Feeding on sponge exudates by a holothuroid at Davies Reef, Great Barrier Reef

Full description

In the lagoon at Davies Reef, the substrate was cleared around a large specimen of the sponge, Ianthella basta located at a depth of 20m. All specimens of the holothuroid, Synaptula lamperti were removed and the sponge was enclosed in a polythene bag containing glucose and proline labelled with tritium and incubated for 2.5 hours. After incubation, 81 Synaptula lamperti were returned to the sponge and 5 were retained as a control for background radiation. Five Synaptula lamperti were removed from the sponge after 2, 4, 8, 19.5, 28, 43, 52.5 and 67 hours and dissected into gut and body wall components. Three small pieces were cut from the sponge before the addition of labelled material and at 4, 19.5, 52.5 and 67 hours after returning the holothuroids to the sponge. All tissue samples were frozen and later digested and assayed for radioactivity.The 41 holothuroids remaining on the sponge were removed for chemical extraction. Soxhlet extractions of sponge and holothuroid tissues were made using organic solvents and then chromatographically fractionated.To determine whether sponges provided protection to holothuroids against predation, equal numbers of Synaptula lamperti were placed on Ianthella basta and on artificial sponges made of hessian, placed neaby. The experiment was conducted at two depths (5 and 17m) and survival after 1 and 5 days was recorded.
This research was undertaken to determine if the holothuroid, Synaptula lamperti, was ingesting exudates directly from the sponge, Ianthella basta. This was investigated by radiolabelling sponge tissue and later examining the holothuroids for evidence of transfer of labelled material. Experiments were also conducted to determine whether the holothurians used the sponge for protection against predators.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The sponge was incubated in situ for 2.5 h in a 25 litre polythene bag containing uniformly tritiated labelled glucose and proline (3 mCi = 111 MBq of each).All tissue samples were digested in NCS tissue solubilizer (Amersham) and assayed for radioactivity in PCS II scintillation cocktail (Amersham) on a Packard Tri-Carb liquid scintillation spectrometer.

Notes

Credit
Hammond, Laurie S, Dr (Principal Investigator)