Lemmus Trimucronatus Research Articles

Development of Pelodera strongyloides (Schneider, 1860) Schneider, 1866 (Nematoda: Rhabditidae) in culture.

Dauerlarvae of Pelodera strongyloides, recovered from two species of lemmings, Dicrostonyx groenlandicus (Traill) and Lemmus trimucronatus (Richardson) trapped at Eskimo Point, N.W.T, were cultured on agar medium with E. coli. Development from egg to adult stage was followed. Eggs hatched between 22 and 26 hours at 22 degrees C. The first moult occurred 24 to 28 hours after the eggs hatched, the second at 40 to 48 hours, the third at 60 to 64 hours and the fourth at 84 to 88 hours at 22 degrees C. Adults lived approximately 5 to 6 days and females oviposited for 2 to 3 days during this time. All stages were measured and described. The effect of temperature on development was examined. Dauerlarvae survived freezing temperatures, short periods of desiccation and prolonged periods without food.

The Effects of Cross-Fostering On the Behavior of Two Species of North American Lemmings, Dicrostonyx Groenlandicus and Lemmus Trimucronatus. Iii. Agonistic Behavior

Abstract 1. The role of the maternal environment in development of species-specific agonistic behavior was investigated by reciprocally cross-fostering two species of lemmings (Discrostonyx groenlandicus and Lemmus trimucronatus). Non-fostered and within-species-fostered (in-fostered) animals served as controls. 2. When adult, cross-fostered male lemmings engaged in more frequent contact social behavior with the foster species than with conspecifics. However, since cross-fostered animals retained their ability to interact with conspecifics in a species-specific manner, cross-fostering appears to have resulted in a broadening of "species identity" to include the foster species. 3. In-fostering reduced the aggressiveness of Dicrostonyx but had little effect on the behavior of Lemmus. 4. Both the intensity and orientation of agonistic behavior were altered as a result of cross-fostering. In Dicrostonyx, a highly aggressive species, cross-fostering resulted in decreased aggression directed at the foster species and increased aggression toward conspecifics. In Lemmus, a less aggressive species, cross-fostering appears to have resulted in a broadening of the response range to stimuli provided by the foster species. When paired with aggressive Dicrostonyx, cross-fostered Lemmus engaged in more frequent and intense aggression than did controls. However, when paired with nonaggressive (in-fostered) Dicrostonyx, cross-fostered Lemmus engaged in less frequent and intense aggression than controls. In contrast, non-fostered and in-fostered Lemmus males had a relatively narrow response range to Dicrostonyx. 5. In general, the results suggested that agonistic behaviour in lemmings is the product of a complex interaction between genotype and maternal environment.

Interspecific aggression in captive male lemmings

Two experiments were conducted with lemmings to determine which of two species, Lemmus trimucronatus and Dicrostonyx groenlandicus, was capable of exercising aggressive social dominance over the other in staged, dyadic encounters, and which was able to outcompete the other for a single shelter. Agonistic behaviour occurred in all dyadic encounters, but dominance was not established by either species. A sequential analysis of encounters revealed that each species had a distinct fighting strategy. In shelter competition, prior residence was a crucial factor in the outcome. However, one species did not completely exclude the other. Further evidence to support species differences in fighting strategies was derived from the shelter experiments. These results are discussed in relation to ecological considerations.

Estrogen and progesterone interactions influencing sexual and social behavior in the brown lemming, Lemmus trimucronatus

The effects of estrogen and progesterone on the social and sexual behavior of brown lemmings, Lemmus trimucronatus, were investigated. The behavior of hormone-treated and untreated ovariectomized females and sexually vigorous males was observed in six consecutive daily 5-min dyadic encounters. Sexual receptivity, as measured by lordosis, and other social behaviors including nasonasal contact, boxing postures, allogrooming, perineal investigation, and male mounting increased following 48 hr of exposure to daily injections of 0.5 μg estradiol benzoate (EB). Lordosis in EB-primed females was not facilitated or inhibited by short-term (4 hr) exposure to 0.5 mg progesterone (P). Long-term (greater than 24 hr) exposure to P apparently inhibited lordosis and other social behaviors in EB-treated females, although males continued to attempt to mount these females. In EB-treated females a dramatic increase in threat-leaps, directed by the female toward the male, was observed within 4 hr of P injection. Threat-leaps declined when P was withdrawn. Threat-leaps were also observed in ovariectomized females after prolonged exposure to P only (0.5 mg/day). Vaginal perforation and cornification were first apparent 48 hr after EB injection. P-alone treated ovariectomized females also showed vaginal perforation but cornified cells were infrequent and these animals did not show lordosis.

Dauerlarvae of Pelodera strongyloides (Schneider, 1860) (Nematoda: Rhabditidae) in the conjunctival sacs of lemmings

Dauerlarvae of Pelodera strongyloides (Schneider, 1860) Schneider, 1866 were found for the first time in the conjunctival sacs of Dicrostonyx groenlandicus (Traill) and Lemmus trimucronatus (Richardson). Prevalence of dauerlarvae was significantly higher in D. groenlandicus than in L. trimucronatus. The larvae were cultured and populations of P. strongyloides were obtained. Dauerlarvae obtained from the cultures were transmitted to various rodents in the laboratory. Larvae remained in the conjunctival sac for a maximum of 5 days. They had no apparent effect on rodents and were not morphologically different from those reared on agar.

Perianal Pouches of Male Brown Lemmings, Lemmus trimucronatus, and a Technique for Determining the Reproductive Status of Live Animals

The cauda epididymides of male brown lemmings, Lemmus trimucronatus, are located in a pair of perianal pouches. In sexually mature animals, these pouches are heavily pigmented and swollen. In immatures, the perianal area is not noticeably different from the adjacent skin. Development of pigmentation and swelling is closely correlated with attainment of sexual maturity and may be used as a reliable predictor of the animal's sexual status.

The perineal gland of brown lemmings, Lemmus trimucronatus

In adult male brown lemmings, Lemmus trimucronatus, a specialized pad of sebaceous glands forms the perineal gland, consisting primarily of two longitudinal ridges lateral and parallel to the midventral line of the scrotum. The ridges extend from the posterior margin of the penis sheath to the anterior edge of the rectum, and correspond externally with a pair of longitudinal furrows. Externally, the gland is characterized by brown pigmentation and coarse, transparent hairs. Histologically it is comparable to, though larger than, the rump gland of the same species. Development of the perineal gland is correlated with attainment of sexual maturity.On the basis of other studies analogous skin glands in other rodents, a scent-producing function is hypothesized for the perineal gland.

Continuous light and physiology of Arctic birds and mammals.

Many investigations of pineal function have been conducted on animals experiencing artificial laboratory environments. The use of species that naturally experience extreme conditions, such as constant light or darkness, is suggested as a possible way to clarify some of the confusion that exists in the pineal literature at the present time. Arctic species are adapted to an environment in which conditions of constant light are naturally replaced with periods of alternating light. Other conditions of the arctic also vary, including temperature, wind, precipitation, available food, and inter- and intra-species interactions. Arctic species must be highly attuned to their harsh environment. Four species of arctic homeotherms have particular promise as models for the study of pineal function: Snowy owls (Nyctea scandiaca ) and short-eared owls (Asio flammeus ), in contrast with most other owls, must annually switch from being day-active to being at least partially night active. The Arctic fox (Alopex lagopus ) shows regular circannual variations in several parameters alleged to be under the influence of the pineal in other species, including reproduction, activity levels, and seasonal molts. Lemmings (Lemmus trimucronatus ) have two periods of reproductive activity per year, one at the height of the constant light season, and a less intense period that coincides with minimal light. Hormonal activity and possibly pineal activity in lemmings is also implicated in periodic, large scale population fluctuations.

A Radiotracking Study of Home Range and Activity of the Brown Lemming (Lemmus trimucronatus)

Home range was determined for brown lemmings by a radiotracking procedure throughout June and July 1972–1973 with 1795 location fixes obtained for 12 adult males, 10 adult females, and three juveniles (<20 grams) in 1972 and 3000 fixes recorded from 13 males and 12 females in 1973. Home range was calculated by the minimum area method. For 1972 animals mean male home range measured 1.33 ha (hectare) (S.D. .986, range .183 to 2.85 ha); mean female home range was .681 ha (S.D. .901, range .143 to 1.454 ha). For 1973 animals, mean male home range was .876 ha, (S.D. 1.0, range .0004 to 2.80 ha); mean female home range was .413 ha, (S.D. 1.03, range .015 to 1.68 ha). Males tended to have larger home ranges than females; 1972 home ranges tended to be larger than those of 1973 but these differences were not statistically significant. An indirect measure of activity termed change in location was defined as a difference of 2° or more in successive fixes. An analysis of this measure indicated males were significantly more active than females during both years, and 1972 animals were significantly more active than those studied in 1973. Activity was also measured directly by a telemetering system. For a sample of three males and three females, it was determined that males were active (for example, moving, feeding, and grooming) 75 percent of the time during a 24-hour period; females were active 67 percent of the time. Males spent about 69 percent of a 24-hour period outside of burrows, females 55 percent.

Activity Patterns in Natural Populations of the Brown Lemming (Lemmus trimucronatus)

Activity Patterns in Natural Populations of the Brown Lemming (Lemmus trimucronatus)

Carbohydrate reserves of wild rodents from different latitudes

Liver and muscle glycogen, plasma glucose and urea concentrations were compared in thirteen species and subspecies of wild rodents raised and sacrificed under standard conditions ( Microtus oeconomus macfarlani, Microtus oeconomus operarius, Microtus pennsylvanicus, Microtus pennsylvanicus tananaensis, Peromyscus maniculatus bairdii, Peromyscus maniculatus borealis, Calomys ducilla, Calomys callosus, Acomys cahirinus, Lemmus trimucronatus, Lemmus lemmus, Dicrostonyx groenlandicus and Clethrionomys rutilus). o 1. Muscle glycogen concentrations showed a direct relation to latitude with mean values ranging from 0·5 mg/g ( C. callosus) to 2·8 mg/g ( M. o. macfarlani). 2. Plasma glucose concentrations were inversely related to lattitude with values ranging from 1·9 mg/ml ( A. cahirinus) to 0·8 mg/ml ( M. o. operarius). 3. Liver glycogen concentrations showed no clear trend with values ranging from 10 mg/g ( C. callosus) to 23 mg/g ( M. pennsylvanicus) with the three lemmings forming a distinct subset with values below 5 mg/g. 4. Highland C. ducilla (3·8 km) conformed to its thermal environment (∼45–50° lat.) rather than its actual latitude. 5. Urea levels for species ranged from 0·21 to 0·32 mg/ml (average 0·25) but showed no obvious pattern.

A Simulation Model of Energy Acquisition and Utilization by the Brown Lemming Lemmus trimucronatus at Barrow, Alaska

A mathematical model is developed for the ecological energetics of individual brown lemmings. This model incorporates expressions for obtaining energy through grazing as a function of grass and sedge density, size of the lemming and its energy needs. Utilization of energy is divided into maintenance metabolism, growth, and reproduction. Expressions for energy spent in reproduction include growth of fetuses and growth of young before weaning. The consequences of the assumptions of the model are shown in a series of graphs relating groups of variables. Computer simulations suggest that availability of energy may be a critical factor for reproductive females (especially small ones) during the winter. During most summers availability of food should present no problem. On the basis of the simulation model several critical areas for further research are identified. Most important among these are the relationship between food density and consumption rate, deposition and utilization of fat, the time-activity budget of animals in their natural habitat, and the functional relationships between maximal growth rates and other variables such as age and sex.

Fatty acid composition of tissue lipids of captive and wild brown lemmings

1. 1. The fatty acid composition of the lipids of white adipose tissue (WAT), brown adipose tissue (BAT), skeletal muscle (MUS) and liver was determined from brown lemmings ( Lemmus trimucronatus Merriam = L. sibiricus Kerr) subjected to different conditions of captivity and from wild lemmings caught in the field at Barrow, Alaska. 2. 2. The slight changes in the fatty acid composition of WAT, BAT or MUS of captive lemmings acclimated to two different diets, two ambient temperatures (5 and 20°C) and two photoperiods (16 and 0 hr of light/24 hr) were not statistically significant. 3. 3. The fatty acid composition of the livers of captives differed with diet and with acclimation temperature becoming more unsaturated in the cold. 4. 4. There were marked seasonal differences in the fatty acid composition of WAT, BAT and liver of wild caught lemmings. Muscle was not analyzed. High amounts of linolenic acid in summer and of linoleic acid in winter may have been correlated with diet. 5. 5. There was an increase in the percentage unsaturation of the fatty acids in WAT and BAT during winter but not of those in liver. The double-bond index, indicating the degree of unsaturation, was also high in winter but remained high in summer due to large amounts of linolenic acid in the tissues.

Preliminary Evidence of Periodontal Disease in Lemmus trimucronatus Skulls from Northern Alaska

A random collection of 100 Lemmus trimucronatus skulls obtained on the tundra near Point Barrow, Alaska, were examined for evidence of periodontal disease. Alveolar bone pathosis was observed in 26% of the skulls. The severity or frequency of this disorder in lemming populations may show cyclic fluctuations that can be correlated with the cyclic fluctuations of population density.

Efficiency of Winter Scavengers in the Arctic

Frozen carcasses of brown lemmings, Lemmus trimucronatus , were systematically placed under the snow in various tundra habitats in the fall of 1961 (188), 1962 (201) and 1963 (205) near Barrow, Alaska. Only 8 carcasses were recovered in the following springs. Removal of the carcasses is attributed to: arctic fox ( Alopex lagopus) and red fox ( Vulpes fulva ); brown lemming; the least weasel ( Mustela rixosa ). Observations of behaviour, systematic trapping and examination of scats were used to suggest the relative importance of these consumers of lemming carrion in the order given above. The inability of investigators of lemming population cycles to find the carcasses of lemmings that die during the winter months is explained by the unusual efficiency of these species in locating and using frozen carrion during the winter months.

Seasonal changes in lemming pituitary-adrenal response to cold exposure

1. 1. Seasonal variation of lemming ( Lemmus trimucronatus and Dicrostonynx groenlandicus) adrenal activity was confirmed. 2. 2. Cold acclimation enabled D. groenlandicus to maintain pituitary-adrenal (response) integrity when animals were challenged with severe cold exposure (−40°C for 2 hr), and to survive the cold stress longer. 3. 3. Cold acclimation of L. trimucronatus did not noticeably improve pituitary-adrenal integrity, but did improve survival time. 4. 4. Lemmings from low-density populations displayed similar adrenal-pituitary status to those previously recorded; whether lemmings from high density populations show similar resistance to additional (cold) stress awaits further tests during the lemming cycle.

Endocrine adjustments in a wild lemming population during the 1969 summer season

1. 1. Wild-caught and laboratory-reared, group-housed brown lemming ( Lemmus trimucronatus) were compared regarding pituitary-adrenal and gonadal function. 2. 2. Early trapping periods yielded higher numbers of animals (for equivalent effort) than did later periods; animals which emerged from the snow in June displayed marked adrenal hypertrophy, high basal levels of adrenal steroid secretion, high pituitary ACTH content, and lower sensitivities to exogenous ACTH. 3. 3. Females were less sensitive to adrenal stimulation than were males, and had lower pituitary ACTH content; gravid females were particularly resistant to both ACTH effects and effects of climate and social pressure. 4. 4. Differential mortality of males was revealed by the trapping regimen, and this mortality was consistent with signs of stress (adrenal hyperfunction, cardiac hypertrophy and renal disease) which were more pronounced in males. 5. 5. It was concluded that both physical environmental and social environmental changes modify endocrine balance in wild lemming populations, and that the endocrine status of the population markedly affects both input and output phases of population dynamics. 6. 6. Gross pathological changes which may contribute to mortality are discussed.

Reproduction In Brown Lemmings (&lt;i&gt;Lemmus trimucronatus&lt;/i&gt;) and Its Relevance to Their Cycle of Abundance, by David A. Mullen

Reproduction In Brown Lemmings (&lt;i&gt;Lemmus trimucronatus&lt;/i&gt;) and Its Relevance to Their Cycle of Abundance, by David A. Mullen

Circadian Locomotor Rhythms of Rodents in the Arctic

In both the arctic and subarctic regions of Alaska during the spring and summer pronounced daily periodicity was observed in the field and running-wheel activity of the following diurnal and "nocturnal" rodents: Spermophilus undulatus, Clethrionomys rutilus, Lemmus trimucronatus, Microtus miurus, and M. oeconomus. Animals whose phases were shifted to abnormal times of the day by artificial light cycles regained their normal phases when exposed to the local field conditions. However, difficulty in retaining proper phase was observed in several of these nocturnal species at the time of the summer solstice, i.e., at the time when the amplitude of the daily cycle of illumination is lowest. The usually nocturnal L. trimucronatus centered their activity about noon at this time of year. Temperate zone rodents (Ammospermophilus leucurus and Peromyscus leucopus) taken to Point Barrow, Alaska, also showed pronounced daily periodicity under arctic conditions, although the latter species did not show locomotor activity until August, when the sun moved below the horizon near midnight. All of the species studied from both the arctic and temperate zones were found to have endogenous circadian rhythms of activity. Laboratory experiments showed that those rhythms could be entrained by square wave and approximately sinusoidal cycles of illumination even when the amplitude of the entraining light was as small as that encountered at Point Barrow at the summer solstice (max:min = 23:1). However, individuals differed in their ability to entrain successfully to some light cycles. These experiments and field observations support the conclusion that in the arctic, even during the summer, the environmental light cycle is the principal entraining agent of the endogenous rhythm. When the amplitude of the light cycle was insufficient to entrain an animal "oscillatory free-runs" were frequently observed, i.e., as an organism's rhythm free-ran across the light cycle its period changed systematically. The functional significance of a pronounced circadian locomotor rhythmicity in the arctic may be attributed to two factors: (1) its usefulness during that restricted part of the year when light and dark occur every day, and (2) its historical derivation from temperate zone ancestors, its ability to entrain to low amplitude light cycles being a part of that inheritance.

Notes on the Small Mammals of Churchill, Manitoba

The Churchill area lies in the important zone of transition between the boreal forest which lies to the south and west, and the tundra which extends to the north. This region is inhabited by a large and varied fauna with both forest and tundra forms represented. Among the mammals, certain boreal forest species such as the squirrel, Tamiasciurus hudsonicus; the voles, Clethrionomys gapperi, Phenacomys intermedins and Synaptomys borealis; and the jumpingmouse, Zapus hudsonius , reach the northern limit of their range up the west coast of Hudson Bay in this region. Here too, tundra species such as the hare, Lepus arcticus , the lemmings, Lemmus trimucronatus and Dicrostonyx groenlandicus; and the fox, Alopex lagopus , reach or near their southern distribution limit. The first comprehensive account of the mammals of Churchill is by Preble (1902) who cites most of the scattered early references to mammals, and who reports on collections made there during three weeks in August, 1900. This contribution is still the most useful report on this region, especially with respect to the larger mammals. Workers who have subsequently added to our knowledge of Churchill mammals include: Breckinridge (1936), who collected a few specimens in 1933; Shelford and Twomey (1941), who were concerned primarily with tundra communities; Shelford (1943), who discusses lemming population changes; and Quay (1955), who records brief notes on three species of mammals collected in 1953. In addition, Rand (1948) reports on the mammals of the Herb Lake-Flin Flon area of west-central Manitoba, and appears to be the only other author who deals with the mammals of any part of the entire northern half of the province of Manitoba. During recent summers, the authors had the opportunity to study mammals in the Churchill area while engaged in biological field investigations of a …