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The effects of chronic plasma cortisol elevation on the feeding behaviour, growth, competitive ability, and swimming performance of juvenile rainbow trout.

Plasma cortisol elevation, a common consequence of stress, occurs in salmonids of subordinate rank; these fish acquire a smaller share of available food and grow more slowly. This study examined the role of cortisol itself in these phenomena. Cortisol implants, with parallel sham and control treatments, were used to create a chronic threefold elevation in plasma cortisol levels in juvenile rainbow trout, and the individual feeding patterns of the fish were evaluated using X-ray radiography. The three treatment groups were (1) held alone and fed to satiation, thereby providing a measure of voluntary appetite, or mixed together in equal proportions and fed to either (2) satiation or (3) half-satiation, thereby allowing assessment of the additional effects of competitive interaction and food limitation. Chronic plasma cortisol elevation had significant negative effects on individual appetite, growth rate, condition factor, and food conversion efficiency, independent of whether the fish were held under unmixed or mixed conditions. Under the latter, mean share of meal was reduced and fin damage increased in cortisol-treated fish; negative growth effects were more severe with food limitation, but the response patterns were otherwise unchanged. Even in the absence of other groups, cortisol-treated fish showed more variable feeding patterns. When compared at the same individual ration levels, cortisol-treated fish had lower growth rates, reflecting a higher "cost of living." Cortisol treatment had no effect on aerobic swimming performance. These results suggest that the structure of the feeding hierarchy may not be determined solely by competitive ability but may also be greatly influenced by differences in the feeding behaviour of unstressed fish versus stressed fish caused by cortisol elevation in the latter.

Adaptation, Physiological↗

The relationship between social status, behaviour, growth and steroids in male helpers and breeders of a cooperatively breeding cichlid.

We tested whether subordinate helper males of the Lake Tanganyika cooperatively breeding cichlid Neolamprologus pulcher show elevated excretion levels of the stress hormone cortisol and reduced levels of 11-ketotestosterone and testosterone when living in groups with a small breeder male, compared to similar helper males living in groups with a large breeder male, in a full-factorial repeated measures experimental design. We also measured the same hormones in breeder males with and without helper males. Previous research showed that the size difference between large male helpers and male breeders in groups of this species influences behaviour and growth decisions. Contrary to our expectation, no effect of the size-difference between helper males and breeder males on helper hormone levels was detected. Furthermore, helper males had similar hormone excretion levels to those of size-matched breeder males without helpers, and to small breeder males. There was no influence of egg laying on breeder male and helper hormone levels during the experiment. Interestingly, all three hormone levels were significantly lower in helpers showing elevated levels of submissive behaviour towards the breeders, independently of the size of the breeder males. The low cortisol levels suggest that helper males can successfully reduce stress by appeasing breeder males through submission. Furthermore, helper males showing a high level of submissive behaviour had lower levels of androgens than less submissive helpers, suggesting a lower reproductive potential in submissive helpers. We propose that helper submission may be used as an honest signal of reduced interest in reproduction towards the breeder male in this species.

Aggression↗

GnRH cell size and number in a teleost fish with two male reproductive morphs: sexual maturation, final sexual status and body size allometry.

Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50-100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Animals↗

A comparison of waste-reduction practices and new environmental paradigm of rural and urban Chinese citizens.

This paper compares the public attitudes of three southern Chinese cities/towns, namely Guangzhou, Dongguan, and Yuanzhou on waste recycling and avoidance, and the New Environmental Paradigm (NEP). The latter describes the concept of treating the resources and the ecosystems on Earth as things having their own rights rather than being subordinate and subservient to humans. These three places are chosen to represent areas in different stages of urbanization in the Guangdong province. As Hong Kong is also a southern Chinese city, where data of similar nature are available, comparison with Hong Kong is also made. It was found that the support for source separation of household waste in the rural and urban areas in mainland China was greater than that found in Hong Kong. Concerning actual practices on waste separation, about 85% of the respondents in the cities and almost all of the rural household surveyed have the habit of saving up and selling the recyclables. It is estimated that about 11-13% of the household waste was diverted in such a way. This is higher than the estimated 8% household waste recovery rate of Hong Kong. The majority of the respondents in the three surveyed cities have recovered household recyclables in the past but with higher family incomes, it was now less common. On the contrary, the lower income group tended to recover greater portion of their waste for selling to the waste depots. These findings have implications on the future waste management policy formulation in China. Regarding the acceptance of the New Environmental Paradigm, it was found that the rural population scored better than the urban population and they tended to agree more frequently with the NEP. However, the rural population perceives a greater potential for industrial and urban development without dampening environmental quality. It was also found that the NEP scores of the mainland Chinese are higher, in general, than their Hong Kong counterparts as measured in early 1990s. Insufficient public support has often been a concern for source separation programmes in all countries despite the obvious waste management benefits of recycling. This study shows that there is overwhelming support for source separation of waste in Mainland China, whether it is in rural or urban communities, and that most people are already undertaking source separation due to the redemption value of the recyclables. Therefore, for policy-makers, the concern should not be on whether the public knows how to separate the waste but rather on how to motivate them to separate waste for the good of society, and how to maintain an effective market for recyclables.

Adolescent↗

[Current status of the female condom in Africa].

The female condom was developed in the 1980s. It is a contraceptive device used by women that protects against both pregnancy and sexually-transmitted diseases (STDs) including HIV infection. Two studies have investigated the contraceptive effectiveness of the female condom, and it was found to be as effective as other barrier methods. It has been shown to be effective against STD and HIV transmission in vitro but there is only limited evidence of its efficacy in vivo. No serious local side effects or allergies have been reported and the female condom can be used with any type of lubricant, spermicidal cream or foam. The female condom is the only device other than the male condom that has been shown to prevent HIV transmission. The female condom has been marketed in 13 countries since the summer of 1996. Most of these countries are industrialized and the selling price in these countries is too high for developing countries. Sub-Saharan Africa has very high prevalence rates for HIV infection, at least 30% of the general population in Eastern and Central regions. The epidemic is also spreading fast in some parts of the Western region. In Ivory Coast for example, 12 to 15% of pregnant women are infected. African women are subordinate to men in many aspects of their lives, politically, educationally, socially and sexually. This sexual inequality makes them highly vulnerable to STDs, including HIV, and unwanted pregnancies. This paper reviews 10 of the 15 studies carried out in sub-Saharan African countries between 1990 and 1996 and compiled by the World Health Organization. Recruitment methods, education of subjects, methodology and assessment of acceptability differed between studies. Despite these limitations, most studies concluded that the women who participated in the trials generally found the female condom acceptable. Acceptability was established quicker among prostitutes than among other women and men found the female condom less acceptable than did women. However, the sample size is too small to draw any firm conclusions. Commercial sex workers in the studies reviewed were very interested in this new method because it gave them an additional method of safer protection during sex. However, they were occasionally faced with difficult negotiations with some clients, refusal to use the female condom and sexual violence. Reuse of the device was reported in four studies, but the term reuse is seldom defined. In cases where it was defined, the frequency of reuse, with washing of the device, accounted for no more than 1% of the total number of uses. The acceptability of the female condom among women other than prostitutes faces two obstacles, the reaction of the woman's regular partner and attitudes to the device itself (appearance, difficulties or uneasiness concerning its use). However, some women liked it because it provided dual protection against pregnancy and STDs and sexual pleasure. The moderate level of acceptability to male partners may be overestimated because women whose partners disliked the device would be more likely to discontinue its use. The studies of acceptability reviewed here show that use of the female condom in Africa is realistic and that it provides women with more independent protection. Initial negative perceptions of the device are often replaced with a more positive reaction after several uses. The experience gained with use reduces the technical problems. We need to overcome the stereotypes, simplifications and strong opinions that threaten to damage the acceptance of this new method and efforts to encourage women to adopt it. However, we still require further clinical data on the effectiveness of the female condom at preventing pregnancy and HIV transmission. Availability of the female condom is improving in Africa. Pilot marketing studies were launched in 1996 in Guinea, Zambia, South Africa, followed by Uganda and Tanzania. There are local initiatives in Ivory Coast and Zimbabwe. (ABSTRACT TRUNC

Africa↗