BIOTIC Species Information for Nematostella vectensis
|Researched by||Charlotte Marshall & Angus Jackson||Data supplied by||MarLIN|
|Refereed by||Dr Simon Davy & Dr Martin Sheader|
|Developmental mechanism||See additional information
|Reproductive Season||Insufficient information||Reproductive Location||As adult|
|Reproductive frequency||Annual episodic||Regeneration potential||No|
|Life span||Insufficient information||Age at reproductive maturity||<1 year|
|Generation time||Not relevant||Fecundity||Up to 2000 eggs|
|Egg/propagule size||170-240 µm in diameter||Fertilization type||Internal|
|Reproduction Preferences Additional Information||Nematostella vectensis is known to reproduce both sexually and asexually. In the UK there seems to be only female asexual reproduction (M. Sheader, pers. comm.). males are absent from populations of Nematostella vectensis on the south coast of England suggesting that these populations produce all their offspring asexually (Sheader et al., 1997). Furthermore, it is likely that all the females are from one clone (M. Sheader, pers. comm.). Studies from American sexually reproducing populations have produced valuable information concerning gametes and larvae and some of this information is provided below. Unless otherwise stated, all the information in the asexual reproduction and sexual reproduction sections below are taken from Hand & Uhlinger (1995) and Hand & Uhlinger (1992) respectively.
Asexual reproductionTransverse fission Asexual reproduction is achieved through transverse fission. Transverse fission is known in only four other sea anemones (Shick, 1991, cited in Hand & Uhlinger, 1994). In the laboratory, most fissions were found to take place at night and only in well expanded individuals. The fragment produced by fission is usually shorter than the oral piece and sometimes multiple fission occurs, producing two or three fragments. From the time of fission to the time of the first successful food capture, some fragments regenerated within three days. Although asexual division becomes common at about 10 weeks, it has been noted as early as seven weeks. Increased food intake leads to an increase in the frequency of fission and starvation can suppress the process (Hand & Uhlinger, 1995).
Budding Anemones with multiple oral-crowns are common in both natural and laboratory reared populations of Nematostella vectensis. Fission by such individuals produces normal single-crowned anemones. This is known as budding and is extremely rare in anemones.
Sexual reproductionIn the laboratory, Nematostella vectensis became sexually mature at 3-4 months old and at column lengths of between 1.5-3.5 cm. Gametes were found to be produced at all times of the year. Fritzenwanker & Technau (2002) found that, in the laboratory, a combination of feeding regime, dark-light cycle and temperature shift synergistically induced gametogenesis in adult polyps from the Rhode River in America. They summarized by saying that the combination of 4 days of feeding in the dark at 18 °C followed by illumination at 24 °C produced the highest number of eggs. The number of eggs is dependent on adult size. Large individuals reared in the laboratory can produce up to 2000 eggs. Eggs are 170-240 µm in diameter and are released embedded in a gelatinous mucoid mass. In the laboratory, spherical ciliated planula larvae emerge from the egg masses between 36-48 hours after fertilization. These larvae are active swimmers from the age of about 3 days old but spend periods of inactivity on the bottom. After a week they settle by which point they are between 250-500 µm long and have four tentacles. By the time they are two months old they are approaching sexual maturity, are 2-5 cm long and have up to 16 tentacles.
|Reproduction References||Stephenson, 1935, Sheader et al., 1997, Hand & Uhlinger, 1992, Fritzenwanker & Technau, 2002, Hand & Uhlinger, 1995,|