Luciana Bottoni

Seasonal changes in testosterone metabolism in the pituitary gland and central nervous system of the European starling (Sturnus vulgaris)

Abstract The metabolism of testosterone in the pituitary gland, the hypothalamus, and the hyperstriatum of the male European starling was studied in the breeding season (May) and at the beginning and the end of the photorefractory period (July and November). In the pituitary gland the percentage conversion of testosterone to androstenedione and to 5α-DHT did not show seasonal variation, while the conversion of testosterone to 5β-DHT and to 5β-3α-diol was increased two- to threefold when the birds became photorefractory (July and November). In the hypothalamus, the formation of the 5α-reduced metabolites did not show seasonal variation, while the formation of androstenedione was significantly greater in November than in July. In contrast, the formation of 5β-reduced metabolites in the hypothalamus was greater in May and July than in November. In the hyperstriatum, the formation of 5β-reduced metabolites was also greater in July and November than in May. These observations show that seasonal changes in the metabolism of testosterone in the pituitary gland and central nervous system of the starling are mainly characterized by changes in the formation of 5β-reduced metabolites and androstenedione.

Effect of progesterone on the sexual behavior of the male Japanese quail

The reduced metabolites of testosterone produced in the central nervous system of birds are known to be involved in the regulation of male sexual behavior. Since progesterone may compete with testosterone for 5 alpha- and 5 beta-reduction, it may also interfere with the sexual behavior of birds. In order to test this hypothesis, progesterone was administered to male quail either transferred from short days to long days or kept in short days and treated with testosterone. Sexual behavior and crowing were scored at intervals for 21 days and the size of the cloacal gland was measured at the same times. On Day 21, the birds were killed and their testes were weighed. The administration of a large dose (1 mg/day) of progesterone depressed the sexual behavior of the birds stimulated either by long days or by the administration of testosterone. It is suggested that progesterone may compete with testosterone for the active sites of 5 alpha- and 5 beta-reductase; alternatively, its effect may be due to an antiandrogenic activity.

5 beta-Dihydrotestosterone is weakly androgenic in the adult Japanese quail (Coturnix coturnix japonica).

Abstract Adult male castrated quail received injections of 0 or 2 mg of 5β-dihydrotestosterone (β-DHT) for 14 consecutive days. These treatments were combined with daily injections of 0.1, 0.5, or 1.0 mg testosterone (T). Control birds were injected with the same volume (0.2 ml) of propylene glycol which was the solvent for all steroids. The cloacal gland area and the sexual activity of all birds were repeatedly measured during the period of injections. At the end, the sternotracheal muscles of all males were also weighed. Treatment with T stimulated the cloacal gland growth and increased the sternotracheal muscle weight. β-DHT injections also produced a weak, though quite consistent stimulation of these parameters. The effects of the two steroids were additive, and did not interact with each other. By themselves, β-DHT injections were ineffective on behavior, but they potentiated the stimulating action of 0.5 mg T administration. These results indicate that β-DHT cannot be considered as an inactive steroid in male birds.

PHOTOPERIODIC CONTROL OF TESTOSTERONE METABOLISM IN THE CENTRAL AND PERIPHERAL STRUCTURES OF AVIAN SPECIES

Abstract In many avian species LH secretion is photoperiodically stimulated and is endogenously interrupted during the “photorefractory period”. In order to elucidate the possible role of 5α- and 5β-reduced metabolites of testosterone in these phenomena, the metabolism of testosterone has been studied in vitro in the pituitary gland, in the hypothalamus, in the hyperstriatum and in the cloacal gland of the Japanese quail. The pituitary gland of the quail is able to convert testosterone to 5α-reduced metabolites (5α-dihydrotestosterone, 5α-androstan-3α,17β-diol), to 5β-reduced metabolites (5β-dihydrotestosterone, 5β-androstan-3α,17β-diol) and to androstenedione. The conversion to the 5α-reduced metabolites is significantly higher in the glands of the quails maintained in “long days” and is hardly detectable in those of animals kept in “short days”; a further increase in the conversion of testosterone to 5α-reduced metabolites is observed in the pituitaries of castrated quails maintained in “long days”; in contrast the conversion of testosterone to 5β-reduced metabolites is not significantly affected by the photoperiod. Trace amounts of 5α-reduced metabolites are also found after the incubation of testosterone with the hypothalamus but not with the hyperstriatum. In these two nervous structures, and especially in the hyperstriatum, the 5β-reduced metabolites of testosterone are quantitatively predominant. The cloacal gland is able to convert testosterone in vitro both to androstenedione and to 5α- and 5β-reduced metabolites. The conversion to the 5α-reduced metabolites is significantly higher in the glands of birds kept in “long days” than in those of birds maintained in “short days”; the conversion to 5β-reduced metabolites is not significantly affected by the photoperiod. The administration of 5α- and 5β-reduced metabolites of testosterone to castrated male quails has shown that androgens having a 3-keto-Δ 4 , 3-keto-5α, or 3α-ol-5α configuration are able to lower the high castrate level of plasma LH and to promote the growth of the cloacal gland. The 5β-reduced metabolites do not have any activity either at central or at peripheral level. These results are compatible with the hypothesis that the 5α-reduced metabolites of testosterone play a role in the mechanisms controlling LH release and in maintaining androgen-dependent peripheral structures in birds as in mammals. Further studies are necessary for establishing the role of the 5β-reduction of testosterone.

Risk of invasion by frequently traded freshwater turtles

Risk assessment allows the identification of non-native species most likely to become invasive and cause harm, and helps to set up preventive measures such as trade regulations. Freshwater turtles are among the most traded pets; an increasing number of species are easily available and frequently released by owners in natural wetlands. This study identified a pool of freshwater turtles frequently traded at cheap prices, and performed risk assessment at multiple steps of the invasion process. Establishment risk was assessed through species distribution models (MaxEnt and Boosted Regression Trees) based on global presence records and bioclimatic variables. We also analyzed ecological and life history traits favouring release, establishment and population growth. Besides the already invasive Trachemys scripta, at least 14 species are easily found in the pet market. For most of them, species distribution models identified areas with suitable climate outside the native range. Validation with independent data confirmed the reliability of the modelling approach. Pelodiscus sinensis and Pelomedusa subrufa had the broadest areas of suitable climate outside the native range. For all the species, possibility of coexistence with humans and reproductive traits suggest high risk of invasion, if introduced in areas with suitable climate. The availability of spatially explicit maps of risk allows to identify areas where preventive measures are urgently needed. In Europe, an expansion of trade regulations is needed to avoid that multiple freshwater turtles become invasive.

Assessment of population trends of common breeding birds in Lombardy, Northern Italy, 1992-2007

A knowledge of population trends is essential in order to assess the conservation status of a species and to develop practices to manage ecologically sustainable land use. However, monitoring programmes designed to assess trends are often not carried out due to their high operating costs. Therefore, in order to obtain population trend estimates without a specific monitoring programme, it is necessary to use heterogeneous historical information. The aim of this research was to assess population indices and trends between 1992 and 2007 for common bird species breeding in Lombardy (Italy), applying a previously developed method, which permits data derived from different survey projects to be utilised. Among the 51 species considered, there were seven negative and 10 positive trends, whereas the remaining species did not show a significant population change. Major declines regarded farmland species, namely the Red-backed Shrike Lanius collurio and the Sky Lark Alauda arvensis which, over a 15 year period, decreased by more than 70%. Among forest species, the Common Chiffchaff Phylloscopus collybita declined, whereas the others either increased or did not demonstrate a significant trend. The population index also highlighted recurring patterns of inter-annual changes in the populations of different species, suggesting that certain ecological processes may have an effect on the whole community. The general decline of farmland species, which is known to occur in many other European regions, suggests the need for specific monitoring schemes for birds and their habitats, in order to understand the effects of changes in agricultural practices and to be able to plan effective measures for bird conservation in productive areas.

Effects of sex steroids on testosterone metabolism, plasma gonadotropins, cloacal gland growth and reproductive behaviour in the Japanese quail

Abstract Castrated male quails, exposed to long days (16L:8D), were implanted with 10 mm silastic capsules (internal diameter: 1,57 mm) containing testosterone or 5α-dihydrotestosterone (5α-DHT) or they were injected with estradiol benzoate (EB). The effects of these manipulations on cloacal gland growth, plasma levels of gonadotropins (FSH and LH), sexual behaviour and on testosterone metabolism in the brain and in the anterior pituitary were assessed. The cloacal gland size was much increased by testosterone and 5α-DHT and the conversion of testosterone to 5β-reduced metabolites in the pituitary was depressed by treatments with 5α-DHT and/or EB. Only minor effects were observed in the plasma levels of gonadotropins and in sexual behaviour except crowing, which was stimulated by testosterone and by the combined treatment with 5α-DHT and EB. This study shows that the cloacal gland is more sensitive to androgens than the brain areas that control sexual behaviour through the negative feedback of gonadal ste...

Mate choice and reproductive success in the domesticated budgerigar, Melopsittacus undulatus

Abstract Female budgerigars that had been given the opportunity to choose their mate laid more promptly, produced a higher number of eggs and reared a higher number of fledgings than females that had been denied the possibility to choose a mate and had been paired at ran dom. In addition, males of self‐selected pairs performed courtship singing at higher rate than those of random pairs. However, in the following brood most differences disappeared as the number of eggs laid and young fledged increased in the random group and the rate of courtship singing decreased in the self‐selected group. It appears, therefore, that choosy females do enjoy a reproductive advantage even though they do not necessarily choose genetically superior males. Male budgerigars singing too little might be simply unable to stimulate ovarian development and sexual response of the female.

Annual testicular activity in the gray partridge (Perdix perdix L.)

Seasonal changes in plasma androgens, testicular total protein content, gonosomatic index, and spermatogenic activity were studied in the grey partridge, Perdix perdix. Moreover, testicular androgen output after stimulation with ovine LH (oLH) was tested in vitro during different periods of the sexual cycle. Androgens and the gonosomatic index peaked in April, during which all the spermatogenic stages were observed. Total protein content in the testes was highest in January and March. Gonadal responsiveness to oLH was found to increase in the period April-May in coincidence with the hormone peak in the plasma, while February testes were irresponsive.

Testosterone metabolism in neuroendocrine and peripheral tissues of male Japanese quail during photoinduced sexual maturation

Abstract Changes in testosterone metabolism in neuroendocrine tissues and the cloacal gland of the Japanese quail were studied by an “in vitro” approach in immature birds raised in short day lengths and in maturing birds after 2, 4, 6, 8, 12, 20 days of photostimulation (16 h light, 8h darkness). Androstenedione, 5β-DHT, 5β-3α-diol and 5α-DHT were identified as the main metabolites of testosterone in the pituitary and in the cloacal gland. No 5α-DHT was found in incubates from the hypothalamus and hyperstriatum. In the pituitary gland, the hypothalamic and the hyperstriatal tissue conversion of testosterone into androstenedione was low in short day birds. After photostimulation conversion into androstenedione increased progressively in all tissues studied. Conversion to 5β-reduced metabolites was highest in short days and decreased progressively as the birds matured. Conversion to 5α-DHT was low in short day birds and increased significantly after 12 days of photostimulation. In the cloacal gland conversi...