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Journal articles on the topic "Femmes biologistes"
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Roitberg, B. D., G. Boivin, and L. E. M. Vet. "Fitness, parasitoids, and biological control: an opinion." Canadian Entomologist 133, no. 3 (June 2001): 429–38. http://dx.doi.org/10.4039/ent133429-3.
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AbstractFitness, defined as the per capita rate of increase of a genotype with reference to the population carrying the associated genes, is a concept used by biologists to describe how well an individual performs in a population. Fitness is rarely measured directly and biologists resort to proxies more easily measured but with varying connection to fitness. Size, progeny survival, and developmental rate are the most common proxies used in the literature to describe parasitoid fitness. The importance of the proxies varies between papers looking at evolutionary theories and those assessing ecological applications. The most direct measures of fitness for parasitoids are realised fecundity for females and mating ability for males, although these proxies are more difficult to measure under natural conditions. For practical purposes, measure of size, through body size or mass, is the proxy easiest to use while providing good comparative values; however, care must be taken when using a single proxy, as proxies can be affected differently by rearing conditions of the parasitoid.
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Yusa, Yoichi, Mai Yoshikawa, Jun Kitaura, Masako Kawane, Yuki Ozaki, Shigeyuki Yamato, and Jens T. Høeg. "Adaptive evolution of sexual systems in pedunculate barnacles." Proceedings of the Royal Society B: Biological Sciences 279, no. 1730 (August 31, 2011): 959–66. http://dx.doi.org/10.1098/rspb.2011.1554.
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How and why diverse sexual systems evolve are fascinating evolutionary questions, but few empirical studies have dealt with these questions in animals. Pedunculate (gooseneck) barnacles show such diversity, including simultaneous hermaphroditism, coexistence of dwarf males and hermaphrodites (androdioecy), and coexistence of dwarf males and females (dioecy). Here, we report the first phylogenetically controlled test of the hypothesis that the ultimate cause of the diverse sexual systems and presence of dwarf males in this group is limited mating opportunities for non-dwarf individuals, owing to mating in small groups. Within the pedunculate barnacle phylogeny, dwarf males and females have evolved repeatedly. Females are more likely to evolve in androdioecious than hermaphroditic populations, suggesting that evolution of dwarf males has preceded that of females in pedunculates. Both dwarf males and females are associated with a higher proportion of solitary individuals in the population, corroborating the hypothesis that limited mating opportunities have favoured evolution of these diverse sexual systems, which have puzzled biologists since Darwin.
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Mrosovsky, N., and Jane Provancha. "Sex ratio of loggerhead sea turtles hatching on a Florida beach." Canadian Journal of Zoology 67, no. 10 (October 1, 1989): 2533–39. http://dx.doi.org/10.1139/z89-358.
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Hatchling loggerhead sea turtles (Caretta caretta) were collected over the summer nesting season from a major rookery at Cape Canaveral, Florida, in 1986. Sex was assessed using histological criteria. From data on the distribution of nests over the season, we estimated that in 1986, > 93% of the hatchlings produced on this beach were females. This huge bias toward females is consistent with sand temperatures at the depth of turtle nests; for most of the season these temperatures were above the pivotal level for loggerhead turtles. The results suggest that in the future, turtles in this area will encounter difficulty in overcoming the feminizing effect of global warming and that biologists should pay more attention to the beaches at the northern end of the loggerhead's nesting range.
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Bleich, Vernon C., Jericho C. Whiting, John G. Kie, and R. Terry Bowyer. "Roads, routes and rams: does sexual segregation contribute to anthropogenic risk in a desert-dwelling ungulate?" Wildlife Research 43, no. 5 (2016): 380. http://dx.doi.org/10.1071/wr15231.
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Context Little is known about the consequences of sexual segregation (differential use of resources by the sexes outside of the mating season) for the conservation of large mammals. Roadways (i.e. the strip of land over which a road or route passes) are ubiquitous around the world, and are a major cause of wildlife mortality, as well as habitat loss and fragmentation. Many populations of bighorn sheep (Ovis canadensis) occur at low densities and in a metapopulation structure. Roadways could affect movements of males and females differentially, an outcome that has not been considered previously. Aims We investigated the propensity of the sexes to cross a paved two-lane road and a single-lane, maintained dirt route and predicted that adult males, because of their life-history characteristics, would cross those roadways more often than females. Methods We investigated movements of male and female bighorn sheep from 1986 to 1990. We used a fixed-wing aircraft with an H-antenna on each wing strut to locate individuals each week from October 1986 to December 1990. We estimated the degree of overlap among 50% core areas of use by males and females with the utilisation distribution overlap index (UDOI). Key results We relocated male and female bighorn sheep on 948 occasions during sexual aggregation and on 1951 occasions during sexual segregation. More males than females were likely to cross both types of roadways during segregation, and the dirt route during aggregation. Propensity of males and females to cross roadways was strongly influenced by time of year (i.e. whether the period of sexual aggregation or sexual segregation). The lowest overlap in 50% core areas was between females and males during periods of segregation (UDOI = 0.1447). Conclusions More males than females crossed Kelbaker Road and the unnamed dirt route during segregation, as well as the unnamed route during aggregation. Both of those features could affect males more than females, and could result in reductions in the use of habitat or increased mortality of bighorn sheep from vehicle collisions as a result of spatial segregation of the sexes. Implications During environmental review, biologists should consider sexual segregation when assessing potential anthropogenic effects on movements of bighorn sheep. Biologists also should consider sexual segregation and how roadways, even lightly traveled routes, affect movements of male and female ungulates differently before manipulating habitat, translocating animals, or constructing or modifying roadways.
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Laturney, Meghan, and Amanda J. Moehring. "The Genetic Basis of Female Mate Preference and Species Isolation in Drosophila." International Journal of Evolutionary Biology 2012 (August 23, 2012): 1–13. http://dx.doi.org/10.1155/2012/328392.
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The processes that underlie mate choice have long fascinated biologists. With the advent of increasingly refined genetic tools, we are now beginning to understand the genetic basis of how males and females discriminate among potential mates. One aspect of mate discrimination of particular interest is that which isolates one species from another. As behavioral isolation is thought to be the first step in speciation, and females are choosy more often than males in this regard, identifying the genetic variants that influence interspecies female mate choice can enhance our understanding of the process of speciation. Here, we review the literature on female mate choice in the most widely used model system for studies of species isolation Drosophila. Although females appear to use the same traits for both within- and between-species female mate choice, there seems to be a different genetic basis underlying these choices. Interestingly, most genomic regions that cause females to reject heterospecific males fall within areas of low recombination. Likely, candidate genes are those that act within the auditory or olfactory system, or within areas of the brain that process these systems.
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Luo, Laigao, Yilian Wu, Zhuyuan Zhang, and Xuefeng Xu. "Sexual size dimorphism and female reproduction in the white-striped grass lizard Takydromus wolteri." Current Zoology 58, no. 2 (April 1, 2012): 236–43. http://dx.doi.org/10.1093/czoolo/58.2.236.
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Abstract Sexual size dimorphism (SSD) has long attracted the attention of biologists, and life-history variation is thought to play an important role in the evolution of SSD. Here we quantified SSD and female reproductive traits to identify potential associations between SSD and female reproduction in the white-striped grass lizard Takydromus wolteri. In a population from Chuzhou, China, the largest male and female were 53.0 mm and 57.5 mm in snout-vent length (SVL), respectively. Females were larger in SVL and abdomen length, whereas males were larger in head size and tail length. Females produced up to five clutches of eggs during the breeding season, with large females producing more clutches and more eggs per clutch than small ones. As a result, large females had a higher annual fecundity and reproductive output. Egg size was positively correlated with maternal SVL in the first clutch, but not in subsequent clutches. These results suggest that T. wolteri is a species with female-biased SSD, and that fecundity selection, in which large females have higher fecundity due to their higher capacity for laying eggs, is likely correlated with the evolution of SSD in this species [Current Zoology 58 (2): 236–243, 2012].
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Gavin, Thomas A., and Eric K. Bollinger. "Multiple Paternity in a Territorial Passerine: The Bobolink." Auk 102, no. 3 (July 1, 1985): 550–55. http://dx.doi.org/10.1093/auk/102.3.550.
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Abstract Electrophoretic and behavioral evidence corroborate the conclusion that Bobolink (Dolichonyx oryzivorus) females occasionally copulate with more than one male, which results in the insemination of a single clutch of eggs by those males. In 2 of 12 families from which blood samples were obtained from the mother, the putative father, and the nestlings, at least 2 males were responsible for fertilization of the clutch. We believe this is only the second bird species in which multiple paternity has been documented conclusively in the wild. Our speculation that it may not be uncommon leads to a caution for evolutionary biologists who use apparent reproductive success in birds to address questions about fitness.
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Schuler, Krysten L., Bridget B. Baker, Karl A. Mayer, Carolina Perez-Heydrich, Paula M. Holahan, Nancy J. Thomas, and C. Leann White. "Refining Aging Criteria for Northern Sea Otters in Washington State." Journal of Fish and Wildlife Management 9, no. 1 (March 21, 2018): 208–21. http://dx.doi.org/10.3996/052017-jfwm-040.
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Abstract Measurement of skull ossification patterns is a standard method for aging various mammalian species and has been used to age sea otters Enhydra lutris from Russia, California, and Alaska. Cementum annuli counts have also been verified as an accurate aging method for sea otters in Alaska. In this study, we compared cementum annuli count results and skull ossification patterns as methods for aging the northern sea otter, E. l. kenyoni, in Washington State. We found significant agreement between the two methods, suggesting that either method could be used to age sea otters in Washington. We found that ossification of the squamosal–jugal suture at the ventral glenoid fossa can be used to differentiate male subadults from adults. To assist field biologists or others without access to cementum annuli or skull ossification analysis techniques, we analyzed a suite of morphologic, physiologic, and developmental characteristics to assess whether a set of these more easily accessible parameters could also predict age class. We identified tooth condition score, evidence of reproductive activity in females, and tooth eruption pattern as the most useful criteria for classifying sea otters in Washington. We created a simple decision tree based on characteristics accessible in the field or at necropsy, which can be used to reliably predict age class of Washington sea otters as determined by cementum annuli. These techniques offer field biologists and marine mammal stranding networks a replicable, cost-conscious methodology to gather useful biological information from sea otters.
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Cox, Robert M., Michele M. Barrett, and Henry B. John-Alder. "Effects of food restriction on growth, energy allocation, and sexual size dimorphism in Yarrow’s Spiny Lizard, Sceloporus jarrovii." Canadian Journal of Zoology 86, no. 4 (April 2008): 268–76. http://dx.doi.org/10.1139/z08-002.
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Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually antagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental factors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow’s Spiny Lizard ( Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restriction dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females.
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Grant, T. R., and P. D. Temple–Smith. "Field biology of the platypus ( Ornithorhynchus anatinus ): historical and current perspectives." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353, no. 1372 (July 29, 1998): 1081–91. http://dx.doi.org/10.1098/rstb.1998.0267.
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The field biology of the platypus, Ornithorhynchus anatinus , was first studied by a number of expatriate biologists who visited the Australian colonies to collect specimens in the 1800s. Their work was followed in the early to mid–1900s by a group of resident natural historians and later by an increasing number of academic biologists. All of these workers contributed significantly to the current understanding of the field biology of this unique Australian species. The platypus occupies much the same general distribution as it did prior to European occupation of Australia, except for its loss from the state of South Australia. However, local changes and fragmentation of distribution due to human modification of its habitat are documented. The species currently inhabits eastern Australia from around Cooktown in the north to Tasmania in the south. Although not found in the west–flowing rivers of northern Queensland, it inhabits the upper reaches of rivers flowing to the west and north of the dividing ranges in the south of the state and in New South Wales and Victoria. Its current and historical abundance, however, is less well known and it has probably declined in numbers, although still being considered as common over most of its current range. The species was extensively hunted for its fur until around this turn of this century. The platypus is mostly nocturnal in its foraging activities, being predominantly an opportunistic carnivore of benthic invertebrates. The species is homeothermic, maintaining its low body temperature (32°C), even while foraging for hours in water below 5°C. Its major habitat requirements include both riverine and riparian features which maintain a supply of benthic prey species and consolidated banks into which resting and nesting burrows can be excavated. The species exhibits a single breeding season, with mating occurring in late winter or spring and young first emerging into the water after 3—4 months of nurture by the lactating females in the nesting burrows. Natural history observations, mark and recapture studies and preliminary investigations of population genetics indicate the possibility of resident and transient members of populations and suggest a polygynous mating system. Recent field studies have largely confirmed and extended the work of the early biologists and natural historians.
Books on the topic "Femmes biologistes"
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Margulis, Lynn, and Dorion Sagan. Lynn Margulis: The life and legacy of a scientific rebel. White River Junction, Vt: Chelsea Green Publishing, 2012.
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rahrah, chaima. Tarifs et nomenclature des actes professionnels des médecins, biologistes, chirurgiens-dentistes, sages-femmes et auxiliaires médicaux. [Tunis]: Impr. officielle de la République tunisienne, 1990.
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D, Tyler J., and Labbé Guillaume 1973 traducteur, eds. Le cœur de Hunter. Varennes, Québec, Canada: AdA éditions, 2016.
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Maddox, Brenda. Rosalind Franklin: The Dark Lady of DNA. HarperCollins Publishers, 2013.
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"Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists." In Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists, edited by Timothy P. Parks, Jeffrey M. Kampa, Gene R. Hatzenbeler, and Martin J. Jennings. American Fisheries Society, 2017. http://dx.doi.org/10.47886/9781934874462.ch44.
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<em>Abstract</em>.—Meaningful growth potential information is a critical component of determining minimum length regulations for harvesting Muskellunge <em>Esox masquinongy</em>. The use of tags and recapture-based statistical methods allow managers to assess growth for species like Muskellunge without having to sacrifice fish to obtain traditional size-at-age information from hard-bony structures. The purpose of our study was to determine the growth potential of tagged Muskellunge without age data and to demonstrate two recapture-based statistical methods we used to estimate asymptotic length. Muskellunge asymptotic length was estimated for seven northwestern Wisconsin Lakes using the Ford–Walford and Fabens methods. Using the Ford–Walford method, overall mean asymptotic length of Muskellunge was estimated to be 41.6 in (1 in = 2.54 cm; range = 37.2–49.1 in) and was larger for females (range = 30.3–47.5 in) than for males (range = 36.6–40.4 in). Similarly, using the Fabens method we estimated a mean asymptotic length of 42.3 in (range = 30.6–49.1 in) and estimated asymptotic length was greater for females (range = 28.6–51.3 in) than for males (range = 35.2–40.3 in). Both methods produced fairly similar estimates but differed in estimated precision and potential bias when compared to maximum observed total length. Nonetheless, both methods revealed insights about Muskellunge growth potential without sacrificing fish and both methods should be considered as potential tools for biologists needing to better understand Muskellunge growth.
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"Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists." In Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists, edited by Steven J. Kerr and Brandon Jones. American Fisheries Society, 2017. http://dx.doi.org/10.47886/9781934874462.ch4.
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<em>Abstract</em>.—We report on results of a Muskellunge <em>Esox masquinongy </em>tagging project, which was conducted on the Saint John River, New Brunswick, from 2006 to 2015 (inclusive). During that period of time, 691 Muskellunge were angled, tagged, and released by members of the Saint John River Chapter of Muskies Canada Inc. By the end of the 2015 angling season, a total of 64 (9.3%) tagged Muskellunge had been recaptured by angling. An additional four tagged fish were captured at the Mactaquac Dam fishway. Most Muskellunge were observed to establish discrete summer home ranges from which there was little, if any, movement. Transitional movements were believed to occur during the spring and fall, associated with spawning as well as the establishment of summer and winter ranges. Muskellunge movements that were documented in this study occurred in both upstream and downstream directions in equal proportion. Muskellunge also demonstrated the ability to move long distances both upstream and downstream, including passage over/through the Mactaquac Dam. Observations of Muskellunge behavior and movements from this study are generally consistent with observations (small home ranges, males more sedentary than females, movements seasonal in nature, capable of long distance movements, etc.) reported from similar tagging studies in other North American jurisdictions. Future efforts will be directed to obtaining additional information on recaptured fish. With additional recapture information, a more detailed analysis of Muskellunge in the Saint John watershed can be completed.
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"Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists." In Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists, edited by Kevin S. Page and Edward Lewis. American Fisheries Society, 2017. http://dx.doi.org/10.47886/9781934874462.ch6.
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<em>Abstract</em>.—Voluntary angler catch reports can be a valuable tool for monitoring fisheries. In Ohio, angler reports have been integral for monitoring long-term trends in Muskellunge <em>Esox masquinongy </em>fisheries. The integration of angler catch data into mark–recapture methods has been increasingly advocated as a means of improving estimates of fish population metrics. A mark–recapture study was conducted to evaluate population demographics of Muskellunge during 1981–2006 at Clear Fork Reservoir, Ohio. Each spring, adult Muskellunge (<EM>N </EM>= 4,134; ≥609 mm) were collected and marked using trap nets. Anglers reported catches of marked Muskellunge (i.e., resightings) between marking events. A total of 4,134 Muskellunge were marked (609–1,245 mm), 1,227 (29.7%) were recaptured in trap nets, and anglers reported catching an additional 884 marked fish (21.4%). Recaptures and angler catch reports were analyzed using a joint mark–recapture, tag-resighting, and tag-recovery model (Barker model) within program MARK to estimate the probability of survival, angler catch, and emigration from the reservoir. Mean estimates of Muskellunge annual survival were 0.62 (SD = 0.22) for males and 0.71 (SD = 0.23) for females. The probability of Muskellunge being caught by anglers varied across years, and factors influencing angling vulnerability were unclear. The model tended to underestimate catch-and-release rates based on estimates derived from all angler catch reports, yet the trends toward greater release rates were generally consistent with expectations. The model suggested that emigration from the reservoir was constant over time, with any given Muskellunge having a 0.13 probability of emigrating annually. Angler catch reports provided the data necessary to make valuable inferences about the fishery that would not otherwise be available from survey netting only.
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"Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists." In Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists, edited by Curtis P. Wagner, Max H. Wolter, Corey S. DeBoom, Matthew J. Diana, Michael J. Weber, and David H. Wahl. American Fisheries Society, 2017. http://dx.doi.org/10.47886/9781934874462.ch37.
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<em>Abstract</em>.—Muskellunge <em>Esox masquinongy </em>management programs often rely on stocking to create and maintain populations. In many instances, a native and nearby stocking source is unavailable or a genetically suitable brood source is unclear. Genetic differences among stocks of Muskellunge may influence survival and growth when introduced into novel environments. Consequently, the selection of a suitable brood source can be difficult and possibly critical to the success of Muskellunge stocking programs. We examined differences in long-term survival and growth among introduced Muskellunge stocks from the Ohio and upper Mississippi River drainages and a mixed-origin Illinois broodstock population in three Illinois reservoirs. Catch per unit effort (CPUE) from spring modified-fyke netting suggested that the upper Mississippi River drainage stock at ages 3 and 4 persisted at lower relative abundance compared to conspecifics; however, low lake- and stock-specific catches of older ages precluded robust CPUE comparisons among stocks. Apparent survival, estimated from mark–recapture data with the Cormack-Jolly–Seber open population model, differed among stocks 1-year poststocking, with the upper Mississippi River drainage stock exhibiting markedly lower survival compared to conspecifics. Annual variation in survival to age 1.5 was related to water temperature at stocking, fish size at stocking, first winter temperatures, and first summer temperatures. However, survival did not differ among stocks for Muskellunge age 2 and older, indicating that important factors structuring long-term survival exert their effects most strongly in the first year poststocking. Despite overall low survival of Muskellunge from the upper Mississippi River drainage, males that survived exhibited a slight growth advantage compared to conspecifics. No growth advantage was observed for upper Mississippi River drainage stock females. Our findings suggest that stock selection in addition to environmental conditions can influence survival of introduced Muskellunge and subsequent contribution to the fishery.
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"Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists." In Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists, edited by Neil P. Rude, David C. Glover, William D. Hintz, Shawn C. Hirsrst, Wayne E. Herndon, Rob B. Hilsabeck, and Gregory W. Whitledge. American Fisheries Society, 2017. http://dx.doi.org/10.47886/9781934874462.ch45.
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<em>Abstract</em>.—Accurate estimates of growth and mortality are important for management of recreational fisheries. Accurate age estimates often require the sacrifice of fish; thus, assessments of growth and mortality rates of trophy fishes such as Muskellunge <em>Esox masquinongy </em>often lack sufficient data. Mark–recapture history can be used as a nonlethal alternative to estimate growth and mortality in fishes. To determine the utility of this approach, we used data from a 17-year Muskellunge mark–recapture program conducted on two Illinois reservoirs (Kinkaid Lake and North Spring Lake). Von Bertalanffy parameter estimates by sex, lake, and tag type (passive integrated transponder and T-bar anchor tags) were obtained using a novel modification of the Fabens growth model and compared to von Bertalanffy growth estimates using known- or scale-aged fish. Mortality was calculated using both age- and length-based methods. Fabens growth model estimates of asymptotic length (<em>L</em><sub>∞</sub>) and growth coefficient (<EM>K</EM>) were within 6% (≤62 mm) and 23% (≤0.11) of corresponding von Bertalanffy growth model parameter estimates from known- or scale-aged fish by lake and sex. Provided that all sizes of fish are sampled, 4 years of mark–recapture data with more than 100 recaptures were found to be sufficient to produce reliable parameter estimates. Growth parameters differed between male fish tagged with passive integrated transponder or T-bar anchor tags but did not differ by tag type for females. Differences in Muskellunge growth and mortality rates between the two study lakes suggest that changing from a regionally applied minimum length limit to lake-specific minimum length limits may be warranted. Our results highlight the feasibility of mark–recapture data as a nonlethal technique to estimate population-specific growth and mortality rates for Muskellunge and the potential value of this approach in facilitating lake-specific Muskellunge management.
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Allchin, Douglas. "Male, Female, and/ or — ?" In Sacred Bovines. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190490362.003.0024.
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Intersex individuals are coming out of the closet. Witness, for example, the 2003 Pulitzer Prize in Fiction for Jeffrey Eugenides’s Middlesex. The story follows someone with 5-alpha-reductase deficiency, or late-onset virilization. Imagine yourself raised as a girl, discovering at puberty (through cryptic, piecemeal clues) that you are male instead. Or male also? Or male only now? Or “just” newly virile? The condition confounds the conventionally strict dichotomy between male and female, masculine and feminine. It teases a culture preoccupied with gender. What are male and female, biologically? How does nature define the sexes, and sex itself? The questions seem simple enough. Seeking answers, however, may yield unexpected lessons—about the role of biological definitions; about assumptions concerning universals, rarities, and “normality”; and about the power of mistaken conceptions of nature to shape culture. Conceptualizing sex as male and female seems straightforward. In the standard version (familiar even to those unschooled in biology), females have two X chromosomes, while males have an X and a Y. They have different gametes: one moves, one stays stationary. These differences seem foundational. They seem to explain why male and female organisms have contrasting gonads, contrasting hormone-mediated physiologies, and contrasting secondary sex characteristics. Once-homologous organs follow divergent developmental trajectories. Perhaps even contrasting behaviors express the purported evolutionary imperative of each gamete: the “promiscuous,” uncaring male of cheap sperm, and the cunning, protective female of big-investment eggs. The apparent alignment of the two sexes through all levels of biological organization seems to validate this categorization as scientifically sound. Good biologists know better. First, sex may be determined in many ways. Birds use a “reversed,” WZ system, where females have the distinctive chromosome. Many insects have a haplodiploid system, where sex is determined by having a single or double set of all the chromosomes. Crocodiles and turtles develop their sex in response to temperature cues, not genes alone. The spoonworm Bonellia responds instead to whether females are absent or already present in the area.
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"Paddlefish: Ecological, Aquacultural, and Regulatory Challenges of Managing a Global Resource." In Paddlefish: Ecological, Aquacultural, and Regulatory Challenges of Managing a Global Resource, edited by Dennis L. Scarnecchia, Jason D. Schooley, K. Michael Backes, Aaron Slominski, and Steven Dalbey. American Fisheries Society, 2019. http://dx.doi.org/10.47886/9781934874530.ch1.
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<i>Abstract</i>.—In the past decade, advances in our understanding of Paddlefish <i>Polyodon spathula</i> life history have provided additional insight into the information needed for sustainable harvest management of this long-lived species. Recovery of known-age fish in some stocks has enabled stock assessment biologists and managers to not only validate ages of individual fish, but to begin to validate the life histories. A framework for potentially recruited Paddlefish life history can be broken into five stages: 1) immature, 2) maturing, 3) somatic growth and reproduction, 4) prime reproduction, and 5) senescence to death. These stages involve measurable changes in growth in length and weight, gonadosomatic index (GSI), gonadal fat storage (GFBs), reproductive periodicity, natural mortality rates, and, in some cases, fish migrations. Stages 2–5 are typically initiated at younger ages for males than for females. Metabolic demands on Paddlefish result in them progressing through these life history stages more rapidly in southern stocks, inhabiting warmer waters, than in northern ones, inhabiting colder waters. Lifespans in most northerly stocks tend to be 2–3 times longer than for southern stocks. Natural mortality is also typically lower in northern stocks. These differences necessitate fundamentally different harvest management strategies among stocks. Regardless of the stock, however, in the prime reproduction stage, somatic growth is slow or negative, as energy is routed more strongly into reproduction, GSI is at a maximum, the period of gonadal recrudescence (i.e., spawning interval) is minimized, and GFBs are largely or completely depleted in females. Consistent with recommendations for other long-lived freshwater and marine species, harvest management strategies should be specifically planned to retain some older, prime spawning females in the population. In addition, sporadic or episodic recruitment in many stocks makes steady-state harvest models unrealistic, necessitating that harvest be appropriately matched to recruitment rates or events.
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Rhen, Turk, and David Crews. "Sex and Gender." In Evolutionary Ecology. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195131543.003.0017.
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In this chapter, sex will refer to the central process of meiosis and syngamy in eukaryotic organisms. Although some form of sexuality characterizes the life cycle of many eukaryotic organisms (i.e., virtually all fungi, plants, and animals), not all eukaryotes are sexual (e.g., many protists) (Margulis 1970, 1996; Bell 1982). Certain asexual protists, for example, only undergo mitosis and never alternate between haploid and diploid stages by way of meiosis and syngamy. Consequently, one of the most fundamental questions in biology is: Why do certain organisms go through meiosis and syngamy while others do not? Despite the apparent simplicity of this query, evolutionary biologists have not provided an entirely satisfactory explanation for the evolution of sex. Much of the difficulty arises because there appears to be no single answer. Moreover, sex is often confused with other associated phenomenon. For instance, one completely subordinate, but intimately related, occurrence is the evolution of gender in organisms that go through meiosis and syngamy. In his essay on the evolution of sex, Ghiselin (1988) aptly wrote, “Gender means the differentiation into males, females, and such alternatives as hermaphrodites. It also includes the differences between sperm and eggs. Such differences are important because they create the circumstances that make sex a puzzle” (p. 9). Yet he dismisses this subject in the next sentence: “Otherwise we are not much concerned about gender either.” Here we clarify the relationship between the evolution of sex and the evolution of gender. This is a critical concept to comprehend because gender differences are nearly universal in sexual organisms. We also discuss some of the major hypotheses proposed to explain why sex exists and recent empirical work that sheds light on the factors that may favor meiosis and syngamy, regardless of gender differences. In the remainder of the chapter, we present a more thorough analysis of the evolution of gender, including a discussion of what the fundamental gender difference is and why there are so many different mechanisms that produce more derived gender differences.
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"Invasive Asian Carps in North America." In Invasive Asian Carps in North America, edited by Diana M. Papoulias, James Candrl, Jill A. Jenkins, and Donald E. Tillitt. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874233.ch18.
Full textAbstract:
<em>Abstract</em>.—The Asian black carp <em>Mylopharyngodon piceus </em>is of interest to the aquaculture industry in the United States as a biological control for snails and mollusks. However, past experience in North America with other Asian carps has raised concern that black carp will establish wild populations and negatively affect native populations of fish and invertebrates, especially mollusks. The demand for black carp has led biologists to seek ways to allow their use while at the same time maintaining control over their distribution and reproduction. Physical containment and restrictions on importation, release, and stocking have mostly failed. Control of reproduction holds more promise. The induction of triploidy (having three sets of chromosomes), which can render an individual biologically sterile, is of particular interest. The main purpose of this study was to evaluate the efficiency of proposed testing procedures used to assure genetic triploidy in black carp prior to distribution by the state of Missouri, using black carp and grass carp <em>Ctenopharyngodon idella</em>. Our objectives were to (1) verify if the ploidy determination methodology (nuclear size) employed was 100% accurate, (2) determine growth and survival of juvenile black carp over extended periods of time under laboratory and pond conditions, and (3) histologically examine development and gametogenesis in gonads collected from triploid and diploid black and grass carps of different ages and stages of maturation. Comparison of erythrocyte nuclear size using the Coulter counter method versus the more accurate method of flow cytometry that measures DNA content indicated an error rate of 0.25% by the former method. Black carp grew and survived well in mid-Missouri ponds. Triploid grass carp males appeared to produce functional gametes, and some triploid black carp male testes had apparently normal spermatocytes within cysts. A few normally developing oocytes at previtellogenic and vitellogenic stages were observed in triploid grass carp females, and a few normal perinuclear oocytes could be identified in triploid black carp females. Currently, the standards of the U.S. Fish and Wildlife Service’s triploid grass carp voluntary inspection program are being followed by some states to manage triploid black carp. Our results indicate that although the percentage of diploid black carp that could pass through the currently proposed screening program is small, overall numbers of diploid black carp distributed in a state could be substantial depending on the number of triploids distributed. Furthermore, despite indications that triploid male black carp can be expected to be functionally sterile, reproductive studies may be warranted given the large wild populations of diploid grass carp, bighead carp <em>Hypophthalmichthys nobilis</em>, and silver carp <em>H. molitrix </em>in the Mississippi River basin system.
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"Invasive Asian Carps in North America." In Invasive Asian Carps in North America, edited by Diana M. Papoulias, James Candrl, Jill A. Jenkins, and Donald E. Tillitt. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874233.ch18.
Full textAbstract:
<em>Abstract</em>.—The Asian black carp <em>Mylopharyngodon piceus </em>is of interest to the aquaculture industry in the United States as a biological control for snails and mollusks. However, past experience in North America with other Asian carps has raised concern that black carp will establish wild populations and negatively affect native populations of fish and invertebrates, especially mollusks. The demand for black carp has led biologists to seek ways to allow their use while at the same time maintaining control over their distribution and reproduction. Physical containment and restrictions on importation, release, and stocking have mostly failed. Control of reproduction holds more promise. The induction of triploidy (having three sets of chromosomes), which can render an individual biologically sterile, is of particular interest. The main purpose of this study was to evaluate the efficiency of proposed testing procedures used to assure genetic triploidy in black carp prior to distribution by the state of Missouri, using black carp and grass carp <em>Ctenopharyngodon idella</em>. Our objectives were to (1) verify if the ploidy determination methodology (nuclear size) employed was 100% accurate, (2) determine growth and survival of juvenile black carp over extended periods of time under laboratory and pond conditions, and (3) histologically examine development and gametogenesis in gonads collected from triploid and diploid black and grass carps of different ages and stages of maturation. Comparison of erythrocyte nuclear size using the Coulter counter method versus the more accurate method of flow cytometry that measures DNA content indicated an error rate of 0.25% by the former method. Black carp grew and survived well in mid-Missouri ponds. Triploid grass carp males appeared to produce functional gametes, and some triploid black carp male testes had apparently normal spermatocytes within cysts. A few normally developing oocytes at previtellogenic and vitellogenic stages were observed in triploid grass carp females, and a few normal perinuclear oocytes could be identified in triploid black carp females. Currently, the standards of the U.S. Fish and Wildlife Service’s triploid grass carp voluntary inspection program are being followed by some states to manage triploid black carp. Our results indicate that although the percentage of diploid black carp that could pass through the currently proposed screening program is small, overall numbers of diploid black carp distributed in a state could be substantial depending on the number of triploids distributed. Furthermore, despite indications that triploid male black carp can be expected to be functionally sterile, reproductive studies may be warranted given the large wild populations of diploid grass carp, bighead carp <em>Hypophthalmichthys nobilis</em>, and silver carp <em>H. molitrix </em>in the Mississippi River basin system.