Jacques Mathieu

COMPARATIVE STUDY ON THE BEHAVIORAL, VENTILATORY, AND RESPIRATORY RESPONSES OF HYPOGEAN AND EPIGEAN CRUSTACEANS TO LONG-TERM STARVATION AND SUBSEQUENT FEEDING

Abstract Survival, oxygen consumption, locomotory activity and ventilatory activity were recorded during a 180-day starvation period and a subsequent 15-day feeding phase in 3 hypogean crustaceans, Niphargus rhenorhodanensis, Niphargus virei, and Stenasellus virei. For comparison, these parameters were also recorded during a 28-day starvation period and a subsequent 7-day feeding phase in two morphologically close epigean crustaceans, Gammarus fossarum and Asellus aquaticus. Hypogean crustaceans were better adapted to lack of food than epigean ones and all crustaceans previously studied, with survival times largely longer than 200 days. During long-term starvation, the locomotory, ventilatory, and respiratory rates were drastically lowered in subterranean species, whereas surface species showed lower decreases in these rates and responded by a marked and transitory hyperactivity. The higher reduction in metabolic rate by hypogean species would ensure their survival during prolonged periods of food deprivation. We propose an energy strategy for food-limited hypogean crustaceans involving the ability 1) to withstand long-term starvation, and 2) to use the consumed food very efficiently. Resistance to starvation would probably involve a state of temporary torpor during which the subterranean crustaceans subsist on a high energy reserve, such as lipid stores.

Behavioral, Ventilatory, and Metabolic Responses to Severe Hypoxia and Subsequent Recovery of the Hypogean Niphargus rhenorhodanensis and the Epigean Gammarus fossarum (Crustacea: Amphipoda)

Two aquatic amphipod crustaceans were investigated: Niphargus rhenorhodanensis (a hypogean species, which has to cope with severe hypoxic conditions during about 6 mo per year during the hydrological cycle) and Gammarus fossarum (an epigean species, which lives continuously in well-oxygenated water). The lethal times for 50% of the population (LT50) for these closely) related species were 46. 7 and 6.3 h, respectively, in very severe hypoxia (<0.2 Torr) at 11°C. Therefore, the aim of this study was to examine some possible reasons why the subterranean Niphargus survived severe hypoxia longer than Gammarus and numerous other epigean crustaceans. During severe hypoxia Niphargus reduced its energetic expenditures compared with Gammarus. This reduction was associated with changes in locomotion and ventilation. In both species, anaerobic metabolism was fueled in severe hypoxia by the breakdown of glycogen and arginine phosphate. In Niphargus, however glutamate was also utilized. This resulted in the production of l-lactate as the major end product in both species. Alanine was found to be a minor end product in Gammarus, while alanine and succinate were found to be the minor end products in Niphargus. Compared to Gammarus, and to most other epigean crustaceans, Niphargus showed high amounts of stored glycogen and arginine phosphate. During severe hypoxia, both organisms excreted lactate into the medium, which is unusual for crustaceans. The differences in the stores of phosphagen and glycogen, and in behavioral and ventilatory responses, are probably the main reasons for their different resistance to severe hypoxia. During recovery, both species displayed a characteristic hyperventilation and their metabolism was predominantly aerobic. Gammarus excreted a great part of the lactate accumulated during severe hypoxia, whereas Niphargus remetabolized it, the latter possessing a higher glyconeogenesis capacity from lactate. After 24 h recovery, energy charge in both amphiods was not completely restored, and only Niphargus showed a total removal of the accumulated end products. Niphargus showed a faster replenishment of ATP concentration.

Behavioral, Ventilatory, and Metabolic Responses of the Hypogean Amphipod Niphargus virei and the Epigean Isopod Asellus aquaticus to Severe Hypoxia and Subsequent Recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean amphipod Niphargus virei and the epigean isopod Asellus aquaticus were compared during severe hypoxia (<0.03 kPa) and subsequent recovery. The aims of this study were (1) to determine why the subterranean species displayed a greater tolerance of hypoxia than A. aquaticus and numerous other epigean crustaceans, (2) to confirm previous results obtained with the hypogean amphipod Niphargus rhenorhodanensis and the epigean amphipod Gammarus fossarum, (3) to provide an interspecific comparison of epigean species in order to see if responses showed by epigean amphipods during hypoxia and recovery can be extended to epigean isopods, and (4) to better understand the ecological problems of the hypogean organisms survival and perennation in subterranean habitats. Both organisms responded to long-term experimental severe hypoxia with classical anaerobic metabolism, characterized by a decrease in ATP and phosphagen, the use of glycogen and glutamate, and the accumulation of lactate (with some alanine). In addition, some accumulation of succinate was found in N. virei. Lactate (and succinate for N. virei) was also largely excreted by both amphipods, which is unusual for the crustacea in general Compared with A. aquaticus and most other epigean crustaceans, N. virei showed large amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce glycolytic flux and energetic expenditures linked to locomotion and ventilation, extended the survival of hypogean crustaceans under experimental anaerobiosis (LT50 was 52.1 h for N. virei and 19. 7 h for A. aquaticus during severe hypoxia at 11° C). During recovery, both species displayed characteristic hyperventilation, slow locomotory activity, and predominantly aerobic metabolism. Asellus aquaticus excreted a large part of the lactate accumulated during severe hypoxia, whereas N. virei remetabolized it, as it had a higher lactate-derived glyconeogenesis capacity. The disposal of endproducts and replenishing of glycogen, ATP, and phosphagen required more than 24 h for both organisms. Niphargus virei showed a faster and more complete replenishment of ATP and arginine phosphate levels than A. aquaticus. Data concerning locomotory, ventilatory, and metabolic responses to hypoxia and subsequent recovery in N. virei and A. aquaticus are similar to those obtained with N. rhenorhodanensis and G. fossarum.

Biomotoring groundwater contamination: Application to a karst area in Southern France

In order to assess the descriptive value of subterranean organisms with regard to groundwater contamination, faunal sampling was carried out at two unimpacted sites and one sewage-polluted site located in the south-eastern part of the Lez karst system (Hérault, France) from 1991–1993. Invertebrates were collected by means of an air-lift pump in 8 deep monitoring wells (from 43 to 90 m deep) which intersected Cretaceous and/or Jurassic limestones. Wells of the unimpacted sites had faunal assemblages dominated by crustaceans (from 92.4 to 98.3% of the total number of organisms), and they harboured a high number of stygobite species (from 15 to 24) which usually represented a major component of the total number of invertebrates (from 48.1 to 81.5%). At the sewage-polluted site, the wells had significant relative abundances of oligochaetes (from 8.4 to 40.4% of the total number of invertebrates), low stygobite richnesses (from 3 to 7 species) and their groundwater fauna consisted mainly of stygoxene taxa (from 20 to 34) whose relative abundance could be as high as 88%. The spatio-temporal distribution of organisms was related to the groundwater and sewage flow patterns. During low-water periods sewagepolluted water moved preferentially through the conductive fractures of the saturated zone whose faunal assemblages were dominated by stygoxenes such as the polysaprobiont oligochaeteTubifex tubifex. When floods occurred, these stygoxenes were flushed out of the site and were also disseminated throughout the thinly fissured part of the saturated zone where they were associated with stygophiles. As the source of sewage pollution decreased in intensity with time, preliminary signs of groundwater fauna recovery were observed. Oligochaetes became less abundant but recolonization of groundwater by stygobites was not yet observed. On the basis of our results and those of other authors we emphasize the advantages which could result from the development of biomonitoring programmes for the assessment of karstic groundwater contamination.

Oxygen Consumption and Ventilation in Declining Oxygen Tension and Posthypoxic Recovery in Epigean and Hypogean Crustaceans

ABSTRACT Respiratory and ventilatory responses to declining O2 tension and posthypoxic recovery were investigated in 3 hypogean and in 2 epigean aquatic crustaceans. The aims of this study were to determine how these species reacted to declining O2 tension, to investigate their changes in ventilation and metabolic rate during progressive hypoxia, and to extend our knowledge on the fate of anaerobic end products during subsequent recovery. Hypogean organisms had normoxic O2 consumption rates 1.7―3.5 times lower than the epigean species. All 5 crustaceans were able to maintain their O2 consumption rates (1) at relatively constant levels and (2) independent of Po2 between normoxia and the critical Po2. Hypogean species also possessed lower critical Po2 than epigean ones, which may indicate that these organisms are better adapted to low O2 content and are better equipped to stay aerobic under hypoxia. For all species, posthypoxic recovery resulted in a high O2 debt. The payment of this debt was smaller in hypogean than in epigean species. The main explanations of the lower 0, debt shown by hypogean organisms are the lower energetic expenditures noticed during hypoxia, partly due to a decrease in locomotory and ventilatory activities.

Locomotory, ventilatory and metabolic responses of the subterranean Stenasellus virei (Crustacea, Isopoda) to severe hypoxia and subsequent recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean aquatic isopod crustacean Stenasellus virei were investigated in severe hypoxia (PO2 < 0.03 kPa) and subsequent recovery. The aims of this study were i) to determine why the subterranean species displayed a greater tolerance of hypoxia than numerous other epigean crustaceans, ii) to confirm previous results obtained with four hypogean and epigean crustaceans, iii) to compare the responses to severe hypoxia in hypogean amphipods and isopods, and iv) to better understand the ecological problems of the hypogean organisms survival in subterranean habitats. S. virei responded to experimental long-term, severe hypoxia with classical anaerobic metabolism mainly characterized by a decrease in adenosine triphosphate (ATP) and phosphagen, utilization of glycogen and glutamate, and accumulation of lactate and alanine. Lactate was also largely excreted by this organism, which is unusual for crustaceans in general. Compared to most other epigean crustaceans, the isopod S. virei showed high amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce energetic expenditures linked to locomotion and ventilation, extended the survival of S. virei under experimental anaerobiosis. During recovery, the isopod S. virei showed a higher capacity for glyconeogenesis from lactate and a faster and total replenishment of ATP and arginine phosphate levels than epigean crustaceans. Data concerning responses to hypoxia and subsequent recovery in S. virei are similar to those previously obtained with two other hypogean amphipods, except that this isopod did not synthesize succinate in anaerobiosis.

Comparative responses to severe hypoxia and subsequent recovery in closely related amphipod populations (Gammarus minus) from cave and surface habitats

AbstractThe locomotory and ventilatory activities, oxygen consumption, and the intermediary and energy metabolism modifications of a spring and a cave population of the aquatic amphipod crustacean Gammarus minus were investigated in normoxia, severe hypoxia (

Comparative study on the metabolic responses of subterranean and surface-dwelling amphipods to long-term starvation and subsequent refeeding

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