Brood chamber isolation during salinity stress in two estuarine mollusk species: from a protective nursery to a dangerous prison

The influence of season and the tidal cycle on division of labour by the radula during feeding in the estuarine brooding gastropod Crepipatella dilatata (Calyptraeidae)

“…Under these conditions the mantle cavity is sealed from the external environment, suspension-feeding ceases and there is no production of a mucous cord. This behaviour has been recorded previously for C. dilatata by Montory et al [49] and for C. peruviana and the oyster Ostrea chilensis by Chaparro et al [17]. The difference in the critical salinity between females [23] and males [19] may be attributable to the fact that larval stages of marine invertebrates are often more sensitive than adults to low salinity [50][51][52][53].…”

“…Salinity variation, particularly low salinity, is an important stress factor in estuarine systems [15,16] and a significant regulator of physiological and behavioral processes in estuarine organisms [11,13,17]. The feeding behaviour of marine invertebrate suspension-feeders can be strongly impacted by exposure to low salinity, which frequently results in cessation of feeding or at least a reduction in clearance rate [1,8,11,13,17]. In many cases the individual also responds by partially or completely isolating itself from the surrounding environment to minimise osmatic stress [17].…”

“…The feeding behaviour of marine invertebrate suspension-feeders can be strongly impacted by exposure to low salinity, which frequently results in cessation of feeding or at least a reduction in clearance rate [1,8,11,13,17]. In many cases the individual also responds by partially or completely isolating itself from the surrounding environment to minimise osmatic stress [17]. Critical values of salinity have been identified below which calyptraeid gastropods adhere closely to the substrate, isolating the mantle cavity from the exterior, with the result that suspension-feeding ceases (e.g.…”

“…This species lives in an environment in which variation in salinity and seston is high, owing to high winds and rainfall in winter and spring [7]. In order to minimize osmotic stress to the soft tissues and to the capsules, the female seals the shell to the substrate when the salinity falls below 22.5, preventing entry of water to the mantle cavity and thereby curtailing suspension-feeding [8,17]. There is little information on the action of the radula, particularly in relation to environmental variables, although it is more associated with motile individuals (all males and juveniles) than with sessile individuals (females), in which the scraping action of the radula is reduced and suspension-feeding is the principal means of food acquisition [23,25].…”

“…Temporal variation in factors such as water temperature, salinity, suspended particulate matter and oxygen concentration in bays and estuaries is well known [1,[5][6][7][8][9] and generally results in physiological and behavioral responses by organisms living in these environments [10][11][12][13]. Salinity is one of the most important environmental variables in estuarine systems [14][15][16] and may be a significant source of stress for estuarine invertebrates and other organisms [11,13], particularly sessile forms that are unable to move to more favorable locations [17].…”