ORDER NUDIBRANCHIA (Nudibranchs)

SUBORDER DORIDOIDEA (Dorids)

Nudibranchs are the largest group of Opisthobranchs and dorids are the largest group of nudibranchs. Typically most dorids have a pair of rhinopores at the front of the head. The antennae like rhinopores of nudibranchs are used to locate food or a partner by "smelling"minute chemical signatures in the water. Most also have a cluster of gills in the centre of the back surrounding the anus. Dorids are an increadibly diverse and colourful group frequently observed by divers.

Species: Jorunna funebris (Family Dorididae)

Location: "Bay of Anemones" North Solitary Island, New South Wales
Depth: 10-12 metres
Date: 7/7/98
Photo by: Simon L Hartley

Species: Jorunna sp.

Location: "Nursery" Julian Rocks Marine Reserve, Byron Bay, New South Wales
Depth: 10-12 metres
Date: 8/2/98
Photo by: Simon L Hartley

Diet and general lifecycle of nudibranchs: Diet and lifecycle are inextricably linked for most nudibranchs. Most nudibranchs (with the notable exception of Hypselodoris bennetti, illustrated here) start their life as free swimming planktonic larvae. Once these larvae locate a food source (diet may be very specific often a single species of sponge or bryozoan) they settle and rapidly grow to adults. Most predation of nudibranchs occurs in the planktonic larval stage with adults employing camouflage or a range of toxins (some extracted from prey) to ward off predators. Some nudibranchs are even able to extract the intact stinging cells from prey and incorporate these into their own defenses. Gaudy colours warn potential predators of bad taste or poison or mimic the colours of poisonous relatives. Nudibranchs are hermaphradites (both partners are male at the time of mating) that reproduce by exchanging packets of sperm with any mature individual of the same species (or in some cases in communal mating groups) via a pore on the side of the neck. After mating both individuals produce intricately woven egg masses (large species may produce millions of eggs). The life cycle of most nudibranchs is very short (usually one to two months no more than a year). Often a species appears in large numbers for a short space of time breeding occurs then they disappear.

Species: Chromodoris splendida (Family Chromodorididae)

Location: Julian Rocks Marine Reserve, Byron Bay, New South Wales
Depth: 12-14 metres
Date: from 8/3/97 to 7/7/98
Photo's by: Simon L Hartley

Chromodoris splendida is a nudibranch which shows a great deal of variability in pattern even among individuals recorded at the same time in the same location. Unlike Aphelodoris varia however the base colours remain the same.

Photo by: Danny Bucher

Species: Chromodoris fidelis (black colour of gills and rhinopores distingushes from splendida)

Location: Cook Island (western side), off Fingal Headland, New South Wales
Depth: 10-14 metres
Date: 29/3/98
Photo by: Simon L Hartley

Species: Chromodoris geometrica

Location: Ballina break wall, Ballina, New South Wales
Depth: 4-6 metres
Date: 13/4/98
Photo by: Simon L Hartley

Species: Chromodoris odhneri

Location: "Hugho’s Trench" Julian Rocks Marine Reserve, Byron Bay, New South Wales
Depth: 9-10 metres
Date: 29/11/97
Photo by: Simon L Hartley

Species: Chromodoris nigrostriata

Location: "Hugho’s Trench" Julian Rocks Marine Reserve, Byron Bay, New South Wales
Depth: 10-12 metres
Date: ????
Photo by: Simon L Hartley

Species: Chromodoris kuiteri

Location: Outer Nearings, Mooloolabah, Queensland
Depth: 15-18 metres
Date: 27/12/98
Photo by: Simon L Hartley

a) Common

b) Variant (note blue gills)

c) Mating

Species: Hypselodoris obscura (a to c)

Location: Ballina break wall, Ballina, New South Wales
Depth: 5-7 metres
Date: 13/4/98
Photo’s by: Simon L Hartley

Species: Hypselodoris bennettii

Location: "Hugho’s Trench" Julian Rocks Marine Reserve, Byron Bay, New South Wales
Depth: 12-14 metres
Date: 29/11/97
Photo by: Simon L Hartley