Satiation time and predatory behaviour of the dragonfly nymph Mesogomphus lineatus

Summary The dragonfly nymph Mesogomphus lineatus satiated predating 21 larvae of Culex fatigans in 50 minutes; number of attack and predatory efficiency decreased precipitously from 2 attacks/min and 70% during the first 10 minutes of feeding to 0.04 attack/min and 0.01% efficiency respectively during the sixth 10 minutes interval. The nymphs fed after 6, 12, 18, 24, 36 or 42 hours of deprivation consumed 4, 13, 15, 20, 21 or 21 larvae; apparently, the maximum appetite is returned after about 36 hours of deprivation. Satiation time, which was 50 minutes at the density of 15 larvae/aquarium, decreased to 30 minutes in aquaria containing 200 larvae. The nymphs predated increased the number of prey when they were exposed to higher densities of C. fatigans and Anopheles stephansi larvae, and pupa of C. fatigans. They consumed equal weight (but different number) of Culex and Anopheles larvae at all the tested prey densities and selectively selected Culex larva over the pupa or Anopheles larva. Comparative analyses suggest that the dragonfly nymphs deserve serious consideration as larvivorous predators.     

Food selection and utilization in a danid butterfly

Summary Larvae of the danid butterfly Danaus chrysippus, fed on the milkweeds Calotropis gigantea and Asclepias curassavica grew successfully during the 9-day feeding period and pupated. In the presence of these milkweeds, the larvae preferred to feed on C. gigantea. Their preference was more pronounced during the final 2 instars than during the initial 3 instars. They consumed 605 mg, defecated 308 mg, and converted 115 mg of C. gigantea; those receiving A. curassavica consumed 563 mg, defecated 287 mg and converted 85 mg. They assimilated either food with equal efficiency (: 46%; : 50%). But they differed significantly in their efficiency in converting the assimilated food. The presence of a greater amount of latex in C. gigantea than in A. curassavica and/or the nutritional inadequacy of the latter food may perhaps be the reason(s) for the preference of C. gigantea by D. chrysippus larvae over A. curassavica.     

Posthatching development of Alligator mississippiensis ovary and testis

We investigated ovary and testis development of Alligator mississippiensis during the first 5 months posthatch. To better describe follicle assembly and seminiferous cord development, we used histochemical techniques to detect carbohydrate‐rich extracellular matrix components in 1‐week, 1‐month, 3‐month, and 5‐month‐old gonads. We found profound morphological changes in both ovary and testis. During this time, oogenesis progressed up to diplotene arrest and meiotic germ cells increasingly interacted with follicular cells. Concomitant with follicles becoming invested with full complements of granulosa cells, a periodic acid Schiff's (PAS)‐positive basement membrane formed. As follicles enlarged and thecal layers were observed, basement membranes and thecal compartments gained periodic acid‐methionine silver (PAMS)‐reactive fibers. The ovarian medulla increased first PAS‐ and then PAMS reactivity as it fragmented into wide lacunae lined with low cuboidal to squamous epithelia. During this same period, testicular germ cells found along the tubule margins were observed progressing from spermatogonia to round spermatids located within the center of tubules. Accompanying this meiotic development, interstitial Leydig cell clusters become more visible and testicular capsules thickened. During the observed testis development, the thickening tunica albuginea and widening interstitial tissues showed increasing PAS‐ and PAMS reactivity. We observed putative intersex structures in both ovary and testis. On the coelomic aspect of testes were cell clusters with germ cell morphology and at the posterior end of ovaries, we observed “medullary rests” resembling immature testis cords. We hypothesize laboratory conditions accelerated gonad maturation due to optimum conditions, including nutrients and temperature. Laboratory alligators grew more rapidly and with increased body conditions compared with previous measured, field‐caught animals. Additionally, we predict the morphological maturation observed in these gonads is concomitant with increased endocrine activities. J. Morphol. 2010. © 2009 Wiley‐Liss, Inc.     

Characterization of Staphylococcus aureus mutants expressing reduced susceptibility to common house-cleaners

AIMS: To characterize mutants of Staphylococcus aureus expressing reduced susceptibility to house cleaners (HC), assess the impact of the alternative sigma factor SigB on HC susceptibility, and determine the MIC of clinical methicillin-resistant S. aureus (MRSA) to a HC. METHODS AND RESULTS: Susceptibility to HC, HC components, H2O2, vancomycin and oxacillin and physiological parameters were determined for HC-reduced susceptibility (HCRS) mutants, parent strain COL and COLsigB::kan. HCRS mutants selected with three HC expressed reduced susceptibility to multiple HC, HC components, H2O2 and vancomycin. Two unique HCRS mutants also lost the methicillin resistance determinant. In addition, all HCRS mutants exhibited better growth at two temperatures, and one HCRS mutant expressed reduced carotenoid production. COLsigB::kan demonstrated increased susceptibility to all HC and many HC components. sigB operon mutations were not detected in one HCRS mutant background. Of 76 clinical MRSA, 20 exhibited reduced susceptibility to a HC. CONCLUSIONS: HCRS mutants demonstrate altered susceptibility to multiple antimicrobials. While sigB is required for full HC resistance, one HCRS mechanism does not involve sigB operon mutations. Clinical MRSA expressing reduced susceptibility to a common HC were detected. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that HCRS mutants are not protected against, nor selected by, practical HC concentrations.     

Conservation of gene expression signatures between zebrafish and human liver tumors and tumor progression

The zebrafish (Danio rerio) has been long advocated as a model for cancer research, but little is known about the real molecular similarities between zebrafish and human tumors. Comparative analysis of microarray data from zebrafish liver tumors with those from four human tumor types revealed molecular conservation at various levels between fish and human tumors. This approach provides a useful strategy for identifying an expression signature that is strongly associated with a disease phenotype.     

Extrachromosomal transmission of microinjected DNA to the progeny of silkworm Bombyx mori

Vector DNA (pBmFRT) microinjected into the silkworm eggs (preblastoderm stage) persisted in different conformational forms throughout the period of embryonic development. Southern blot analysis confirmed the persistence of DNA as extrachromosomal copies. Slot blot analysis showed the inheritance of the injected DNA to the subsequent progenies; however the copy number of the injected vector declined in the progenies.