Opisthobranch of the Week Data
Costasiella paweli is considered to be uncommon in Okinawan waters; I've not seen the animal here on Okinawa although I've collected a series of related, undescribed members of the species from Okinawa's main island (included in list below). Atsushi mentions (pers. comm.) seeing over one hundred individuals of C. paweli. * In addition, Atsushi mentions the species is found on the green alga, Avrainvillea erecta, found growing on open sandy bottoms.
Ichikawa (1993) described this species from six specimens found off Miyako Island (part of an island chain about 300km southeast of Okinawa's main island). The following description is taken from Ichikawa (1993):
The large contiguous eyes are situated between the long, simple rhinophores. Many inflated cerata are arranged in about 10 dense rows, and the pointed tail protrudes behind the cerata. The anterior corners of the foot are produced into long tentacles. The color of the head and tail is white, and rhinophores are black or dark blue. A distinctive dark mark is located behind the eyes; the anterior part of the mark is somewhat star-shaped and its posterior part is elongated. The anterior margin of the foot and the area dorsal to the mouth are darkly pigmented. The cerata are green with white tips and are spotted with small, black chromatophores.
The body length ranged from 3 to 7 mm.
Kathe Jensen (2002) reporting in the Sea Slug Forum, mentions that she has a series of Costasiella species from Singapore. She apparently at one time was to have described these along with Jon Sigurdsson, but that the paper didn't get started as per her following statement:
" . . . this awful paper by Ichikawa appeared. In this paper she describes 6 species of Costasiella based on photos and serial sections. There are so many characters not mentioned in these descriptions that it is impossible to compare these species with others."
I've added a second page with an additional image of Costasiella paweli, also kindly furnished by Atsushi, as well as an image with a short discussion of the alga Avrainvillea erecta.
Previously I've featured several species of Costasiella on these pages and as of the current date (April, 2015) there are several described and undescribed species of Costasiella, reported from Okinawan waters. The featured animals are as follows:
C. kuroshimae C. paweli (the above featured animal) C. usagi C. vegae C. sp. 1 C. sp. 2 C. sp. 3
NOTE: This is a "reworked" page with several new images furnished by Atsushi Ono.
* Keramas = the Kerama Islands Group, located 30 ~ 40 kilometers west of the Okinawa capitol, Naha.