The behavior of peripheral males during the mating season inMacaca fuscata

The mating season behavior of peripheral male Japanese macaques (Macaca fuscata) at Arashiyama West were studied during the 1994/1995 mating season. Although all peripheral males increased their proximity to the main troop, there was great variation in this behavior, from those who became virtually indistinguishable from the main troop males to those who moved in and out of the main troop in a clandestine fashion, to those who had only visual contact, from a distance of 25 m, with the main troop. The subsequent behavior of males displaying these patterns was compared, as was the behavior of peripheral to main troop males. Specifically, they were investigated for variation in three behavioral strategies which may function to increase access to mates: aggressive intimidation; affiliation with unrelated main troop females; and courtship display. The results show that peripheral males are a more diverse group than previously described, and that one group of peripheral males was able to successfully join the main troop, becoming indistinguishable from main troop males with regard to these behaviors which enhance access to mates.     

Food selection by brook trout in a subalpine stream

The diet and food selection of brook trout (Salvelinus fontinalis) and macroinvertebrate drift are described for a high altitude stream (3 205 m above mean sea level) adjacent to the alpine zone on the Snowy Range in the Medicine Bow National Forest, Wyoming. Diet composition differed between brook trout of two length classes, 150 mm and > 150 mm in total length. The number of prey organisms per stomach generally declined and the proportion of terrestrial prey items increased from July to September, 1985. Fish of both length classes selected for Trichoptera and Coleoptera over the three sampling months, and fish > 150 mm also selected for terrestrial insects in August and September.The Unit is jointly supported by the University of Wyoming, the Wyoming Game and Fish Department, and the US Fish and Wildlife ServiceThe Unit is jointly supported by the University of Wyoming, the Wyoming Game and Fish Department, and the US Fish and Wildlife Service     

The energetic cost of mating in a promiscuous cephalopod

Costs that individuals incur through mating can play an important role in understanding the evolution of life histories and senescence, particularly in promiscuous species. Copulation costs, ranging from energy expenditure to reduced longevity, are widely studied in insects but have received substantially less attention in other taxa. One cost of mating, the energetic cost, is poorly studied across all taxa despite its potential importance for the many species where copulation is physically demanding and/or frequent. Here, we investigated the energetic cost of mating in both male and female dumpling squid (Euprymna tasmanica). In this species, copulation can last up to 3 h and requires that the male physically restrains the female. We report that the act of copulation halves the swimming endurance of both sexes, and that they take up to 30 min to recover. Such a reduction in post-copulatory performance may have important implications for predator avoidance, foraging ability and energy allocation. Therefore, quantifying this cost is essential to understand the evolution of reproductive strategies and behaviours such as female receptivity and male and female mating frequency.     

Learning ability of triploid brook trout

Triploid brook trout ( Salvelinus fontinalis ) did not differ from diploids in their initial directional preference within a Y-maze, electrical shock response threshold, or learning ability.     

The role of alpha 2-macroglobulin in furunculosis: a comparison of rainbow trout and brook trout.

1. The molecular basis for the high survival rate of rainbow trout, Oncorhynchus mykiss, infected with furunculosis was investigated. 2. Alpha 2-macroglobulin (alpha 2M), a major serum protease inhibitor, was partially purified from rainbow trout and brook trout, Salvelinus fontinalis, sera; the latter species shows marked disease susceptibility. 3. It is shown that a 10-fold species-based difference in alpha 2M inhibitory activity exists against a furunculosis associated bacterial protease. 4. A possible basis for the observed disparity is discussed. 5. Results suggest that the high mol. wt form of teleost (trout) albumin is a dimer composed of two 85,000 subunits.     

The critical swimming velocity of diploid and triploid brook trout

No significant difference was found in the critical swimming velocity of diploid and triploid brook trout Salvelinus fontinalis , suggesting that the triploid state is not associated with a reduced aerobic capacity.     

Silver-banded karyotypes of the rainbow trout and the brook trout and their hybrids: disappearance in allotriploids of Ag-NORs originated from the brook trout

Silver-banded karyotypes of the rainbow trout Salmo gairdneri, the brook trout Salvelinus fontinalis, and their hybrids were described. Diploid-type and triploid-type hybrids were obtained. Triploid-type hybrids had two maternal genomes of the rainbow trout and one paternal genome of the brook trout. The rainbow trout had one pair of M or SM with Ag-NORs near the satellite. In the brook trout, Ag-NORs were observed in four pairs of chromosomes, but each cell had different number of chromosomes with Ag-NORs. In all observed cells of triploid-type hybrids, Ag-NORs originated from the brook trout were not recognized, whereas those from the rainbow trout were found.     

The population dynamics of young trout (Salmo trutta L.) in a Danish brook

The population size, dispersal of fry, growth of fry in relation to density, mortality and production of young trout ( Salmo trutta L.) were studied in a Danish brook during 1970–1972. In the first few months after emergence downstream emigration of fry took place both in 1971 and 1972, after which the trout became stationary. Growth was inversely density dependent and mortality was density dependent in the months just after emergence. Later mortality was constant and independent of density. Trout production varied between 10 g/m² and 18.6 g/m² in the 2 years.     

Population response to habitat fragmentation in a stream-dwelling brook trout population

Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival ( approximately 45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tributary populations caused rapid (2-6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7-46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results suggest that local adaptation can 'rescue' isolated populations, particularly in one-dimensional stream networks where both natural and anthropogenically-mediated isolation is common. However, whether rescue will occur before extinction depends critically on the race between adaptation and reduced survival in response to fragmentation.     

The cost of males in Daphnia pulex

Sex is paradoxical, because asexuals should replace their sexual ancestors by avoiding the demographic cost of producing males (hereafter referred to as the cost‐of‐males). Despite the large body of theoretical and empirical work dealing with the paradox of sex, the cost‐of‐males assumption has been rarely tested. In the present study, we tested the cost‐of‐males assumption in the cladoceran Daphnia pulex. Populations of this species consist of both cyclically parthenogenetic (i.e. sexuals) and obligately parthenogenetic (i.e. asexuals) lineages. In addition, some of the asexual lineages produce only female offspring, whereas others produce functional males, which can mate with sexual females. We compared the reproductive investment of sexuals, male‐producing asexuals, and non‐male‐producing asexuals when raised separately under various environmental conditions. We also determined the outcome of competition between pair‐wise combinations of these reproductive modes. The cost of males was evident when sexual and asexual females were raised separately: sexuals produced fewer female offspring. However, there was no cost of males when reproductive modes were raised in pairs, as sexuals won the competition with asexuals. Our results directly relate to the field conditions experienced by D. pulex. Sexuals might suffer the cost of males at the beginning of the season, when resource competition is low; but when conditions deteriorate as the population approaches carrying capacity, sexuals seem to be better competitors in spite of male production.     

Influence of growth rate on white muscle dynamics in rainbow trout and brook trout

In trout, fast growth stimulated white muscle fibre hypertrophy ( P 0·001) and hyperplasia ( P <0·01) in outer fibres but not in deep fibres. Glycogen was most prevalent in outer fibres ( P <0·01) and in brook trout ( P <0·01) that on average had three to four times larger fibres than rainbow trout.     

Non‐native trout limit native brook trout access to space and thermal refugia in a restored large‐river system

We used direct observation via snorkeling surveys to quantify microhabitat use by native brook (Salvelinus fontinalis) and non‐native brown (Salmo trutta) and rainbow (Onchorynchus mykiss) trout occupying natural and restored pool habitats within a large, high‐elevation Appalachian river, United States. Permutational multivariate analysis of variance (PERMANOVA) and subsequent two‐way analysis of variance (ANOVA) indicated a significant difference in microhabitat use by brook and non‐native trout within restored pools. We also detected a significant difference in microhabitat use by brook trout occupying pools in allopatry versus those occupying pools in sympatry with non‐native trout—a pattern that appears to be modulated by size. Smaller brook trout often occupied pools in the absence of non‐native species, where they used shallower and faster focal habitats. Larger brook trout occupied pools with, and utilized similar focal habitats (i.e. deeper, slower velocity) as, non‐native trout. Non‐native trout consistently occupied more thermally suitable microhabitats closer to cover as compared to brook trout, including the use of thermal refugia (i.e. ambient–focal temperature >2°C). These results suggest that non‐native trout influence brook trout use of restored habitats by: (1) displacing smaller brook trout from restored pools, and (2) displacing small and large brook trout from optimal microhabitats (cooler, deeper, and lower velocity). Consequently, benefits of habitat restoration in large rivers may only be fully realized by brook trout in the absence of non‐native species. Future research within this and other large river systems should characterize brook trout response to stream restoration following removal of non‐native species.     

Seasonal changes in the physiology of brook trout, Salvelinus fontinalis (Mitchill), in a sub-Arctic river system

Wild herring larvae were sampled from the Firth of Clyde, Scotland in 1980 and 1981 to assess the suitability of otolith ageing methods for herring larval studies. The ages and growth rates were estimated directly from otolith ring counts, by comparison of ring counts with the results of validation studies on reared larvae of known age, and by back-calculation. Growth rates based on otolith data were compared with indirect calculations based on length at capture. The assumption of daily ring deposition, even allowing for a period of lag before the initiation of daily ring deposition, led to incorrect predictions for age at yolk-sac absorption, and back-calculations led to overestimated growth rates, indicating that ring deposition does not begin at hatching and that light microscope counts give a rate different from one ring per day in wild herring larvae.     

Sperm stock and mating of males in a parasitoid wasp

Hymenoptera are haplodiploid insects, consequently sex ratio depends on female's sperm management which itself arises from the reproductive capacity of neighbouring males. To study the influence of ageing on male reproductive potential, laboratory experiments were conducted on Dinarmus basalis (Hymenoptera, Pteromalidae) males, a tropical wasp in which sperm counts are known to constrain sex ratio. Two groups of virgin males were compared: 1-day and 30-days old. Parameters recorded were sperm quantity and viability in seminal vesicles, shape of testis, mating ability in both individual and competitive situations and sperm stored by females after male multiple mating. Older males had twice as much sperm as young males, but their reproductive capacities did not differ. They were able to copulate with 20 successive virgin females in a short period. Sperm stored in spermathecae decreased with female mating order. In competition, old and young males had the same access to females. The difference between old and young males was visible at the level of reproductive tract: young males have functional testis and old males have empty non-functional testis. Spermatozoa are kept viable in male seminal vesicles for long periods. In this species, the reproductive potential of males is not altered by ageing. At the population level this may represent an adaptation for maintaining continuous reserves of sperm at the disposal of females.     

Responses of pineal photoreceptors in the brook and rainbow trout

Summary Electron microscopy of the pineal receptor cells in light- and dark-adapted brook trout, Salvelinus fontinalis and the rainbow trout, Salmo gairdneri, revealed no significant differences in the tubular and filamentous elements of the inner segment, neck and supranuclear regions. However, changes in synaptic relations between the photoreceptor and nerve cell were induced by light and darkness. In the light-adapted state, the synaptic relationship between axon terminals and photoreceptor basal processes predominates, while in darkness the synapses between photoreceptor basal processes and ganglion cell dendrites are more prominent. Further, in darkness, the photoreceptor basal processes show a number of synaptic vesicles and synaptic ribbons. These findings suggest that the sensory function of the fish pineal is enhanced during darkness but inhibited by light, and that the synaptic relationships are involved in the control of sensory activity in the pineal photoreceptor and ganglion cells. These results corroborate those of electrophysiological studies in that the maximal spontaneous discharge frequency of the ganglion cells occurs in the dark, and it also shows a burst when light is removed. The typical chemical synapse between the axon terminal and the photoreceptor basal process in light seems to function as an inhibitor.The authors thank Dr. Mary Ann Klyne for her assistance in several aspects of this work. Financial assistance was provided by the NSERC of Canada and the Ministry of Education of Québec     

The physiological response of diploid and triploid brook trout to exhaustive exercise

Using triploidy as an experimental model, we examined whether cell size limits the post-exercise recovery process in fish. Because triploids generally possess larger cells, which could affect many physiological and biochemical processes, we hypothesized that triploids would take longer to recover from exhaustive exercise compared to diploids. To test this, we measured plasma lactate, glucose and osmolality, and white muscle energy stores (glycogen, phosphocreatine and ATP) and lactate before and immediately following exhaustive exercise and during recovery at 2 and 4 h post-exercise. In addition, oxygen consumption and ammonia excretion rates were determined before and after exhaustive exercise. Overall, diploid and triploid brook trout showed similar metabolic responses exercise, but plasma osmolality, white muscle lactate, white muscle ATP and post-exercise oxygen consumption rates recovered earlier in triploids compared to diploids. The results of this study suggest that the characteristic larger cell size of triploidy does not limit the physiological response to, or recovery from, exhaustive exercise.     

Heritability of morphology in brook trout with variable life histories

Distinct morphological variation is often associated with variation in life histories within and among populations of both plants and animals. In this study, we examined the heritability of morphology in three hatchery strains of brook trout (Salvelinus fontinalis), which were historically or are currently used for stocking and supplementation of both migratory and resident ecotypes in the upper Great Lakes region. In a common garden experiment, significant variation in body morphology was observed within and across populations sampled at three time periods. The most notable differences among strains were differences in dorso-ventral body depth and the shape of the caudal peduncle, with some differences in the anterior-posterior placement of the dorsal and ventral fins. Variation with and among 70 half-sib families indicates that heritabilities of morphology and body size were significant at most developmental time points both within and across strains. Heritabilities for morphological characters within strains ranged from 0 to 0.95 across time points. Significant within-strain heritabilities for length ranged from 0 to 0.93 across time points and for weight ranged from 0 to 0.88. Significant additive genetic variation exists within and across hatchery brook trout strains for morphology and size, indicating that these traits are capable of responding to natural or artificial selection.