|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 species, below.
- Sexual maturity of Chthamalus stellatus was attained at a rostro-carinal diameter of 4.0-6.8 mm (O'Riordan et al., 1992). A pre-1976 observation by Southward & Crisp (1954) suggests that Chthamalus stellatus is able to breed in its first year after 9 to 10 months of settlement. 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).
Fertilised egg masses (egg lamellae) are brooded in the mantle cavity (O'Riordan et al., 1995), outside the body (Barnes, 1989).
Barnacles generally reproduce by cross-fertilisation, but Chthamalus spp. have been shown to self-fertilise when isolated (Barnes & Barnes, 1950; Barnes & Crisp, 1956; Barnes, 1989); this usually occurs high up on shore. However, it has been noted that oviposition is delayed (Barnes & Barnes, 1950; Barnes, 1989) and the resulting eggs can be slightly abnormal and are considered less viable (Barnes, 1989).
- The onset of the breeding season in the United Kingdom was noticed by Crisp (1950) to spread up the shore level over several months. 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 and August (O'Riordan et al., 1995). 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; Barnes & Barnes, 1977; 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. 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.
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). Crisp (1950) suggested that for Chthamalus montagui and Chthamalus stellatus in the United Kingdom, breeding commenced earlier with decreasing longitude and easterly longitude. However, in the Mediterranean the breeding season usually occurs in July and August (Mizrahi & Achihuv, 1990, in O'Riordan et al., 1995).
Breeding of Chthamalus stellatus in France occurs in April (Barnes, 1992), and correlates with mean air and sea temperatures of 11 - 12 °C, and maximum temperatures of 14 °C. Barnes (1992) found that at an upper temperature limit of 20 - 21 °C in the sea and 24 - 25 °C in the air reproductive activity decreased. Southward & Crisp (1956) noted that the interval between broods in Chthamalus stellatus and Chthamalus montagui became shorter at higher temperatures. Barnes & Barnes (1965) found that in high suspended solids and low salinity there was a decrease in the number of eggs per brood of Chthamalus stellatus in Europe.
Older barnacles are able to breed at a smaller size than younger barnacles. For instance, experiments by O'Riordan et al. (1992) showed that in their first year Chthamalus stellatus and Chthamalus montagui breed once or more, and more than once thereafter.
Chthamalus stellatus / Chthamalus montagui are very tolerant of high periods of emersion, yet Patel & Crisp (1960) found that when barnacles which were brooding eggs were kept out of the water, a second batch of eggs was not produced.
- 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), whereas Burrows (1988, in Kendall & Bedford, 1987) found that at 15 °C it took 26 days, and Achituv & Barnes (1976) reported a value of 25 days, although the temperature is not known.
Annual recruitment and lifespan
- Burrows et al. (1992) found that the number of eggs per brood of Chthamalus stellatus ranged between 1,274 - 3,391 in Britain, depending on body size and weight. It was also noted by Burrows et al. (2000) 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. Fecundity in protected areas such as harbours is usually lower, possibly due to increased turbidity (Barnes, 1989). However, in Archachon (France) in highly turbid waters the effect was not so noticeable, probably due to higher nutrient concentrations (Barnes, 1989).
- Life span of Chthamalus stellatus / Chthamalus montagui is considered to be approximately 2-3 years (Southward & Crisp, 1950). However, growth is more rapid and the mortality rate is greater lower down on the shore (Southward & Crisp, 1950).Towards the northern limits of distribution annual recruitment is low (Kendall & Bedford, 1987) and they have an increased longevity (Lewis, 1964).