Ultrastructure of pedal muscle as a function of temperature in nacellid limpets

Abstract

Temperature and mitochondrial plasticity are well studied in Wshes, but little is known about this relationship in invertebrates. The eVects of habitat temperature on mitochondrial ultrastructure were examined in three confamilial limpets from the Antarctic (Nacella concinna), New Zealand (Cellana ornata), and Singapore (Cellana radiata). The eVects of seasonal changes in temperature were also examined in winter and summer C. ornata. Stereological methods showed that limpet pedal myocytes were 1-2 orders of magnitude smaller in diameter (t3.5 m) than in vertebrates, and that the diameter did not vary as a function of temperature. Mitochondrial volume density (Vv (mt,f) ) was approximately 2-4 times higher in N. concinna (0.024) than in the other species (0.01 and 0.006), which were not signiWcantly diVerent from each other. Mitochondrial cristae surface density (Sv (im,mt) ) was signiWcantly lower in summer C. ornata ). The surface area of mitochondrial cristae per unit Wbre volume was signiWcantly higher in N. concinna, due largely to the greater mitochondrial volume density. These results and previous studies indicate that mitochondrial proliferation in the cold is a common, but not universal response by diVerent species from diVerent thermal habitats. Seasonal temperature decreases on the other hand, leading preferentially to an increase in cristae surface density. Stereological measures also showed that energetic reserves, i.e. lipid droplets and glycogen in the pedal muscle changed greatly with season and species. This was most likely related to gametogenesis and spawning.

Field studies and projections of climate change effects on the bearded horse mussel Modiolus barbatus in the Gulf of Thermaikos, Greece

“…This metabolic response is in line with that observed in the congeneric Modiolus modiolus (Lesser & Kruse 2004) dria found in tissues of cold-acclimated active marine invertebrates (Sommer & Pörtner 2002). During coldinduced hypoxia, the level of oxidative stress may rise, causing a compensatory expression of antioxidant enzymes (Viarengo et al 1995, Abele et al 2002, Lesser & Kruse 2004, Lurman et al 2010. These processes are known to stimulate the expression of Hsps (Kassahn et al 2009).…”

Effect of Thermal Acclimation on Organ Mass, Tissue Respiration, and Allometry in Leichhardtian River PrawnsMacrobrachium tolmerum(Riek, 1951)

“…Mitochondria generally proliferate in the cold either in response to reduced oxygen delivery (Guderley 2004) or in response to a reduced efficiency of mitochondria to produce ATP (Pörtner et al 2000). It has been shown, however, that rather than a proliferation in mitochondria (commonly seen in ectothermic vertebrates), the likely predominant mechanism in invertebrates is to change the surface density of mitochondrial cristae in response to cold acclimation (Lurman et al 2010). We found an overall effect of thermal acclimation on the metabolic rates of tail and chelae muscle (independent of mass), such that these tissues were 1.8-fold higher in animals acclimated to 16ЊC compared with animals acclimated to 25ЊC when measured at 21ЊC.…”

“…As such, when measured at the same temperature, organisms from cold environments tend to have higher metabolic rates than those from warm environments (Addo-Bediako et al 2002). This observation has been dubbed metabolic cold adaptation (MCA); it has been evidenced as an evolutionary response in insects (Addo-Bediako et al 2002), and although there is some empirical evidence for its existence in aquatic arthropods (e.g., Rastrick and Whiteley 2011;Whiteley et al 2011), its existence in aquatic animals in general is heavily debated (Holeton 1974;Clarke 1993;Steffensen 2002;Lurman et al 2010;White et al 2012a).…”

“…Temperature acclimation involves alteration of rates of chemical and enzymatic reactions, rates of diffusion, and changes in protein structure (e.g., Kleckner and Sidell 1985;Lucassen et al 2003;Lurman et al 2010;Whiteley et al 2011). When exposed to the cold, ectothermic animals have to compensate for the slowing effect of temperature on these processes and uphold functional equilibrium between adenosine triphosphate (ATP) demand and ATP formation.…”

Role of sequential low-tide-period conditions on the thermal physiology of summer and winter laboratory-acclimated fingered limpets, Lottia digitalis

“…Lipids and glycogen are the primary energetic source for gametogenesis in gastropods, including limpets (Blackmore 1969;Simpson 1982;Gabbott 1983;Lurman et al 2010), so it is not surprising that limpets in the winter trial displayed depleted glycogen levels. Additional research is needed to better understand the potential trade-offs in thermal physiology and reproduction of L. digitalis during the winter.…”