Many amphibians lay their eggs in gelatinous masses up to 10­20 cm in diameter, posing problems for diffusive oxygen delivery. Oxygen may also be provided by water convection between eggs or by oxygen production by endogenous algae. We studied egg masses of two local amphibians, Rana sylvatica and Ambystoma maculatum, to estimate the importance of each of these processes. We injected dye to...

Root-knot nematodes (Meloidogynespp.) are the most important pests of vegetables, field crops, and ornamental plants. During our previous study, twenty eight okra cultivars were examined against resistance and Pusa Swami was ranked the most susceptible. The purpose of this study was to investigate the effects of increasing initial population density (Pi) of M. incognita on nematode reproduction...

Aedes aegypti is the major vector of dengue, yellow fever and chikungunya viruses that put millions of people in endemic countries at risk. Mass rearing of this mosquito is crucial for strategies that use modified insects to reduce vector populations and transmission of pathogens, such as sterile insect technique or population replacement. A major problem for vector mosquito mass rearing is the...

Selection against large eggs has been proposed for aquatic environments, putatively because large eggs should have more difficulty obtaining the required oxygen. Here, we use brown trout (Salmo trutta) eggs to provide an experimental test of this hypothesis. At high levels of dissolved oxygen (14 mg l(-1)), egg survival was high and independent of egg size. At low oxygen levels (2.3 mg l(-1)), ...

The metabolic cost of egg production in birds (passerines) has been measured as a 16-27% increase in basal or resting metabolic rate (BMR and RMR, respectively) when comparing non-breeding values with those in egg-producing individuals. However, available data to date have been obtained in free-living birds and may thus be confounded by the effect of variable ecological conditions on non-reprod...

In egg laying species, breeding females may adjust the allocation of nutrients or other substances into eggs in order to maximise offspring or maternal fitness. Cooperatively breeding species offer a particularly interesting context in which to study maternal allocation because helpers create predictably improved conditions during offspring development. Some recent studies on cooperative specie...

The aim of the present work conducted at the Refugio de Vida Silvestre Bahía Samborombón is to analyse the most relevant aspects of the fecundity of Chasmagnathus granulatus and Uca uruguayensis. Samplings were carried out from March 2001 to February 2003. Ovigerous females of U. uruguayensis (N = 13) and C. granulatus (N = 25) were found during spring and summer, their sizes (CW) varied from 9...

Variation in sperm precedence was examined in the Colorado potato beetle, Leptinotarsa decemlineata Say, using neutral allozyme markers. Two temporal components were studied: (1) pairing duration and (2) time since initial pairing. We used two pairing protocols that differed in the timemales and femaleswere allowed tomate for Þrst and secondpairings.Whenpairingswere limited to 8 h each for the ...

A total of 150 Hy-Line W-36 laying hens at 38 week of age were randomly assigned into 5 dietary treatments and 3 replicates each with 10 birds. Hens were fed diets including: low-selenium diet without selenium supplementation (basal diet), basal diet plus 0.3 ppm Na-selenite, or basal diet plus 0.1, 0.2 and 0.3 ppm Sel-Plex. The hens performance, eggshell quality and egg selenium content were e...