Gary P. Moberg

Individual differences in temperament of domestic dairy goats: constancy and change

Change is an essential property of development, yet some element of stability or consistency is necessary for the maintenance of individual distinctiveness. The issues of constancy and change were addressed in a study of individual differences in temperament of domestic dairy goats, Capra hircus. Within-individual stability was assessed on an absolute basis by evaluating changes in mean scores on five behavioural measures monitored in goat-human encounters at 14, 22 and 30 weeks of age. Between-individual stability was examined by comparing rank orders of individuals across successive ages and situations. Human-reared goats consistently expressed low levels of timidity. Behaviour of dam-reared goats increasingly resembled that of human-reared goats, while relative individual differences remained stable. Individual differences in timidity scores, derived from five interrelated behaviour measures, reliably predicted differences in pituitary-adrenal responsiveness at 14–30 weeks and behavioural outcomes in five different situations at 55 weeks. Timidity scores of all dam-reared goats exceeded scores of human-reared goats. Among seven pairs of fraternal twins, a goats rank within the dam-reared group predicted its siblings rank within the human-reared group. An individuals genotype and its early postnatal environment both contributed to processes underlying the development of stable individual differences in temperament of domestic dairy goats.

Observations on the reproductive cycle of cultures white sturgeon, Acipenser transmontanus

Males and females of cultured white sturgeon, Acipenser transmontanus, mature at an average age of 4 and 8 years, respectively. However, the onset of ovarian vitellogenesis and puberty are highly asynchronous in the female stock. Gonadal cycles are annual in males and biennial in females, and gametogenesis is influenced by season. Neuroendocrine regulation of reproduction appears to involve a dual gonadotropin system controlling gonadal development and spawning. Labile puberty and sex-specific duration of the gonadal cycle are distinct characteristics of cultured and wild sturgeon. Photoperiod and temperature play a significant role in environmental regulation of the reproductive cycle, but further studies are necessary to elucidate the roles of endogenous and environmental factors in sturgeon reproduction which is critically important for both aquaculture and conservation of endangered wild stocks.

Reproductive conditions of the Atlantic sturgeon (Acipenser oxyrinchus) in the Hudson River

Ninety-four prespawning adult Atlantic sturgeon (Acipenser oxyrinchus) were sampled in the Hudson River for age, sex, body size, gonad weight, fecundity, mature oocyte size, and plasma concentrations of gonadotropins, sex steroids, and vitellogenin during the spring spawning migrations in 1992 and 1993. In males, the age and total length ranged from 12 yr to 19 yr and from 133 cm to 204 cm and in females from 14 yr to 36 yr and from 197 cm to 254 cm. The majority of males were 13–16 yr old, and females were 16–20 yr old. Some females had residual atretic ovarian bodies, presumably remaining from a previous spawning and indicating iteroparity. Pre-ovulatory condition was recognized by migration of the germinal vesicle or by germinal vesicle breakdown and by significantly elevated plasma gonadotropins, progesterone, and vitellogenin. All pre-ovulatory females were captured upriver from Hudson River kilometer 136. Individual fecundity ranged from 0.4 million to 2.0 million eggs and oocyte diameter from 2.4 mm to 2.9 mm, and both characters exhibited a significant (p<0.05) positive relationship with female body size. Iteroparous females, tentatively identified by the presence of atretic bodies remaining in the ovary from a previous spawning, had significantly (p<0.05) higher fecundity and produced larger eggs, compared with females spawning presumably for the first time.

Effects of short-term management stress and ACTH injections on plasma cortisol levels in cultured white sturgeon, Acipenser transmontanus

Abstract General management practices including capture, handling and transportation in fish hatcheries can induce a stress response indicated by a plasma cortisol increase in many species. However, this phenomenon is not well established in cultured white sturgeon ( Acipenser transmontanus ). We determined resting levels of cortisol and the cortisol responses to two management stressors and to exogenous adrenocorticotropic hormone (ACTH 1–24 ) injections in cannulated mature male white sturgeon. Mean resting cortisol level was 8.6 ng/ml and ranged over 5.8–12.8 ng/ml through a 22-h period. Water reduction and transportation+handling stressors elicited significant cortisol increases above pre-stress and post-stress levels. Exogenous ACTH 1–24 injections of 0.5 and 5.0 μM caused dose-dependent peak cortisol increases above those produced by either the water reduction or transportation+handling stressors.

Preliminary observations on the effects of holding temperature on reproductive performance of female white sturgeon, Acipenser transmontanus Richardson

Abstract Commercial sturgeon farms in California have observed poor spawning performance and ovarian regression in fish maintained at constant 16–20°C water temperatures. The effects of the pre-spawning thermal regime on oocyte germinal vesicle migration (GVM), in vitro maturation (GVBD), plasma concentrations of reproductive hormones, and hormonally-induced ovulation in white sturgeon females were examined. Gravid females were exposed to three temperature treatments (seasonal 10–15°C, constant 15°C, and constant 18°C), and ovulation was induced when females reached the responsive stage. While all females ( n =5 per treatment) in the seasonal temperature treatment ovulated and produced fertile eggs, oocyte development (GVM) and ovulation were inhibited in the constant temperature treatments, and follicular atresia ensued in three out of five females exposed to 18°C water temperature. Temperature treatment did not have a significant effect on plasma hormone concentrations throughout the pre-spawning and spawning periods, but plasma concentrations of androgens and oestradiol declined in females that experienced developmental arrest and atresia. The spawning results provided empirical evidence for the negative effects of elevated temperatures on ovulatory response and egg quality. The pre-spawning thermal regime appears to be an important environmental factor for normal ovarian development in cultured white sturgeon and should be considered in management of wild stocks reproducing in rivers with regulated water flows.

Endocrine sensitivity to novelty in squirrel monkeys and titi monkeys: Species differences in characteristic modes of responding to the environment.

The present study examined plasma cortisol and behavioral responses to environmental novelty in squirrel monkey and titi monkey male-female pairs. Overall, seemingly trivial increments in novelty evoked sustained plasma cortisol elevations. In individually tested animals, the minimal level of novelty sufficient to evoke a cortisol response was smaller, and the ability of the response to discriminate among levels of novelty was greater, in titis than in squirrel monkeys. When tested with the pairmate, the sensitivity of the response was reduced in titis but not in squirrel monkeys. Behavioral measures were not as sensitive to novelty as was the cortisol response. The results suggest that differential endocrine responsiveness to novelty is an important physiological concomitant to previously described differences between squirrel monkeys and titi monkeys in their characteristic modes of relating to the environment.

Physiological evidence for two sturgeon gonadotrophins in Acipenser transmontanus

Abstract Physiological evidence in white sturgeon Acipenser transmontanus suggests that two gonadotrophins, termed sturgeon gonadotropin I (stGTH I) and sturgeon gonadotropin II (stGTH II), are involved in regulating reproduction. Pituitary and plasma concentrations of stGTH I were found to be higher than concentrations of stGTH II during vitellogenesis and the early stages of spermatogenesis. Conversely, pituitary and plasma concentrations of stGTH II were greater compared with stGTH I during ovulation and spermiation. The gonadotropin releasing hormone analog D-Ala 6 -des-Gly 10 -GnRH ethylamide (GnRHa) was effective in stimulating the release of both gonadotrophins in mature males and preovulatory females, with a maximal response occurring in the spring. Collectively, the data supports our view that sturgeon possess a dual gonadotropin system controlling reproduction.

Social modulation of pituitary-adrenal responsiveness and individual differences in behavior of young domestic goats

The effects of three variables known to influence pituitary-adrenal activity were examined in kid goats who were accompanied by adult goats in standard goat-human encounters. Serum corticosteroid concentrations in bold kids who characteristically spent above average amounts of time closely interacting with the person were never significantly different from control values. Corticosteroids in timid kids who spent little time near the person depended on the adult goats behavior toward the person and the nature of the social relationship between the kid and the adult goat. When timid kids were accompanied by adult goats (familiar pen-mates or strangers) who behaved as if they were fearful of the person, their corticosteroids were significantly greater than control values. In contrast, bold pen-mates or bold strangers effectively reduced pituitary-adrenal responsiveness in timid kids. Only mothers unconditionally reduced kid pituitary-adrenal responsiveness and systematically affected kid behavior toward the person. The functioning of behavioral and pituitary-adrenal systems in young goats was influenced by consistent individual differences in responsiveness and the differing capacities of social companions to modulate this responsivity.

Effect of raphe lesions on the circadian pattern of wheel running in the rat

Abstract In order to investigate whether a serotoninergic (5-HT) system might be involved in the regulation of the circadian pattern of wheel running in rats, the effect on running of ablation of the medial and dorsal raphe nuclei was studied. It was found that sham lesioned and dorsal raphe lesioned animals initially displayed reduced total daily running, although the animals returned to preoperative running levels by the end of testing. Throughout the entire period there was no effect upon the circadian distribution of running in the two groups. During the first week following surgery, however, the animals which had received both medial and dorsal raphe lesions were initially hyperactive, showing a 200% increase in running during the light period. For one week following surgery and then throughout the rest of the testing period the total amount of running of this group dropped below control levels while the circadian pattern of running returned to normal. These data suggest that although a 5-HT system projecting from the medial raphe may modulate the circadian pattern of running, the system is not essential and other neural components can compensate for the absence of this system.

Effect of midbrain raphe nuclei lesions on the circadian rhythm of plasma corticosterone in the rat.

Throughout the 24-h day the concentration of corticosteroids in plasma shows a definite circadian rhythmL The neural systems which are essential in transforming the environmental cues that entrain this rhythm have not been identified, however, evidence from limited studies has suggested that serotoninergic (5-hydroxytryptamine, 5-HT) systems projecting to the forebrain may be involved in modulating this rhythmic release of corticosterone. Correlations have been made between the rhythmic changes in whole brain or limbic structure 5-HT content in rats and the daily fluctuations of plasma corticosterone 14,17. Investigators have found that pharmacological disruption of the synthesis of 5-HT will alter the normal circadian rhythm ofplasmacorticosteroids. For example, Krieger and Rizzo 10 found in cats that various drugs which alter 5-HT melabolism were effective in blocking the normal daily rise in cortisol. Also, in rats it is found that blocking 5-HT synthesis with para-chlorophenylalanine (pCPA) not only results in decreased brain 5-HT content but also the abolishment of the circadian rhythm of plasma corticosteronel4.19. These data support the conclusion that 5-HT neurons are involved in the control of the circadian rhythm of the adrenal axis. In contrast to the above findings, Van Delft et al. is found that pCPA treatment in rats had only a partial effect on the circadian rhythm of corticosteroids and these authors suggested that 5-HT is not directly involved in the control of the adrenal rhythm but that the altered corticosterone levels reflect secondary effects of the drug. Certainly, pCPA not only inhibits the synthesis of 5-HT but also produces small depletions in brain catecholamines 7 as well as competing in the transport mechanisms for tryptophan, phenylalanine, and other amino acidsL Also, pCPA drastically alters many behavioral characteristics, causing insomnia, anorexia, and changes in patterns of motor activity, any of which may interfere with basal adrenal function, irrespective of an effect on the serotoninergic system per se. Therefore, to assess the role of the 5-HT neural system in the tonic control of the pituitary-adrenal axis without resorting to the use of drugs which may have non-