Re: Hermaea sp. at Woody Point
August 12, 2008
From: Kathe R. Jensen
Concerning message #21775:
Dear David and Bill,
You are raising a couple of questions here: First, is this species Hermaea evelinemarcusae? No, I don't think so. H. evelinemarcusae has sparse lateral branches from the central digestive tubule throughout the length of the cerata (not the "cruciate" pattern at the tip). Also, H. evelinemarcusae was feeding on a species of Griffithsia, tentatively identified as G. ovalis, which has large, bubble-like cells rather than the fine filamentous algae seen on these pictures.
The second question is concerning the esophageal pouch and its function. In some species the muscular esophageal pouch seems to be involved in the process of "buccal regurgitation", during which the sacoglossan regurgitates an amount of cell sap (cytoplasm plus the contents of the central vacuole) back into the algal filament, possibly mixed with saliva. The function of this process could be to make it easier to suck up the remaining cell sap by starting some enzymatic breakdown inside the algal filament, or maybe preventing the "wound-healing" process that many siphonalean algae have. In some sacoglossans, notably the Oxynoidae, the esophageal pouch seems to have a glandular wall rather than a muscular one, but I have no idea what the function of that might be. As far as I remember oxynoids do not have buccal regurgitation.
Best wishes,
Kathe
krjensen@snm.ku.dk
Jensen, K.R., 2008 (Aug 12) Re: Hermaea sp. at Woody Point. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21792Thanks Kathe,
I agree that even taking size into account, David's animals look rather different to H. evelinemarcusae. So I'll put them on a separate page as Hermaea sp. 1.
Best wishes,
Bill Rudman
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