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Mating system and sexual size dimorphism of green anaconda ( Eunectes murinus )

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... The first male to find the female is likely to remain for days (or even weeks) coiled around her. Inevitably, other males are attracted as well, all of them surrounding the female and competing to introduce one of their hemipenes into the female's cloaca. This orgy is essentially a patient battle among the males who are not aggressive toward each other (Rivas et al. 2007). ...
... An interesting feature of anacondas, and many other boids, is the presence of small "spurs" adjacent to the cloaca, with those of males larger than those of females. The spurs are mobile, and may assist in mating by stimulating the female's cloaca for reception (Rivas et al. 2007). ...
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We here revisit the natural history of Green Anacondas and give our personal view of how Ecotourism can affect their existence.
... Since the early efforts of Fitch (1970) to elucidate the reproductive cycles of tropical reptiles, research on the reproductive phenology of tropical snakes has increased in response to the historical disparity between temperate and tropical zone studies (Mathies, 2011). In particular, researchers in the South American tropics of Brazil and Argentina have expanded our knowledge about the phenology and reproductive traits of more than 10 elapid species (Almeida-Santos et al., 1998Ávila et al, 2010;Valdujo et al., 2002), 10 viper species (Almeida-Santos et al., 1999Almeida-Santos & Salomao, 2002;Hartmann et al., 2004;Janeiro-Cinquini, 2004;Leão et al., 2014;Marques et al., 2013;Monteiro et al., 2006;Nogueira et al., 2003), nine boine species (Bretona & Chiaraviglio, 2003;Chiaraviglio, 2006;Miranda et al., 2017;Pizzatto, 2005;Pizzatto & Marques, 2007;Rivas et al., 2007), and 26 colubrid species (Alencar et al., 2012;Ávila et al., 2006;Balestrin & Di-Bernardo, 2005;Bizerra et al., 2005;Braz et al., 2014;da Costa-Prudente et al., 2014;Dos Santos-Acosta et al., 2006;Gaiarsa et al., 2013;Goldberg, 2004bGomes & Marques, 2012Gualdrón-Durán et al., 2019;Hartmann et al., 2002;Leite et al., 2009;López & Giraudo, 2008;Marques, 1996;Marques et al., 2009;Marques & Puorto, 1998;Pizzatto et al., 2008;Pizzatto & Marques, 2002;Scartozzoni et al., 2009;Silva & Vadez, 1989;Vitt, 1996). ...
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Based on histological analyses and field studies, this research describes the reproductive ecology of a population of Ninia atrata snakes inhabiting an oil palm plantation. Furthermore, through a multivariate approach, we explored the main drivers of reproductive output in N. atrata. Results showed that prey abundance and food intake were crucial variables contributing to reproductive output. Multiple linear regression models showed that neonates had high sensitivity ( R2=55.29%) to extreme changes in climate, which was strongly related to slug and snail abundance variability and microhabitat quality. Reproductive cycles were markedly different between the sexes, being continuous in males and cyclical in females. Despite this variation, reproductive cycles at the population level were seasonal semi-synchronous. Constant recruitment of neonates all year, multiple clutches, high mating frequency, and continuous sperm production characterized the reproductive phenology of N. atrata. In addition, a significant number of previtellogenic females presented oviductal sperm as well as uterine scars, suggesting a high precocity in the species. The main drivers of reproductive output also differed between the sexes. In females, clutch size and secondary follicle variability were highly related to stomach bolus volume, fat body area, and body mass. In males, height of piles of palm leaves and body mass, rather than intrinsic reproductive traits, were the main drivers of sperm production. Nevertheless, in both cases, the relationship between body mass, prey abundance, and food intake suggests that N. atrata follows the income breeding strategy to compensate for reproductive costs and to maximize fitness.
... 2009), Calle et. al. (1994), , Cope (1869), Gay (1993), Gilmore and Murphy (1993), Infante-Rivero et. al. (2008), Lamonica et. al. (2007), Müller (1970), Petzold (1983) Rivas (1998, 2000, Rivas and Corey (2008), Rivas and Burghardt (2001), Rivas and Owens (2000), Rivas et. al. (1995Rivas et. al. ( , 1999Rivas et. al. ( , 2001Rivas et. al. ( , 2007aRivas et. al. ( , 2007b, Schreitmüller (1924), Starace (1998), Strimple (1993, , Trutnau (1982) and Vaz-Silva (2007 forms have been consistently recognized, namely Green (Eunectes murinus) and Yellow (E. notaeus), with most authors not recognizing other described variants until the period post- dating year 2000(see McDiarmid et. al. 1999). In recent years a nu ...
Article
A review of the taxonomy of the New World boids finds several genera as currently recognized to be paraphyletic. There are available genus names for those species within genera that have been found to be composite, should they be split to ensure monophyletic genera. The only potential exception to this is within the genus Eunectes Wagler, 1830 as currently recognized. There is a strong argument in favor of splitting the so-called Yellow Anacondas away from the so-called Green Anacondas, at the genus level as a result of clear and consistent differences between the relevant taxa. This paper formalizes this division by taking a conservative position and naming and defining a new subgenus, Maxhoserboa subgen. nov. for the Yellow Anaconda and related species.
... This still does not explain why some snakes with typical malemale combats have highly ornamented hemipenes while others do not. Rivas et al. (2007) reported another mechanism for successful copulation between snakes: in Eunectes murinus (Linnaeus, 1758) the male coils around the female during copulation, preventing the other males in the breeding ball from copulating with the female. This "coiling" behavior may impact the hemipenial ornamentation and serve as an alternative to successful copulation and such behaviors should definitely be considered. ...
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In the present study, we investigated and documented the morphology of the male copulatory organs (hemipenes) in fifteen wide-ranging snake species. The species represent four families (Boidae, Colubridae, Lamprophiidae, and Viperidae) and ten genera. We applied the same preparation techniques for all species, successfully everting and expanding the organs completely. The detailed description of the general morphology of the male copulatory organs was based on 31 specimens. Our data were compared with published observations and we point out some incorrectly described details in previous investigations. We provide the first description of the hemipenial morphology for three ophidian species (Elaphe sauromates, Telescopus fallax, and Malpolon insignitus). In addition to the morphological characteristics of the hemipenes presented in the research, we propose the adoption of a standardized index describing the hemipenial proportions. The immense variation in hemipenial morphology presupposes its dynamic evolution, but we suggest that many of the significant structures observed here may have escaped previous researchers due to differing methodologies. Some of the highly ornamented morphologies that we describe are consistent with a locking mechanism during copulation. However, other morphologies may relate to the variety of mating behaviors observed. As a result, we propose that sexual selection is the major driver affecting the hemipenial ornamentation in snakes.
... Our understanding of the biology of adult Green Anacondas has improved in recent years. There have been comprehensive studies of their mating system (Rivas and Burghardt, 2001;Rivas et al., 2007a), general natural history (Rivas, 2000;Rivas et al., 2007b), conservation and sustainable use (Rivas, 2007(Rivas, , 2010, predation (Rivas et al., 1999Rivas and Owens, 2000), diseases (Calle et al., 1994, foraging (Rivas, 1998(Rivas, , 2004, and demography (Rivas and Corey, 2008), along with notes on field techniques (Rivas et al., 1995;Raphael et al., 1996;Rivas, 2008). Adult anacondas live in shallow, stagnant water that is often covered by aquatic vegetation (Rivas, 2000;Rivas et al., 2007b). ...
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Our knowledge of the biology of neonatal snakes has lagged behind that of adult animals, mostly due to the difficulty of finding and studying neonatal snakes in the wild. Traditional approaches view neonatal reptiles as miniature replicates of their adult counterparts. In this contribution, we present data on the natural history of neonatal Green Anacondas from opportunistic captures in the wild over a 17-year period, as well as from a brief study on captive-born radio-tagged individuals. Both approaches converge in presenting a picture of the ecology of neonatal anacondas showing many similarities between their natural history and that of adult anacondas in spite of the great size difference. The neonates' biology resembles that of adults, especially males, in their preference for birds in their diet, the relative prey size they choose, slow growth rates they experience, low feeding frequency, little mobility, and preference for similar habitats of stagnant, shallow water covered by aquatic vegetation. The conventional wisdom that neonatal reptiles are replicates of their adult counterparts seems to be largely on target in Green Anacondas. © 2016 by the American Society of Ichthyologists and Herpetologists.
... In polygynous species (in which a male mates with more than one female in a single breeding season), this is potentially sustainable, since most matings are by only a few males, leaving a theoretical surplus available for harvesting. Anacondas, however, are polyandrous (in which a female mates with more than one male in a single breeding season; Rivas 2000, Rivas and Burghardt 2001, Rivas et al. 2007a, 2007b and females are larger. Also, the largest females contribute the most offspring (females >340 cm are responsible for nearly 60% of new offspring every year, and females >300 cm contribute nearly 75% of each new generation; Rivas, 2000). ...
Chapter
In the epistemology of knowledge/ignorance about females in sexual selection, this chapter demonstrates many different ways in which knowledge about active and multiply mating females have emerged—through agricultural pest-control, natural history observations, population genetic research, interdisciplinary methodological development, and studies of specific animals—illustrating that such knowledge is not always driven by feminist incentives or women scientists to change perceptions about females. Insect researchers knew about female multiple mating early on; snake research shifted toward including female multiple mating in mating system classifications; frog research showed female choice through “the brain of the female”; feminist fish researchers highlighted active females; and spider research has been female-focused from the start. Lastly, I discuss taxonomic bias and asymmetric knowledge circulation in sexual selection research—that is taxonomic ignorance.KeywordsAnimalsSexual selectionGender biasTaxonomic biasSituated knowledgesEpistemology of ignorance
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