Coping with environmental stress may involve combinations of behavioral and physiological responses. We examined potential interactions between adult mussels' simple behavioral repertoire – opening/closing of the shell valves – and thermal stress physiology in common-gardened individuals of three Mytilus congeners found on the West Coast of North America: two native species ( M. californianus and M. trossulus ) and one invasive species from the Mediterranean ( M. galloprovincialis ). We first continuously monitored valve behavior over three consecutive days on which body temperatures were gradually increased, either in air or in seawater. A temperature threshold effect was evident between 25 and 33°C in several behavioral measures. Mussels tended to spend much less time with the valves in a sealed position following exposure to 33°C body temperature, especially when exposed in air. This behavior could not be explained by decreases in adductor muscle glycogen (stores of this metabolic fuel actually increased in some scenarios), impacts of forced valve sealing on long-term survival (none observed in a second experiment), or loss of contractile function in the adductor muscles (individuals exhibited as many or more valve adduction movements following elevated body temperature compared with controls). We hypothesize that this reduced propensity to seal the valves following thermal extremes represents avoidance of hypoxia–reoxygenation cycles and concomitant oxidative stress. We further conjecture that prolonged valve gaping following episodes of elevated body temperature may have important ecological consequences by affecting species interactions. We then examined survival over a 90 day period following exposure to elevated body temperature and/or emersion, observing ongoing mortality throughout this monitoring period. Survival varied significantly among species ( M. trossulus had the lowest survival) and among experimental contexts (survival was lowest after experiencing elevated body temperature in seawater). Surprisingly, we observed no cumulative impact on survival of 3 days relative to 1 day of exposure to elevated body temperature. The delayed mortality and context-specific outcomes we observed have important implications for the design of future experiments and for interpretation of field distribution patterns of these species. Ultimately, variation in the catalog of physiological and behavioral capacities among closely related or sympatric species is likely to complicate prediction of the ecological consequences of global change and species invasions.

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Behavior and survival of Mytilus congeners following episodes of elevated body temperature in air and seawater

Litopenaeus vannamei were reared in close cycle over seven generations and tested for their capacity to digest starch and to metabolise glucose at different stages of the moulting cycle. After acclimation with 42.3% of carbohydrates (HCBH) or 2.3% carbohydrates (LCBH) diets and at high salinity (40 g kg(-1)) or low salinity (15 g kg(-1)), shrimp were sampled and hepatopancreas (HP) were stored. Total soluble protein in HP was affected by the interaction between salinity and moult stages (p 0.05). Total hexokinase specific activity (range 17-215 mU mg protein(-1)) showed a significant interaction between dietary CBH and salinity (p<0.05) with highest value (mean value 78.5 mU mg protein(-1)) found in HCBH-high salinity treatment, whereas in the other treatments the activity was not significantly different (mean value 35.93 mU mg protein(-1)). A synergistic effect of dietary CBH, salinity and moult stages over hexokinase IV-like specific activity was also observed (p<0.05). As result of this interaction, the highest value (135.5+/-81 mU mg protein(-1)) was observed in HCBH, high salinity at D0 moult stage. Digestive enzymes activity is enhanced in the presence of high starch diet (HCBH) and hexokinase can be induced at certain moulting stages under the influence of blood glucose level. Perspectives are opened to add more carbohydrates in a growing diet, exemplifying the potential approach for less-polluting feed.

Factorial effects of salinity, dietary carbohydrate and moult cycle on digestive carbohydrases and hexokinases in Litopenaeus vannamei (Boone, 1931).

The microsporidia are a large group of highly specialized obligate intracellular protozoan parasites. Disturbances in the biochemical composition of tissues infected by intracellular parasites are of interest because such infections often significantly alter the electrolyte, carbohydrate, protein, and free amino acid pools of host cells. Until recently, biochemical investigations of the metabolic processes of the microsporidia have suffered because of insufficient numbers of the different parasite stages and inadequate methods for the in vitro cultivation and maintenance of these organisms. The authors have observed the disappearance of glycogen granules in the host cell cytoplasm during the early stages of parasite development without any concomitant change in the size or quantity of lipid droplets. The microsporidian species Spraguea lophii is a model for investigating externally mediated signal transduction and subsequent activation of the internal signal pathway for triggering of a missile cell, the microsporidian spore. Microsporidian meront stages appear to have actin-myosin and kinesin-associated molecular motors. This chapter focuses on keratin filaments found in two domains: (i) within the spore stage, the microsporidian sporophorous vesicle, and (ii) keratin in the host cell cytoplasm domain but situated at its interface with the parasite. Recently, however, some success has been achieved in isolating and maintaining meronts and discharged sporoplasms in extracellular support medium. Developing a simple in vitro model will be useful for many subsequent biochemical analyses.

Microsporidian Biochemistry and Physiology

A species possesses an internal genetic structure that is compounded on the genetic architecture of constituent local populations. Each local population may be subtly unique in its coadapted gene ensemble, including the fine tuning of its genic regulatory system. More obviously and more approachably, populations may be differentiated in allele frequencies at single structural loci. This study describes the regional genetic patterns of allozyme loci in the amphipod crustacean Gammarus minus Say in a karst area of southeastern West Virginia. It is a part of an investigation of this species throughout the mid-Appalachian portion of its range, whose initial purpose is to map the genetic relationships among populations onto the highly structured environment of this region. Gammarus minus is highly differentiated in allele frequencies at several loci over short distances. There are at least three possible reasons for this fact. (1) As in other pericardians, females of G. minus brood their young in a ventral marsupium, and there is no specific migratory stage in the life history. (2) This species is principally found in freshwater lotic streams. Individual streams are essentially one-dimensional habitats from the viewpoint of gene flow, and drainage networks have a dimensionality between one and two (analogous to roads in Cavalli-Sforza and Bodmer, 1971). There is a greater decrease of genetic correlation with distance as dimensionality decreases in stepping-stone models of isotropic gene flow (Kimura and Weiss, 1964; Kimura and Maruyama, 1971). (3) G. minus in the Mid-Appalachians is largely confined to springs, spring runoff, and stream caves situated in carbonate strike valleys. Each local population is partially isolated from others in the local drainage system, and more profoundly isolated from populations in other streams and in other regions of carbonate outcrop. Holsinger (1969) discusses the Appalachian zoogeography of the Gammaridae in greater detail. In Virginia and West Virginia this species is widely distributed in the Ridge and Valley physiographic province and flanking areas, where its populations are mainly located in the headward reaches of feeders of trunk streams that trend northeast-southwest along linear strike valleys floored by Paleozoic limestones and dolomites. Some of these valleys are marked by karst development. A particularly extensive karst topography is displayed on the Greenbrier Limestone of Mississippian age in Pocahontas, Greenbrier, and Monroe Counties of southeastern West Virginia. This is a highly structured environment in which G. minus is found in three ecophenotypic forms. The primary aim of this study has been to map allozyme allele frequencies and levels of heterozygosity onto the structured topography to determine their concordance. The second goal has been to determine if the ecophenotypic

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1979.tb04674.x

The relation of genetic structure to environmental structure: gammarus minus in a karst area.

(1974). Metabolisme des acides amines et controle du volume cellulaire. Archives Internationales de Physiologie et de Biochimie: Vol. 82, No. 3, pp. 423-589.

Métabolisme des acides aminés et controle du volume cellulaire

1. 1. Optimum specific activities and maximal catalytic capacities for twelve of the enzymes of the glycolytic and pentose phosphate pathways were measured in gill, hepatopancreas and muscle tissue extracts from Pachygrapsus crassipes. 2. 2. Oxygen consumption studies with gill and hepatopancreas, utilizing both intact and homogenized preparations, showed no significant difference between these tissues. 3. 3. Results are discussed and compared to available crustacean data, as well as to data from vertebrate tissue studies. 4. 4. Possible mechanisms for the control of glycolysis in crustacean tissues are discussed.

J.L. Sutko

Papers

Carbohydrate metabolism in the striped shore crab, Pachygrapsus crassipes—I. The glycolytic enzymes of gill, hepatopancreas, heart and leg muscles