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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). ...
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). ...
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 ...
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. ...
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). ...
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). ...
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
Understanding of snake ecology has increased over the past two decades, but is still limited for many species. This is particularly true for the recently described Beni anaconda (Eunectes beniensis). We present the results of a radio-telemetry study of nine (3M:6F) adult E. beniensis, including home range, and habitat use. We located the snakes 242 times in wet season, and 255 in dry season. Mean wet season home range (MCP) was 25.81 ha (6.7 to 39.4 ha); while mean dry season home range was 0.29 ha (0.13 to 0.42 ha). We found no relationship between home range size and either snout-vent length, weight, or sex. Beni anacondas seem to prefer swamps, and patujusal, while avoiding forest, and rice fields. However, habitat use by individual snakes seems to vary based on the habitats available within their respective home range. Notably, rice fields were avoided by most snakes, which suggests that this type of habitat is unsuitable for anaconda management.
Imantodes cenchoa (Linnaeus, 1758) is distributed from the east coast of Mexico to Argentina. In Brazil, it occurs in the north, central-west and northeast regions. We present information on the reproductive biology and diet of I. cenchoa from analysis of 314 specimens deposited in the Herpetological Collection of the Museu Paraense Emilio Goeldi (MPEG). Imantodes cenchoa displays sexual dimorphism in the snout-vent length, where sexually mature females are larger than mature males (t = 4.02, p < 0.01; N males = 150, N females = 71), head length (f(1.218) = 98.29, p < 0.01; N males = 150, N females = 71), and head width (f(1.218) = 112.77, p < 0.01, N males = 150; N females = 71). Bi-sexual maturity is observed, with males becoming sexually mature earlier than females. Females with eggs were recorded from November to January (rainy season) and from April to July (dry season), suggesting two reproductive peaks throughout the year, with recruitment occurring mainly during the rainy season, when there is a greater supply of food. Imantodes cenchoa is a nocturnal active forager, capturing prey that are asleep on the vegetation. In 32.80% of the analyzed specimens, food contents were present, of which 84.11% were lizards of the genera Norops (69.16%, N = 74) and Gonatodes (14.95%, N = 16). The other 15.89% of the contents were made up of items in an advanced state of digestion, preventing their identification. Some specimens had more than one food item in their digestive tract, accounting for 107 prey items in total. There was no ontogenetic variation in the diet of I. cenchoa, and the predominant direction of prey ingestion was antero-posterior (71.96%). Larger snakes tended to feed on larger prey, although these did not exclude small prey from their diet.
Female adders are known to mate with several males during the mating season. The presence of a "copulatory plug", permitting only the first male to fertilize the eggs, has been reported. To test this paradox, female adders were mated under laboratory conditions with males carrying different, electrophoretically detectable markers. Females mated twice do produce bipaternal broods. Furthermore, single mated females can also produce multipaternal broods, showing that sperm from previous year(s) can be used. /// Известно, что самки гадюк спариваются с несколькими самцами в течение периода размножения. Установлено наличие "копулятивного стопора", позволяющего лишь первому самцу оплодотворять яйцa. Для проверки этого парадокса самок гадюк спаривали в лаборатории с самцами, имеющими различные метки, определяемые электрофоретическим методом. Самки, спаривавшнеся дважды давали потомство от обоих отцовских особей. Более того, самки, спаривавштеся один раз, могут также давать потомство от разных отцов, что показывает возможность использования спермы прошлого года (прошлых лет).
Female adders (Vipera berus) have been observed to copulate several times per season with different males. Observations of matings may not truly reflect paternity because prolonged contractions of the female uterus may function as a "copulatory plug." We performed breeding experiments with adders and used DNA fingerprinting to determine paternity and possible between-season sperm storage. Multiple paternity was detected in all broods investigated, and associated males were the genetical fathers in all cases but one. We conclude that, although there may be a copulatory plug, it does not prevent multiple paternity following multiple matings within a short period of time.
Many phenotypic traits perform more than one function, and so can influence organismal fitness in more than one way. Sexually dimorphic traits offer an exceptional opportunity to clarify such complexity, especially if the trait involved is subject to natural as well as sexual selection, and if the sexes differ in ecology as well as reproductive behaviour. Relative tail length in sea-snakes fulfils these conditions. Our field studies on a Fijian population of yellow-lipped sea kraits (Laticauda colubrina) show that relative tail lengths in male sea kraits have strong consequences for individual fitness, both via natural and sexual selection. Males have much longer tails (relative to snout–vent length) than do females. Mark-recapture studies revealed a trade-off between growth and survival: males with relatively longer tails grew more slowly, but were more likely to survive, than were shorter-tailed males. A male snake's tail length relative to body length influenced not only his growth rate and probability of survival, but also his locomotor ability and mating success. Relative tail length in male sea kraits was thus under a complex combination of selective forces. These forces included directional natural selection (through effects on survival, growth and swimming speed) as well as stabilizing natural selection (males with average-length tails swam faster) and stabilizing sexual selection (males with average-length tails obtained more matings). In contrast, our study did not detect significant selection on relative tail length in females. This sex difference may reflect the fact that females use their tails primarily for swimming, whereas males also must frequently use the tail in terrestrial locomotion and in courtship as well as for swimming.
The courtship behavior of Crotalus atrox, always initiated by males, follows a triphasic schema: tactile-chase, tactile-alignment, and intromission and coitus. The third phase is longer than in other snakes (20-28 h). Female lateral tail-whipping and the slower tail-waving are apparently not indicative of her receptivity, although the latter is correlated with an increased male tongue-flick rate. Cloacal gaping by females apparently indicates female receptivity and occurs prior to successful intromission. Combat behavior between males is similar to other viperids. The vertical display is punctuated by periodic topping movements until a dominant individual is established. Evidence is presented that indicates subordinate males are refractory to courtship while dominant males actively court females following combat. In one instance a female assumed a vertical stance similar to that of a combatting male.
Four male and one female Python molurus were maintained together and their social interactions observed for 85 days. The acts and act systems involved in communication encompassed the entire elongate morphology of the snake. The sequence of events comprising the male combat ritual was observed over 60 times; a stable linear social hierarchy between the four males was established. The combat consisted of: recognition-investigation, ascent, alignment, orientation, topping and submission. Biting and vigorous use of pelvic spurs were recorded. Individual recognition of other males either provoked a snake to engage in combat or to withdraw. Courtship and copulatory sequences were triphasic: tactile-chase, tactile-alignment, and intromission and coitus. The number of successful copulations corresponded to the hierarchial status of the males and male combat occurred in only three instances after breeding.