Eberhard Haase

Allometric Comparison of Brain Weight and Brain Structure Volumes in Different Breeds of the Domestic Pigeon, Columba livia f.d.(Fantails, Homing Pigeons, Strassers)

In three breeds of domestic pigeons (fantails, homing pigeons, and strassers) the volumes of fresh, i.e. unfixed tissue of 14 brain structures were determined (telencephalon, diencephalon, nervus opticus, tectum, cerebellum, tegmentum and hyperstriatum accessorium, hyperstriatum ventrale, neostriatum, paleostriatum, hippocampus, septum, regio praepiriformis, bulbus olfactorius). Allometric comparisons that take into account differences in body weight and size were made among these three breeds. The tectum, hippocampus, paleostriatum and especially the neostriatum and olfactory bulb are remarkably larger in homing pigeons. These data are discussed in a functional context, in which the homing ability of homing pigeons is considered.

A comparison of seasonal changes in the concentrations of androgens in the peripheral blood of wild and domestic ducks

Abstract Blood samples taken in monthly intervals over a 2-year period from individually marked wild mallard and Khaki Campbell drakes were assayed for testosterone (T) and 5α-dihydrotestosterone (DHT). In the first year plasma T and DHT were measured simultaneously using a competitive protein binding (CPB) method, while in the second year T (without separation from DHT) was determined with a commercial radioimmunoassay (RIA). The wild mallard drakes showed a bimodal pattern in the annual variation of the T concentrations, one peak coinciding with the reproductive season and the second in autumn. The Khaki Campbell drakes had high T levels in spring, late summer, and in autumn/winter. In some of these birds the depression of the T concentrations usually observed in June and/or July was only slight. In both wild and domestic drakes plasma T and LH concentraitons were linearly correlated. The late autumnal peak of these hormones was not accompanied by an increase in testis weight, in neither wild nor domestic drakes. This peak seems to be related to pair formation. The plasma DHT concentrations of our drakes were higher than those known for mammals. The patterns of the seasonal variations were similar to those of the respective T concentrations. Domestication seems to flatten the seasonal fluctuations of the hormones studied. Maximal values of plasma DHT as well as of plasma LH concentrations were similar in wild and domestic drakes, but in their maximal T levels the domestic drakes by far exceeded the wild ancestor.

Flight stimulates adrenocortical activity in pigeons (Columba livia)

The influence of long-distance flight on corticosterone secretion has been examined in trained racing pigeons. Flights of 315-561 min from release sites 115-557 km from the home loft greatly increased the circulating corticosterone concentration in comparison with the levels in nonexercised controls sampled before release or bled in the loft at the times of release or arrival. The increase in corticosterone concentration was unrelated to the distance flown or duration of flight. Flights of less than 1 min duration (from release sites 100 m from the loft) increased the corticosterone concentration, in comparison with that in the loft controls, but to levels much lower (P less than 0.001) than those following long-distance flights and to concentrations similar to those in birds that were returned to the loft by hand.

The annual reproductive cycle in mallards

In wild mallard drakes plasma FSH and LH levels were elevated at the height of the breeding season in spring, decreased towards the end of the reproductive phase and were low during the time of photorefractoriness in summer, when the testes were regressed. In contrast plasma prolactin concentrations increased only towards the end of the breeding season and were at their annual height during the summer. Castration of photorefractory mallards caused a steep rise of plasma LH levels indicating that the testes were involved in the maintenance of the low LH concentrations during the refractory period. In these drakes LH titers remained high throughout the year and, thus, in the absence of the testes the birds did not become photorefractory. In photorefractory drakes removal of 90% of the testicular tissue not only increased plasma LH levels but induced complete spermatogenesis in the testicular remains within 6 weeks. Therefore it seems that photorefractoriness in mallards is due to an increased sensitivity of the hypothalamo-hypophyseal system to the negative feedback action of testicular androgens. After injection of tritiated testosterone the hypothalamus, anterior pituitary and testes, but not other organs studied, took up more radioactivity during the refractory phase than at the height of the breeding season. It is speculated that the increased sensitivity of the hypothalamo-hypophyseal unit to the negative androgenic feedback during photorefractoriness depends on an increased number of androgen receptors in these structures which, again, could be due to the elevated prolactin levels during this phase of the annual cycle.

Environmental and hormonal factors in seasonal breeding in free-living male Indian rose-ringed parakeets (Psittacula krameri).

Seasonal changes in testicular activity, plasma luteinizing hormone (LH), estradiol (E2), testosterone (T), and 5 alpha-dihydrotestosterone (5 alpha-DHT) were related to pair bond formation, nest building, nest defense, and parental behavior in free-living Indian rose-ringed parakeets (Psittacula krameri) in northwest India. Spermatozoa production occurred between January and March when daylengths were short (10-12 hr) and ambient temperature was seasonally low (8-20 degrees C). At other times of the year the testes were regressed. Plasma LH levels increased during the prebreeding period (September-December) when the birds were forming pairs and selecting or defending nest sites. Plasma LH levels increased further between January and March and decreased to seasonal low values during the post breeding period between April and June when the birds were caring for young. Concentrations of plasma androgens and estrogens were similar during the prebreeding and postbreeding phases of the breeding cycle. During the breeding period, the ratios between plasma 5 alpha-DHT and testosterone and between plasma estradiol and testosterone increased. It is proposed that the absence of marked seasonal changes in plasma steroid levels is related to nest defense behavior which occurs during the prebreeding, breeding, and postbreeding phases of the breeding cycle. Winter breeding makes it possible for the parakeets to avoid competition with other birds for nesting sites, to avoid fledging young during the monsoon period, and to take advantage of the winter pea crop which provides the female with extra nutrients for egg production.

The effects of testosterone propionate on secondary sexual characters and testes of house sparrows, Passer domesticus

Abstract Male house sparrows were captured in October and transferred to artificial short days of 8L 16D. Beginning on November 19th they were injected either with 0.4 mg testosterone propionate (group T) or with sesame oil only (group C) every other day. Within 24 days the androgen injections caused a change in the inner and outer surfaces of the bill from light brown to black (Figs. 1,2) and a pronounced enlargement of the glomus vesicles (Table 1). In group C bill coloration was unchanged compared with the start of the experiment. In contrast, therefore, to other recent findings the development of ornamental structures in Passer domesticus does not depend on gonadotropins. No significant differences were observed between the testes of the two groups which were all regressed and inactive.

The effects of castration on the seasonal pattern of plasma LH concentrations in wild mallard drakes

Abstract Castration of photorefractory wild mallard drakes caused a significant increase in their plasma LH concentrations. Blood samples were then taken at monthly intervals for 16 months from 10 castrated drakes living outdoors in Kiel (54°N). Mean plasma LH levels remained elevated throughout the year. It is suggested that the testicular feedback is important for the maintenance of low LH levels during the refractory period, for the typical seasonal fluctuations of the plasma LH concentrations of intact birds, and probably for the induction of photorefractoriness.

Zur Wirkung von Androgenen auf die Induktion des Schlichtkleids bei kastrierten Stockerpeln (Anas platyrhynchos)

An 15 seit mehreren Jahren kastrierten Stockerpeln wurde die Wirkung der Androgene Testosteron (T) und 5α-Dihydrotestosteron (DHT) auf die Umfärbung in das Schlichtkleid untersucht, die nach Literaturangaben von Estrogenen abhängig sein soll. Von Anfang März bis Anfang Mai wurden 5 Vögeln täglich 5 mg T subcutan injiziert. 5 weitere erhielten im gleichen Zeitraum täglich 5 mg DHT, und die restlichen 5 dienten als Kontrollen. Gegen Ende der postnuptialen Mauser in der zweiten Julihälfte trugen die Kontrollerpel (wie alle 15 Vögel in den Vorjahren) das Prachtkleid. Die mit T behandelte Gruppe hatte dagegen ein fast vollständiges Schlichtkleid angelegt. Die DHT injizierten Erpel zeigten ein individuell sehr variables Mischgefieder mit durchschnittlich etwa 70% Schlichtkleid- und 30% Prachtkleidanteil. Die schwächere Wirksamkeit des DHT im Vergleich zu T bei der Induktion des Schlichtkleids wird in Zusammenhang mit einer Aromatisierbarkeit der Androgene zu Estrogenen diskutiert. According to the literature the eclipse colouration in wild Mallard drakes seems to depend on estrogens. I studied the effects of the 2 androgens testosterone (T) and 5α-dihydrotestosterone (DHT) on the induction of eclipse colouration in 15 wild Mallard drakes which were castrated since several years. From the beginning of March to the beginning of May 5 castrates were daily injected with 5 mg T, 5 birds received daily injections of 5 mg DHT, and the remaining served as controls. In the second half of July, near the end of the postnuptial moult, the 5 controls (like all castrates in previous years) exhibited the nuptial colouration. The T treated group had moulted into an almost complete eclipse plumage. The DHT injected birds showed a mixed colouration with distinct individual variation, the estimated average being about 70% eclipse and 30% nuptial plumage. The weaker effect of DHT, compared with T, on the induction of the eclipse colouration is discussed with regard to an aromatization of the androgens to estrogens.

Identification of 5α-dihydrotestosterone in avian plasma

Conscious adult domestic mallard drakes were intravenously injected with tritiated testosterone. After 30 min of in vivo conversion the steroids were extracted from the plasma and submitted to thin-layer chromatography (TLC). Using radiogas chromatography, labeled 5 alpha-dihydrotestosterone (5 alpha-DHT), androsterone, and epiandrosterone could be identified in the androstanolone fraction. 5 alpha-DHT was separated in a second TLC system and definitively identified by recrystallization to constant specific activity.