Genetic modelling: an analysis of a colour polymorphism in the Snow Goose (Anser caerulescens)

Previous studies of colour polymorphism in the Snow Goose [ Anser caerulescens ; failed to consider and reject alternative hypotheses to that of a single locus with incomplete dominance. Utilizing data from a long-term study of a wild population, we test the validity of these earlier results by considering two alternatives: (1) a single locus with multiple allelism and (2) a threshold polygenic system. Our analyses corroborate the original model, but emphasize the importance of testing all plausible hypotheses.     

Age effects on clutch size and laying dates of individual female Lesser Snow Geese Anser caerulescens

It is well known in many species of birds that mean clutch size increases and laying date advances with increasing age of the female. This has been interpreted widely as being due to some maturation process in which the performance of individual birds improves as they age. There are two alternative explanations, however. Birds which lay small clutches and lay late may have a higher mortality and be under-represented in the later year samples, or birds with a propensity to lay large and early clutches may enter the breeding population at a later age. In an attempt to discriminate between these alternatives, the reproductive performances of individual Snow Geese were examined over a series of years. Clutch size increased and laying date advanced for these individuals as it did for the population as a whole, thus confirming the maturation hypothesis.     

Changes in Calcium Reserves in Breeding Lesser Snow Geese (Chen caerulescens caerulescens)

Calcium and fat reserves of the femur medullary bone were examined in sexually mature lesser snow geese (Chen caerulescens caerulescens) collected during the 1974–1975 season. In females, femur calcium and fat levels increased by 80 and 30%, respectively, during the spring migration, much of the increase taking place while the birds staged in southwestern Manitoba and North Dakota prior to their departure for the breeding area. In males. femur calcium levels showed no seasonal change but femur fat increased in a manner similar to that found in the females, although the increase was not as great (17%). In the females, femur fat content fell by 40% during egg-laying whereas in males a decrease in femur lipid was not evident until incubation was well underway. Femur calcium levels in females declined during egg production and early incubation, showing a 56% decrease over spring migratory levels, indicating that dietary calcium intake was limited during the nesting period. However, the low femur calcium levels in birds collected during the spring were not significantly different from those of wintering birds, suggesting that no calcium deficiencies were apparent. Plasma calcium levels in males remained relatively constant throughout the year, although there was some elevation in May. Plasma calcium levels in the females increased almost threefold during egg laying and returned to pre-laying levels during incubation. Medullary bone was evident only in reproducing females and appeared during spring migration, concomitant with increased femur weight, fat and calcium content. Medullary bone degradation commenced during the first week of incubation and no medullary bone was in evidence by molt. Calcium reserves of medullary bone accounted for only 17.2% of the calcium required for eggshell production, suggesting that. at least during the laying period, the female must depend on some exogenous source, perhaps from grit or brackish water.     

Seasonal changes in plasma LH levels in domestic ducks.

Seasonal changes in plasma LH concentrations were measured by radioimmunoassay every month for 1 year in nine Khaki Campbell drakes kept under natural lighting conditions in Kiel, Germany. The LH levels rose in all the birds in March and April and reached a mean (+/-S.E.) maximum of 2-4 +/- 0-2 ng/ml early in May. Thereafter, LH levels remained high in three drakes, but decreased in the other six to between 0-9 and 0-4 ng/ml early in June and/or July and rose to about 2-5 ng/ml by the beginning of August. Plasma LH levels started to fall in all nine drakes in September and by early October had reached winter values of about 1-2 to 1-5 ng/ml. A small transient increase in the level of circulating LH was observed in most drakes during November or December.     

Assortative mating and gene flow in the Lesser Snow Goose: A modelling approach

Nonrandom mating with respect to color is well documented in the dimorphic Lesser Snow Goose. A set of mathematical models and data from the long-term study at La Pérouse Bay, Manitoba, Canada are used to examine various hypotheses advanced to explain the mechanisms behind the assortative mating. Among the factors considered are mate choice based on familial color, accidental formation of genetically unrelated families, and nonuniform distribution of colors in the region where mate selection occurs.     

Goose hybrids, captive breeding and restocking of the Fennoscandian populations of the Lesser White-fronted goose (Anser erythropus)

The lesser white-fronted goose (Anser erythropus) isthe most threatened of the Palearctic goose species with a decliningpopulation trend throughout its distributional range. The currentestimate of the Fennoscandian subpopulation size is 30–50 breedingpairs, whereas it still numbered more than 10000 individuals at thebeginning of the last century. Reintroduction and restocking have beencarried out in Sweden and Finland using captive lesser white-frontedgoose stock with unknown origins. We have carried out a study of thegenetic composition of captive-bred stock by sequencing a 221 bphypervariable fragment of the mitochondrial DNA (mtDNA) control regionfrom 15 individuals from the Hailuoto farm, Finland. Two out of thethree maternal lineages detected in the captive stock are also presentin wild populations. The third maternal lineage among the captive lesserwhite-fronted geese originates from the closely related greaterwhite-fronted goose (Anser albifrons). None of the investigatedwild lesser white-fronted goose individuals carried the mtDNA of thegreater white-fronted goose. The presence of greater white-fronted goosemtDNA in the lesser white-fronted goose captive stock suggests thathybridization has occurred during captive propagation.     

Identification of restriction-fragment-length polymorphisms in genomic DNA of the lesser snow goose (Anser caerulescens caerulescens)

A genomic library of partially EcoRI-digested DNA from the lesser snow goose, Anser caerulescens caerulescens, was constructed in the phage vector Charon 4. Phage containing only unique sequences were identified by screening plaques with 32P-labeled genomic DNA. Restriction-fragment- length polymorphisms (RFLPs) were identified by probing DNA from 11-13 male birds from the breeding colony at La Perouse Bay. Of the 17 probes examined, all detected RFLPs with at least one of EcoRi, HindIII, Msp1, and Taq1. Several of them identified highly variable regions with multiple alleles. These RFLPs are valuable DNA markers that can be used for (1) the examination of DNA variation, relatedness, and genetic distance and (2) assessing paternity and maternity. These data suggest that there are higher levels of variation of DNA sequence in birds than had previously been thought to exist.      

Seasonal variations of plasma prolactin and LH concentrations in the female blue fox (Alopex lagopus)

A heterologous radioimmunoassay system developed for the rabbit and suitable for a wide range of mammalian species has been shown to measure prolactin in the plasma of the blue fox. Evaluation of prolactin levels throughout the year showed the concentrations displayed a circannual rhythm with the highest values occurring in May and June. Prolactin concentrations remained low (approximately 2.5 ng/ml plasma) from July until April with no consistent changes found around oestrus (March-April). In 8 pregnant females, the prolactin increase in late April and May coincided with the last part of gestation and lactation: concentrations (mean +/- s.e.m.) increased to 6.3 +/- 0.6 ng/ml at mid-gestation, 9.7 +/- 2.1 ng/ml at the end of gestation and 26.7 +/- 5.0 ng/ml during lactation. In 10 non-pregnant animals, the mean +/- s.e.m. values were 7.2 +/- 1.2 ng/ml in April, 8.8 +/- 2.2 ng/ml in May and 9.8 +/- 1.3 ng/ml in June. The prolactin profile in 4 ovariectomized females was similar to that observed in non-pregnant animals, but the plasma values tended to be lower during the reproductive season (April-June). In intact females, the only large LH peak (average 28 ng/ml) was observed around oestrus. During pro-oestrus, baseline LH levels were interrupted by elevations of 3.1-10.4 ng/ml. During the rest of the year, basal levels were less than 3 ng/ml. In ovariectomized females, LH concentrations increased within 2 days of ovariectomy and remained high (35-55 ng/ml) at all times of year.     

Ultrastructural Studies of Microgametogenesis and Macrogametogenesis of Eimeria truncata of the Lesser Snow Goose1

ABSTRACT. Microgamonts and macrogamonts of Eimeria truncata were observed in renal epithelial cells of collecting tubules and ducts and occasionally in macrophages of experimentally infected lesser snow geese (Anser c. caerulescens) beginning 8.5 days post inoculation. Intraparasitophorous vesicles in parasitophorous vacuoles of both types of gamonts appeared to originate in host cell cytoplasm and enter gamonts through micropores by budding of plasmalemma or by pinocytosis. Within the parasite's cytoplasm, the vesicles were broken down in Golgi-associated vacuoles. The surfaces of microgamonts were highly invaginated to facilitate extrusion of numerous microgametes. Formation and maturation of microgametes were similar to those of other eimerian species. Each microgamete had two flagella, a mitochondrion, and a peculiarly shaped electron-dense nucleus that was oval anteriorly in cross section and somewhat dumbbell-shaped posteriorly. A longitudinally arranged inner membrane complex lay between a portion of the mitochondrion and the plasmalemma. About five subpellicular microtubules extended the length of the microgamete body. Macrogametogony differed little from that described in other eimerian species. Type 1 wall-forming bodies (WFB) formed in Golgi complexes early in macrogametogony, and type 2 WFB formed in cisternae of endoplasmic reticulum in intermediate stages of macrogamont development.     

Seasonal changes in inhibin activity in seminal plasma and serum concentrations of FSH, LH and testosterone in the male goat (Capra hircus)

Inhibin activity in goat seminal plasma was measured by in vitro assay throughout successive 9 months and its relationship with the serum FSH, LH and testosterone concentrations was investigated. Total inhibin activity (TIA) in seminal plasma gradually increased from spring to summer, reduced in autumn (P<0.05) and recovered toward winter (P<0.05). Serum FSH and LH reached a peak in mid-summer (P<0.01) and returned to the low levels in autumn. Serum testosterone also increased in mid-summer and kept the high levels until the early winter (P<0.05). Some positive correlation was found in monthly levels between seminal TIA and serum FSH (r=0.305; P<0.05). Results suggest that the summer increase of inhibin activity in seminal plasma relates with the mid-summer rise of serum FSH levels in the male goat.     

High-altitude respiration of birds. The primary structures of the alpha D-chains of the Bar-headed Goose (Anser indicus), the Greylag Goose(Anser anser) and the Canada Goose (Branta canadensis)

The primary structures of the alpha D-chains of the minor component Hb D of Anser indicus, Anser anser and Branta canadensis are presented. Following chain separation by RP-HPLC, the amino-acid sequences were established by automatic Edman degradation of the globin chains and the tryptic peptides. The three chains show a high degree of homology. For the high altitude respiration the alpha 1 beta 1 interface at position alpha 119 is important. For the Bar-headed Goose a mechanism for high altitude respiration involving both Hb A having alanine at position 119 and Hb D having proline at that position is suggested. Furthermore, a possible genetical development of the avian alpha D-gene expression based on a new B alpha-box mutation in the three geese and an unusual 5' splice junction (GT/GC-transition) in the duck gene is discussed. We consider the possibility that the alpha D-gene is an intermediate between a functional gene, reduced in its expression, and a pseudogene.     

Ultrastructural Studies of the Zygote and Oocyst Wall Formation of Eimeria truncata of the Lesser Snow Goose1

ABSTRACT. Zygote development and oocyst wall formation of Eimeria truncata occurred in epithelial cells in renal tubules and ducts of experimentally infected lesser snow geese (Anser c. caerulescens). Post-fertilization stages were present throughout the kidneys beginning nine days post-inoculation. Initially, a single plasmalemma enclosed the zygote, and type 1 wall-forming bodies (WF1) became labyrinthine and moved toward the surface. There, WF1 degranulated and formed the outer layer of the oocyst wall between the plasmalemma and a newly formed second subpellicular membrane. Several WF2 fused and formed the inner layer, of the oocyst wall between the third and fourth subpellicular membranes. Six subpellicular membranes were observed during wall formation. Other features of oocyst development were similar to those of other eimerian species.     

Isoenzyme status and genetic variability of serum esterases in the lesser snow goose,Anser caerulescens caerulescens

A maximum of 22 bands comprising four esterase subgroups—acetylesterase, carboxylesterase, cholinesterase, and acetylcholinesterase—were detected following electrophoresis of lesser snow goose sera on polyacrylamide gels. A minimum of seven structural genes was surmised to be involved in the biosynthesis of these enzymes following physiochemical characterizations. The genetic variability of these loci was calculated to be 1.25% average heterozygosity, while 14.3% of the loci were polymorphic. These estimates of genetic variability were substantially lower than those reported for other vertebrate species. The low degree of genetic variability found in snow goose serum esterases coupled with the extensive protein multiplicity observed may possibly reflect an adaptive strategy based on biochemical plasticity rather than genic heterozygosity for this species. The nature of evolutionary forces acting upon multiple enzyme systems such as esterases is discussed. The concept of conditional neutrality is introduced and defined within this context.This research was carried out under grants from the National Research Council of Canada and the Canadian Wildlife Service to F. Cooke. J. Grossfield was supported by grants from the National Institutes of Health, GM 21630 and FRAP 10576.     

Seasonal changes in the concentrations of plasma gonadotropins and prolactin in wild mallard drakes

Seasonal changes in the concentrations of plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin were measured in serial samples taken from seven captive wild mallard drakes exposed to natural lighting and temperature in Kiel, West Germany (54 degrees N), for 20 months. The seasonal pattern of plasma LH levels was characterized by high titers during the reproductive phase in the spring, a steep decrease toward the end of this phase (May/June), low levels during the summer, and a second annual peak in the fall. Plasma FSH levels increased during February and March, the period of rapid testicular growth, and reached the highest values at the end of March/beginning of April. Later in the spring FSH levels decreased and remained low for the rest of the year. The concentrations of plasma prolactin increased progressively during April and May, reaching their highest values at the end of the breeding season, coinciding with the steep fall in the levels of plasma gonadotropins. Prolactin concentrations fell during July and August and were at their lowest level in the autumn. It is concluded that the development of photorefractoriness is associated with an increase in the concentrations of plasma prolactin.     

Seasonal changes in testicular contents and plasma concentrations of androgens in the desert gerbil (Gerbillus gerbillus)

Gerbils were caught in the Béni-Abbès area (Algeria). Testicular endocrine activity was highest in spring (testicular wt 298 +/- 10 mg; seminal vesicle wt 603 +/- 62 mg; testicular testosterone and androstenedione content 9.2 +/- 1.7 and 0.5 +/- 0.1 ng/testis; plasma testosterone 832 +/- 200 pg/ml). Values decreased in summer, were lowest in late summer and in autumn (84 +/- 17 mg; 40 +/- 14 mg; 0.20 +/- 0.06 and 0.02 +/- 0.01 ng/testis; 228 +/- 54 pg/ml, respectively) and increased again in winter (December-January). The onset of testicular endocrine activity was concomitant with the lowest temperatures and the shortest photoperiod; it increased when temperatures and daylength were increasing and began to decline when temperatures and photoperiod were still maximal. These seasonal changes in the endocrine activity of the testis of the gerbil differ from those of the sand rat inhabiting the same area.