[Coral-List] Soft corals and benthic ctenophores

tomascik at novuscom.net tomascik at novuscom.net
Wed May 15 18:03:52 UTC 2019

Hi everyone,

I would like to reach out to our soft coral research colleagues to  
find out if anyone is (or was) working on benthic ctenophores  
ectosymbionts (e.g., Class: Tentaculata; Order: Platyctenida; Family  
Coeloplanidae; Coeloplana spp.) associated with soft corals (Order:  
Alcyonacea) belonging to the Family Alcyoniidae.

My interest in this was recently awakened when I came across a recent  
paper by Glynn et al 2018 [Benthic ctenophores (Platyctenida:  
Coeloplanidae) in South Florida: predator-prey interactions. Inv Biol  
137(2): 133-150] which prompted me to dig out an old video footage  
that was taken on coral reefs in the Banda Sea (Indonesia) some 26  
years ago, while working on “The Ecology of the Indonesian Seas”. I  
still recall my excitement when during one night dive we observed long  
sticky strands steaming from soft corals. These strands were streaming  
mainly from Sinularia spp. in reef areas with strong currents  
(0.5.m/sec). The sticky strands were extended from the surface of the  
soft corals and then reeled in once plankton and other suspended  
material became attached to them. I tried to take video footage of  
this activity and succeeded to some extent, but due to strong currents  
and high density of soft corals (thus hard to grab onto something  
solid) it was difficult to do a good job with close-ups. Looking at  
the surface of the soft corals we thought that the sticky strands were  
emerging from ‘pores’ on the coral’s capitulum. I have done thousands  
of dives, but I have never seen this type of feeding activity  
associated with Sinularia spp. during daylight hours. Initially I  
thought that these strands originate from the soft corals themselves,  
but I think that they are actually the feeding tentacles of benthic  
ctenophores that may be associated with some of these soft corals.

Looking and the video of this activity it makes me wonder to what  
extent is this feeding activity also contributing to the nutrition of  
the soft coral itself. The sticky strands that are being reeled in are  
loaded with numerous particles (consisting of live plankton and other  
suspended organic matter) that are attached to them and they are being  
reeled in to the soft coral’s capitulum. Are the soft corals able  
somehow to utilize some of this food source via heterotrophy? It’s  
been demonstrated that one feeding mechanism that corals deploy to  
capture food is through mucus secretion [Brown & Bythell, 2005.  
Perspectives on mucus secretion in reef corals. MEPS 296: 291-309].  
Could the mucus secreted by soft corals, and then ingested, catch some  
of the food particles that are reeled in by the ectosymbionts?

I would like to find out if anyone else has observed this during their  
field observations and if they know which species of ctenophores were  
involved. If anyone would like to see a short video of this activity  
please visit:




Download the File: Sinularia and Coeloplana.mp4

The video was taken during a night dive in strong currents and with a  
JVC mini-VHS camcorder.

Thanks, Tomas

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