Biometry, shell resistance and attachment of zebra and quagga mussels at the beginning of their co-existence in large European lakes

Abstract

20In invasive dreissenid communities, the zebra mussel usually appears earlier and then is 21 displaced by the quagga mussel. We analysed length-weight allometric relationships, 22 attachment strength (2 days, 1 week and 1 month of exposure), shell crushing resistance and 23 glycogen content across the entire size range of both species in large shallow European lakes 24where this displacement has recently occurred. In Lake Balaton (Hungary) and Ijsselmeer 25 (The Netherlands), the soft tissue dry weight increment of zebra mussels per unit length 26 decreased after the quagga mussel invasion and became lower than that of quagga mussels. In 27 Lake Markermeer (The Netherlands), having relatively worse environmental conditions, dry 28 weight increment per unit length was always higher in quagga mussels than in zebra mussels, 29 but no negative change in dry weight increment occurred in zebra mussels during the quagga 30 mussel invasion. Small zebra mussels had more resistant shells and stronger attachment than 31 quagga mussels. These differences were reduced (shell hardness) or reversed (long-term 32 attachment) in larger individuals. Zebra mussels had lower glycogen content than quagga 33 mussels across the entire size range. Thus, the quagga mussel advantage over zebra mussel 34 likely consists in the faster dry weight increment per unit length and higher storage product 35 contents of the former, due to its lower investments in attachment strength and shell crushing 36 resistance. 37 38

Zebra or quagga mussel dominance depends on trade-offs between growth and defense—Field support from Onondaga Lake, NY

“…These morphological and behavioral responses to predators resulted in lower vulnerability to predation for zebra mussels compared to quagga mussels and both round goby and rusty crayfish (Orconectes rusticus) preferred quagga mussels over zebra mussels. Greater investments in anti-predator behavior and morphology by zebra mussels than by quagga mussels have been observed repeatedly in laboratory experiments elsewhere [29,30,34,35].…”

“…Selective predation cannot be the direct cause for the displacement of zebra mussels by quagga mussels as quagga mussels are more vulnerable to predation because of their thinner shells, less aggregation behavior, lower propensity to seek refuges, and lower attachment strength [29][30][31][32][33][34][35]. However, these anti-predation adaptations have a cost.…”

Dreissenids’ breaking loose: differential attachment as a possible driver of the dominance shift between two invasive mussel species

“…Studies assessing the attachment strength and byssal thread synthesis rate in laboratory setups found higher values for D. polymorpha compared to D. bugensis (Peyer et al 2009;Grutters et al 2012;Collas et al 2018). Balogh et al (2019) unravelled a more complex pattern as the attachment strength increased with shell size. For larger individuals the previously observed pattern reversed as larger ([ 1.2 cm) D. bugensis individuals had a higher attachment strength than D. polymorpha individuals of the same size (Balogh et al 2019).…”

“…Balogh et al (2019) unravelled a more complex pattern as the attachment strength increased with shell size. For larger individuals the previously observed pattern reversed as larger ([ 1.2 cm) D. bugensis individuals had a higher attachment strength than D. polymorpha individuals of the same size (Balogh et al 2019). Next to the shell size, the number and thickness of byssal threads have a positive impact on the attachment strength of dreissenids as well (Bell and Gosline 1997;Kobak 2006).…”

“…These characteristics proved a competitive benefit for D. bugensis over D. polymorpha. However, several other plausible mechanisms have not been studied extensively, such as differences between both species in mobility, attachment strength and detachment ability (Peyer et al 2009;Balogh et al 2019).…”