Physiological Adaptations of Freshwater Crayfishes that Permit Successful Aquacultural Enterprises

SYNOPSIS. There are over 400 species and three families of freshwatercrayfishes. Many species are collected for food and/or fishbait but fewer than ten are commercially cultivated. We discussthe physiological adaptations that permit these species to besuccessfully cultivated. The most important cultured speciesinclude: Northern Hemisphere—Cambaridae— Orconectesimmunis, Procambarus clarkii, and Procambarus zonangulus, andSouthern Hemisphere—Parastacidae—Cherax destructor.Procambarus clarkii is, by far, the most important species andhas been successfully introduced to all continents, save Antarcticaand Australia, from its native North America. All species maybe cultivated entirely in closed, intensive systems; however,economics are such that they are commercially produced, forthe most part, by establishing perpetuating populations in earthenpond systems. All species tolerate low oxygen, adapt well toaerial exposure, and persist for extended periods in burrowsystems in the absence of surface waters. The cultured specieshave high fecundities, rapid growth rates, and mature quickly.Aquaculture of freshwater crayfish is in its infancy. Therefore,it is likely that additional species with favorable adaptationsdiscussed here will be identified for cultural purposes     

Sex roles, parental effort and offspring desertion in the monogamous Eurasian Curlew Numenius arquata

The reasons for female desertion of offspring and the evolution of predominantly male care among monogamous bird species are not clearly understood. We studied parental effort during the incubation and chick rearing periods in the Eurasian Curlew Numenius arquata in western Finland, and compared timing of brood desertion with other populations in Europe. Males and females contributed equally to incubation and showed no differences in the intensity of mobbing behaviour towards a potential nest predator (stuffed crow) shortly after hatching. However, females deserted their offspring approximately halfway through the brooding period ( c. 16 d after hatching), while males remained with chicks until independence ( c. 35 d). Females with late-laid clutches deserted their offspring sooner after hatching than those with clutches produced earlier in the season. Curlew females deserted younger chicks in northeast Europe, where laying dates were later, breeding seasons shorter and migration distances were longer, than in western and central Europe. We suggest that the most likely reasons for offspring desertion by females may be associated with increased female survivorship and maintenance of pairbond between years.     

Measurement of 7 methyl and 7 2 hydroxyethyl guanine DNA adducts in white blood cells of smokers and non smokers

The goal of the present study was to measure the levels of 7-methylguanine and 7-(2- hydroxyethyl)guanine DNA adducts in human white blood cells in relation to smoking. DNA was isolated from samples of 11 smokers and eight non-smokers. The 32P-postlabelled 7-methylguanine and 7-(2-hydroxyethyl)guanine adducts were analysed by thin-layer chromatography (TLC) combined with a high pressure liquid chromatography (HPLC) assay. In smokers the mean 7-methylguanine and 7-(2-hydroxyethyl)guanine levels were 32.3 +/- 7.1 and 6.6 +/- 2.3 adducts per 108 nucleotides respectively. The corresponding values in non-smokers were 25.0 +/- 7.0 and 3.7 +/- 2.4 adducts per 108 nucleotides. There were significantly higher levels of 7-methylguanine and 7-(2-hydroxyethyl)guanine adducts in WBC in smokers than in non-smokers (p = 0.041; p = 0.018), respectively. A positive correlation between 7-methylguanine and 7-(2-hydroxyethyl)guanine levels was observed.