Predator-Induced Behavioral and Morphological Plasticity in the Tropical Marine Gastropod Strombus gigas

Abstract

Florida queen conch stocks once supported a significant fishery, but overfishing prompted the state of Florida to institute a harvest moratorium in 1985. Despite the closure of the fishery, the queen conch population has been slow to recover. One method used in the efforts to restore the Florida conch population has been to release hatchery-reared juvenile conch into the wild; however, suboptimal predator avoidance responses and lighter shell weights relative to their wild counterparts have been implicated in the high mortality rates of released hatchery juveniles. We conducted a series of experiments in which hatchery-reared juvenile conch were exposed to a predator, the spiny lobster (Panulirus argus), to determine whether they could develop behavioral and morphological characteristics that would improve survival. Experiments were conducted in tanks with a calcareous sand substrate to simulate a natural environment. Conditioned conch were exposed to caged lobsters while conch in the control tanks were exposed to empty cages. Conditioned conch moved significantly less and buried themselves more frequently than the naive control conch. Morphometric data indicated that the conditioned conch grew at a significantly slower rate than the naive conch, but the shell weights of the two groups were not significantly different. This implies that the conditioned conch had thicker or denser shells than the control group. As a result, the conditioned conch had significantly higher survival than naive conch in a subsequent predation experiment in which a lobster was allowed to roam free in each tank for 24 hours. In the future, the conditioning protocols documented in this study will be used to increase the survival of hatchery-reared conch in the wild.

What can aquatic gastropods tell us about phenotypic plasticity? A review and meta-analysis

“…Soft-bottom taxa are mostly absent (but see Martín-Mora et al, 1995 andDelgado et al, 2002 for examples of a species found on both rocky and softbottom substrates), as are studies involving predators that use methods other than shell breakage (but see Bourdeau, 2009 for exceptions). It is possible that gastropods living in softsediment habitats or those preyed on mainly by slow-moving shellentry predators (for example, seastars) may rely chiefly on plastic avoidance and/or escape behaviour as their antipredator defense, rather than plastic morphological defenses.…”

“…We are aware of only one tropical species in which shell plasticity has been demonstrated. The queen conch (Strombus gigas) shows marked developmental plasticity in shell shape (Martín-Mora et al, 1995) and predator-induced plasticity in behaviour, growth and shell thickness (Delgado et al, 2002). We need many more studies on tropical marine and freshwater gastropods, as it would be interesting to know whether shell plasticity is a general phenomenon in tropical gastropods and to test whether patterns of variation in shell plasticity in temperate and tropical aquatic snails reflect differences in environmental variation between temperate and tropical zones.…”

Application of anaesthetics for sex identification and bioactive compound recovery from wild Dicathais orbita

“…Larger animals have presumably survived predation attempts by remaining hidden within the shell for longer, a key defence 16 against predation in marine gastropods (Bertness et al, 1981). Delgado et al (2002) demonstrated this with queen conch (Strombus gigas, Linneaus), where defensive response time for specimens previously exposed to predators was more acute than those with no prior exposure.…”

La thanatocénose du lagon de l'atoll Niau (Polynésie française) avec la description d'une nouvelle espèce deStrombus(Mollusca, Gastropoda, Strombidae)

“…Absence or presence of predators has bearing on shell mor− phology. In laboratory conditions, the presence of the lobster Panulirus argus induced changes in both behavior and shell growth, i.e., shells exposed to the lobsters grew slower, yet the shell weight remained the same (Delgado et al 2002). Also Herbert et al (2004) noted the development of anti− predatory traits in members of the Strombus alatus complex in presence of a predator.…”