Michael R. Warburg

Isopods and Their Terrestrial Environment

Publisher Summary The chapter reveals that the terrestrial adaptations of the oniscoid isopods range from structural and behavioral to ecological and physiological traits. Oniscoid isopods have emerged on land through the littoral zone, and the whole series of isopod species as if they were amidst the process of emerging from the seashore onto land. The chapter presents the isopods inhabiting littoral zone, beach, grassland, woodland, and desert habitats, only a few of that have been studied. All of the species show various degrees of adaptive traits enabling their survival on land in their respective habitats. These adaptations are thought to be largely behavioral but it now appears that there are also well established physiological adaptations, based on anatomical structures. The reproductive pattern is largely dependent on environmental factors: light, temperature, and moisture conditions in the soil. Moisture appears to be the main single factor of importance for survival of most terrestrial isopod species. The chapter explores that many isopods found today, demonstrate the different ways by that they have adapted to life on land.

Breeding patterns in the oniscid isopod, Porcellio ficulneus Verh., at high temperature and under different photophases

Summary Porcellio ficulneus Verhoeff inhabits xeric Mediterranean grassland habitats. During winter vitellogenesis takes place and mancas are released in April. Under natural conditions some oocytes (about 20%) were lost. Both high temperature (25°C) at long or short photophases affected the reproductive pattern. Thus at 25°C and constant light vitellogenesis was markedly shorter than under field conditions. Oocytes matured sooner, but many were resorbed. The marsupium was formed earlier and contained fewer eggs. In some cases mancas that had developed could not emerge from the marsupium and died inside. In conclusion, P. ficulneus responds to warmer conditions by breeding earlier and reducing the number of offspring.

Water loss in three species of xeric-adapted isopods: Correlations with cuticular lipids

1. 1. Water loss rates (WLR) and cuticular lipid/hydrocarbon composition were determined for two desert-adapted isopods (Hemilepistus reaumuri and Armadillo albomarginatus) and an oak-woodland isopod (Armadillo officinalis). 2. 2. WLR were positively correlated with temperature, with mean values lowest for H. reaumuri and highest for A. officinalis. 3. 3. The hydrocarbon fraction of all three species featured numerous components; however, long-chain branched molecules were characteristic of only H. reaumuri surface hydrocarbons. 4. 4. Cuticular lipids/hydrocarbons probably contribute to the reduced transcuticular water loss exhibited by all three species, enabling them to occupy atypical isopod habitats.

Comparing the soil macro-fauna in two oak-wood forests: does community structure differ under similar ambient conditions?

Summary Taxa, specimen richness and biodiversity were compared in the forest floor of two old natural oak forests in the Mediterranean region in the Galil mountains and in the Golan Heights. The study sites, about 35 km (by air) apart, had similar tree species composition, similar climatic and micro-climatic conditions, but different soil physical texture. The fauna was extracted from samples of leaf litter and top soil. Decomposition parameters (organic matter, nitrogen, calcium, phosphorus) and climatic conditions (precipitation, air and forest floor temperature, leaf litter and top soil water content) were measured. The dynamics of taxa moving between the leaf litter and top soil, were determined. The two forests did not differ significantly in biodiversity, taxa and specimen richness, except for the taxa numbers in the soil phase. However the forest floor community composition differed. Thus, oligochaetes were more abundant in the Golan whereas diplopods, isopods and hymenoptera were more abundant in the Galil, and gastropods were found exclusively in the Galil. In both forests, no correlation was found between specimen richness and the decomposition parameters, though some groups (oligochaetes, arachnids and insects) were influenced by mineral levels. In both forests, climate affected the dynamics of taxal vertical movement. Moreover, in both forests, (leaf litter and top soil), specimen richness and biodiversity index were low during the dry season and high during the wet season. The influence of climatic changes on the taxa composition and vertical movement, were similar in the two forests. We conclude that in similar forest types under similar climatic conditions, the soil composition and texture do not directly affect biodiversity and fauna richness. The soil texture has a direct influence on the relative abundance of certain animal taxa.

Hormonal Effect on the Osmotic, Electrolyte and Nitrogen Balance in Terrestrial Amphibia

Abstract Two main hormones regulate water balance in amphibian. First, mesotocin (MT) acting as a diuretic agent, and second arginine vasotocin (AVT) being an anti-diuretic hormone. In addition, prolactin (PRL), aldosterone, corticosterone, angiotensin II and atriunatriuretic hormones, play a role too in regulating water and ion balance. The hormones affect the epidermis and bladder permeability to water and ions as well as the kidney through the control of the glomerular filtration rate (GFR). The main questions concern the presence and action of these hormones during the amphibians life history. Are they present in both larval and adult stages? Are these hormones being synthesized in both aquatic and terrestrial adult phases? Under what circumstances are they being stored or released? Would the target organs (epidermis, bladder, kidney) respond in a similar way during all periods? The problem is the fact that under most circumstances an amphibian while in an aquatic environment responds physiologically differently than when on land. Only partial information concerning hormone presence, release and control of water balance is available at the moment, and even that is fragmentary and based on only a very small number of amphibian species.

Oosorption and oocyte loss in a terrestrial isopod under stressful conditions

An increased number of resorbed oocytes was observed in ovaries of terrestrial isopods which were kept under different experimental temperature and photophase regimes compared with those observed in the natural population. Regardless of the nature of the stimulus: high or low temperature or long and short photophases, the female always responded through oosorption. In an iteroparous species such as Porcellio ficulneus B.-L., recruitment of resources for future utilization could be its main response to adverse ambient conditions.

Cannibalistic phenomena in salamandra salamandra larvae in certain water bodies and under experimental conditions

Salamandra salamandra larvae originating from a single batch (layed by one female) were raised at different temperatures and on ion-rich or distilled water. Temperature, but not the presence or absence of ions affected growth. Larvae originating from one batch or from several batches born on the same day, were kept without food for long periods of several months in order to observe cannibalistic predation under such conditions. This phenomenon is known in natural populations of salamanders inhabitating either rain pools in rocks or permanent springs poor in aquatic life. It was found that cannibalism increased under experimental conditions proportionally to the increase in size between the larvae.

Thermal effect on evaporative water loss and haemolymph osmolarity in scorpions at low and high humidities

Abstract 1. 1. Evaporative water loss and haemolymph osmolarity were studied in four scorpion species: two from mesic habitats, Scorpio maurus fuscus ( Scorpionidae ) and Nebo hierochonticus (Diplocentridae); and two from xeric habitats, Buthotus judaicus and Leiurus quinquestriatus (both Buthidae). 2. 2. Low humidity and high temperatures increased both the percentage and the rate of water loss. This effect was more pronounced in the two mesic species. 3. 3. Haemolymph osmolarity increased at high temperature and low humidity. In humid air osmolarity dropped only in the mesic species but remained high in the xeric species. 4. 4. Haemolymph osmolarity was low in winter and high in summer.

Biogeographic and demographic changes in the distribution and abundance of scorpions inhabiting the Mediterranean region in northern Israel

A recent survey of the scorpion fauna in the Mediterranean region of northern Israel, has shown that the desert buthid, Leiurus quinquestriatus, formerly restricted to the arid and semi-arid regions in southern and eastern Israel, has penetrated through the Jordan Valley deep into the Mediterranean region, reaching into the northern Galil Mountains. At the same time, the oakwood scorpionid, Scorpio maurius fuscus, formerly the most abundant scorpion in the Mediterranean region, showed a marked decline in numbers. Various aspects of this apparent colonization and replacement in the scorpion fauna are discussed.

Growth and population structure of Salamandra salamandra (L.) larvae in different limnological conditions

Salamandra salamandra (L.) larvae were studied in three types of aquatic systems, a permanent spring, a rock pool and temporary ponds. Growth was followed throughout ontogenesis until completion of metamorphosis. Growth patterns changed according to the pond type. Temporary ponds were rich in organic matter and subsequently larvae matured more rapidly there than those in a permanent pool or a spring. In the latter, cannibalism appears to be of major ecological importance, enabling survival and metamorphosis of large size tadpoles. The pattern of growth and metamorphosis is compared with European salamanders and the differences are discussed considering adaptations for survival of this species under xeric conditions.