Maternal behavior and clutch manipulation in the ring-legged earwig (Dermaptera: Carcinophoridae)

The expression and maintenance of maternal behavior in the earwig,Euborellia annulipes, was examined through manipulation of clutch size, age, and species and through observations of interactions between brooding females. Females underwent discrete gonadotrophic cycles culminating in oviposition of first clutches that were highly variable in size. Neither the head capsule width nor the age of the mother was correlated with clutch size. Maternal care extended through embryogenesis and for the week following hatching. Clutch removal significantly shortened the interclutch interval, indicating that the presence of brood inhibited the onset of the second gonadotrophic cycle. Brooding females readily accepted replacement clutches of the same age. Thus, mothers did not appear to distinguish their own eggs from those of other females. Experimental doubling of clutch size did not significantly reduce the proportion hatching or fledging. In contrast, reducing clutch size diminished the percentage successfully fledging. Manipulation of clutch age resulted in reduced hatching/fledging success. Placing two females, each with newly laid clutches, in the same cage usually resulted in egg transfer from the nest of one female to that of the other within 12 h. Nests of females with larger forceps were significantly more likely to contain both clutches. When mothers with first clutches were paired with mothers with third clutches, eggs were more likely to be transferred to the nest of the older female.E. annulipes females with newly laid clutches appeared to accept as replacement clutches eggs of the earwigDoru taeniatum. Alien clutches were maintained for the typical duration of embryogenesis; however, noD. taeniatum hatchlings were observed.     

The influence of habitat structure on arthropod diversity in Argentine semi-arid Chaco forest

Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels.     

Diurnal rhythm of galanin-like immunoreactivity in the paraventricular and suprachiasmatic nuclei and other hypothalamic areas

The peptide galanin (GAL), when injected into the rat hypothalamus, is known to stimulate feeding behavior and affect the secretion of various hormones, including insulin and the adrenal steroid, corticosterone. To determine whether endogenous peptide levels shift in relation to natural rhythms of feeding and circulating hormone levels, rats were sacrificed at different times of the light/dark cycle, and their GAL levels were measured, via radioimmunoassay, in medial hypothalamic dissections and micropunched hypothalamic areas. The results suggest the existence of two distinct diurnal rhythms for hypothalamic GAL. One rhythm, detected exclusively in the area of the SCN, is characterized by bimodal peaks of GAL, threefold higher than basal peptide levels, around the onset of the dark and light periods. The second rhythm shows a single peak of GAL towards the middle of the nocturnal feeding cycle, specifically between the third and sixth hour. This latter rhythm is evident in the dorsal region of the medial hypothalamus, localized specifically to the lateral portion of the PVN. Moreover, it is inversely related to circulating insulin but unrelated to the adrenal steroids, suggesting a possible association between this pancreatic hormone and GAL in the PVN.     

An improved method for the measurement of total lipid-bound sialic acids after cleavage of α2,8 sialic acid linkage withVibrio cholerae sialidase in the presence of cholic acid,SDS and Ca2+

In the measurement of total lipid-bound sialic acids involving periodic acid oxidation, as in the periodate-resorcinol assay, the inner sialic acids of disialoglycolipids (such as GD₃ and GD₂) are not involved because their 2,8 ketosidic linkages are resistant to periodic acid oxidation, even after acid/enzyme hydrolysis or alkali pretreatment. However, the sialic acids from these glycolipids can be recovered completely after cleavage of 2,8 linkages byV. cholerae sialidase in the presence of cholic acid, sodium dodecyl sulphate and calcium. Interestingly, removal of calcium or detergent(s) or both significantly minimizes the sialidase action on the disialyl residues of these gangliosides. Therefore, we recommend sialidase (Vibrio cholerae) pretreatment of the glycolipids in the presence of cholic acid, SDS and Ca²⁺ for complete recovery of sialic acids from di- and polysialogangliosides and for accurate measurement of total lipid-bound sialic acids by periodate-resorcinol assay.Presented at the Second International Glycobiology Symposium which was held in San Francisco, CA, USA (14 February 1994).     

Interaction of mithramycin with isolated GC and CG sites

We have studied the interaction of the GC-specific, minor groove-binding ligand, mithramycin, with cloned DNA inserts containing isolated GC and CG sites flanked by regions of (AT)_n and A_n · T_n using DNase I and hydroxyl radical footprinting. We find that mithramycin binds to GC better than CG and that AGCT is a better site than TGCA. Sites flanked by (AT)_n appear to be bound better than those surrounded by A_n · T_n. Although no footprints are produced at T₉GCA₉ and T₁₅CGA₁₅, DNase I cleavage is enhanced with the GC sites suggesting that there is some interaction with the ligand. Mithramycin also alters the DNase I cleavage of (GA)_n · (CT)_n.     

Effect of plant genotype on the transformation of cultivated alfalfa (Medicago sativa) by Agrobacterium tumefaciens

The trait for somatic embryogenesis is being introduced sexually into alfalfa (Medicago sativa) breeding populations to facilitate genetic transformation of this crop. Cocultivation experiments were conducted with an agronomically-improved embryogenic clone from one such population as well as with two other embryogenic clones, one of which was the source of the embryogenic trait in the breeding populations. Transgenic plants were produced from the agronomically-improved clone whereas none were produced from the other two clones. Among the 16 transgenic plants analyzed there was a range in both copy number and number of integration sites for the NPT-II gene; those plants regenerated after a prolonged selection phase in vitro generally had the highest numbers in both respects. There was no evidence of sectoral chimerism of the transgene in a subsample of transgenic plants analyzed by PCR.     

Use of a fluorescent dye to measure secretion from intact bovine anterior pituitary cells

The fluorescent dye FM1-43 has been used to indicate membrane changes in individual bovine anterior pituitary cells exposed to secretory stimuli. After ten minutes incubation with FM1-43 (2 M), cells showed three patterns of dye fluorescence: annular, partly filled and uniformly filled. FM1-43 fluorescence was increased in 61% of the cells by TRH (40 nM), a physiological stimulus for prolactin secretion, and in 89% of the cells by 60 mM external K⁺. The fluorescence also increased when cells incubated in the presence of quinpirole, a dopamine D2-receptor agonist which inhibits prolactin secretion, were exposed to raclopride, a D-2 antagonist. The increases in FM1-43 fluorescence caused by these treatments suggests that the dye acts as an indicator of secretion, possibly through incorporation into secretory vesicle membranes exposed on the cell surface during exocytosis. If the dye was washed away after loading, the fluorescence of partly and uniformly filled cells was retained and a rise in fluorescence could still be seen on stimulation by TRH. This suggests that some dye had been taken up by endocytosis and trapped in an intracellular compartment, which expanded through membrane recapture after TRH stimulation. FM1-43 could therefore be a useful probe for membrane cycling associated with secretory responses.