Philinopsis ctenophoraphaga, Gosliner, 2011

Gosliner, Terrence, 2011, Six new species of aglajid opisthobranch mollusks from the tropical Indo-Pacific, Zootaxa 2751 (1), pp. 1-24 : 10-12

publication ID	https://doi.org/ 10.11646/zootaxa.2751.1.1
persistent identifier	https://treatment.plazi.org/id/394D87A1-FFF5-2341-FF5E-FEF6FA4E6F8A
treatment provided by	Felipe
scientific name	Philinopsis ctenophoraphaga
status	sp. nov.

Treatment

Philinopsis ctenophoraphaga View in CoL n. sp.

( Figures 1D View FIGURE 1 , 7 View FIGURE 7 )

Philinopsis sp. Behrens, 2003 .

Philinopsis sp. 1 Gosliner et al., 2008: 40, top photo.

Aglajid sp. 9 Rudman, 2005a; Koretz, 2005b; Francisco, 2008.

Aglajid sp. 11 Rudman, 2006a.

Material examined. Holotype: CASIZ 096249 , 3 m depth, old site of Seafari Resort , also known as Basura , Anilao , Mabini , Batangas Province, Luzon, Philippines, 13.756788°S, 120.921605° E, 17 March 1994, Bob Jackson GoogleMaps . Paratype: CASIZ 096245 , one specimen, dissected, 3 m depth, old site of Seafari Resort , also known as Basura , Anilao , Mabini, Batangas Province, Luzon, Philippines, 13.756788°S, 120.921605° E, 16 March 1994 GoogleMaps , T. M. Gosliner .

Geographical distribution. Philippines ( Behrens 2003), Indonesia ( Francisco 2006) and the Red Sea ( Koretz 2005b).

Etymology. The name comes from Ctenophora (Greek, meaning comb-bearer) and from the Greek phago, meaning to eat referring to the fact that this species has been observed feeding on benthic ctenophores.

Natural history. This species is nocturnally active. A specimen has been observed feeding on benthic ctenophores, identified here as Coeloplana meteoris Thiel ( Francisco 2006) .

Description. External morphology. The general body color of the living animal ( Fig. 1D View FIGURE 1 ) is light pinkish to maroon red. The pigment is a darker red on the anterior portion of the head, along the parapodial margins and along the elongated appendage on the posterior end of the cephalic shield. The entire dorsal and lateral surfaces of the body are ornamented with scattered opaque white spots that are surrounded by a faint halo of lighter pigment. Living animals are elongate (18–40 mm long), and wide (6–15 mm). The anterior end of the cephalic shield is slightly trilobate. The cephalic shield is roughly rectangular and terminates posteriorly into an elongate triangular appendage ( Fig. 7A View FIGURE 7 ) that is held upright when the animal is actively crawling ( Gosliner et al. 2008, top figure). The posterior shield is slightly rounded anteriorly and terminates in a bilobed pair of extensions that are relatively short, forming a skirt around the edge of the mantle. The parapodia are relatively short, leaving most of the cephalic and posterior shields visible. The gill is simply plicate consisting of 10 primary folds and is situated on the right posterior side of the animal.

Shell. The shell was completely dissolved during fixation, but occupies only the posterior extreme of the animal. The membranous periostracum remains and is relatively thin and evenly arched.

Digestive system ( Fig. 7B View FIGURE 7 ). The buccal mass is large and bulbous but is only weakly muscularized, without the thickened dense musculature observed in most other species of aglajids. The thin, translucent nature of the extruded buccal mass can be seen in the photo accompanying the comment on feeding of this species of ctenophores ( Rudman, 2006b). The buccal bulb entirely lacks any vestige of a radula. Anterior to the buccal bulb are small ventral and dorsal oral glands. 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, slightly narrower 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. 7B View FIGURE 7 ): 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 there is no distinct genital ganglion.

Reproductive system ( Fig. 7C, D View FIGURE 7 ). The arrangement of reproductive organs is monaulic ( Fig. 7C View FIGURE 7 ). From the large ovotestis, which is intermingled with the digestive gland, emerges the convoluted ampulla. The ampulla narrows into the hermaphroditic duct, which curves around the receptaculum seminis and enters short, coiled albumen and membrane glands with a single opening. At the point where the hermaphroditic duct coils around the receptaculum, it consists of several coils rather than being a straight duct. The larger mucous gland is bilobed with a massive primary lobe and smaller secondary one. The hermaphroditic duct 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 short and of uniform diameter throughout its length, including where it joins the genital atrium. From the genital atrium, the open, ciliated sperm groove leads to the cephalic penis. The penis ( Fig. 7D View FIGURE 7 ) consists of a penial sac and a simple curved prostate gland that is joined to the penial sac by a wide duct. Within the penial sac is a large rounded simple penial papilla ( Fig. 7D View FIGURE 7 ) that lacks any trace of armature.

Remarks. Philinopsis ctenophoraphaga is the only species of Philinopsis with a pink to maroon coloration and opaque white spots. It is also unique in having a more elongate and acutely pointed triangular posterior end of the cephalic shield. In most other species of Philinopsis , the posterior end of the head shield is rounded and shorter. In most members of Philinopsis , as in the present species, the posterior end of the cephalic shield is held upright when the animal is actively crawling. Philinopsis ctenophoraphaga is clearly more similar to the group of Philinopsis species that have a highly muscularized bulbous buccal mass (such as P. speciosa Pease, 1860 ), but is unique having a weakly muscularized buccal bulb compared the thick mass with dense rings of muscles evident in other species. This may be an adaptation to feeding on benthic ctenophores rather than more solid and muscular molluscan prey. Most species of Philinopsis with a bulbous buccal bulb also have a specialized penial morphology and have a very specialized penial morphology that Marcus & Marcus (1966) called a type D penis. The only species in this group that lack this type of penis are P. depicta Renier ( Gosliner 1980; present study) and P. falciphallus and P. coronata described here. These latter two species have elaborate penial armature. In P. depicta the simple penis and prostate are much longer the than the entire buccal bulb ( Gosliner 1980; present study), while in P. ctenophoraphaga the penis and prostate are much shorter than the buccal mass. Several unique features of the external morphology, digestive system and reproductive anatomy clearly distinguish this species of aglajid from all other described taxa.