whitish with a “v”-shaped maroon patch present on the head. Maroon spots are present along the parapodial margins. The entire dorsal and lateral surfaces of the body are ornamented with scattered, irregular yellow spots and a few whitish patches. The ventral surface of the single animal is pale pink with a series of large yellowish and maroon spots on the foot. Living animals are elongate and wide. The anterior end of the cephalic shield is indented but blunt and quadrangular. The cephalic shield is roughly rectangular and terminates posteriorly with an elongate, rounded papilla. The posterior shield is slightly rounded anteriorly and terminates in an elongate conical posterior protrusion that is well-elevated from the base of the shield. The two lateral posterior lobes of the posterior shield are elongate and simply rounded. The left posterior lobe is longer than the right one. The parapodia are very short, leaving most of the cephalic and posterior shields visible. The gill is simply plicate consisting of 13 primary folds and is situated on the right posterior side of the animal.

Shell ( Fig. 2B ). The shell is relatively thickly calcified and consists of a narrow band that occupies the posterior extreme of the animal. There is a thin membranous periostracum that is slightly more extensive anteriorly than the calcified portion. The area at the base of the shell near the protoconch is more thickly calcified than the rest of the shell and a posterior lobe is present on the left side of the shell.

Digestive system ( Fig. 5A ). The buccal mass is large, highly muscularized and slightly elongate posteriorly. It occupies the entire length of the cephalic shield. The buccal bulb lacks any vestige of a radula. There is a large ventral oral gland and the small dorsal oral glands were indistinct. At the posterior end of the buccal mass, near the junction with the crop, is a pair of elongate salivary glands. The crop is large and saccate, wider than the buccal bulb. The crop narrows posteriorly and enters the digestive gland. The intestine emerges from the right side of the digestive gland and terminates near the posterior end of the body near the base of the gill.

Central nervous system ( Fig. 5A ): The circumesophageal nerve ring consists of paired cerebral, pedal and pleural ganglia and a single supraintestinal ganglion on the right side. The cerebral and pedal commissures are both elongate with well-separated respective ganglia. Immediately adjacent and posterior to the right pleural ganglion is the supraintestinal ganglion. From its posterior end is the right branch of the visceral loop and the osphradial nerve. The two lateral branches of the visceral loop join posteriorly at the posterior ganglia. The left visceral loop enters the subintestinal ganglion, while the right lateral nerve enters the visceral ganglion. The visceral ganglion is larger than the subintestinal ganglion. From the visceral ganglion is the genital nerve, which has a distinct genital ganglion.

Reproductive system ( Fig. 5B, C , 6 ). The arrangement of reproductive organs is monaulic ( Fig. 5A ) with a single branch to the albumen and membrane glands. From the large ovotestis, which is intermingled with the digestive gland, emerges the convoluted ampulla. The ampulla narrows into the hermaphroditic duct, curves around the receptaculum seminis and has a single branch to the short, coiled albumen and membrane glands. The larger mucous gland is bilobed with a massive primary lobe and smaller secondary one. The ampulla then joins the duct of the receptaculum seminis and continues to the genital atrium where it joins the duct of the bursa copulatrix. The bursa is large and spherical. Its duct is narrow where it joins the bursa and widens until its widest portion at the highly muscularized genital atrium. From the genital atrium, the open, ciliated sperm groove leads to the cephalic penis. The penis ( Fig. 5C , 6 ) consists of a penial sac and a lobate prostate gland that is joined to the penial sac by a narrow duct. Within the penial sac is a large, rigid conical penial papilla ( Fig. 6A,B ). Anterior to the penial papilla and posterior to it are two areas of spines on the folds of the penial sac ( Fig. 5C , 6A ). The apex of the papilla is covered with a ring of rounded tubercles.

Remarks. Philinopsis coronata is very similar in its external and internal appearance to P. falciphallus , described above. The external anatomy and color pattern are very similar. In P. coronata , there is more yellow pigment with less maroon and the posterior lobe of the posterior shield is more elongate than in P. falciphallus . Also, P. coronata has more elongate posterior extension of the foot than does P. falciphallus . Both species have yellow and maroon on the foot, but in P. coronata there is no maroon line, but rather a series of maroon spots. The shell of P. coronata has a more elongate posterior wing on the right side than is found in P. falciphallus . Internally, the digestive and central nervous systems of the two species exhibit no apparent differences. The arrangement of the posterior reproductive organs of the two is also quite similar, but the genital atrium of P. coronata appears to be more highly muscularized. The most significant difference between these two species is found in the structure of the penis. Both species have a simple penis and prostate connected by a narrow duct and both are the only species of Philinopsis with an armed penial papilla. Despite these similarities, the armature of the penis is markedly different in the two species. In P. falciphallus , there is a large chitinous spine and a series of smaller spines on the penial papilla. In P. coronata there are two regions of spines, one anterior to the penial papilla and the other one situated posteriorly to the papilla. The apex of the papilla of P. coronata has a ring of rounded tubercles that is not present in P. falciphallus . The specimens are similar in size and maturity so it is likely that the observed penial differences are due to differences in maturity or preservation. These significant differences in penial morphology confirm that these specimens represent distinct taxa.

Figures

FIGURE 1. Living animals A. Philinopsis falciphallus n. sp., paratype, CASIZ 177678, Mabini, Philippines, arrow indicates location of posterior lobe. B. Philinopsis falciphallus n. sp., CASIZ 177678, Mabini, Philippines, ventral view showing markings on foot. C. Philinopsis coronata n. sp., holotype, CASIZ 182887, Mabini, Philippines. D. Philinopsis ctenophoraphaga n. sp. CASIZ 096245, Mabini, Philippines, E. Chelidonura mandroroa n. sp., holotype, CASIZ 173595, Radama Islands, Madagascar F. Chelidonura alisonae n. sp., CASIZ 174177. G. Odontoglaja mosaica, paratype, CASIZ 173419, Radama Islands, Madagascar. H. Odontoglaja mosaica, paratype, CASIZ 173415, Radama Islands, Madagascar. Photos by T. M. Gosliner.

FIGURE 2. Shells. A. Philinopsis falciphallus. n. sp., paratype, CASIZ 177678, Mabini, Philippines. B. Philinopsis coronata n. sp., holotype, CASIZ 182887, Mabini, Philippines. C. Chelidonura mandroroa n. sp., paratype, CASIZ 182002, Radama Islands, Madagascar D. Chelidonura alisonae n. sp., paratype, CASIZ 174146, Easter Island.

FIGURE 5. Internal anatomy, Philinopsis coronata n. sp., holotype, CASIZ 182887 A. Digestive and central nervous system anatomy, bb buccal bulb, c cerebral ganglion, cr crop, gg genital ganglion, pe pedal ganglion, pl pleural ganglion, sg salivary gland, sp supraintestinal ganglion, su subintestinal ganglion, v visceral ganglion. B. Posterior reproductive organs, al albumen gland, am ampulla, bc bursa copulatrix, ga gential atrium, me membrane gland, mu1 mucous gland large, mu2 mucous gland small, ot ovotestis, rs receptaculum seminis. C., D. Penis, as anterior penial spine, p penial papilla, pr prostate, ps posterior penial spines.

FIGURE 6. Philinopsis coronata n. sp., holotype, CASIZ 182887, scanning electron micrographs of penis A. Penial sac showing location of as anterior spines, pp penial papilla, ps posterior spines B. Penial papilla and posterior spines C. Penial papilla showing ring of tubercles on apex. D. Detail of anterior spines. E. Detail of posterior spines.