BIOTIC

BIOTIC Species Information for Laminaria digitata

Researched by

Jacqueline Hill

Data supplied by

MarLIN

Refereed by

This information is not refereed.

Reproduction/Life History

Reproductive type

Gonochoristic
Alternation of generations
Oogamous

Developmental mechanism

Spores (sexual / asexual)

Reproductive Season

All year

Reproductive Location

Reproductive frequency

Annual protracted

Regeneration potential

Life span

6-10 years

Age at reproductive maturity

1-2 years

Generation time

1-2 years

Fecundity

In excess of 1,000,000

Egg/propagule size

Zoospores ca 5µm across

Fertilization type

External

Larvae/Juveniles
Larval/Juvenile dispersal potential	100-1000m	Larval settlement period	All year (see additional information)
Duration of larval stage	1 day

Reproduction Preferences Additional Information

Laminaria digitata is a perennial and lives for 4 to 6 years (Birkett et al., 1998b).
Laminarians exhibit alternation of generations with morphologically dissimilar (heteromorphic) reproductive phases. An asexual diploid phase (the sporophyte) is usually of considerable size and a haploid dioecious phase (the gametophyte) is microscopic.
The sporophyte produces vast numbers of haploid zoospores from sporangia which develop in small patches called sori on the lamina.
The flagellated zoospores are about 5 microns in diameter and may be transported at least 200 m from the parent (Birkett et al., 1998b). They loose their flagella after 24 hrs and settle on any available substrata.
The zoospores develop into microscopic dioecious haploid gametophytes, male plants producing spermatozoid and female plants developing oogonia. The gametophytes become fertile in under 10 days in optimal conditions: low temperatures and blue light.
Maturation of the gametophytes can be delayed under less optimal conditions, for example in red light development remains vegetative. Fragments of damaged vegetative gametophytes may develop into separate gametophytes (only a few cells are required) hence reproductive potential may be increased. If optimal conditions return the gametophyte may become fertile and produce gametes (Hoek van den et al., 1995).
Male and female gametes must settle at a high density (within 1mm of each other) if the maturing gametangial egg is to be fertilized. On fertilization of the extruded egg, young sporophytes start to grow in-situ.
Sori are produced over most of the blade surface (except most distal or proximal areas) all year round with maxima in July - August and November - December.
Young sporophytes (germlings) appear all year with maxima in spring and autumn.
Chapman (1981) demonstrated that substantial recruitment of Laminaria digitata plants to areas barren of kelp plants was possible up to 600m away from reproductive plants.

Reproduction References

Birkett et al., 1998b, Kain, 1979, Chapman, 1981, Hoek van den et al. 1995,