Bubble shells are the most primitive order of Opisthobranchs. Neither
of the species illustrated below are able to fully withdraw their
mantles into their shells and all burrow into the sand for protection
from predators. There are three common bubble shells in northern NSW.
I have illustrated them below but will add further images as they
become available.
Species: Bullina lineata (Family Bullinidae)
Location: "The Nursery" Julian Rocks Marine Reserve,
Byron Bay, New South Wales
Depth: 10-12 metres
Date: 4/10/97 Photo by: Simon L Hartley
Species: Hydatina physis (Family Hydatinidae)
Location: Ballina break wall, Ballina, New South Wales
Depth: 7-8 metres
Date: 6/12/97 Photo by: Simon L Hartley
Species: Micromelo undata (Family Hydatinidae)
Location: Tweed River, Tweed Heads, Queensland
Depth: 6-7 metres
Date: 30/9/04 Photo by: Simon L Hartley
Nudibranchs
evolved from molluscs that abandoned their shells in favour of other
types of protection like camouflage and toxins. Some Opisthobranchs
(like bubble shells (ORDER CEPHALASPIDAE), members of the family Tylodinidae
and Umbraculidae, side gilled sea-slugs (Pleurobranchidae) and sea hares
(ORDER ANASPIDAE, family Aplysiidae)) have retained some form of shell.
Side gilled sea-slugs (picured to the right) burrow into the
sand during the day for protection only coming out at night to feed
and mate. I see these critter regularly on night dives, this one was
photographed at the Tassie II shipwreck off main beach Byron Bay, New
South Wales. This species is Berthellina citrina.
Members the family Tylodinidae and Umbraculidae (pictured to the
left) both possess limpit like shells which are too small for the
animal to retreat into. The shell is usually covered with algae and
encrusting animals making the animals difficult to detect. These images
were taken in Port Stephens (north of Newcastle on the NSW mid coast).
The species is Umbraculum sinicum (Photo's by: Simon L Hartley).
Nudibranchs
evolved from molluscs that abandoned their shells in favour of other
types of protection like camouflage and toxins. Some Opisthobranchs
(like bubble shells (ORDER CEPHALASPIDAE), members of the family Tylodinidae
and Umbraculidae, side gilled sea-slugs (Pleurobranchidae) and sea hares
(ORDER ANASPIDAE, family Aplysiidae)) have retained some form of shell.
Side gilled sea-slugs (picured to the right) burrow into the
sand during the day for protection only coming out at night to feed
and mate. I see these critter regularly on night dives, this one was
photographed at the Tassie II shipwreck off main beach Byron Bay, New
South Wales. This species is Berthellina citrina.
