This thesis examined the influence of hormones of the pituitary-adrenocortical axis ('stress hormones') and gonadal steroids on intra-specific intermale fighting in the house mouse (Mus musculus L.). Experiments were described which investigated both acute and chronic effects of stress hormones on aggressive motivation. These involved administration of ACTH, ACTH analogues (peptide fragments of the ACTH molecule), dexamethasone and corticosterone to intact or adrenalectomised animals. Studies concerning gonadal steroids involved administration of cyproterone acetate (an anti-androgen) to male and female mice in early life while others were designed to determine the relevance of the 'aromatisation hypothesis' (i.e. that androgens are converted to oestrogens before exerting behavioural effects) to intermale fighting between mice. The latter experiments involved administration of oestradiol benzoate, 19-hydroxytestosterone, androstenedione, testosterone and 5 x dihydrotestosterone to adult castrated males. Results indicated that chronically, activation of the pituitary-adrenocortical axis attenuated fighting behaviour - an effect apparently mediated by ACTH. Acutely, aggressive behaviour was enhanced - an effect apparently mediated by corticosterone. These effects were thought to be independent of the pituitary gonadal axis, not the result of gross changes in motor activity and unrelated to changes in sensory cues e.g. olfactory signals. Cyproterone acetate did not block the 'androgenisation' of the CNS in early life but appeared to act as a weak androgen. The aromatisation hypothesis was supported by findings that oestrogens were at least as effective as androgens in maintaining aggressive motivation and that 19-hydroxytestosterone (an intermediate between testosterone and 17/3 oestradiol) was also effective. However, aromatisation of the steroid 'A' ring did not appear to be an essential prerequisite for behavioural action since 5x dihydrotestosterone, which cannot be aromatised, also maintained fighting to some extent. Hormonal influences on aggressive behaviour investigated were disussed in terms of possible contributions to the biological fitness of individuals. Findings were also briefly related to current medical research.

This thesis examined the relationships between gonadal hormones and intra-specific aggressive behaviour in the house mouse (Mus musculus L.) and the golden hamster (Mesocricetus auratus Waterhouse). A literature review concerning gonadal hormones and aggressive behaviour and a discussion of relevant semantic problems associated with familiar terms such as 'aggression' and 'pheromone' were presented. Experiments were described which differentiated 'motivational' (i.e. direct effects on brain function) and 'somatic' (i.e. modulation of sensory cues) effects of hormones on behaviour. Results indicated that androgens had a more pronounced motivational effect on male aggressiveness in mice than in hamsters. However, aggressive motivation in male mice was not immediately related to levels of circulating androgen, but a complex relationship involving temporal, social and environmental factors prevailed. Isolated female hamsters were aggressive but similarly housed female mice were not. However, aggressive responses were induced in adult, ovariectomized mice by chronic administration of androgen without prior treatment in a perinatal 'critical period'. Androgen-dependent olfactory signals, which can elicit aggressive responses from conspecifics, were detected in urine from male mice. Male hamsters also produced androgen-dependent cues with similar effects, but the modality and source of such signals remained undetermined. Olfactory signals, which can reduce aggressive responses and elicit sexual behaviour from males, were also detected in urine from female mice. These signals were independent of ovarian control, but could be attenuated by androgen treatment. Vaginal secretions from hamsters contained similar cues. It was concluded that the olfactory signals identified did not 'inhibit' or 'release' stereotyped responses, but receiving animals react flexibly to identical cues according to social status and previous experience. Furthermore, a close correlation between high levels of aggressive motivation, male gender and androgen was not found to be a consistent characteristic of the Rodentia. Arguably, this reflects the adaptive requirements of diverse social and physical milieu.

Background studies relevant to hatchery and cultivation work were undertaken on two species of cockles. The age structure, settlement, growth, density and mortality of a lagoon population of Cerastoderma glaucum in South Wales were monitored. It was demonstrated that an artificial substrate can be efficiently used to collect and grow spat in the field. The reproductive cycles of C. glaucum and C. edule in discrete populations were studied over two breeding seasons using stereological analysis of their gonads. Both species are "opportunistic" breeders. They normally exhibit a monocyclic reproductive pattern spawning from May through the summer; but following a severe winter (1981-82) C. glaucum exhibited an "epidemic" spawning while C. edule adopted a polycyctic pattern. A method for conditioning cockles for spawning is presented. Using this method it was possible to advance or delay the spawning of C. glaucum but not C. edule. Repeated thermal shock was used to elicit spawning in both species of Cerastoderma. Gametes released by C. glaucum were of good quality enabling satisfactory fertilization and development to be achieved. The response of C. edule was poor. The eggs of C. glaucum retain their fertility longer (30 h or more) than they were previously thought to. The life span of the spermatozoa was prolonged to 6 days by cold storage but this treatment impaired the viability of the eggs. Salinity and egg density ranges for satisfactory fertilization and embryonic development of C. glaucum in laboratory cultures were determined. Some dietary and temperature requirements of spat and larvae (diet only) of this species were also investigated. Observations were made on the byssus systems of the spat of the two species of Cerastoderma and interpreted with reference to their ecology. It was concluded that C. glaucum was more amenable to artificial propagation than C. edule.

No description available.

A number of studies have emphasised the diversity of motivations underlying different types of aggression tests in laboratory mica. An attempt was made to extend such considerations by studying the effects of gonadal hormones on a variety of models of aggression in Swiss albino mice. The treatments given included,- 1) Gonadeotomy for 7, 14 or 28 days 2) Replacement of castrates with 25, 50 and 100 ug of testosterone (T) for 7, 1 or 28 days; 3) Replacement with 0.1, 0.5 and 1.0 tag f oestradiol-17y (S) for 7, 14 or 28 days;4) Replacement with 50, 100 and 200 ug of 5aM hihydrotestosterone (5a mIT) for 7,14 or 28 days. The models used included the,- a) 'Standard opponent' test for social conflict; b) Maternal defense test; c) locust killing test; d) Electroshock induced attack test; and e) Tube restraint-induced biting test. The basic findings includes- i) Gonadectomy reduced and hormonal (T, T and501 DHT) replacement restored the attack in social conflict and electroshock induced situations. ii) Gonadectomy and 5j JET replacement had no influence but T and E replacements inhibited attack by lactating mice in the maternal defense test. iii) All the treatments mentioned above had no influence in locust killing and tube restraint induced test. Me data presented confirm that different models of 'aggression' (even in the am species) are modulatedby hormones in different ways. It is maintained that one should be cautious in extrapolating between different tests. This data is of especial importance in understanding the relationships between endocrinology and behaviour.

Time-Depth-Recorders (TDRs) and satellite transmitters were deployed onto five Green turtles, <i>Chelonia mydas. </i>The attachment of these devices was to examine their mid-water diving behaviour, as they travelled back to Ascension Island after being experimentally displaced. The functions of two types of mid-water dives were examined, by investigating their patterns of occurrence, profiles and relationship with the speed of travel. The high-resolution pressure information was then used to investigate the descent and ascent tactics during these two types of mid-water dives. Short-term variations in the rtes of vertical movement were shown to reflect behavioural adaptations to deal with changes in lung volume and buoyancy with depth. Satellite-Relay-Data-Loggers (SRDLs) were deployed onto four Green turtles in order to study their diving behaviour and movements during the inter-nesting period at Ascension Island. The data obtained from the SRDLs allowed the reconstruction of complete dive profiles. Swim speed (<i>N</i> = 1 turtle), depth utilisation and the role of U-shaped dives to the sea bed were reported. Lung volumes were modelled in order to estimate aerobic dive limits of turtles resting at different depths. The routine swimming depth of Green turtle hatchlings was estimated, by direct observation, during their swimming frenzy. In agreement with predictions on the optimisation of swimming depth with regards to wave drag, it was found that hatchlings tended to swim at about 3.5 times their body thickness below the surface. This behavioural adaptation was thought to increase survival rtes. Information on the temporal occurrence of Leatherback turtles, <i>Dermochelys coriacea,</i> in the Bay of Biscay (French Atlantic coast) was presented for the period 1979-2000. The seasonal distributions of strandings and sightings were reported. The results indicated that ecological requirements (such as presence/absence of foraging material) were probably major factors driving the seasonal patterns of Leatherback turtle occurrences in temperate waters.

No description available.

These studies investigate relationships between "stress" (especially from social stressors), hormonal changes, reticulo-endothelial system activity and immune responsiveness in male laboratory "TO" strain mice. The particular processes examined include the production of total and mercaptoethanol resistant (MER) haemagglutinins and haemolysins produced in response to challenge with standard suspensions of i.p. injected sheep red blood cells (SRBC). The effects of manipulations on indirect measures of endocrine function including adrenal, sex accessory, thymic and splenic weights were concomitantly established. A variety of stressors including defeat and exposure to ether vapour increased adrenocortical and suppressed gonadal function. They also suppress primary but not secondary immune responses to SRBC challenge. Acute actions are much more obvious than chronic ones. Adrenalectomy, gonadectomy and combined adrenalectomy/gonadectomy influenced splenic and/or thymic weights which could also be manipulated by treatment with glucocorticoids or sex steroids. Stress, however, often influenced measures in the absence of these glands. In addition, surgery and stress applied even to adrenalectomized/gonadectomized mice could alter some measures of primary immune responding to SRBC challenge. These results consequently establish that neither sex steroids nor glucocorticoids are essential for the apparent decline in immunocompetence in 'stressed' animals. In view of the recently revealed complexities of cellular mediated immune responses, it seems essential to emphasize that attempts to establish that 'stress' naturally modifies an animal's response to potentially invasive factors require systematic investigation of the time courses of these processes. It seems probable that stress may sometimes enhance aspects of these responses. Emphasis on a single endocrine factor or a single measure of disease resistance is likely to simply add to the current confusion. This area requires a blending of expertise in behavioural analysis, endocrinology and immunology/parasitology.

Many of the early studies have emphasized the diverse nature of different forms of attack. Consequently, approximately 2,600 male and female 'To' strain mice, rendered aggressive by a variety of methods, were employed to examine the extent to which one can regard aggression as a non-unitary concept in this species. Experimental manipulations systematically employed throughout included: i) Situational factors such as housing condition, social status, sex of intruder, anosmia, stage of lactation, presence of young, presence of mate, sex of resident and age of resident; ii) Experience and selection of performance levels on different forms of aggression; iii) Food deprivation; iv) hormonal manipulations (effects of castration and treatment with dexamethasone and ACTII); v) Lithium chloride injection. Models of aggression investigated included: 1) Social aggression: fighting between non-habituated male mice; 2) Predatory aggression: attack on a locust; 3) Maternal aggression: attack by lactating mouse on a conspecific. 4) Electroshock-induced aggression; 5) Tube restraint-induced aggression: biting on an inanimate target by mice confined in a narrow tube. Basic findings included: A) that social aggression in isolated and mated males, and electroshock-induced aggression are generally manipulated by similar experimental factors. There was only slight evidence (from bite target studies) that the electroshock-induced attack is defensive. B) Maternal aggression in very situation-dependent and differs in its physiological control from the above. It appears to be a defensive response. C) Locust-killing is unlike the other types of aggression. D) Tube-restraint-induced aggression is rather different from the other forms of attack: a few experimental manipulations seemed to alter this activity. Consequently, one can confirm that aggression is not a unitary concept even in a single strain of mouse. Different responses seem likely to have different physiologies and workers should emphasise which form of attack they are looking at before attempting to make general statements about 'aggression'.

No description available.