Byssus-thread formation by the mussel Mytilus edulis: effects of environmental factors

Abstract

Temperature, excision, salinity, tidal regime, and seasonality all affected byssus production in the mussel Myfilus edulisL.; however, the most influential factor studied was agitation. Mussels agitated every 4.5 S produce 15.8 threads ind-' d-l, a rate twice that stimulated by any of the other factors. An acclimation period of up to 2 wk was required for byssus-thread formation to return to that of control mussels after exposure to high temperatures, low salinities and rapid agitation. Byssus-thread production during experiments was neither random nor steady, but rather in response to a number of contributing factors, the relative importance of which will ultimately depend on the environment in which the mussel is found.

Seasonal influence of wave action on thread production in Mytilus edulis

“…Field experiments indicate that 90% of the variation in thread production can be predicted from changes in temperature, wave height and reproductive condition; temperature explains the largest amount of the variation. Similar observations have been made previously (Allen et al, 1976;Clarke and McMahon, 1996c;Young, 1985) suggesting that temperature may be a better predictor of thread production in mussels than wave action. However, it is unknown whether temperature is the underlying mechanism driving this change or another factor that varies concomitantly with temperature.…”

“…These results are not surprising, as previous studies have also found that agitation, the combination of byssal loading and acceleration, produces conflicting responses in mussels. Young (1985) observed a marked increase in thread production following the agitation of M. edulis, whereas, in D. polymorpha, byssal thread production was found to be both reduced and enhanced in response to agitation (Clarke and McMahon, 1996b;Rajagopal et al, 1996). The inconsistent response to byssal loading across months observed in this study is most probably due to the variable amount of load that was experienced by each individual mussel, which was directly proportional to the number of threads produced by the mussel and placed in tension.…”

“…Wave action exposes mussels to three potential stimuli for increased thread production: (1) mean flow, (2) acceleration (vertical displacement of the mussel body) and (3) hydrodynamic loading of the byssal retractor muscle by transferring tension from the byssal complex. Of these potential stimuli, flow is presently thought to be the primary cue for increased thread production in M. edulis (Dolmer and Svane, 1994;Lee et al, 1990;Van Winkle, 1970;Witman and Suchanek, 1984;Young, 1985). Previous research has suggested a positive linear relationship between water flow and mussel attachment (Dolmer and Svane, 1994).…”

“…The response of mussels to agitation, the combination of both acceleration and byssal loading, has been examined to a lesser extent, with conflicting results. Van Winkle (Van Winkle, 1970) determined that increased agitation of Geukensia demissa led to a 33% decrease in thread production when compared with stationary mussels, whereas Young (Young 1985) suggested that thread production increases notably with increased rate of agitation in M. edulis. Thus it is unclear how agitation, and more specifically acceleration and byssal loading, affect thread production and attachment strength in M. edulis.…”

Predicting wave dislodgment of mussels: variation in attachment strength with body size, habitat, and season

“…Mussels respond to their flow environment by altering their attachment strength. In the laboratory, water agitation increases the number of byssal threads produced (Young 1985). In the field, attachment strength varies with location in a mussel bed (Witman & Suchanek 1984, Bell & Gosline 1997, wave exposure of the site (Witman & Suchanek 1984), and, seasonally with wind conditions (Price 1982).…”