BIOTIC Species Information for Cordylophora caspia
|Researched by||Dr Harvey Tyler-Walters & Paolo Pizzolla||Data supplied by||MarLIN|
|Refereed by||This information is not refereed.|
|Reproductive Season||June-August||Reproductive Location||As adult|
|Reproductive frequency||Annual episodic||Regeneration potential||No|
|Life span||See additional information||Age at reproductive maturity||<1 year|
|Generation time||<1 year||Fecundity||See additional information|
|Egg/propagule size||Insufficient information||Fertilization type||Internal|
|Reproduction Preferences Additional Information||Most hydroids (including Cordylophora caspia) are dioecious. The reproductive organs are carried in gonophores. Sperm are released into the sea and eggs are fertilized within the female gonophores where the embryos develop into planulae. Sperm swim towards female gonophores, however, sperm probably have a limited life span and hence a limited range for fertilization of only a few metres. Hence the growth of hydroids in clumps may enhance fertilization rates, albeit at the cost of intraspecific competition. Temperature is critical for stimulating or preventing reproduction in hydroids (see distribution; Gili & Hughes, 1995).
Early seasonal growth from winter dormancy in early spring is rapidly followed by formation of gonophores and sexual reproduction in midsummer followed by active growth in late summer. However, sexual reproductive effort may retard growth (see general biology). Jormalainen et al. (1994) reported that reproduction began in early June, peaked in July (80% uprights with gonophores) and rapidly reduced by August (30% uprights with gonophores). Similar reproductive periods have been reported by other authors (Allman, 1871-1872; MBA, 1957; Roos, 1979; Foster-Smith, 2000). Roos (1979) and Jormalainen et al. (1994) reported that the sex ratio was biased in favour of females.
Each upright branch may bear between 1-3 gonophores each with between 10 - 6 eggs, the number decreasing in autumn (Hincks, 1868; Jormalainen et al., 1994). Therefore, fecundity is dependant on the number of branches and hence the number of gonophores, and in large colonies of 70-2000 polyps (Fulton, 1962), may be high. The larvae are released as planulae and no medusoid stage occurs. However, in some cases the larvae may develop directly into juvenile polyps in the gonophore before release (Bouillon, 1963).
Hydroids may reproduce asexually by budding to from another colony. A common form of asexual reproduction in hydroids is the formation of vertical stolons, which then adhere to adjacent substratum, detach and form another colony (Gili & Hughes, 1995). Hydroids exhibit remarkable powers of regeneration and Cordylophora caspia can be cloned in culture from detached uprights or excised tissue (Moore, 1952;Fulton, 1961, 1962). Asexual reproduction by fission or mechanical fragmentation of the colony may be an important factor in dispersal (Gili & Hughes, 1995).
While uprights have a short, finite life span from about early spring to autumn, no information concerning the life span of the dormant stages (menonts) was found. Unless destroyed by predators or physical damage, the colony may have a long life span (perhaps very long (Gili & Hughes, 1995). The ability to reproduce asexually and regenerate from damaged sections means that although any individual colony may have a finite life span the genetic individual (genet) may be considerably longer lived (Gili & Hughes, 1995).
Rapid growth, budding and the formation of stolons allows hydroids to colonize space rapidly. Hydroids are often the first organisms to colonize available space in settlement experiments (Gili & Hughes, 1995). Planula larvae swim or crawl for short periods (e.g. <24hrs) so that dispersal away from the parent colony is probably very limited (Gili & Hughes, 1995). Fragmentation may also provide another route for short distance dispersal. However, it has been suggested that rafting on floating debris (or hitch hiking on ships hulls or in ship ballast water) as dormant stages or reproductive adults, together with their potentially long life span, may have allowed hydroids to disperse over a wide area in the long term and explain the near cosmopolitan distributions of many hydroid species, including Cordylophora caspia (Gili & Hughes, 1995; Folino, 1999).
|Reproduction References||Hincks, 1868, Gili & Hughes, 1995, MBA, 1957, Arndt, 1989, Fulton, 1961, Fulton, 1962, Roos, 1979, Jormalainen et al. 1994), Bouillon, 1963, Folino, 1999,|