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A new technique to distinguish between immature and adult snakes and between males and females in six species of the Neotropical colubrid snakes Philodryas
Abstract
This paper reports the observed maximum and minimum SVL's of six species of the neotropical colubrid snakes Philodryas. A new sexing technique using the SVL: W‐ratio is presented, in addition to a proposed SVL critical value, which is useful in distinguishing between adult and immature snakes within the species studied. There is no sexual dimorphism of SVL x W for any of the studied species.
... Philodryas is a genus composed of twenty-three oviparous species widely distributed in South America (Grazziotinet al. 2012;Zaher et al. 2014;Caccialiet al. 2016), which are geographically separated by the Andes Mountains forming two recognized groups of species (Thomas 1976(Thomas , 1977Zaher et al. 2014). Some authors have suggested that the reproductive biology of Philodryas species is phylogenetically conservative, showing characteristics such as a high number of vitellogenic follicles (Vitt 1980;Fowler et al. 1998;López and Giraudo 2008;Mesquita et al. 2011), the ability to simultaneously produce eggs and vitellogenic follicles (Mesquita et al. 2011(Mesquita et al. , 2013Loebenset al. 2018) and a similar size of sexual maturation (Fowler and Salomão 1995;Mesquita et al. 2013). Despite the aforementioned, the abundant data on the reproduction of the cis-Andean species of the genus, especially P. aestiva (Fowler and Salomão 1995;Fowler et al. 1998), P. nattereri (Fowler and Salomão 1995;Fowler et al. 1998;Passoset al. 2014), P. olfersii (Mesquita et al. 2012(Mesquita et al. , 2013, P. patagoniensis (Hartmann and Marques 2005;López and Giraudo 2008;Loebenset al. 2018), and P. trilineata (Gómez-Alés et al. 2016) contrast with the lack of studies for the species of trans-Andean group, which is composed of P. amaru, P. chamissonis, P.simonsii and P. tachymenoides. ...
... Some authors have suggested that the reproductive biology of Philodryas species is phylogenetically conservative, showing characteristics such as a high number of vitellogenic follicles (Vitt 1980;Fowler et al. 1998;López and Giraudo 2008;Mesquita et al. 2011), the ability to simultaneously produce eggs and vitellogenic follicles (Mesquita et al. 2011(Mesquita et al. , 2013Loebenset al. 2018) and a similar size of sexual maturation (Fowler and Salomão 1995;Mesquita et al. 2013). Despite the aforementioned, the abundant data on the reproduction of the cis-Andean species of the genus, especially P. aestiva (Fowler and Salomão 1995;Fowler et al. 1998), P. nattereri (Fowler and Salomão 1995;Fowler et al. 1998;Passoset al. 2014), P. olfersii (Mesquita et al. 2012(Mesquita et al. , 2013, P. patagoniensis (Hartmann and Marques 2005;López and Giraudo 2008;Loebenset al. 2018), and P. trilineata (Gómez-Alés et al. 2016) contrast with the lack of studies for the species of trans-Andean group, which is composed of P. amaru, P. chamissonis, P.simonsii and P. tachymenoides. ...
... Some authors have suggested that the reproductive biology of Philodryas species is phylogenetically conservative, showing characteristics such as a high number of vitellogenic follicles (Vitt 1980;Fowler et al. 1998;López and Giraudo 2008;Mesquita et al. 2011), the ability to simultaneously produce eggs and vitellogenic follicles (Mesquita et al. 2011(Mesquita et al. , 2013Loebenset al. 2018) and a similar size of sexual maturation (Fowler and Salomão 1995;Mesquita et al. 2013). Despite the aforementioned, the abundant data on the reproduction of the cis-Andean species of the genus, especially P. aestiva (Fowler and Salomão 1995;Fowler et al. 1998), P. nattereri (Fowler and Salomão 1995;Fowler et al. 1998;Passoset al. 2014), P. olfersii (Mesquita et al. 2012(Mesquita et al. , 2013, P. patagoniensis (Hartmann and Marques 2005;López and Giraudo 2008;Loebenset al. 2018), and P. trilineata (Gómez-Alés et al. 2016) contrast with the lack of studies for the species of trans-Andean group, which is composed of P. amaru, P. chamissonis, P.simonsii and P. tachymenoides. ...
The long-tailed snake Philodryas chamissonis is an oviparous rear-fanged species endemic to Chile, whose reproductive biology is currently based on anecdotic reports. The characteristics of the eggs, incubation time, and hatching are still unknown. This work describes for the first time the oviposition of 16 eggs by a female in captivity at Zoológico Nacional in Chile. After an incubation period of 59 days, seven neonates were born. We recorded data of biometry and ecdysis of these neonates for 9 months. In addition, a review about parameters of egg incubation and hatching for Philodryas species is provided.
... Straight-line length is occasionally used but the most commonly reported length measurement is snout to vent length (SVL; Seigel and Ford 1988). It is important to state which measurement technique is being used (Fowler and Salamao 1995). ...
... Although previous studies measured snake length using snout to vent length (Fowler and Salamao 1995), we used snout to tail length for two reasons: the measurement data attained from this study came from a larger project requiring minimal handling; and to compare our data to that of Barnard et al. (1979). Because of this, snakes were digitally and not manually measured. ...
... Specimens were divided into three age classes that broadly reflect ontogenetic differences: neonate, juvenile, and adult (Supplementary Table S2). Individuals were categorized as: adults if they had a TL equal to or over 700 mm, as this is the average size reported for sexual maturity in different populations of P. patagoniensis 9,24,25,48 ; juveniles if their TL was lower than 700 mm; neonates if they retain egg tooth and exhibited umbilical scar that persists for few days to weeks in colubroidean snakes 49,50 . Due to the significant differences between sexes in jaw complex structures (e.g. ...
Dipsadidae is one of the largest clades of extant reptiles, showing an impressive morphological and ecological diversity. Despite this fact, the developmental processes behind its diversity are still largely unknown. In this study, we used 3D reconstructions based on micro-CT data and geometric morphometrics to evaluate the skull morphology of Philodryas agassizii, a small, surface-dwelling dipsadid that consume spiders. Adult individuals of P. agassizii exhibit a cranial morphology frequently observed in juveniles of other surface-dwelling colubroideans, represented in our analysis by its close relative Philodryas patagoniensis. Large orbits, gibbous neurocranial roof and a relatively short jaw complex are features present in juveniles of the latter species. Furthermore, we performed an extensive survey about diet of P. patagoniensis in which we detected an ontogenetic dietary shift, indicating that arthropods are more frequently consumed by juveniles of this dietary generalist. Thus, we infer that P. agassizzii retained not only the ancestral juvenile skull morphology but also dietary preferences. This study reveals that morphological changes driven by heterochronic changes, specifically paedomorphosis, influenced the retention of ancestral life history traits in P. agassizii, and therefore promoted cladogenesis. In this way, we obtained first evidence that heterochronic processes lead speciation in the snake megadiverse clade Dipsadidae.
... Localidad tipo: Brasil. Tipo de reproducción: Ovípara (Fowler & Salomão, 1995;Fowler et al., 1998). Ponen entre 4 y 11 huevos (Mesquita et al., 2013a). ...
Wildlife surveys are essential to conserve the biodiversity of a given region or area. In addition, in the light of ecosystem conservation problems, these surveys allow us to quickly identify which species should be a priority for conservation policies. Almost two decades have gone by since the last commented list of the snakes of Argentina was published, a period in which numerous and significant taxonomic changes have been made at a generic and specific level, and new species have been described, in addition to the inclusion of others previously recorded only in neighboring countries. This work is intended to update the systematic status of Argentine snakes and assemble information on their feeding habits, conservation, reproduction, etymology, common names, taxonomic changes, and main symptoms reported in accidents involving several colubrids and medically important viperid snakes. For this purpose, we carried out an extensive bibliographic review about Argentina and neighbouring countries snakes. In addition, we reviewed digital databases, and included our own unpublished data from herpetological collections and field work. To determine conservation status, we used the most recent categorization of Argentine snakes and the IUCN digital database. We present novel data for 8 families and 129 snake species that inhabit the Argentine territory.
... Studies of snakes have shown that on the average females are larger than males (approximately 15%) in species where males do not compete for mates, Shine (1994). The sexual dimorphism occurring in the SVL of P. patagoniensis indicates than the sexes reach maturity at different sizes; however, according to Fowler & Salomão (1995) it is known that growth is not a continuous process. Table 3. ...
The current study aimed to verify the relationship between the patterns of coloration, the morphometrical
features and pholidosis of specimens of Philodryas patagoniensis from Brazil, with the sexual dimorphism of this species. We studied specimens of P. patagoniensis deposited in several herpetological collections from Brazil. A total of 355 specimens were analyzed, of these 145 were males (87 adults and 58 juveniles) and 210 were females (134 adults
and 76 juveniles). Adult specimens exhibit sexual dimorphism in snout-vent length, tail length, head length, number of ventral shields, and number of subcaudal shields. The analysis of variance showed that the adult females are significantly longer than adult males, both at snout-vent length and tail length. Females have a greater number of ventral shields (138-210) than males (151-200). The specimens studied also exhibit two distinct patterns of coloration unrelated to geographical or sexual variations.
... O gênero Philodryas também pode ser encontrado em outros biomas e sua biologia é razoavelmente bem conhecida (cf. VITT, 1980;FOWLER & SALOMÃO, 1994;FOWLER & SALOMÃO, 1995;FOWLER et al., 1998;OLIVEIRA et al., 1999;HARTMANN & MARQUES, 2005 , 1937;THOMAS & DIXON, 1977;JENNER, 1981;ARGÔLO, 1999a,b;PUORTO et al., 2001;MORATO, 2005). ...
High-temperature chlorination of HPLC fullerene fractions containing mainly C92 /C94 and C102 /C104 resulted in the isolation and X-ray structural characterization of chloro derivatives of azafullerenes, C59 NCl5 and C97 NCl21 . It was assumed that formation of azafullerenes in the arc-discharge synthesis of fullerenes occurred due to air leakage into the reactor. The molecule of C59 NCl5 contains an isolated aromatic pyrrole ring on the fullerene cage and possesses C5v symmetrical shape typical of other known C59 NR5 derivatives. The molecule of non-classical (NC) C97 N(NC)Cl21 contains an NC6 heptagon on the azafullerene cage that assumes its formation by a C2 loss from C99 N in the course of chlorination. The chlorination pattern is characterized by the presence of stabilizing isolated aromatic systems and isolated double C=C bonds on the C97 N(NC) azafullerene cage.
We studied the reproductive biology of a subtropical population of Philodryas olfersii through the analysis of 263 museum specimens. Females were found to have larger bodies with males having longer tails. Testicular volume has a tendency to decrease in colder months but histological analyses are still needed to validate the macroscopic evidence. In females, secondary follicles were found throughout the year but ovulation was restricted to three months during the warmer period. Clutch size was correlated with female size and varied between 4 and 11 eggs, with a mean relative clutch mass of 0.187. Ovigerous females frequently also presented secondary follicles, and potential fecundity was significantly higher than real fecundity. We suggest that estimates of clutch size based on the number of vitellogenic follicles may be inappropriate. In addition, although some patterns of the reproductive biology of Philodryas olfersii were similar to other members of the tribe Philodryadini, we found important differences such as shorter reproductive season of females, indicating that phylogenetical traits and environmental conditions influence aspects of the life history of the species.
Oxyrhopus guibei Hoge and Romano, 1977 normally has terrestrial habits and nocturnal activity. This snake is found in the Brazilian states of Mato Grosso, Minas Gerais, Sao Paulo and Parana. Present work is a sequence of the previous study published in Biomedical Research (1999; 10: 35-40) and analyses body morphology and allometry in O. guibei using 30 adult animals (15 males and 15 females), none of which showed apparent signs of anomalies or pregnancy. Allometric study was carried out taking the body mass (BM) in grams and tail length (TL), mandibular width (MW), rostro-labial length (RLL), snout-vent length (SVL), and head length (HL) in millimeters. These data were correlated using the equation of the form log y = (b) log x + log a. Results of the allometric study showed the tail length with positive allometry and all the others body elements with negative allometry. The presence of tail length sexual dimorphism is associated to the occupation of terrestrial habitat; heavier females with positive allometry concerning width and rostral-labial comissure are related to advantages in reproduction and probably the existence of disproportional throphic structures in O. guibei.
Three reproductive traits in females were studied in NE New York near the northern limits of the species' range. The annual proportion of gravid females varied significantly, from 25% to 1985 to 77% in 1988. Most females (57%) reproduced at 3-yr intervals (triennial cycle) and 27% reproduced at 4-yr intervals (quadrennial cycle). Age of first reproduction ranged from 7-11 yr, with 61% of females reproducing for the first time at 9 and 10 yr. Among five populations of C. horridus, females from New York have the second highest proportionate increase in body length from birth to maximum adult size (2.79), the lowest prereproductive growth rate (7.9 cm/yr), and the latest minimum age of first reproduction (7 yr). A mean mass difference of 306 g between gravid and postpartum females may exceed a female's recovery ability in one nonreproductive year. This mass-recovery constraint may be a major proximate cause of the low-frequency reproduction in this population. Low growth rates and delayed age of first reproduction are other traits that co-vary with low-frequency reproduction. -from Author
The insular body size trends for different vertebrate families are compared. Certain groups such as lagomorphs, bats, artiodactyls, elephants, foxes, raccoons, snakes, and teiid and lacertid lizards are habitually represented by relatively smaller forms on islands. On the other hand, cricetid rodents, iguanid lizards, tortoises, and bears often have races with larger body sizes on islands. Contrary to conventional niche theoretic concepts, in many instances knowledge of the body sizes of some of these animals' insular and mainland competitors does not help explain the difference in that species body size in the 2 places. To account for these divergent size changes I examine optimum body size models that use as the optimization criterion the net energy gained by an organism over a given time period. These models predict that increases in the mean amount of available food should lead to evolutionary increases in body size, but only if body size is not tightly constrained by additional physical or biotic factors: such additional factors might be important if a change in body size alters an animal's effectiveness in finding or handling preferred food items or increases competition with its neighbors. Next using arguments derived from simple non-age-structured 2 species predator-prey models, the availability of food for a given consumer species at equilibrium is compared in theoretical island and mainland situations. Because islands usually contain fewer competitors and the insular physical environment is often more moderate, food availability for colonists is initially expected to be high. On the other hand, as the population grows resources will become depleted. Further, the loss of many predator species on islands may allow consumer densities to increase to such an extent that at equilibrium food may become relatively more limiting for consumers on islands than on the mainland. Whether the supply to demand ratio (S:D) of consumers for their food is ultimately greater or lower will depend on the relative magnitude of these various factors. Within this framework, a necessary condition for island S:D ratios to be greater than on the mainland is that the consumers maintain individual feeding territories. For animals whose body sizes are not tightly bound within narrow limits by physical or competitive restraints, an increase in S:D should lead to an evolutionary increase in body size. Accordingly, a good association is found between the presence or absence of territoriality and the direction of the insular body size shift in a number of different vertebrate groups. Yet there are exceptions which fall into 2 categories: First, if a species' mainland predators preferentially take larger individuals, selection favoring small size may override selection based on optimizing energy input. Such may have been the case for the now extinct mainland relatives of certain giant relictual insular reptiles. Secondly, an animal's body size may be tightly constrained by physical or competitive factors. The body size of island foxes, rattlesnakes, and some lizards appears to be primarily adjusted to the competitive milieu along typical niche theoretic lines. That is, body size may be predicted quite well from knowing the size class of competitors which are absent from an island or from differences in the species' prey-size distribution between island and mainland sites.
SYNOPSIS. Studies on the relation of temperature to tolerance, preference, metabolic rate, performance, circulation, and growth of sockeye salmon all point to a physiological optimum in the region of 15°C. Natural occurrence is limited in time and space at temperatures above 18°C despite being able to tolerate 24°C. Forms of physiological inadequacy can be demonstrated which account for such restrictions in distribution. Predictive power for locating and accounting for concentrations of young fish in thermally stratified lakes appeared to provide "proof" for the controlling influence of the physiological optimum temperature. Early literature on the ecology of sockeye supported this view. Recent studies using midwater trawls and sonar detection reveal a diurnal behavior pattern which points to a more subtle interaction of biotic andabiotic factors governing vertical distribution in which the controlling force appears to be bioenergetic efficiency. It is concluded that a mechanism of behavioral thermoregulation has evolved which favorably balances daily metabolic expenditures in order to conserve energy when food is limited.