Aspects of the breeding biology of Janaira gracilis Moreira & Pires (Crustacea, Isopoda, Asellota)

The biological aspects of incubating females of Janaira gracilis Mbreira & Pires, are described. The marsupium is formed by 4 pairs of oostegites arising from pereopods I-IV. The oostegites appear for the first time at the post-marsupial stage 7 (preparatory stage 1), growing successively at each moult until stage 9 (brooding stage 1), when they reach fully development. The sizes of the eggs increase with the body size of the females. The number of eggs, per female, is a linear function of the body volume, i.e., the fecundity increases with the female's body size. The number of eggs, embryos and juveniles decrease during the marsupial development. This decrease in brood number is higher between the last two marsupial stages, i.e., from stage C to D, than between the preceding marsupial stages. The average and overall brood mortality rate is of 38.95%.São descritos, no presente trabalho, vários aspectos relacionados à biologia de fêmeas grávidas de Janaira gracilis Moreira & Pires. O marsúpio é formado por 4 pares de oostégitos, que partem dos pereópodos I-IV. Os oostégitos, que surgem pela primeira vez no estádio 7 do desenvolvimento pós-marsupial (estágio preparatório 1), crescem nas sucessivas mudas, atingindo no estágio 9 (estágio reprodutor 1) seu pleno desenvolvimento. O tamanho dos ovos é proporcional ao tamanho das fêmeas. O número de ovos, por fêmeas, e proporcional ao volume das fêmeas, isto é, a fecundidade é mais elevada nos exemplares de maior comprimento. O número de ovos, embriões e jovens decresce com o desenvolvimento marsupial, sendo este decréscimo maior entre os dois últimos estágios marsupials (i.é., entre os estágios C e D) do que entre os estágios precedentes. A taxa média de mortalidade marsupial é de 38.95%

How insects survive the cold: molecular mechanisms - a review

Insects vary considerably in their ability to survive low temperatures. The tractability of these organisms to experimentation has lead to considerable physiology-based work investigating both the variability between species and the actual mechanisms themselves. This has highlighted a range of strategies including freeze tolerance, freeze avoidance, protective dehydration and rapid cold hardening, which are often associated with the production of specific chemicals such as antifreezes and polyol cryoprotectants. But we are still far from identifying the critical elements behind over-wintering success and how some species can regularly survive temperatures below -20°C. Molecular biology is the most recent tool to be added to the insect physiologist’s armoury. With the public availability of the genome sequence of model insects such as Drosophila and the production of custom-made molecular resources, such as EST libraries and microarrays, we are now in a position to start dissecting the molecular mechanisms behind some of these well-characterised physiological responses. This review aims to provide a state of the art snapshot of the molecular work currently being conducted into insect cold tolerance and the very interesting preliminary results from such studies, which provide great promise for the future

The alien terrestrial invertebrate fauna of the High Arctic archipelago of Svalbard: potential implications for the native flora and fauna

Experience from the Antarctic indicates that the establishment of alien species may have significant negative effects on native flora and fauna in polar regions and is considered to be amongst the greatest threats to biodiversity. But, there have been few similar studies from the Arctic. Although the terrestrial invertebrate inventory of the Svalbard Archipelago is amongst the most complete for any region of the Arctic, no consideration has yet been made of alien terrestrial invertebrate species, their invasiveness tendencies, threat to the native biology or their route of entry. Such baseline information is critical for appropriate management strategies. Fifteen alien invertebrate species have established in the Svalbard environment, many of which have been introduced via imported soils. Biosecurity legislation now prohibits such activities. None of the recorded established aliens yet show invasive tendencies but some may have locally negative effects. Ten species are considered to be vagrants and a further seven are classified as observations. Vagrants and the observations are not believed to be able to establish in the current tundra environment. The high connectivity of Svalbard has facilitated natural dispersal processes and may explain why few alien species are recorded compared to isolated islands in the maritime Antarctic. The vagrant species observed are conspicuous Lepidoptera, implying that less evident vagrant species are also arriving regularly. Projected climate change may enable vagrant species to establish, with results that are difficult to foresee

The ecophysiology of under-ice fauna

During exposure to low salinity, the under-ice amphipods Gammarus wilkitzkii and Onisimus glacialis appeared as euryhaline osmoregulators, displaying regulation of haemolymph concentrations of sodium and chloride. Free amino acids took part in the regulation. During freezing and brine formation, the amphipods were freeze-sensitive and did not tolerate being frozen into solid ice. However, they could stay in the vicinity of the ice, conforming osmotically to the ambient brine and thus lowering the melting point of the amphipods' body fluids. This prevented internal ice formation in the absence of antifreeze agents (THF) in the haemolymph. When G. wilkitzkii, O. glacialis and Apherusa glacialis were exposed to dilute seawater, elevated rates of oxygen consumption and ammonia excretion were observed. The O:N atomic ratio was kept nearly constant during hyposmotic stress, indicating protein/lipids as metabolic substrate. Rates of oxygen consumption and ammonia excretion increased with increasing osmotic differences between the haemolymph and the medium, indicating higher energy requirements for osmotic and ionic regulation at low salinities. A minor decrease in haemolymph sodium concentrations coincided with the increased ammonia output during hyposmotic stress, indicating a possible counter ion regulation of NH+4 and Na+. An increased rate of oxygen consumption, ammonia excretion and 0:N ratio versus temperature was observed for all species