ECOLOGY
Habitat
Hydatina physis is commonly found in areas with sea grass, sand and rubble (Behrens 2005).
Sand
Sand may range from white intertidal beaches to stark red, or black. Sand can be flour fine or comprised of shell grit.
Rubble
Rubble may be large pieces of broken coral or rock, shells and other bottom detritus that have accumulated. Over time, rubble will eventually become grit and then sand; H. physis may also be found on, in or among these.
Figure 4. The reef crest, indicated by the black circle, on the Heron Island Reef, Queensland, Australia, where Hydatina physis was found among the sand and coral rubble. Photo from Google Earth.
Majority of opisthobranchs living in these habitats are infaunal burrowers. Many appear to be nocturnal, so they are seen on the surface during the late afternoon, at night, and early morning on a rising tide.
Predatory species generally find their prey on the surface of the sand where it is eaten on the spot. Some species come to the surface and search for sand-dwelling sort corals, gorgonians, solitary corals or sea pens on which they feed and then burrow back under the sand after they have had their dinner.
Sea grass (Sub-tidal)
Sea grass meadows prodivde both food and shelter for a wide range of opisthobranchs that feed on sea grass directly or through epiphytes (algae, hydroids, bryozoan, ascidians, sponges) growing on them.
 
Figure 5. Hydatina physis inside a tank on top of a rock (left) and crawling on the bottom of the tank (right) in the Goddard aquarium.
|