Growth, physiological rates and behaviour of mytilus edulis exposed to the predator Asterias rubens

161

130

Growth rates, condition indices and shell shapes of Mytilus galloprovincialis, an invasive alien mussel that has colonised the west coast of South Africa, were measured at a series of sites with different wave exposure regimes in 2 regions 500 km apart. Wave action at the sites was determined by maximum wave-force dynamometers. M. galloprovincialis grew faster and had higher condition values on exposed than on sheltered shores, probably due to higher food availability at sites with greater water flow. Growth rates and condition values, however, declined at sites experiencing extreme wave action. This resulted in a polynomial relationship between the growth coefficient K, and wave force. Mussels grew slower in the southern region, where food concentrations are lower. The shells of M. galloprovincialis tended to be lower and narrower at exposed sites, perhaps reducing the effect of hydrodynamic forces. Mussel shells were thickest on sheltered and extremely exposed shores. The results are discussed in the context of the impact that M. galloprovincialis is likely to have on indigenous species. Because M. galloprovincialis is scarce and slow-growing at sheltered sites, its competitive effects there are likely to be minimal, whereas on exposed sites its density, growth and condition are highest and its effects will peak, diminishing again at extremely exposed sites.

Section: Shell Shape Of Mytilus Galloprovincialismentioning

confidence: 99%

Growth rate, condition, and shell shape of Mytilus galloprovincialis: responses to wave exposure

Steffani¹,

Branch²

2003

161

130

“…The presence of predators can depress prey foraging behaviour (Appleton & Palmer 1988), and mussels in particular were found to lower their filter-feeding activity (Reimer et al 1995) and increase their heart rate (Rovero et al 1999) when exposed to chemical stimuli of predators. Such impacts will affect metabolic rate, energy acquisition and the growth of prey organisms.…”

Section: Discussionmentioning

confidence: 99%

“…Potential trade-offs between shell thickness and size might be involved in predatorinduced defences (Smith & Jennings 2000) and the advantage of increased shell thickness has to be balanced with the benefit of rapid shell growth (Smith & Jennings 2000). Ultimately, limited shell growth will restrict increases in soft tissue growth (Palmer 1981) and might lead to a smaller size, which results in reduced gonad production and smaller reproductive output (Smith & Jennings 2000).The presence of predators can depress prey foraging behaviour (Appleton & Palmer 1988), and mussels in particular were found to lower their filter-feeding activity (Reimer et al 1995) and increase their heart rate (Rovero et al 1999) when exposed to chemical stimuli of predators. Such impacts will affect metabolic rate, energy acquisition and the growth of prey organisms.…”

mentioning

confidence: 99%

Phylogenetically mediated anti-predator responses in bivalve molluscs

Fässler

Kaiser

2008

Sedentary, group-living taxa, such as bivalves, respond to waterborne predator cues by enhancing tissues that increase anti-predation attributes such as muscle and shell mass. The ability of bivalves to differentiate among cues generated by the consumption of different prey species that vary in phylogenetic relatedness is unknown. We exposed mussels to cues generated by crabs feeding on mussels, cockles and periwinkles to test whether there was a relationship between the magnitude of the induced response and the level of relatedness to the cue source. Mussels exposed to either effluents of unfed crabs or seawater only served as controls. Exposure to cues from conspecifics and cockles caused significantly reduced growth in shell size of mussels compared to control mussels. Shell growth of mussels exposed to cues from crabs feeding on periwinkles did not differ significantly from mussels exposed to effluents from unfed crabs only. Tissue dry weight increased least in mussels exposed to cues of crabs fed conspecifics, followed by mussels exposed to crabs fed cockles. Cues of crabs that were fed mussels caused increased byssus thread production, whereas the other treatments did not. Exposure to cues from crabs fed mussels and crabs fed cockles resulted in significantly thicker and heavier shells compared to unexposed control mussels. The results of this study indicate that alarm cues of progressively more closely related molluscs cause a higher degree of induced morphological anti-predator responses in mussels. The physiological and behavioural responses of mussels to these cues may therefore have a phylogenetic basis. KEY WORDS: Alarm cues · Heterospecifics · Inducible defences · Mytilus edulis · Phylogenetic relationshipResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 363: 217-225, 2008 1996, Leonard et al. 1999, Smith & Jennings 2000, Reimer & Harms-Ringdahl 2001, Freeman & Byers 2006. Furthermore, these responses are specific in character since attack modes vary considerably between predators. Leonard et al. (1999) reported that mussels produced thicker shells when exposed to cues from crabs Carcinus maenas and to cues from damaged conspecifics. Smith & Jennings (2000) observed the same response when they exposed mussels to effluents from whelks Nucella lapillus and crabs. Thickening the shell provides effective protection against drilling and crushing predators, but is less effective against predators that use different predation strategies. Starfishes, for example, pull the shell valves apart using their tube feet and insert their stomach through the resulting aperture (Norberg & Tedengren 1995). Accordingly, mussels exposed to cues from starfish Asterias rubens were found to increase the mass of their adductor muscles to resist higher pulling forces (Reimer & Tedengren 1996, Reimer & HarmsRingdahl 2001. Other responses to predator cues are enhanced byssus thread production (Côté 1995, Leonard et al. 1999, Reimer & Harms-Ringdahl 2001 and clumping be...

“…Morphological responses to a perceived risk of predation can improve the fitness of some marine invertebrates. Thus, exposure of Mytilus edulis to Asterias rubens led to the development of more compact and rounded shells, without changes in shell mass (Reimer et al 1995, Reimer & Tedengren 1996). The mussels also secreted Table 6.…”

Section: Discussionmentioning

confidence: 99%

Comparison of cultured and wild sea scallops Placopecten magellanicus, using behavioral responses and morphometric and biochemical indices

Lafrance¹,

Cliche²,

Haugum³

et al. 2003

As the survival of juvenile scallops released onto the seabed is of critical importance in programs seeking to enhance scallop populations, the basis of the vulnerability of seeded cultured scallops needs to be understood. High mortality rates following seeding operations could reflect weaker predator escape responses by cultured scallops. Thus, we compared behavioral responses as well as morphometric and biochemical measurements of cultured and wild sea scallops Placopecten magellanicus (35 to 45 mm shell height) sampled in August 1999 in the Gulf of St. Lawrence, eastern Canada. Cultured scallops had larger somatic tissues and higher muscle energetic contents than their wild counterparts. This may reflect the more favorable temperatures and better food supply during suspension culture. When faced with the starfish predator Asterias vulgaris, cultured scallops responded with a greater number of claps, longer clapping period and faster recuperation of clapping performance. However, wild scallops had stronger shells and showed more intense escape responses (higher clapping rate) to the starfish. These differences contribute to making cultured scallops more vulnerable to predation by grasping predators (crabs) and asteroids.