|Reproduction Preferences Additional Information||Before 1976 there was no distinction between Chthamalus stellatus and Chthamalus montagui. Since 1976 the existence of two separate species was recognised (Southward, 1976). Therefore, papers pre-1976 on Chthamalus stellatus have been recorded as for both Chthamalus stellatus and Chthamalus montagui, below.
- Sexual maturity of Chthamalus montagui was attained at a rostro-carinal diameter of 4.4.5-6.4 mm (O'Riordan et al., 1992). Chthamalus montagui is able to breed in its first year (Burrows, 1988; Southward & Crisp, 1954), after 9 to 10 months of settlement (Southward & Crisp, 1954). Sperm is activated by the oviducal gland and transferred to the oviducal sac via the penis of a neighbouring barnacle (Barnes, 1989). The barnacle penis is substantially longer than the body and is capable of searching an area around the adult to find a receptive 'functional female' (Rainbow, 1984).
- Barnacles generally reproduce by cross-fertilization, but Chthamalus has been shown to self-fertilize when isolated (Barnes & Barnes, 1958; Barnes, 1989); this usually occurs high up on shore. However, it has been noted that in self-fertilized individuals oviposition is delayed (Barnes & Barnes, 1958; Barnes, 1989) and the resulting eggs can be slightly abnormal and are considered less viable (Barnes, 1989). Egg masses (egg lamellae) are brooded in the mantle cavity (O'Riordan et al., 1995; Barnes, 1989).
- Southward (1978) suggested that Chthamalus montagui breeds one to two months later than Chthamalus stellatus. However, Crisp et al. (1981) found little difference in SW Britain, with the main breeding peak in June/July and August. Throughout the breeding season most individuals produce several broods (Burrows et al., 1992; O'Riordan et al., 1992), with a small percentage of the population remaining reproductively active throughout the year (O'Riordan et al., 1995); Barnes, 1989). After maturation of each brood ovarian and penis re-development takes place (O'Riordan et al., 1995; Barnes & Barnes, 1965; Burrows, 1988; Anderson, 1994).
According to Hines (1978) temperature and food availability are the main factors controlling the duration of the breeding season and the embryonic development rate of other Chthamalus species. In fact, Burrows (1988, in Kendall & Bedford, 1987) found the onset of the breeding season to be correlated with a sea temperature of 10 °C or above (Burrows et al., 1992). Southward & Crisp (1956) noted that the interval between broods in Chthamalus stellatus and Chthamalus montagui became shorter at higher temperatures.
- The onset of the breeding season was noticed by Crisp (1950) to spread up the shore level over several months. Brooding in Aberystwyth was noted to be in May/June to August (Kendall & Bedford, 1987), with approximately 80 % containing a naupliar mass. Cyprid settlement occurred in late July to early September at a sea temperature of 15.3 to 18.8 °C (Kendall & Bedford, 1987). In northern Spain the brooding period tends to be longer, between April and early October, with 30 % containing a naupliar mass (Kendall & Bedford, 1987).
- The breeding period, period of larval settlement and density of recruits are all reduced near the northern limits of its distribution. Crisp (1950) suggested that for Chthamalus montagui and Chthamalus stellatus in the United Kingdom, breeding commenced earlier with decreasing longitude and easterly longitude. Breeding of Chthamalus stellatus and Chthamalus montagui usually takes place earlier in the year in continental Europe than in the British Isles (Relini & Matricardi, 1979; Relini, 1983; Miyares, 1986, all in O'Riordan et al., 1995). In the Mediterranean the breeding season usually occurs in July and August (Mizrahi & Achituv, 1990, in O'Riordan et al., 1995).
- Experiments by O'Riordan et al. (1995) showed that in their first year Chthamalus stellatus and Chthamalus montagui breed once or more, and more than once thereafter.
Recruitment and lifespan
- In both Chthamalus stellatus and Chthamalus montagui it took approximately 23 days for embryos to develop completely in vivo at 15 °C (Burrows et al., 1992; Burrows, 1988, in Kendall & Bedford, 1987). Chthamalus montagui will only breed if temperatures exceed 15 degrees C (Patel & Crisp, 1960).
- Towards the northern limits of the species distribution annual recruitment is low (Kendall & Bedford, 1987) and individuals have an increased longevity (Lewis, 1964). The normal life span of Chthamalus stellatus / Chthamalus montagui at mid-shore level is considered to be approximately 2-3 years (Southward & Crisp, 1956). However, growth is more rapid and the mortality rate is greater lower down on the shore (Southward & Crisp, 1956).
- (Burrows et al., 1992) found that the number of eggs per brood for Chthamalus montagui ranged between 1,030 to 1803 in Britain, depending on body size and weight. It was also noted by (Burrows et al., 1992) that the fecundity generally increased with lower shore levels colonized, with estimations of 1-2 broods per year at high shore levels, 2 to over three at mid shore levels, and over 2 to over 4 at low shore levels.