Kimberly M. Cheng

INTROMITTENT ORGAN MORPHOLOGY AND TESTIS SIZE IN RELATION TO MATING SYSTEM IN WATERFOWL

Abstract The waterfowl family Anatidae is one of very few avian taxa that possesses an intromittent organ. This paper examines the adaptive significance of the intromittent organ in waterfowl by determining the relationships between intromittent organ morphology and the intensity of sperm competition (as reflected by frequency of forced extrapair copulations [FEPCs]). Intromittent organ morphological characteristics, including length and circumference (adjusted for body size), number of ridges and knobs (per unit area), ridge or knob height, ridge or knob span, and area covered by ridges and knobs, were measured from scaled drawings of museum specimens of 54 waterfowl species (33 genera), 27 of which were ranked by frequency of FEPC (1 = monogamous, 2 = rare FEPC, 3 = frequent FEPC, and 4 = polygynous or promiscuous). Testes sizes were also investigated in relation to FEPCs, where testes mass (adjusted for body size) from 44 species (24 genera) were obtained (29 species with mating strategies). The size of the testes, the length of the intromittent organ, the height of the intromittent organ ridges and knobs, and the area covered by ridges and knobs increased significantly with the frequency of FEPC, and those relationships exist after correcting for common ancestry constraints. These results are consistent with the hypothesis that waterfowl intromittent organs are involved in sperm competition. Further research into the actual mechanism by which the intromittent organ is involved would be worthwhile.

Heritability and phenotypic correlations of behaviour and dominance rank of Japanese quail

The frequency and heritability of 13 behavioural acts of hatchling Japanese quail,Coturnix japonica, were measured in a laboratory experiment to examine their relationship to juvenile and adult dominance. The heritability of similar acts in adult quail were also quantified to determine how heritability estimates changed with age. Juvenile dominance rank, determined by frequency of winning conflicts, was uncorrelated with the frequency of any hatchling behaviour or hatchling body size but contained significant additive genetic variance in both males and females. Dominance rank in adult females, measured similarly, also had a high heritability estimate. Dominance in adult males, measured as frequency of initiating a fight and frequency of mounting, had only low heritability. Dominance ranking in adults was uncorrelated with the dominance ranking of juveniles. Dominance may be heritable but may not respond to natural selection because of the interaction between the genotype and the environment.

Forced copulation in captive mallards (Anas platyrhynchos): II. Temporal factors

Abstract A study of temporal trends in forced copulation was conducted in flight-pens with eight pairs of captive mallards to test the hypothesis that forced copulation is an evolved breeding strategy in waterfowl. Significantly more forced copulation attempts were directed at females during egg-laying than during the non-laying period preceding laying, and few forced copulations occurred after the laying of the last egg of the clutch. Most forced copulations occurred in the morning when the females were leaving the nests after egg-laying. Thus, forced copulations occurred at times when fertilization was most likely to result, supporting the insemination strategy hypothesis.

Dominance relationship and mating behavior of domestic cocks: a model to study mate-guarding and sperm competition in birds

A random-bred strain of domestic chickens (Gallus gallus) in single-male and two-male mating groups was used as a model to study strategies of mate guarding and sperm competition. The experiment was designed to examine influences of (a) the presence of a rival male, (b) dominance status of the males in the two-male groups, and (c) the time of day on the frequencies of male courtship and copulations. In the absence of rivalry, male chickens copulated infrequently in the morning and increased the frequency of copulations throughout the day until a maximum was reached in late afternoon. In the two-male groups the dominant males copulated more frequently than the subordinate males. They also competed by altering their diurnal pattern of mounting attempts and increasing their rate of successful copulation per attempt. The subordinate males made frequent attempts to mount the females regardless of whether they were receptive. However, their success rate was low because of interference by the dominant males, especially at that time of the day when a successful insemination would likely fertilize eggs. The experiment showed that not only the relative numbers of copulations by different males, but also the timing and success of copulations by different males may influence the probability of paternity. Furthermore, the interplay of proximate mechanisms and evolutionary factors contributed to variations in mating strategies.

Mate preference in wild and domesticated (game-farm) mallards: II. Pairing success

Abstract Experiments were designed to determine whether assortative mating occurs in wild and game-farm mallard strains (Anas platyrhynchos). Mallard males of either strain raised with females of their own strain courted females of their own strain more than females of the opposite strain, and these males were only successful in pairing with females of their own strain. Males raised with females of the opposite strain courted wild and game-farm females with equal intensity. They were successful in pairing with females of either strain. While this study does not settle the question of possible gene flow between these two mallard populations, it does indicate that there is a potential barrier to panmixia.

Mate preference in wild and domesticated (game-farm) mallards (Anas platyrhynchos): I. Initial preference

Abstract Wild and game-farm mallards (Anas platyrhynchos) raised in pure strain and mixed groups were tested for initial mate preference in a choice test. Female mallards showed no significant preference but males of either strain raised with females of their own strain significantly preferred female models of their own strain during the test. Males raised with females of the other strain merely showed attenuation of their preference for female models of their own strain and did not show preference for female models of the other strain. Game-farm mallards approached models significantly sooner than wild mallards and there was a significant sex × mate interaction.

Effects of oxidant-induced injury on heme oxygenase and glutathione in cultured aortic endothelial cells from atherosclerosis-susceptible and -resistant Japanese quail.

Recent studies on cultured aortic endothelial cells (AECs) from atherosclerosis-susceptible (SUS) and -resistant (RES) strains of Japanese quail suggest that differences in atherosclerosis susceptibility between RES and SUS may be due to differences in endothelial heme oxygenase (HO) and antioxidant components. We have now investigated the effects of oxidant-induced injury on HO and glutathione (GSH) in AECs from SUS and RES quail. We report that cultured AECs from SUS and RES birds differ in their response to oxidative stress. AECs from the SUS strain cells are more susceptible than those from the RES strain to oxidative stress induced by tert-butylhydroperoxide, as judged by lower HO activity, HO-1 expression, ferritin and GSH levels. Aortic endothelial cells from SUS birds also showed higher levels of catalytic iron, TBARS production and LDH release compared with RES cells, indicating that SUS AECs are more susceptible to oxidative stress than cells from the resistant strain. Furthermore, independently of genetic status, AECs from old birds have higher TBARS and lower levels of HSP70 induction than AECs from younger birds, suggesting that aging is associated with a decreased ability of AECs to respond to oxidative stress, and this may be relevant to the permissive effect of aging on the process of atherogenesis. Our results indicate that genetic factors and endogenous antioxidant systems in the blood vessel wall may be important in determining the susceptibility of vascular cells to oxidative stress and atherosclerotic plaque formation.

Ratite oils promote keratinocyte cell growth and inhibit leukocyte activation

Traditionally, native Australian aborigines have used emu oil for the treatment of inflammation and to accelerate wound healing. Studies on mice suggest that topically applied emu oil may have anti-inflammatory properties and may promote wound healing. We investigated the effects of ratite oils (6 emu, 3 ostrich, 1 rhea) on immortalized human keratinocytes (HaCaT cells) in vitro by culturing the cells in media with oil concentrations of 0%, 0.5%, and 1.0%. Peking duck, tea tree, and olive oils were used as comparative controls. The same oils at 0.5% concentration were evaluated for their influence on peripheral blood mononuclear cell (PBMC) survival over 48 hr and their ability to inhibit IFNγ production in PBMCs activated by phytohemagglutinin (PHA) in ELISpot assays. Compared to no oil control, significantly shorter population doubling time durations were observed for HaCaT cells cultured in emu oil (1.51×faster), ostrich oil (1.46×faster), and rhea oil (1.64×faster). Tea tree oil demonstrated significant antiproliferative activity and olive oil significantly prolonged (1.35×slower) cell population doubling time. In contrast, almost all oils, particularly tea tree oil, significantly reduced PBMC viability. Different oils had different levels of inhibitory effect on IFNγ production with individual emu, ostrich, rhea, and duck oil samples conferring full inhibition. This preliminary investigation suggests that emu oil might promote wound healing by accelerating the growth rate of keratinocytes. Combined with anti-inflammatory properties, ratite oil may serve as a useful component in bandages and ointments for the treatment of wounds and inflammatory skin conditions.

Understanding the Behavior of Domestic Emus: A Means to Improve Their Management and Welfare—Major Behaviors and Activity Time Budgets of Adult Emus

Information on domestic emu behavior is sparse and hence a study was undertaken to identify and describe the behavior of domestic emus in a farm setting. The behavioral repertoires, activity time budgets, effect of time of the day, sex, weather, and relative humidity on activities of adult emus were investigated. Eight randomly selected emus were observed using one-zero sampling method for 12 days, each period of observation lasting 30 minutes. The major behavioral categories identified were ingestive drinking, standing, locomotion, grooming, socialization, vocalization, and resting. The emus spent most of their time walking, standing, and eating. Immediately after moving to a new pen, emus were found to huddle together to keep away from emus already resident in the pen. The time spent on each activity was not significantly different between the sexes. The findings from this study provided important information on the behavior and activities of emus. The observed behaviors need to be further examined to assess their relations to the birds’ welfare.