Carbohydrate metabolism in the central nervous system of the megalobulimus oblongus snail during anoxia exposure and post‐anoxia recovery

Abstract

The effects of anoxic exposure and the post-anoxia aerobic recovery period on carbohydrate metabolism in the central nervous system (CNS) of the land snail Megalobulimus oblongus, an anoxia-tolerant land gastropod, were studied. The snails were exposed to anoxia for periods of 1.5, 3, 6, 12, 18, or 24 hr. In order to study the post-anoxia recovery phase, snails exposed to a 3-hr period of anoxia were returned to aerobic conditions for 1.5, 3, 6, or 15 hr. Glycogen and glucose concentrations in the CNS, hemolymph glucose concentration, and glycogen phosphorylase (active form, GPa) activity in the CNS were analyzed. Anoxia does not significantly affect the concentration of CNS glucose but induces hyperglycemia and a reduction of CNS GPa activity. The glycogen concentration was decreased at 12 hr of anoxia; however, by 18 and 24 hr in anoxia, the glycogen content was not significantly different from basal control values. During the post-anoxia period, the reduction in GPa activity and the increased hemolymph glucose concentration induced by anoxia returned to control values. These results suggest that the CNS of M. oblongus may use hemolymph glucose to fulfill the metabolic demands during anoxia. However, the hypothesis of tissue metabolic arrest cannot be excluded.

Control of carbohydrate metabolism in an anoxia‐tolerant nervous system

“…It has already been reported that this species can survive after 48 hr of anoxia (Haeser and De Jorge, '71). In an earlier report, we showed 100% snail survival exposing the animal to 24 hr of anoxic stress (De Fraga et al, 2004).…”

“…This behavior could expose the snail to reduced oxygen availability. This natural tolerance has stimulated the use of this species as an experimental model in physiological approaches, including metabolism control (Rossi, '98; Dias, 2000) and anoxia tolerance (Dias, 2000; De Fraga et al, 2004). It has already been reported that this species can survive after 48 hr of anoxia (Haeser and De Jorge, '71).…”

“…Gastropod metabolism is also based on carbohydrate utilization (Livingstone and De Zwaan, '83), and glycogen mobilization plays an important role during anoxic stress in snails (Haeser and De Jorge, '71; Wieser, '81; Wijsman et al, '85, '88; Whitwam and Storey, '90). However, although some tissues of M. abbreviatus , such as the heart, deplete glycogen reserves during anoxia exposure (Dias, 2000), the central nervous system (CNS) of the snail continues to maintain a high glycogen concentration (about 1 g%) even exposed to anoxia (De Fraga et al, 2004). This regulation necessarily involves controlling glycogen‐metabolizing enzymes.…”

Seasonal changes of energy reserves in Bulimulus tenuissimus (d'Orbigny, 1835) (Mollusca, Bulimulidae)

“…The short days (autumn-winter) tend to stimulate the synthesis, whereas long days (springsummer) tend to inhibit it (Joosse and Geraerts, 1983;Wayne, 2001;De Fraga et al, 2004;Garcia and Pinheiro, 2007).…”

“…The reproductive behavior as well as gametogenesis, is controlled by the neuroendocrine system, which is dependent of external stimuli (Joosse, 1988;Wayne, 2001;De Fraga et al, 2004) Bulimulus tenuissimus is a native land snail widely distributed throughout Brazilian territory (Simone, 2006) and that stands out to act as intermediate host of helminths of veterinary importance and also as an agricultural pest (Thiengo and Amato, 1995). This species is iteroparous and has a long life cycle, with eggs laying occurring during the spring-summer (Silva et al, 2008).…”