Sagaminopteron bilealbum Carlson & Hoff, 1973

Description

A small batwing slug 3.5–12 mm in length, translucent white with numerous fine orange to reddish-orange spots scattered over the entire body. The head shield is small and triangular, bearing a well-developed siphonal crest. The large parapodia are flapped up and down for swimming, giving rise to the common name "batwing slug." A slender flagellum extends from the right side of the body, and a weakly calcified internal shell is retained.

Distribution

The type locality is Bile Bay, Guam, Marianas Islands. Subsequent records include the Marshall Islands (Kwajalein Atoll) and the Philippines (Anilao), indicating a wide distribution in the tropical Indo-Pacific.

Etymology

The specific epithet bilealbum is a compound name combining the type locality "Bile Bay" with the Latin album (white), meaning "the white species from Bile Bay." It pairs with the simultaneously described sister species Sagaminopteron nigropunctatum ("the one with black spots").

Remarks

The species feeds on sponges of the genus Dysidea and is often found sympatrically with its congener Sagaminopteron nigropunctatum, which inhabits a different species of the same sponge genus. S. nigropunctatum differs from S. bilealbum in bearing black spots and orange pigment on the rhinophoral crest and flagellum, in having more reduced parapodia, and in rarely swimming. The radular formula in S. bilealbum is 37 × 8-1-0-1-8, with inner lateral teeth bearing an elongate curved cusp and two large inner denticles (Gosliner, 1989).

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References

• Sagaminopteron bilealbum n.sp., Carlson C.H. & Hoff P.J. (1973). Two new species of Gastropteridae from Guam, Marianas Islands (Opisthobranchia: Cephalaspidea). Publications of the Seto Marine Biological Laboratory. 21(2): 141-151.
• Sagaminopteron bilealbum Carlson & Hoff, 1973, Gosliner T.M. (1989). Revision of the Gastropteridae (Opisthobranchia: Cephalaspidea) with descriptions of a new genus and six new species. The Veliger 32(4): 333-381.
• アカテンウミコチョウ（新称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Sagaminopteron bilealbum, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.