Dendrodoris nigra - egg ribbon

March 20, 2003
From: Rachel Przeslawski


Hi Bill,
Here's the information on the Dendrodoris egg masses you asked about. Unfortunately the quality of some of the photos is low. One set is of Dendrodoris nigra and the other is of Dendrodoris fumata. The photos in this message are of D. nigra. [Note: inset in upper photo is of D. fumata for comparison]. The ones of D. fumata are in a separate message.

Both species laid in the laboratory and both laid thin upright spiral orange egg ribbons. D. nigra laid a looser "messier" spiral while D. fumata laid a neatly coiled mass. D. nigra had a wider egg ribbon (5.5-6mm) than D. fumata (3-5mm) although this is likely variable considering only 3 egg masses were examined. D. fumata had a much higher density of embryos very tightly packed while D. nigra [see inset] only had 2 layers of embryos in moderate density. D. nigra had larger eggs and capsules (125um, 175um ) than D. fumata (< 75um, 100um).

As with most nudibranch egg masses there was only 1 egg per capsule with occasional twins. I allowed both ribbons to hatch, and found that embryos hatched at swimming veliger stage in both. D. nigra had a very noticeable large bi-lobed velum.

Keep in mind these observations are only from 2 D. fumata and 1 D. nigra egg masses so further observations would be great to see potential variations within each species. You'll also be pleased to know that I've gotten access to a camera that has a better capacity for close-ups than the one I've been using. Hopefully you won't receive any more of these bad photos from me, but I thought it was better than nothing in this case!
Cheers
Rachel

rachelp@uow.edu.au

Przeslawski, R., 2003 (Mar 20) Dendrodoris nigra - egg ribbon. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9435

Thanks Rachel,
The cup-shaped arrangement of many gills in your photo would seem to confirm this is Dendrodoris nigra. I will be good to get some further photographed animals and their egg ribbons to confirm these differences.
Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Mar 20). Comment on Dendrodoris nigra - egg ribbon by Rachel Przeslawski. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9435

Factsheet

Dendrodoris nigra

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