BIOTIC

BIOTIC Species Information for Aphelochaeta marioni

Researched by

Will Rayment

Data supplied by

MarLIN

Refereed by

Dr Peter Gibbs

Reproduction/Life History

Reproductive type

Gonochoristic

Developmental mechanism

Lecithotrophic

Reproductive Season

October and November in Plymouth

Reproductive Location

Water column

Reproductive frequency

Annual episodic

Regeneration potential

Life span

3-5 years

Age at reproductive maturity

1 year

Generation time

1-2 years

Fecundity

Up to approx 540 eggs

Egg/propagule size

Fertilization type

Larvae/Juveniles
Larval/Juvenile dispersal potential	See additional information	Larval settlement period
Duration of larval stage	Not relevant

Reproduction Preferences Additional Information

The lifecycle of Aphelochaeta marioni varies according to environmental conditions. In Stonehouse Pool, Plymouth Sound, Aphelochaeta marioni (studied as Tharyx marioni) spawned in October and November (Gibbs, 1971) whereas in the Wadden Sea, Netherlands, spawning occurred from May to July (Farke, 1979). Spawning, which occurs at night, was observed in a microsystem in the laboratory by Farke (1979). The female rose up into the water column with the tail end remaining in the burrow. The eggs were shed within a few seconds and sank to form puddles on the sediment. The female then returned to the burrow and resumed feeding within half an hour. Fertilization was not observed, probably because the male does not leave the burrow. The embryos developed lecithotrophically and hatched in about 10 days (Farke, 1979). The newly hatched juveniles were ca 0.25 mm in length with a flattened, oval body shape, and had no pigment, chaetae, cirri or palps. Immediately after hatching, the juveniles dug into the sediment. Where the sediment depth was not sufficient for digging, the juveniles swam or crawled in search of a suitable substratum (Farke, 1979). In the microsystem, juvenile mortality was high (ca 10% per month) and most animals survived for less than a year (Farke, 1979). In the Wadden Sea, the majority of the cohort reached maturity and spawned at the end of their first year, although some slower developers did not spawn until the end of their second year (Farke, 1979). However, the population of Aphelochaeta marioni in Stonehouse Pool spawned for the first time at the end of the second year of life (Gibbs, 1971). There was no evidence of a major post-spawning mortality and it was suggested that individuals may survive to spawn over several years. Gibbs (1971) found that the number of eggs laid varied from 24-539 (mean=197) and was correlated with the female's number of genital segments, and hence, female size and age.

Dispersal
Under stable conditions, adult and juvenile Aphelochaeta marioni disperse by burrowing (Farke, 1979). In the microsystem, a glass barrier in the sediment prevented the movement of animals to new areas over a period of some months, even though dispersal could have occurred by creeping on the surface or swimming. When the barrier was removed, the new areas were soon colonized (Farke, 1979). Farke (1979) reported that Aphelochaeta marioni (studied as Tharyx marioni) was capable of swimming but only did so under abnormal circumstances, e.g. when removed from the sediment. Farke (1979) suggested that as there was no pelagic stage, dispersal and immigration to new areas must mainly occur during periods of erosion when animals are carried away from their habitat by water currents.

Reproduction References

Farke, 1979, Gibbs, 1971, Beukema, 1995,