Phyllidiid Suctorial Feeding

We are occasionally fortunate enough to encounter and record a nudibranch feeding, that is, to actually see that they are feeding, because most often the process is hidden from us beneath them. In those instances, with the sponge-feeders, the buccal mass can be seen protruding and pressed against the sponge tissue that is being rasped away by their radula and leaving a scar.

Of course some sponge-feeders don’t have a radula, feeding instead by secreting digestive enzymes upon the sponge tissue and sucking up the liquified tissue – suctorial feeding. These are the porostomes – the Phyllidiidae and Dendrodorididae families of nudibranchs.

This process is definitely hidden from us and requires a little bit of intervention to actually see what is going on underneath them. The following sequence illustrates what was revealed when a large Phyllidiella pustulosa was carefully detached from a sponge upon which it was feeding.

– Located a large specimen of Phyllidiella pustulosa feeding upon a large and distinctive sponge. (Often it is difficult to discern what they are feeding on.)

– Carefully detached the nudibranch, which released its foot but was still attached to the sponge by its protruded buccal mass.

– Once the nudibranch fully retracted its buccal mass, the feeding scar on the sponge was revealed together with a white fluid, on the sponge and also being washed away as streaks, that may represent the enzymes applied to liquify the sponge tissue or a combination of both.

Images recorded on the Gneering Shoals, Sunshine Coast, Queensland, Australia.

(Sometimes, in order to know and record just what is happening the animal has to be removed. I would not suggest the above to be a regular practice as it takes an inordinate amount of time and patience to get phyllidiids to reattach themselves to the substrate.)

David A. Mullins – July 2021

References:

– Brunckhorst, D. J. (1993). The Systematics and Phylogeny of Phyllidiid Nudibranchs (Doridoidea). Records of the Australian Museum, Supplement 16: 1–107.

– Rudman, W. B., (1998). Family Phyllidiidae Pp.1000-1001 in Beesley, P. L., Ross, G. J. B. & Wells, A. (Eds) Mollusca: The Southern Synthesis. Fauna of Australia. Vol.5 CSIRO Publishing, Melbourne, Part B 565-1234 pp.

– Mullins, D. A., (2020). Uniquely United But Deceptive Display – The Suctorial Feeding Porostomata Nudibranchs. NudiNotes at www.nudibranchdomain.org