Costasiella rubrolineata M. Ichikawa, 1993

Description

A small sacoglossan; the holotype measures 4 mm in body length. A black transverse band crosses each rhinophore at midlength, and there is a rounded dark red mark behind the eyes. Three red lines run from the bases of the rhinophores to the mouth area on the anterior part of the head, with the middle line the broadest. The cerata are green with white pointed tips, and an orange-red band lies within the distal white area.

Distribution

Type locality: Ishigaki Island, between Uganzaki and Yarabuzaki, 0.5-1 m deep, on the green alga Avrainvillea erecta. The original description was based on a single specimen collected in June 1991 (holotype NHMW 85999).

Etymology

The specific epithet rubrolineata is Latin for "red-lined", in reference to the characteristic red lines on the head.

Remarks

The colour pattern of the anterior head is not seen in other congeners. The anterior corners of the foot are not produced into long tentacles as in C. paweli and C. usagi, and the eye-shaped pattern on the cerata seen in C. vegae is absent.

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References

• Costasiella rubrolineata n. sp., Ichikawa M. (1993). Saccoglossa (Opisthobranchia) from the Ryukyu Islands. Publications of the Seto Marine Biological Laboratory. 36(3): 119-139. https://doi.org/10.5134/176229