Opisthobranch of the Week Data
Dermatobranchus dendronephthyphagus is considered to be very rare in the waters of Okinawa's main island as I have seen and collected only the single above featured animal. It was collected from Horseshoe Cliffs (Onna area) on the 13th of December, 1996 from 140 feet of water. It was found on a colony of a soft coral Dendronephthya sp. (family Nephtheidae)** at 0845am.
This animal was previously seen in Gosliner, et al, 2008 (as Dermatobranchus sp. 15, p. 313). Also, Rudman (2005) shows an animal from New South Wales, Australia, which he identified as D. nigropunctatus. Gosliner & Fahey (2011) feel that animal differs externally in many respects from D. nigropunctatus and that it is identifiable with D. dendronephthyphagus. The authors of a recent paper (Gosliner & Fahey, 2011) have now described the animal and the featured animal is the holotype*. I've also added a second page w/ several additional images of D. dendronephthyphagus, showing photos of the animal on its host coral.
The following information on external morphology and remarks are taken from Fahey & Gosliner (2011):
External morphology: The body shape of the living animal is elongate, but broad, slightly flattened, and narrows at the posterior end. The foot does not project beyond the mantle margin. The dorsum has approximately 14 well-elevated, longitudinal ridges on either side of the midline that may further branch posteriorly. The oral veil is large and expansive with rounded corners. The well-separated, bulbous rhinophores are situated behind the oral veil. They have a series of longitudinal lamellae on the rounded club, which has a small rounded apex. The stalk does not narrow noticeably. There are noticeable marginal sacs along the mantle edge.
There are no branchial or hyponotal lamellae under the mantle margin. The genital opening is situated in the anterior quarter of the body. The anus is situated approximately half of the way to the posterior end of the body.
The ground colour of the dorsum is white with a series of dark brown to black lines situated between the dorsal ridges. There are areas of denser dark pigment scattered over the surface of the notum. The oral veil has a series of large black spots that are more diffuse around the margins. There is a marginal yellow-orange band on both the notum and the oral veil. The rhinophore stalk is white with black pigment and the club is white with black pigment on the lamellae. The tips of the rhinophores are white.
Remarks: Externally, D. dendronephthyphagus resembles D. striatus with its dark brown to black lines and mottling. However, D. striatus has orange pigment on its rhinophores and a series of dark brown concentric arches on the oral veil, whereas D. dendronephthyphagus has a series of black mottlings. More significantly, the jaws and radula of these species differ markedly. In D. striatus, the jaws have a well-developed masticatory margin with several rows of well-developed denticles, whereas in D. dendronephthyphagus the masticatory margin and black pigment is entirely smooth with no trace of denticles. The rachidian and inner lateral teeth of D. striatus are highly denticulate whereas in D. dendronephthyphagus both the rachidian and inner lateral teeth entirely lack denticles. The reproductive systems of these species also differ. In D. striatus, the penial sheath is bulbous and the vaginal duct gradually narrows distally. In D. dendronephthyphagus, the penis is cylindrical and the vaginal duct is wide basally with an abrupt narrowing more distally.
Dermatobranchus dendronephthyphagus is considered to be very rare in Okinawan waters as I have seen and collected only the above single individual over a period of many years of diving in Okinawa.
As of the current date (Early-April, 2014) thirteen described species of Dermatobranchus from Okinawa's main island and the Keramas are featured on these pages. These thirteen species are:
D. albus D. caeruleomaculatus D. cymatilis D. dendronephthyphagus - The featured animal above (Holotype*) D. diagonalis D. fasciatus D. fortunatus D. funiculus D. gonatophora D. oculus D. ornatus D. primus D. rodmani
* Holotype: See "Type" Dictionary for explanation.
** Kindly identified by Gary Williams of California Academy of Sciences.