22 – Worms
255
BOX 22.1 MASS SPAWNING OF POLYCHAETE SPECIES
In the late 1980’s when mass coral spawning was discovered, often polychaetes were
also seen swimming in the water column and they too were spawning. Such mass spawning has been known and exploited by the Samoans for centuries. They could predict the
night on which these sedentary eunicids, the ‘Palolo’ worms that live deep within the
coral substrate, would swim up into the water column where their posterior ends would
split open to release their gametes, triggered by the particular phase of the moon. The
Samoans would collect these swimming sacs full of protein-rich eggs and sperm and dry
them to produce a nutritious flour that they would make into biscuits or else trade with
highlanders. On the GBR a suite of species spawn at particular phases of the moon during the summer months including species of nereidids, amphinomids, syllids and phyllodocids (Fig. 22.2L). In these species the entire worm develops swimming chaetae and
large eyes, and leaves the substratrum and swarms in the water column where the males
secrete a pherome that stimulates the females to spawn. By the end of the night the
beaches are littered with the remains of their bodies. All the gametes are released into the
water column, providing fish and other predators with an amazing feast. Almost certainly eunicids spawn on the GBR like in Samoa but to date this has not been documented. In all these cases, while water temperature and light levels are critical for
co-ordinating spawning, other factors must be involved months before to ensure that the
germinal epithelium of these worms proliferate the gametes and that there is sufficient
time for the eggs and sperm to develop to maturity within the coelom. Again, laboratory
studies have revealed that all these processes are controlled by an endocrine system that
responds to external cues such as temperature and light.
BOX 22.2 ASEXUAL REPRODUCTION OF POLYCHAETES
Some species of polychaete can undertake asexual reproduction as well as sexual reproduction. Dodecaceria (family Cirratulidae) is common in dead coral substratum as it can
bore into such habitats. An adult worm is capable of splitting into individual segments
and each one develops a new head and tail to become a new individual. Another family
that exhibits asexual reproduction is the syllids. In some cases the worm develops a series of stolons, resembling railway carriages, with the most posterior one the next one to
be released as a new individual (Fig 22.3J); in other cases the stolons are proliferated off
at angles to the adult worm.
Studies on the diversity of marine oligochaetes on
the GBR are few and have tended to concentrate on
soft sediment habitats close to research stations where
facilities exist to carefully sort the sediment under a
dissecting microscope, or elutriate the sediments under
running seawater to allow the meiofauna to float off
and be collected for study.
Oligochaetes are segmented worms without parapodia, but have segmental bundles of simple hook-like
or capillary chaetae; often only a few are present, or
255
BOX 22.1 MASS SPAWNING OF POLYCHAETE SPECIES
In the late 1980’s when mass coral spawning was discovered, often polychaetes were
also seen swimming in the water column and they too were spawning. Such mass spawning has been known and exploited by the Samoans for centuries. They could predict the
night on which these sedentary eunicids, the ‘Palolo’ worms that live deep within the
coral substrate, would swim up into the water column where their posterior ends would
split open to release their gametes, triggered by the particular phase of the moon. The
Samoans would collect these swimming sacs full of protein-rich eggs and sperm and dry
them to produce a nutritious flour that they would make into biscuits or else trade with
highlanders. On the GBR a suite of species spawn at particular phases of the moon during the summer months including species of nereidids, amphinomids, syllids and phyllodocids (Fig. 22.2L). In these species the entire worm develops swimming chaetae and
large eyes, and leaves the substratrum and swarms in the water column where the males
secrete a pherome that stimulates the females to spawn. By the end of the night the
beaches are littered with the remains of their bodies. All the gametes are released into the
water column, providing fish and other predators with an amazing feast. Almost certainly eunicids spawn on the GBR like in Samoa but to date this has not been documented. In all these cases, while water temperature and light levels are critical for
co-ordinating spawning, other factors must be involved months before to ensure that the
germinal epithelium of these worms proliferate the gametes and that there is sufficient
time for the eggs and sperm to develop to maturity within the coelom. Again, laboratory
studies have revealed that all these processes are controlled by an endocrine system that
responds to external cues such as temperature and light.
BOX 22.2 ASEXUAL REPRODUCTION OF POLYCHAETES
Some species of polychaete can undertake asexual reproduction as well as sexual reproduction. Dodecaceria (family Cirratulidae) is common in dead coral substratum as it can
bore into such habitats. An adult worm is capable of splitting into individual segments
and each one develops a new head and tail to become a new individual. Another family
that exhibits asexual reproduction is the syllids. In some cases the worm develops a series of stolons, resembling railway carriages, with the most posterior one the next one to
be released as a new individual (Fig 22.3J); in other cases the stolons are proliferated off
at angles to the adult worm.
Studies on the diversity of marine oligochaetes on
the GBR are few and have tended to concentrate on
soft sediment habitats close to research stations where
facilities exist to carefully sort the sediment under a
dissecting microscope, or elutriate the sediments under
running seawater to allow the meiofauna to float off
and be collected for study.
Oligochaetes are segmented worms without parapodia, but have segmental bundles of simple hook-like
or capillary chaetae; often only a few are present, or