High-arctic lemmings, Dicrostonyx groenlandicus. II. Demography

1975 ◽  
Vol 53 (6) ◽  
pp. 867-878 ◽  
Author(s):  
W. A. Fuller ◽  
A. M. Martell ◽  
R. F. C. Smith ◽  
S. W. Speller
Keyword(s):  
Significant Variation ◽  
Sexual Maturity ◽  
Late Summer ◽  
High Arctic ◽  
Age Classes ◽  
Devon Island ◽  
Dicrostonyx Groenlandicus ◽  
Early Maturing ◽  
Males And Females ◽  
Old Females

Captures of Dicrostonyx groenlandicus on northeastern Devon Island peaked in 1969 and 1973, were higher than expected in 1971, and were minimal (< 5 per 1000 trap-nights) in 1970 and 1972. Captures declined from July to August in at least five of seven summers and may have declined in a 6th year (1973). No change was detected in 1972. Body size was maximal in 1973 for mature and immature males and females and for all pelage (=age?) classes. Sexual maturity was delayed, at least in males, in 1973. Wintering females conceive under the snow in May and the litter is weaned at the normal time of snowmelt. Two other summer cohorts are produced by surviving old females and early maturing females of the first litters. None of the late summer cohort matures before the onset of winter. No female examined bore more than two summer litters. Mean summer litter size was 5.7 with no significant variation between years. Mean sex ratio was 50.3% male. It is suggested that density-related effects ought to occur in winter, rather than summer, but evidence on this point is equivocal. Arctic adaptations of D. groenlandicus are discussed.

Asynchronous spermatogenesis and biennial female cycle of the viviparous lizard Phymaturus antofagastensis (Liolaemidae): reproductive responses to high altitudes and temperate climate of Catamarca, Argentina

2006 ◽  
Vol 27 (1) ◽  
pp. 25-36 ◽  
Author(s):  
Nora Ibargüengoytía ◽  
Jorgelina Boretto
Keyword(s):  
Reproductive Cycle ◽  
Sexual Maturity ◽  
Late Summer ◽  
Thermal Fluctuations ◽  
Operational Sex Ratio ◽  
Temperate Climate ◽  
Head Width ◽  
Adult Males ◽  
Males And Females ◽  
Reproductive Cycles

AbstractThis paper studies minimum SVL at sexual maturity, sexual dimorphism, operational sex ratio, male and female reproductive cycles, and litter size of viviparous Phymaturus antofagastensis, a species living at high altitude in the temperate climate of Catamarca, Argentina. Males reached sexual maturity at 90 mm, and females at 79 mm. Adult males attained significantly larger body size and head width than adult females. Histological analysis showed asynchrony in spermatogenesis timing among males and spermatozoa storage in epididymis throughout the reproductive season (spring to early autumn). Females showed a biennial reproductive cycle taking at least one activity season to perform either vitellogenesis or pregnancy. Brood size resulted in two offspring, a condition similar to other species of the genus, with births occurring in late summer. The reproductive cycle of Phymaturus antofagastensis shows a new response in males and females to harsh environments characterized by short activity seasons, long hibernation periods and large daily and seasonal thermal fluctuations.

Age, Sex and Season: Factors which Determine the Trap Response of the European Wild Rabbit, Oryctolagus cuniculus

1980 ◽  
Vol 7 (3) ◽  
pp. 421 ◽  
Author(s):  
JC Daly
Keyword(s):  
Individual Differences ◽  
Natural Population ◽  
Breeding Season ◽  
Sexual Maturity ◽  
Oryctolagus Cuniculus ◽  
Adult Population ◽  
Late Summer ◽  
Wild Rabbit ◽  
Males And Females ◽  
Probability Of Capture

Factors determining the trap-response of the rabbit, investigated in a natural population at Urana, N.S.W., included the age and the sex of the rabbit and the season in which it was trapped. Differences were also observed between rabbits living in two adjacent habitats. Mark-recapture data, derived from 52 trips undertaken over 30 months, did not show a uniform probability of capture within the adult population. Adult rabbits were most trappable when they were not breeding (late summer to midwinter); at this time males and females were equally trappable but individual differences were noted. During the breeding season all adults were difficult to trap, males more so than females. Trappability increased with age in young rabbits and declined at sexual maturity. Trap-response was random with respect to the animal's genotype as determined by four polymorphic enzyme loci. Markrecapture- analysis is unlikely to be an accurate means of estimating the parameters of rabbit populations; full enumeration of the population is necessary.

scholarly journals Distribution and abundance of Canadian High Arctic belugas, 1974-1979

2002 ◽  
Vol 4 ◽  
pp. 87 ◽  
Author(s):  
William R Koski ◽  
Kerwin J Finley
Keyword(s):  
Late Summer ◽  
High Arctic ◽  
Delphinapterus Leucas ◽  
Polar Cod ◽  
Canadian High Arctic ◽  
Devon Island ◽  
The North ◽  
Polar Cod Boreogadus Saida ◽  
North Water ◽  
Somerset Island

We conducted >236,000 km of aerial surveys and some supplementary studies of belugas (Delphinapterus leucas) in the central and eastern Canadian High Arctic in 974-79. Belugas that wintered in the “North Water” in Baffin Bay moved southwest into Lancaster Sound in April and early May. The main westward migration into Lancaster Sound occurred over a 2 to 3 week period during late June to late July. Estuaries along Somerset Island were occupied for <3 weeks from mid-July to mid-August. Little feeding occurred in estuaries. From mid-August until fall migration began in mid-September belugas occupied estuaries and offshore waters in Peel Sound. Fall migration eastward through Lancaster Sound was exclusively along the south coast of Devon Island, highly co-ordinated, and rapid; most of the population passed through the sound in <1 week. The whales then moved north along the east coast of Devon Island; some entered Jones Sound while others crossed directly to SE Ellesmere Island. Most calving occurred in July and early August; calving was not seen in estuaries and probably occurred offshore. Excluding calves, adults and yearlings formed 77% and 8.4%, respectively, of the population. The proportion of calves during mid-August was consistent with a triennial calving cycle. During late summer, belugas fed on coastal concentrations of polar cod (Boreogadus saida), under pan ice offshore (probably on cod), and in deep offshore waters. The size of the Canadian High Arctic population in the late 1970s was estimated to be at least 10,250 to 12,000 animals without allowing for animals that may have passed between surveys or that were below the surface at the time of the counts.

A survey of mycorrhizal plants on Truelove Lowland, Devon Island, N.W.T., Canada

1990 ◽  
Vol 68 (9) ◽  
pp. 1848-1856 ◽  
Author(s):  
C. Bledsoe ◽  
P. Klein ◽  
L. C. Bliss
Keyword(s):  
Plant Species ◽  
High Arctic ◽  
Cenococcum Geophilum ◽  
Soil Extracts ◽  
Vaccinium Uliginosum ◽  
Devon Island ◽  
Ericoid Mycorrhizae ◽  
Arctic Regions ◽  
Arctic Soils ◽  
Mycorrhizal Associations

Although mycorrhizal associations are commonly found on roots of most plant species, little is known about the presence or absence of mycorrhizae in arctic regions. In the Canadian High Arctic, roots of 55 herbaceous and woody plant species were examined for mycorrhizae during the summers of 1987 and 1988 on Devon Island, N.W.T. Ectomycorrhizal associations were found on roots of Salix arctica, Dryas integrifolia, and Potentilla hyparctica; ericoid mycorrhizae formed on Cassiope tetragona and Vaccinium uliginosum. Ectomycorrhizal roots were often covered with black hyphae resembling the fungus Cenococcum geophilum; sclerotia characteristic of this fungus were found in soil extracts. Plants expected to have endomycorrhizal associations were apparently nonmycorrhizal in the traditional sense, since no arbuscules, vesicles, or pelotons were found on any roots during two field seasons. Although extensive fungal hyphae were often present on and within roots, these hyphae could not be conclusively identified as endomycorrhizal. Some dark, septate hyphae were present; their function, although unknown, may be beneficial to the host. In a series of greenhouse bioassays using arctic soils, no endomycorrhizal associations developed on test plants. Spores of vesicular–arbuscular fungi were not found in soil extracts. Thus in this survey, only ectomycorrhizal associations were observed, suggesting that the cold, dry winter and cold, wet summer climates in this area of the High Arctic severely limit formation of endomycorrhizae. Key words: roots, fungi, ectomycorrhizae, endomycorrhizae, arctic.

Variation within and between Rivers in Adult Size and Sea Age at Maturity of Anadromous Brown Trout, Salmo trutta

1991 ◽  
Vol 48 (6) ◽  
pp. 1015-1021 ◽  
Author(s):  
Jan Henning L'Abée-Lund
Keyword(s):  
Brown Trout ◽  
Sexual Maturity ◽  
Salmo Trutta ◽  
Adult Size ◽  
Age At Maturity ◽  
Migration Distance ◽  
Spawning Area ◽  
Brown Trout Salmo Trutta ◽  
Males And Females ◽  
The Mean

I compared adult size and sea age at sexual maturity among nine populations of anadromous brown trout, Salmo trutta, in two Norwegian rivers to determine the extent of inter- and intrariverine variations. Variation in the mean length of spawners and in the mean sea age at sexual maturity were mainly dependent on the variations found within rather than between rivers. Mean lengths and mean age at maturity of males increased significantly with increasing altitude of the spawning area and with migration distance in freshwater. In females, positive significant correlations were found with mean lengths and altitude of the spawning area and with mean sea age at maturity and both spawning site altitude and migration distance. Mean lengths and ages of males and females were not significantly correlated with the rate of water discharge in the streams during spawning. The size of gravel substrate for spawning was of minor importance in explaining interpopulation variation in mean female size. The increase noted in mean length and in mean sea age at maturity of both males and females is probably an adaptation to greater energy expenditure to reach the uppermost natal spawning areas.

Taxonomic and ecologic observations of zoosporic fungi in soils of a high-arctic ecosystem

1976 ◽  
Vol 54 (5-6) ◽  
pp. 533-538 ◽  
Author(s):  
Tom Booth ◽  
Paul Barrett
Keyword(s):  
Species Diversity ◽  
Species Composition ◽  
Soil Acidity ◽  
High Arctic ◽  
Arctic Ecosystem ◽  
Devon Island ◽  
Zoosporic Fungi

Phylctochytrium arcticum Barr and Rhizophlyctis harderi Uebelmesser are reported as additional taxa in soils of Truelove Lowland (Devon Island, N.W.T.) and Nowakowskiella spp., Olpidium pendulum Zopf, Pythium irregularae Buisman. Pythium spp., Phlyctochytrium arcticum, and Rhizophydium sphaerotheca Zopf are readily detectable as active organisms in Lowland microhabitats. Species diversity is greatest in mesic and warm soils and species composition of water-logged soils is different than dry soils. Soil acidity effects on distribution are discussed and autecological considerations of Nowakowskiella elegans and R. sphaerotheca with respect to pH, percentage N, C, and P, milliequivalents Ca2+ and Mg2+, moisture, and temperature are presented.

Nitrogen fixation and photosynthesis in high arctic forms of Nostoc commune

1994 ◽  
Vol 72 (7) ◽  
pp. 940-945 ◽  
Author(s):  
R. Lennihan ◽  
D. M. Chapin ◽  
L. G. Dickson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Terrestrial Ecosystems ◽  
Growing Season ◽  
High Arctic ◽  
Colony Morphology ◽  
Nostoc Commune ◽  
Devon Island ◽  
Low Levels ◽  
Temperature Optima

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies of N. commune found on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction in N. commune (2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arctic N. commune but lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1 PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpina and Gleotrichia sp.), N. commune had higher rates of nitrogen fixation. Key words: Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosynthesis.

Breeding characteristics of Townsend's vole (Microtus townsendii) during population fluctuations

1980 ◽  
Vol 58 (4) ◽  
pp. 623-625 ◽  
Author(s):  
Terry D. Beacham
Keyword(s):  
British Columbia ◽  
Sexual Maturity ◽  
Fraser River ◽  
Population Fluctuations ◽  
Peak Density ◽  
Decline Phase ◽  
Early Maturing ◽  
Fraser River Delta ◽  
Peak Phase ◽  
Microtus Townsendii

A 2-year livetrapping study on Townsend's vole (Microtus townsendii) on Reifel Island in the Fraser River delta in British Columbia, Canada, showed that there was an early stop to summer breeding in the peak phase summer compared with the increasing phase summer. Selective dispersal and death of early-maturing voles may account for this result. A delay occurred in the onset of breeding in the decline phase. Voles in peak density populations had the highest median weights at sexual maturity, and males matured at heavier weights than did females.

scholarly journals Longevity of Willow Tits (Poecile montanus): the significance of flock membership, social rank and body size

2018 ◽  
Vol 41 ◽  
pp. 13-18
Author(s):  
Olav Hogstad ◽  
Tore Slagsvold
Keyword(s):  
Body Size ◽  
Social Rank ◽  
Late Summer ◽  
High Rank ◽  
Subalpine Forest ◽  
Social Hierarchies ◽  
Willow Tit ◽  
Males And Females ◽  
Winter Flocks ◽  
Main Factor

The Willow Tit Poecile montanus is highly sedentary and breeding pairs remain in their exclusive areas throughout the year. During the winter, these areas are defended by small, non-kin flocks, formed as the roaming yearlings become sedentary and join adults during late summer and autumn. Once established, stable social hierarchies are maintained in these flocks during the winter. The winter flocks consist normally of the socially dominant adult mated pair and two mated juvenile pairs, one higher-ranked and one lower-ranked. Individually colour-ringed juvenile Willow Tits were followed over years in subalpine forest in Norway from ringing in the autumn till they disappeared. None of the lower ranked birds survived their first winter, whereas only 4 of 71 higher-ranked juvenile pairs disappeared during this time. Half of the 71 pairs survived their first winter, about 25 % survived two winters, 8.5% survived three winters, and 5.6% survived four winters. Survival was similar for males and females. Alpha pairs remained mated and defended their common territory across years. Maximum age as revealed by ringing showed one female became six years old and two males ringed as adults were at least nine years old when last observed. The main factor associated with survival was early flock establishment that led to a high rank position among the juvenile flock members. Body size seemed insignificant. Birds that survived their first winter either succeeded to establish as territory owners or they were forced into the role as floaters and probably perished.

scholarly journals Sexual maturation in Atlantic salmon male parr may be triggered both in early spring and late summer under standard farming conditions

2021 ◽  
Author(s):  
Elia Ciani ◽  
Kristine von Krogh ◽  
Rasoul Nourizadeh-Lillabadi ◽  
Ian Mayer ◽  
Romain Fontaine ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Sexual Maturation ◽  
Late Summer ◽  
Early Spring ◽  
Plasma Testosterone ◽  
Farmed Salmon ◽  
Early Maturing ◽  
Advanced Stages ◽  
One Year ◽  
Immature Fish

AbstractMale Atlantic salmon (Salmo salar) display different sexual strategies, maturing either as parr during the freshwater phase (as sneaky spawners), or as post smolts following one or several years at sea. First sexual maturation (puberty) occurs at different times depending on environmental and genetic factors. To improve our knowledge on the timing (age and season) of first sexual maturation in Atlantic salmon male parr, we investigated pubertal activation in second generation farmed salmon from the Norwegian river Figgjo, reared under natural conditions of photoperiod and water temperature. Histological analysis, in combination with morphometric measurements, plasma androgen levels and pituitary gonadotropin gene expression analysis revealed that, as previously reported, some male parr initiated early sexual maturation in spring at one year of age. Interestingly, some male parr were observed to initiate sexual maturation already in autumn, six months after hatching (under-yearlings), much earlier than reported in previous studies. One-year old maturing males showed a low induction in gonadotropin levels, while under-yearling maturing males displayed a significant increase in fshb transcripts as compared to immature fish. Plasma testosterone, detectable also in immature males, increased constantly during testes development, while 11-ketotestosterone, undetectable in immature and early maturing males, increased during more advanced stages of maturation. A mild feminization of the testes (ovotestes) was detected in a subset of samples. This study brings new knowledge on the little investigated field of sexually maturing under-yearlings in Atlantic salmon. This is also the first study comparing the physiology of under-yearling vs one-year old maturing male parr, thus bringing new insights to the remarkable plasticity of Atlantic salmon puberty.

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