Morphometric measurement selection: an invertebrate case study based on weevils from sub-Antarctic Marion Island

A character-selection procedure initially applied in vertebrates (viverrid carnivores and murid rodents), but with a potential, more general application, was used to select appropriate characters for a morphometric investigation of weevils on Marion Island. An initial set of 23 linear measurements, adopted from a previous morphometric study, was subjected to cluster and ordination procedures to summarize patterns of correlations between measurements. Criteria were developed for the selection of representative measurements within cluster analysis-generated sub-clusters, after the exclusion of redundant measurements. This reduced the 23 initial variables to a final set of 15 measurements. The general grouping of variables was broadly consistent across all weevil species examined. Apart from economizing, by reducing the number of characters that have to be measured for subsequent analyses, the procedure also provides a way to adequately represent the phenotype, and to investigate morphological integration.     

Dynamic rearrangement of the filamentous actin network occurs during zoosporogenesis and encystment in the oomycete phytophthora cinnamomi

The organization of filamentous actin (F-actin) in living cells of the oomycete Phytophthora cinnamomi was determined during zoosporogenesis and zoospore encystment by microinjecting sporangia with fluorescently labeled phalloidin and observing resultant fluorescence by confocal microscopy. In multinucleate sporangia prior to the induction of cleavage, phalloidin labeling took the form of plaques which occurred mainly in the periphery of the sporangia. After induction of cleavage, phalloidin labeling showed that the plaques disappeared and that F-actin began to accumulate along the developing cleavage planes and around nuclei and water expulsion vacuoles. F-actin labeling was also observed near the plasma membrane in zoospores and young cysts but reverted to the plaque form in older cysts. Localization of F-actin close to the developing cleavage planes is consistent with the idea that actin microfilaments function in the positioning and expansion of the cleavage membranes. Observations of plaques of actin in living sporangia provide evidence that plaques are not aldehyde-induced fixation artifacts. Copyright 1998 Academic Press.     

Serglycin expression during monocytic differentiation of U937-1 cells

Serglycin is the major proteoglycan in most hematopoietic cells, including monocytes and macrophages. The monoblastic cell line U937-1 was used to study the expression of serglycin during proliferation and differentiation. In unstimulated proliferating U937-1 cells serglycin mRNA is nonconstitutively expressed. The level of serglycin mRNA was found to correlate with the synthesis of chondroitin sulfate proteoglycan (CSPG). The U937-1 cells were induced to differentiate into different types of macrophage-like cells by exposing the cells to PMA, RA, or VitD3. These inducers of differentiation affected the expression of serglycin mRNA in three different ways. The initial upregulation seen in the normally proliferating cells was not observed in PMA treated cells. In contrast, RA increased the initial upregulation, giving a reproducible six times increase in serglycin mRNA level from 4 to 24 h of incubation, compared to a four times increase in the control cells. VitD3 had no effect on the expression of serglycin mRNA. The incorporation of (35S)sulfate into CSPG decreased approximately 50% in all three differentiated cell types. Further, the (35S)CSPGs expressed were of larger size in PMA treated cells than controls, but smaller after RA treatment. This was due to the expression of CSPGs, with CS-chains of 25 and 5 kDa in PMA and RA treated cells, respectively, compared to 11 kDa in the controls. VitD3 had no significant effect on the size of CSPG produced. PMA treated cells secreted 75% of the (35S)PGs expressed, but the major portion was retained in cells treated with VitD3 or RA. The differences seen in serglycin mRNA levels, the macromolecular properties of serglycin and in the PG secretion patterns, suggest that serglycin may have different functions in different types of macrophages.      

Respiratory Metabolism of sub-Antarctic insects from different habitats on Marion Island

Oxygen uptake of the foliage-dwelling larvae ofEmbryonopsis halticella Eaton (Lepidoptera: Yponomeutidae) and adults ofEctemnorhinus marioni Jeannel (Coleoptera: Curculionidae), the litter-dwelling larvae ofPringleophaga marioni (Lepidoptera: Tineidae) and the wrack-dwellingParactora dreuxi Séguy (Diptera: Helcomyzidae) was examined over the range of temperatures experienced by these insects in their microhabitats. With the exception of the kelp fly,P. dreuxi, Q₁₀s and activation energies were generally lower than those found in temperate and Arctic insects, but were similar to values found in beetles from sub-Antarctic South Georgia Island. Q₁₀ and activation energy of each species reflected the temperature regime found in its microhabitat. Activation energies of the Marion Island species were intermediate between those found in temperate and polar arthropods, but towards the polar end of the range. The hypothesis that insects are capable of showing respiratory adaptation to temperature is supported.     

Rh isoimmunization,Manitoba, 1963-75.

The number of Rh-isoimmunized pregnancies in Manitoba has been reduced from 223 and 228 in the years ending Oct. 31, 1963 and 1964 to 60 and 62 in the years ending Oct. 31, 1974 and 1975. The number per 1000 total births in the same years has decreased from 10.0 and 10.6 to 3.4 and 3.5 Perinatal mortality rates in those years decreased from 13.8 amd 15.7% to 0 and 2.2%, respectively. The number of perinatal deaths has been reduced from 55 in the first 2 years reported to 1 in the last 2 years. Among the 121 isoimmunized women pregnant in the 2-year period ending Oct. 31, 1975, isoimmunization was due to failure to give Rh immune globulin after delivery in 33 and failure to give it during pregnancy in 48. Of the remaining 40, 37 were immunized before Rh immune globulin became available. Complete prevention of Rh isoimmunization and therefore of all perinatal deaths from Rh erythroblastosis can only be achieved through universal Rh testing prenatally and immediately after delivery, and institution of an antenatal Rh prophylaxis program.     

Water balance and osmoregulation in weevil larvae (Coleoptera: Curculionidae: Brachycerinae) from three different habitats on sub-antarctic Marion Island

Summary Ectemnorhinine weevils are the most successful group of beetles in the sub-antarctic region, which is undoubtedly due partly to the ability of these weevils to tolerate a wide variety of abiotic conditions. In the laboratory, larvae of three species of ectemnorhinine weevils, from three diverse habitats on Marion Island, were exposed to desiccating conditions and to water of two different salinities to elucidate the physiological basis of their ability to tolerate various abiotic conditions. In the desiccation experiment, the supralittoral Palirhoeus eatoni (C.O. Warerhouse) larvae lost water faster than larvae of the inland epilithic species, Bothrometopus randi Jeannel, and could not fully replenish lost water by drinking. However, larvae of P. eatoni showed greater osmoregulatory ability than the latter species when exposed to hypoand hypcrosmotic conditions. The detritus-dwelling larvae of Ectemnorhinus similis C.O. Waterhouse showed rates of water loss similar to those of the B. randi larvae in the desiccation experiment, but took longer to replace lost water by drinking. All three species showed little change in haemolyrnph water activity despite approximately 28% reduction in water content during desiccation. These physiological responses seem to reflect an equilibrium between the species and their environments which may be considered an adaptation (sensu Coddington 1988) in the case of B. randi, but which appears to be a result of phylogenetic constraint in E. similis. P. eatoni's status as a marine weevil is confirmed.     

Differential responses of thermal tolerance to acclimation in the sub-Antarctic rove beetle Halmaeusa atriceps

Abstract. Investigations of the responses to acclimation of upper and lower lethal limits and limits to activity in insects have focused primarily on Drosophila. In the present study, Halmaeusa atriceps (Staphylinidae) is examined for thermal tolerance responses to acclimation, and seasonal acclimatization. In summer and winter, lower lethal temperatures of adults and larvae are approximately −7.6 ± 0.03 and −11.1 ± 0.06 °C, respectively. Supercooling points (SCPs) are more variable, with winter SCPs of −5.4 ± 0.4 °C in larvae and −6.3 ± 0.8 °C in adults. The species appears to be chill susceptible in summer and moderately freeze tolerant in winter, thus showing seasonal acclimatization. Similar changes cannot be induced solely by acclimation to low temperatures in the laboratory. Upper lethal temperatures show a weaker response to acclimation. There are also significant responses to acclimation of critical thermal limits. Critical thermal minima vary between −3.6 ± 0.2 and −0.6 ± 0.2 °C in larvae, and from −4.1 ± 0.1 to −0.8 ± 0.2 °C in adults. By contrast, critical thermal maxima vary much less within adults and larvae. These findings are in keeping with the general pattern found in insects, although this species differs in several respects from others found on Marion Island.     

Human impacts, energy availability and invasion across Southern Ocean Islands

Aim Ongoing biological invasions will enhance the impacts of humans on biodiversity. Nonetheless, the effects of exotic species on diversity are idiosyncratic. Increases in diversity might be a consequence of similar responses by species to available energy, or because of positive relationships between human density, energy and propagule pressure. Here we use data from the Southern Ocean island plants and insects to investigate these issues. Location The Southern Ocean Islands ranging from Tristan da Cunha to Heard Island and South Georgia. Methods Generalized linear models are used to explore the relationships between indigenous and exotic species richness for plants and insects on two different islands. Similar models are used to examine interactions between indigenous and exotic species richness, energy availability and propagule pressure at the regional scale. Results Positive relationships were found between indigenous and exotic species richness at local scales, although for plants, the relationship was partially triangular. Across the Southern Ocean Islands, there was strong positive covariation between indigenous and exotic plant species richness and insect species richness, even taking spatial autocorrelation into account. Both exotic and indigenous plant and insect species richness covaried with energy availability, as did human visitor frequency. When two islands with almost identical numbers of human visits were contrasted, it was clear that energy availability, or perhaps differences in climate‐matching, were responsible for differences in the extent of invasion. Conclusion In plants and insects, there are positive relationships between indigenous and exotic diversity at local and regional scales across the Southern Ocean islands. These relationships are apparently a consequence of similar responses by both groups and by human occupants to available energy. When visitor frequency is held constant, energy availability is the major correlate of exotic species richness, though the exact mechanistic cause of this relationship requires clarification.     

Metabolic rate in the whip-spider, Damon annulatipes (Arachnida: Amblypygi)

Metabolic rate estimates as well as a measure of their repeatability and response to laboratory acclimation are provided for the amblypygid Damon annulatipes (Wood). This species (mean +/- S.E. mass: 640+/-66 mg) shows continuous gas exchange, as might be expected from its possession of book lungs, and at 21 degrees C has a metabolic rate of 30.22+/-2.87 microl CO2 h(-1) (approximately 229.6+/-21.8 microW, R.Q. = 0.72). The intraclass correlation coefficient (r=0.74-0.89) indicated substantial repeatability in metabolic rate which did not change with laboratory acclimation over a period of 2 weeks. By contrast, absolute metabolic rate declined by c. 16-33%, although this was not a consequence of changes in mass (which were non-significant over the same period). Rather, it appears that a reduction in overall stress or activity in the laboratory might have been responsible for the decline in mass-independent metabolic rate. At the intraspecific level, metabolic rate scaled as microW = 342 M(0.857), where mass is in grams. Metabolic rates of this species are in keeping with its sedentary behaviour such that for a given body size they are lower than those of most arthropods (spiders and insects), higher than the very sedentary ticks, and equivalent to scorpions. These findings have implications for the understanding of the evolution of metabolic rates in arthropods.