Allometric Relationship of Postmolt Net Ion Uptake, Ventilation, and Circulation in the Freshwater CrayfishProcambarus clarkii: Intraspecific Scaling

Abstract

There are few intraspecific studies relating physiological parameters to body mass. This study relates scaling of ionic regulation and respiratory parameters with body mass in crayfish (Procambarus clarkii). These animals were chosen because of their direct development, spanning four orders of magnitude in body mass. Usually, these animals are hyperregulators and must maintain hemolymph electrolyte levels above those in the ambient freshwater. This is especially important in the postmolt, when ion imbalance can occur. Maintaining hemolymph ion levels above ambient involves active processes that are independently related to metabolic rate, ventilation, and circulation. Therefore, this study investigates relationships among size and ionic regulation, heart rate, and ventilation in crayfish, spanning a size range of 0.003-24 g. Postmolt net ion uptake of Ca, titratable base, Na, Cl, and NH4 increase with body mass (positive allometry) with slopes of 0.92, 0.79, 0.90, 0.84, and 0.87, respectively. Between 72% and 97% of variation in ionic regulation was related to body mass. The slopes differed from each other for Ca and titratable base but not for Na, Cl, and NH4. For heart rate and ventilation rate, different relationships were derived for animals smaller and larger than 0.01 g (between first and third instar). Animals larger than 0.01 g show a negative allometric relationship between heart rate and body size ([body mass](0.15)), while smaller animals show positive allometry with body size, but only 29% of variation in heart rate is explained by body size alone. For ventilation rates, the negative allometry with body size for animals larger than 0.01 g is present, but less than 15% of variation in ventilation rate is explained by size, while for smaller animals the size dependency disappears. Based on these results, predictions of physiological parameters such as ionic regulation based on body size are useful in crayfish, but estimates of respiratory parameters and body size should be used with caution.

Body size influences energetic and osmoregulatory costs in frogs infected with Batrachochytrium dendrobatidis

“…Moreover, smaller individuals had disproportionally greater rates of ion loss during sloughing than larger individuals. The relationship between body size and ion loss during sloughing in green tree frogs (exponent of 0.87) is similar to that observed in molting crayfish ( Procambarus clarkii ) (scaling exponent of 0.9) 51 . Although Bd load affected rates of ion loss during the non-sloughing phases of the moult cycle, Bd infection did not exacerbate ion loss rates, relative to uninfected animals, during sloughing.…”

The role of sloughing on the pathophysiology of chytridiomycosis in amphibians

“…Moreover, smaller individuals had disproportionally greater rates of ion loss during sloughing than larger individuals. The relationship between body size and ion loss during sloughing in green tree frogs (exponent of 0.87) is similar to that observed in molting crayfish (Procambarus clarkii) (scaling exponent of 0.9) (Zanotto et al, 2004). Although Bd load affected rates of ion loss during the non-sloughing phases of the moult cycle, Bd infection did not exacerbate ion loss rates, relative to uninfected animals, during sloughing.…”

Transporte de cálcio em células isoladas de hepatopâncreas do caranguejo dulcícola Dilocarcinus pagei: efeito do ATP e Ca2+

“…A concentração intracelular de cálcio necessária para metade da ativação máxima (K 0.5 ) do modo de influxo de cálcio em axonios gigantes de lula (DIPOLO, 1979;OSSES et al, 1986DIPOLO & BEAUGÉ, 1988DIPOLO & BEAUGÉ, 1993a,b) e cardiomiócitos HILGEMANN 1990;HILGEMANN et al,. 1992a,b) (BAKER et al, 1969;BEAUGE & DIPOLO, 1991;GADSBY et al, 1991;Fontana et al, 1995), no entanto não parece ser o que ocorre com células de hepatopâncreas, já que seu lado apical está voltado para um meio preenchido com alimento, normalmente mais rico em Na e outros sais no caso de crustáceos terrestres e dulcícolas ZANOTTO et al, 2004) 1999) e é importante para a função cardíaca (REUTER et al, 2002;VERDONCK et al, 2004) e células musculares de mamíferos (BORIN et al, 1994;ARMON et al, 2000a,b;DOSTANIC et al, 2005;LEE et al, 2006 (DIPOLO, 1973(DIPOLO, , 1974(DIPOLO, , 1976 , 1996).…”