Chelidonura alexisi Gosliner, 2015

Gosliner, Terrence, 2015, Three New Species of Aglajid Cephalaspidean Mollusks from the Tropical Indo-Pacific of the Verde Island Passage, Proceedings of the California Academy of Sciences 62 (6), pp. 191-205 : 199-200

Chelidonura alexisi Gosliner , sp. nov.

Figures 1E , 2C , 6.

MATERIAL EXAMINED.— HOLOTYPE: PNM 41062 , dissected, sub-sample removed for molecular study, 20 m depth, crawling on sandy slope, Mainit Bubbles , Mabini, Batangas, Philippines, 13.68651°S 120.89533°E, 18 May 2009, Alexis Principe . PARATYPES: CASIZ 204580 , 3 specimens, not dissected, 17 m depth, crawling on sandy slope, Shipyard , Puerto Galera Bay, Mindoro Oriental, Philippines, 13.516026°S 120.965622°E, 27 March 2015 , T. Gosliner and Kelly Markello.

GEOGRAPHIC RANGE.— Known only from southern Luzon Island, Philippines (present study) and Puerto Galera (northern Mindoro Island) (Carole Harris, pers. comm., unpublished data).

ETYMOLOGY.— The name alexisi is named for dive guide and photographer Alexis Principe who found the only specimen of this species. Alexis has made many new discoveries and has a great passion for the unique biodiversity of the Philippines.

NATURAL HISTORY.— This species was found crawling on the surface of silty sand in the open in 20 m of water.

DESCRIPTION.— External morphology: The living animal is 30 mm in length. The general body color of the living animal ( Fig. 1E ) is uniformly black with numerous minute punctations of opaque white. This pigment pattern is found on the cephalic and posterior shields and parapodia,but opaque white spots are absent from the foot. One specimen observed in Puerto Galera (unpublished data) lacked opaque white spots. The living animals are elongate, and narrow. The anterior end of the cephalic shield is quadrilobate. Fine sensory appendages are evident along the anterior margin of the head and in the preserved specimen individual nerve cells appear to be found at the base of each bristle-like appendage. The cephalic shield is elongate making up almost two-thirds of the body length. It is triangular, broadest anteriorly and terminates posteriorly with a short rounded lobe. The posterior shield is well rounded anteriorly and terminates in a long bilobed appendage on the left side and a short, broad posterior lobe on the right The parapodia are relatively wide, largely covering most of the cephalic shield at its widest part. The gill is plicate with 8 primary folds.

Shell ( Figs. 2C , 6A): The shell is relatively thinly calcified and has a shiny brownish tinge. It occupies most of the posterior shield. The shell is thin and brittle and fragmented into four pieces when it was removed from the holotype. There is a broad anteriorly-directed wing and an elongate extension that is deeply embedded in the posterior shield right to the end of the left posterior lobe. The protoconch is visible at the base of the shell.

Digestive system: The buccal mass is small, highly muscularized, occupying the anterior onefourth of the cephalic shield. The buccal bulb entirely lacks any vestige of a radula. There is a small dorsal oral gland and a large ventral one. At the posterior end of the buccal mass, near the junction with the crop, is a pair of elongate salivary glands. The crop is small and saccate, about the same width as 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. 6B): The circumesophageal nerve ring consists of paired cerebral, pedal, pleural ganglia and a single supraintestinal ganglion on the right side. The cerebral and pedal commissures are both short with poorly separated 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, whereas the right lateral nerve enters the visceral ganglion posterior to its junction with the subintesinal ganglion. The visceral ganglion is larger than the subintestinal ganglion. From the visceral ganglion is the genital nerve, which lacks a distinct genital ganglion.

Reproductive System (Figs. 6C–D): The arrangement of reproductive organs is a modified monaulic arrangement (Fig. 6C). From the large ovotestis, which is intermingled with the digestive gland, emerges the convoluted ampulla. The ampulla narrows into the hermaphroditic duct, which curves along the inner face of the receptaculum seminis and enters short, coiled albumen and membrane glands. It appears to have only a single entrance to these glands. The larger mucous gland is curved with a massive single lobe. The hermaphroditic duct then joins the duct of the long receptaculum seminis and continues to the genital atrium where it joins the thick, muscular genital atrium. The bursa copulatrix is large and spherical. Its duct is wide and short and widens slightly at the genital atrium. From the genital atrium the open, ciliated sperm groove leads to the cephalic penis. The penis (Fig. 6D) consists of a penial sac and an elongate, curved prostate gland that is joined to the penial sac by a short, narrow duct. Within the penial sac is a large penial papilla that is ribbed, lobed and blunt. At the base of the papilla are about 5–7 small glandular structures that have a small chitinous hook extending outward from the glandular base (Fig. 6D). The primary lobe of the penial papilla has a conical protuberance near the middle of its length. A second protuberance is found near the apex of the papilla.

REMARKS.— This species is similar in external color pattern to Chelidonura inornata Baba, 1955 and some color variants of C. sandrana Rudman, 1973 ( Gosliner et al. 2008). In C. inornata the body is black with small opaque white spots, but white spots are absent from the cephalic shield and posterior shield whereas in C. alexisi the spots are present on the entire body except for the inside of the parapodia. Additionally, specimens of C. inornata have a broad anterior opaque white C. mandroroa and C. sandrana , but all of these species have differences in external and internal morphology, as well as genetic differences.

Figures

FIGURE 1. Living animals A–B. Philinopsis aliciae sp. nov., holotype, PNM 41061, Mabini, Philippines. C. Philinopsis buntot sp. nov., holotype, PNM 41060, Mabini, Philippines, ventral view showing markings on foot. D. Philinopsis buntotparatype, CASIZ 185942, Tingloy, Philippines. E. Chelidonura alexisi sp. nov., holotype, PNM 41062, Mabini, Philippines.

FIGURE 2. Shells.A. Philinopsis buntot. sp. nov., paratype, CASIZ 185942, Tingloy, Philippines. B. Philinopsis aliciae sp. nov., holotype, PNM 41061, Mabini, Philippines. C. Chelidonura alexisi sp. nov., holotype, PNM 41062, Mabini, Philippines.