Phyllodesmium iriomotense Baba, 1991

Description

A Phyllodesmium in which the cerata are exceedingly elongate, almost straight to their tips, and entirely smooth (non-nodulose). The cerata are deciduous and flattened. In the preserved state both the oral tentacles and rhinophores are smooth. The foot corners are produced into short horns. The first and second ceratal arches on the right side of the body are each single-rowed. The anus is in the centre of the second right arch, and the nephroproct is in front of this arch. Unlike any other recorded species of the genus, the animal is translucent and entirely colourless. The colourless liver diverticula are visible through the translucent skin of the cerata. Within each ceras the narrow central canal of the liver system gives off bilateral branches regularly and at right angles to the central canal. No zooxanthellae are present in the liver system. Body length 20 mm in the preserved type.

Distribution

Type locality: Funauki Bay (45 m depth), Iriomote-jima, Okinawa, southern Japan; the holotype was collected from a thread-like alcyonarian growing in mud.

Etymology

The specific epithet iriomotense is a toponymic adjective ("of Iriomote") derived from the type locality, Iriomote-jima (Okinawa Pref.), with the neuter Latin locative suffix -ense agreeing with the neuter genus Phyllodesmium.

Remarks

The long, almost straight and smooth cerata, together with the entirely unpigmented body lacking zooxanthellae, are the principal diagnostic features of this species within Phyllodesmium.

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References

• Phyllodesmium iriomotense n. sp., Baba, K. 1991. Taxonomical study on some species of the genus Phyllodesmium from Cape Muroto-misaki, Shikoku, and Okinawa Province, southern Japan (Nudibranchia: Facelinidae). Venus 50(2):109-124.