|Reproduction Preferences Additional Information||Lifespan has not been established for this species but it is probably quite long lived. Individuals tend to die through weakening of the skeleton by boring organisms and subsequent detachment by agents such as foraging fish or careless divers. However, skeletons (dead individuals) have been found still attached to rocks (K. Hiscock, pers. comm.) Populations tend to become extinct through lack of recruitment. Lacaze-Duthiers, (1897) suggests that the sexes are separate. Eggs are laid in succession , at indefinite, fairly well-spaced intervals over a period of time that must be substantial (Lacaze-Duthiers, 1897). Larvae have been successfully produced in aquaria. The eggs are released from the female stomach cavity and those that are unfertilised may float to the surface. Fertilised eggs (young larvae) swim actively in the water column (K. Hiscock pers. comm..) but settle rapidly to the substratum close to the adult, where after a period of freedom they attach themselves in the shape of an ovoid or a ciliated worm (Lacaze-Duthiers, 1897). The larval settling time is generally short but observations from aquaria suggest that the larval stage may exist for up to six weeks before settling. Recruitment is very sporadic. Over 12 years of monitoring on Lundy has shown little or no recruitment and the population there declined by 22 percent between 1993 and 1997. Recruitment may fail for several reasons. Environmental conditions (primarily temperature) are unsuitable for gamete production to occur or to occur synchronously. Alternatively larvae may be swept away into unsuitable habitat by water currents or be consumed by predators before metamorphosing. Recruitment in the Mediterranean is also sporadic. Some recruitment may occur through influx of southern water bodies bringing with it larvae.