Mei-Fang Cheng

Progress and Prospects in Ring Dove Research: A Personal View

Publisher Summary This chapter discusses the more recent work on the reproductive behavior and physiology of the ring dove in the context of Lehrmans research and theoretical formulations, the extension of Lehrmans theoretical framework, and some new directions in which ring dove studies are moving. The most striking feature of the behavioral changes involved in ring dove reproduction is the synchronization between male and female behavior. While, the most striking behavioral change in ring doves during the reproductive cycle is the transition from the highly visible activity of the prelaying phase to minimal activity during incubation and brooding. The chapter outlines some known factors (hormonal and nonhormonal) and their interactions involved in controlling the reproductive cycle of ring doves. The chapter concludes: (1) changes in behavior during the reproductive cycle are influenced by external stimuli and hormones; (2) the time course of behavioral changes is in close relation to that of hormonal changes; (3) external stimuli acting through the hypothalamus–pituitary–gonadal (HPG) system, cause hormonal changes, which (a) influence behavior, and thereby the pattern of external stimuli, (b) stimulate reproductive organs and tracts, and (c) react back to the HPG system; and (4) The activity of the HPG and the ability of external stimuli and hormones to induce behavioral changes show seasonal variation.

Neurogenesis in juvenile and adult ring doves.

Studies in songbirds suggest that neurogenesis during the first few years of life is related to song learning. In this study, we examined whether postnatal neurogenesis occurs in a nonsongbird, the ring dove (Streptoplia risoria), and whether it persists to old age.

For whom does the female dove coo? A case for the role of vocal self-stimulation

Abstract A scries of studies on the courtship behaviour of ring doves, Streptopelia risoria , has revealed a hitherto unsuspected function of the females nest coo, suggesting a new dimension to the, functional analysis of vocal displays. Male and female ring doves perform a predictable sequence of courtship displays that culminate in egg laying. It has been thought the males displays provoke the endocrine changes in the female that lead to ovulation. However, there is now evidence, reviewed here, that the females own nest coos affect her endocrine state. Females prevented from performing the nest coo showed little or no follicular growth despite active courtship by the males. This was true whether the female was devocalized through lesioning the midbrain vocal control region nucleus intercollicularis, severing the syringeal nerves, or deflating the interclavicular sac. Other possible examples of vocal self-stimulation are discussed, and it is suggested that the phenomenon may be widespread.

The role of the midbrain in courtship behavior of the female ring dove (Streptopelia risoria): Evidence from radiofrequency lesion and hormone implant studies

The involvement of the nucleus intercollicularis (ICo) region of the midbrain, an estrogen-sensitive area, in the expression of estrogen-dependent female courtship behavior was examined with radiofrequency lesion and intracranial hormone implant techniques. Bilateral lesions in the ICo region caused a reduction in the females nest coos, and no reduction in other behaviors in response to male courtship. In addition, the follicles of the ICo lesioned females failed to grow in response to male courtship. A second experiment showed that the difference in follicular size between ICo-lesioned and sham-ICo-lesioned females was not observed if females were visually isolated from males, suggesting that tonic ovarian activity was not affected by ICo lesions. In the third experiment, unilateral 30-gauge implant containing estrogen (E) or estradiol benzoate (EB) in the ICo region of bilaterally ovariectomized females restored the nest-coo, though not to the level obtained with systemic EB injections. Other behaviors were not selectively affected by E or EB implants in the ICo region. Diffusion from the implant was probably not responsible for the elicitation of the nest-coo, since the oviduct weights of females implanted with E or EB and cholesterol did not differ. These data are consistent with the hypothesis that the ICo region is involved in the expression of vocal (cooing) courtship behavior in the female ring dove.

Hypothalamic neurogenesis in the adult brain

Adult-born new neurons are continuously added to the hippocampus and the olfactory bulb to serve aspects of learning and perceptual functions. Recent evidence establishes a third neurogenic niche in the ventral hypothalamic parenchyma surrounding the third ventricle that ensures the plasticity of specific brain circuits to stabilize physiological functions such as the energy-balance regulatory system. Hypothalamic lesion studies have demonstrated that regions associated with reproduction-related functions are also capable of recruiting newborn neurons to restore physiological functions and courtship behavior. Induced by lesion or other stimulation, elevated neurotrophic factors trigger neurogenic cascades that contribute to remodeling of certain neural circuits to meet specific transient functions. This insight raises the possibility that event-specific changes, such as increased GnRH, may be mediated by courtship-sensitive neurotrophic factors. We will discuss the potentially integral and ubiquitous roles of neurogenesis in physiological and biological phenomena, roles that await future experimental exploration.

Serum prolactin levels and crop-sac development in ring doves during a breeding cycle

Using a turkey prolactin radioimmunoassay, the serum prolactin levels of male and female ring doves (Streptopelia risoria) during the breeding cycle were measured and their circulating prolactin levels were compared to crop-sac weight on a within-bird basis. During the early phase of the incubation period, crop weight showed a delayed response to prolactin stimulation and there was no correlation; during the midincubation period when prolactin and crop-sac weight were increasing, there was a strong positive correlation; around hatching, when prolactin was at its peak, there was no correlation. There were again strong positive correlations at later samples, when squabs were developing and both prolactin and crop-sac weight were declining. Thus, it appears that the correlation between the circulating prolactin level and crop-sac development depends on the stage of the breeding cycle. While males and females showed similar pattern of circulating prolactin during the period of incubation and parental care, only females consistently showed a postovulatory rise of prolactin. These results were discussed in the context of the role of prolactin in the breeding cycle.

Plasma luteinizing hormone during the breeding cycle of the female ring dove

Abstract Plasma luteinizing hormone (LH) levels in serial blood samples of female ring doves (Streptopelia risoria) were measured by radioimmunoassay method. Our findings indicate the following pattern of LH levels: LH increases during early courtship which reaches a peak (5.43 ± 0.79 ng/ml) during the nesting period. LH declines following egg-laying (3.77 ± 0.33 ng/ml) and again after hatching (2.23 ± 0.28 ng/ml). It remains high in females which laid infertile eggs initially and subsequently showed a further laying. The results are compared with published data on plasma estrogens and progesterone in the doves breeding cycle.

Role of vocalizations in the reproductive cycle of ring doves (Streptopelia risoria): Effects of hypoglossal nerve section on the reproductive behavior and physiology of the female

Abstract The role of vocalizations in the reproductive cycle of female ring doves was investigated. Two-stage bilateral hypoglossal nerve section (HNS) was performed on adult females to alter their cooing and they were observed for courtship behavior with the same stimulus males used in preoperation behavioral tests. The HNS females showed a reduction in both the vocalization and wing flipping components of nest-coos but no changes in other female courtship behaviors. In addition, the HNS females failed to show the typical male courtship-induced follicular growth observed in sham-operated females. The behavior of stimulus males did not differ between groups and therefore could not account for the failure of follicular growth in the HNS females. These data suggest that the females performance of nest-coos, or factors associated with it, may stimulate her own follicular growth.

Effects of Testosterone Metabolites and Estrogen in the Midbrain Control of Courtship Behavior in the Male Ring Dove (Streptopelia risoria)

Relative effectiveness of testosterone (T) and its metabolites in the midbrain to induce courtship behavior was investigated in male ring doves. T, 5 alpha-dihydrotestosterone (5 alpha-DHT), 5 beta-dihydrotestosterone, estradiol-17 beta (E), or cholesterol was implanted in or around the nucleus intercollicularis region (ICo) of the castrated male. Resulting courtship behavior was observed by pairing the treated males with stimulus females. T, 5 alpha-DHT and E activated nest-cooling behavior pattern when placed in the ICo region only. Other male courtship behaviors were not induced, induced in each brain region tested or induced by all the hormones. Hormone diffusions from the implant did not appear to be responsible for these results since many implants within 1 mm of the ICo region failed to activate nest-cooling. These data support the idea that the midbrain along with the hypothalamic region mediate male courtship behavior.

Reciprocal talk between the auditory thalamus and the hypothalamus: an antidromic study.

IN this study we sought to validate physiologically the hypothalamus afferent projections from the auditory thalamus previously identified with tract tracing techniques in the ring dove. In total, we recorded the responses of 628 units in the nucleus ovoidalis (Ov) and its shell region to electrical stimulation applied to anterior hypothalamus and ventromedial nucleus. Ninety-six acoustic units in the shell region displayed good antidromic responses, confirming this regions axonal projections into these nuclei of the hypothalamus. Orthodromic responses (143 units) recorded in the Ov–Ov shell region suggest on the other hand reciprocal projections from the hypothalamus back to the auditory thalamus.