Protaeolidiella atra Baba, 1955 (size unrecorded)
OPISTHOBRANCH OF THE WEEK
Opisthobranch of the Week Data
Frequency on Okinawa:
- Order: NUDIBRANCHIA
- Suborder: Aeolidina
- Family: Protaeolidiellidae
[brackets indicate range for all Okinawa-collected specimens of the species]
- Individual Collection No: RFB #2897
- Hansen South, 3.5 km W Kin-misaki Okinawa (26o 26.2'N, 127o
55.4'E) [Hansen So., Horseshoe, Seragaki]
- Date: 21 December, 1991 [20 Mar '91, 21 Dec '91, 26 Jun '92, 29 Jun '94 (2 indiv),
17 Mar '97 ]
- Depth: 20ft (6m) [10ft, 10ft, 20ft, 45ft, 160ft, 170ft]
- Water temperature at collection depth: Not recorded
- Size: Unrecorded [1 indiv not measured, 11mm, 12mm, 13mm, 14mm, 18mm]
- Specimen deposited: California Academy of Sciences
Protaeolidiella atra is considered to be uncommon on Okinawa; although I've collected only six specimens since the first animal was found in March of 1991, others have been seen but not collected.
P. atra is extremely well camouflaged on its prey hydroid
colony, the single row of white-tipped cerata mimicking the scattered white polyps of
Solanderia (Rudman, 1990). In the case of four of the six collected specimens from
Okinawa, my attention was brought to the animals presence by the brightly colored egg-masses
found coiled around a branch of the hydroid prey, Solanderia sp. Upon closer inspection the adult animal was discovered. An image of a 18mm specimen collected from 14m, shows a nearby egg mass on the Solanderia hydroid. Baba (1992) reports the Solanderia sp. to be S. secunda in Japan while Rudman (1990) finds the host to be S. fusca in the South Pacific.
P. atra is an unusually shaped aeolid, having reduced cerata and the presence of a relatively narrow shape. Rudman (1990, 1999) believes this has possibly occurred so as to allow the animal to be better camouflaged on its prey hydroid colonies.
- Baba, K. 1992. Comment on the taxonomy of Protaeolidiella atra Baba, 1955 and an allied species (Mollusca: Nudibranchia: Aeolidiidae) from Japan. Report of the Sado Marine Biological Station (22):29-35.
- Rudman, W.B. 1990. Protaeolidiella atra Baba, 1955 and Pleurolidia
juliae Burn, 1966; one species, two families (Nudibranchia). Journal of
Molluscan Studies, 56(4): 505-514.
- Rudman, W.B., 1999 (April 1) Protaeolidiella atra Baba, 1955. [In] Sea Slug Forum. http://www.austmus.gov.au/seaslugs/protatra.htm.
Copyright © 1999 Robert F. Bolland
Digitally manipulated photo