Miami University, Ohio
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Cold-shock injury and rapid cold-hardening in the flesh fly, Sarcophaga crassipalpis.
Full text linkDirect exposure to -10 C, in the absence of tissue freezing, causes high mortality
in Sarcophaga crassipalpis: this result suggests that injury is due to cold shock. However, brief acclimation at 0 C enables larvae, pupae, and pharate adults of Sarchophaga crassipalpis to survive -10 C. Chilling for as short a period as 10 minutes enabled 50% of the flies to survive a 2-hr exposure to -10 C. Enhancement of cold tolerance was linear over the first hour of chilling at 0 C. The optimal temperature range eliciting the rapid accumulation response was 6-0 C, but the effect could also be stimulated by high temperature (36 C). The rapid increase in cold tolerance correlates with concomitant increases in hemolymph osmolality and glycerol levels. This response suggests a novel role for glycerol in protecting insects against injury resulting from cold shock, although other unidentified mechanisms may be involved in this response. That both nondiapause- and diapause-programmed flies respond to short-term chilling indicates that this rapid response is not part of the diapause syndrome but probably functions in either type of fly as an adaptation to survive brief periods of low temperature
Cold-hardiness in the Antarctic tick, Ixodes uriae.
Full text linkIxodes uriae White (Ixodidae, Acarina) is the predominant tick on the Antarctic peninsula.This species has a circumpolar distribution in both hemispheres and is associated with or known to parasitize 48 species of seabirds. Large colonies of 1,000 or more individuals of all life stages were found beneath rocks on the periphery of penguin rookeries near Palmer Station, Anvers Island. All life stages (egg, larva, nymph and adult) were intolerant of freezing. Engorged nymphs and larvae had supercooling points between -18 and -20 C. Eggs had the lowest supercooling points (-28.7 C) white adults had the highest values (from -7 to -13 C). Acclimation to temperatures between -12 and +25 C for 2 weeks had no effect on the supercooling point of engorged immobile nymphs. Desiccation of engorged nymphs to 80% of their initial weight resulted in no change in supercooling points or glycerol levels. In January, engorged nymphs enter a state of apolysis and lose mobility. Correlated with this change is an increase in cold tolerance as evidenced by a decrease in supercooling points from -11.5 to -19.5 C. This species exhibits the greatest range of thermal tolerance, from -30 to 40 C, reported for any Antarctic terrestrial arthropod. Except for a short period associated with feeding, I. uriae remains in a permanent state of cold-hardiness throughout the year
Low temperature acclimation in the desert spider, Agelenopsis aperta.
Full text linkAgelenopsis aperta (Gertsch) inhabits desert grasslands and lava beds in the southwestern U.S.A. The capacity of this species to cold-harden was assessed by exposing second generation laboratory- reared specimens to an artificial low temperature cycle simulating the "summer-autumn-winter" transition. Low temperature acclimation had no effect on whole body supercooling points, freeze tolerance or rates of oxygen consumption. Elevated levels of cryoprotectants were not detected using high performance liquid chromatographic techniques. Cold tolerance was similar between males, females and immatures. Exposure to temperatures immediately above the whole body supercooling point caused no apparent injury. It is hypothesized that movement into protected overwintering microhabitats may obviate the necessity for the evolution of seasonal mechanisms of cold-hardening in A. aperta
Do bot flies, Cuterebra (Diptera: Cuterebridae), emasculate their hosts?
Full text linkAsa Fitch, in his description of a new species of
Cuterebra that he named, "emasculator," was the first to suggest
that bot flies castrated their mammalian hosts. In recent years
several major review papers and parasitology texts have continued
to perpetuate this belief. A review of both the literature on
bot flies and their hosts and of the life cycles of both bots and
hosts provides no evidence to substantiate castration. Eastern
Chipmunks (Tamias striatus) experimentally infected with Cuterebra
ernasculator experienced no destruction of testicular tissue.
The concept of castration may have been perpetuated by
observations of bots in the scotal sac of a host. Superficial examination
of a host with a bot(s) in the scrotum would suggest
that the bot had consumed the testis; this is demonstrated on
a White-footed Mouse (Peromyscus leucopus). We conclude that
there is no evidence to support the notion that bot flies castrate
their mammalian hosts. On extremely rare occasions, a bot may
slightly displace a testis, and perhaps this temporarily reduces fertility
Ice nuclei in soil compromise cold hardiness of hatchling painted turtles, Chrysemys picta.
Full text linkHatchling painted turtles (Chrysemys picta) commonly overwinter within their natal nests and survive exposure to temperatures as low as -12 degrees C by supercooling. We report that the supercooling capacity of hatchling C. picta is reduced by direct contact with nest soil which, in samples from northwestern and north-central Nebraska, Indiana, and Ontario, contained potent ice nuclei active in the range of -3.5 degrees to -5 degrees C. These nuclei were sensitive to autoclaving and extractable in water. The supercooling capacity of C. picta hatched in native nest soil, or hatched in sterilized vermiculite (which lacks water-extractable nuclei), and subsequently exposed to nest soil, was reduced by ∼10 degrees C relative to control turtles that were hatched and reared in sterilized vermiculite. The effect of these nuclei was potentiated by the presence of environmental moisture, although even transient exposure to dry nest soil markedly reduced supercooling capacity in ∼ 50% of the turtles. Unlike turtle species that hibernate underwater (Sternotherus odoratus, Chelydra serpentina, Apalone spinifera), hatchlings of C. picta exhibited an extraordinary capacity for supercooling (temperature of crystallization, -16 degrees to -20 degrees C) when cooled in isolation from external ice nuclei. However, hatchlings of these four species were equally susceptible to inoculation by suspensions of the ice-nucleating bacterium, Pseudomonas syringae. Indirect evidence suggests that the soil nuclei are associated with such microbes. Nucleating activity was higher in soil collected within nests than in soil collected at the same depth, adjacent to these nests. Differences in the activities of ice nuclei in nesting soils may account for geographic and local variation in winter survival of hatchling C. picta. Our finding that similar agents occur in various other terrestrial habitats in central North America suggests that such nuclei may pose a formidable challenge to the overwintering survival of ectothermic animals that rely on supercooling to withstand frost exposure