Swimming away or clamming up: the use of phasic and tonic adductor muscles during escape responses varies with shell morphology in scallops

Abstract

SUMMARYThe simple locomotor system of scallops facilitates the study of muscle use during locomotion. We compared five species of scallops with different shell morphologies to see whether shell morphology and muscle use change in parallel or whether muscle use can compensate for morphological constraints. Force recordings during escape responses revealed that the use of tonic and phasic contractions varied markedly among species. The active species, Amusium balloti, Placopecten magellanicus and Pecten fumatus, made more phasic contractions than the more sedentary species, Mimachlamys asperrima and Crassadoma gigantea. Tonic contractions varied considerably among these species, with the two more sedentary species often starting their response to the predator with a tonic contraction and the more active species using shorter tonic contractions between series of phasic contractions. Placopecten magellanicus made extensive use of short tonic contractions. Pecten fumatus mounted an intense series of phasic contractions at the start of its response, perhaps to overcome the constraints of its unfavourable shell morphology. Valve closure by the more sedentary species suggests that their shell morphology protects them against predation, whereas swimming by the more active species relies upon intense phasic contractions together with favourable shell characteristics.

When Behavior and Mechanics Meet: Scallop Swimming Capacities and Their Hinge Ligament

“…The individuals of Amusium balloti, Placopecten magellanicus, Pecten fumatus, Mimachlamys asperrima, and Crassadoma gigantea characterized were those used in a complementary behavioral study (Tremblay et al 2012). The scallop Equichlamys bifrons was collected with and kept in the same conditions as P. fumatus and M. asperrima (Table 2).…”

“…Six scallop species (Amusium balloti, Placopecten magellanicus, Equichlamys bifrons, Pecten fumatus, Mimachlamys asperrima, and Crassadoma gigantea) with different shell shapes (Fig. 2) and distinct swimming strategies, as documented by our measurements of muscle use during induced escape responses (Tremblay et al 2012;summarized in Table 1), were compared. The scallops A. balloti and P. magellanicus (Gmelin, 1791) are active swimmers and perform phasic contractions throughout the escape response (duration 355 sec; Tremblay et al 2012), with A. balloti making phasic contractions at a quicker pace than P. magellanicus.…”

“…2) and distinct swimming strategies, as documented by our measurements of muscle use during induced escape responses (Tremblay et al 2012;summarized in Table 1), were compared. The scallops A. balloti and P. magellanicus (Gmelin, 1791) are active swimmers and perform phasic contractions throughout the escape response (duration 355 sec; Tremblay et al 2012), with A. balloti making phasic contractions at a quicker pace than P. magellanicus. The scallop P. fumatus (Reeve, 1852) performs intense bursts of phasic contractions at the beginning of its escape response, but fatigues quickly and then makes prolonged tonic contractions.…”

“…Principal component analysis (PCA) of these morphological characteristics was used to examine links among the morphological characteristics and how they differentiated our experimental scallop species. Next, a PCA on our data for patterns of muscle use during induced escape responses (Tremblay et al 2012) was carried out to evaluate links among the principal components (PC) describing morphology and those describing behavior in our experimental scallop species. The underlying premise was that the morphological characteristics of the experimental scallopsÕ shell and adductor muscle should reflect their swimming strategies.…”

Escape performance of temperate king scallop, Pecten maximus under ocean warming and acidification

“…The responsible adductor muscle consists of two functional types: the dominant phasic muscle (fast muscle) contracts rapidly and generates claps that enable scallops to swim by jet propulsion; the tonic muscle (catch muscle) contracts more slowly and operates at low energy costs; and it keeps the valves either closed for longer periods or at constant gaping for ventilation and feeding (Chantler 2006). The use of phasic and tonic contractions differs among species suggesting that lifestyle and shell morphology define muscle use during escape responses (Minchin 2003;Alejandrino et al 2011;Tremblay et al 2012; see also Guderley and Tremblay 2013). Furthermore, reliance on tonic contractions was higher in juvenile giant scallops, Placopecten magellanicus directly measured after handling stress compared with individuals given a 3-h recuperation period (Pérez et al 2008a).…”