Crotalus Polystictus Research Articles

Physiological thermal responses of three Mexican snakes with distinct lifestyles.

The impact of temperature on reptile physiology has been examined through two main parameters: locomotor performance and metabolic rates. Among reptiles, different species may respond to environmental temperatures in distinct ways, depending on their thermal sensitivity. Such variation can be linked to the ecological lifestyle of the species and needs to be taken into consideration when assessing the thermal influence on physiology. This is particularly relevant for snakes, which are a very functionally diverse group. In this study, our aim was to analyze the thermal sensitivity of locomotor performance and resting metabolic rate (RMR) in three snake species from central Mexico (Crotalus polystictus, Conopsis lineata, and Thamnophis melanogaster), highlighting how it is influenced by their distinctive behavioral and ecological traits. We tested both physiological parameters in five thermal treatments: 15 °C, 25 °C, 30 °C, 33 °C, and 36 °C. Using the performance data, we developed thermal performance curves (TPCs) for each species and analyzed the RMR data using generalized linear mixed models. The optimal temperature for locomotion of C. polystictus falls near its critical thermal maximum, suggesting that it can maintain performance at high temperatures but with a narrow thermal safety margin. T. melanogaster exhibited the fastest swimming speeds and the highest mass-adjusted RMR. This aligns with our expectations since it is an active forager, a high energy demand mode. The three species have a wide performance breadth, which suggests that they are thermal generalists that can maintain performance over a wide interval of temperatures. This can be beneficial to C. lineata in its cold habitat, since such a characteristic has been found to allow some species to maintain adequate performance levels in suboptimal temperatures. RMR increased along with temperature, but the proportional surge was not uniform since thermal sensitivity measured through Q10 increased at the low and high thermal treatments. High Q10 at low temperatures could be an adaptation to maintain favorable performance in suboptimal temperatures, whereas high Q10 at high temperatures could facilitate physiological responses to heat stress. Overall, our results show different physiological adaptations of the three species to the environments they inhabit. Their different activity patterns and foraging habits are closely linked to these adaptations. Further studies of other populations with different climatic conditions would provide valuable information to complement our current understanding of the effect of environmental properties on snake physiology.

Supernumerary rattle growth in a Mexican lance-headed rattlesnake Crotalus polystictus

Supernumerary rattle growth in a Mexican lance-headed rattlesnake Crotalus polystictus

Hybridization between Crotalus aquilus and Crotalus polystictus Species: A Comparison of Their Venom Toxicity and Enzymatic Activities.

Simple SummaryWhen two different species or subspecies of animals have progeny, we speak about hybrid organisms, which present a mixture of the genetic characteristics of their parents. This phenomenon occurs in nature in a common way, although most of the time the hybrids between species are sterile. In this work, the venom characteristics of hybrids from two species of rattlesnakes were studied: Crotalus aquilus (father) and Crotalus polystictus (mother), both endemic to central Mexico. Scale numbers (phenetic analysis) and venom protein were compared between hybrids (females and males), biological parents, and adult individuals of the two species. The presence and activity of the main types of enzymes in these venoms were analyzed, and the lethal dose was determined in mice. Through the phenetic analysis, it was observed that the hybrids were more similar to C. polystictus (mother), the presence of proteins and enzymatic activity resulted in a combination of the two species, but the lethality of the venom was greater in the hybrids. These results allow us to learn more about the way in which the hybridization phenomenon influences the characteristics of rattlesnake venom. Some of the applications of this knowledge could be used to develop more effective antidotes.Hybridization is defined as the interbreeding of individuals from two populations distinguishable by one or more heritable characteristics. Snake hybridization represents an interesting opportunity to analyze variability and how genetics affect the venom components between parents and hybrids. Snake venoms exhibit a high degree of variability related to biological and biogeographical factors. The aim of this work is to analyze the protein patterns and enzymatic activity of some of the main hemotoxic enzymes in snake venoms, such as serine proteases (trypsin-like, chymotrypsin-like, and elastase-like), metalloproteases, hyaluronidases, and phospholipase A2. The lethal dose of 50 (LD50) of venom from the Crotalus aquilus (Cabf) and Crotalus polystictus (Cpbm) parents and their hybrids in captivity was determined, and phenetic analysis is also conducted, which showed a high similarity between the hybrids and C. polystictus. The protein banding patterns and enzymatic activity analyze by zymography resulted in a combination of proteins from the parental venoms in the hybrids, with variability among them. In some cases, the enzymatic activity is higher in the hybrids with a lower LD50 than in the parents, indicating higher toxicity. These data show the variability among snake venoms and suggest that hybridization is an important factor in changes in protein concentration, peptide variability, and enzymatic activity that affect toxicity and lethality.

Inhibition of cancer cell migration by disintegrins from the venom of Crotalus polystictus snake

Inhibition of cancer cell migration by disintegrins from the venom of Crotalus polystictus snake

The effect of thermal gradient design on the evaluation of thermoregulation in snakes

Hertz et al. (1993) designed what is now the most widely used protocol to analyse the thermal strategies and efficiency of small squamates. Preferred temperature range (Tp) is one of the most important variables required for determining the thermal efficiency index, and is calculated by monitoring the body temperature of the individuals in an enclosure containing a thermal gradient. Although thermoregulation studies of lizards have traditionally employed thermal gradients under laboratory conditions, this approach is not suitable for snakes given that such thermal gradients do not accurately represent their natural thermal environment and thus may result in snakes selecting suboptimal temperatures. Here, we compare the results of this thermal efficiency protocol using a laboratory thermal gradient (LG) and a semi-captivity thermal gradient (SCG) in the rattlesnake Crotalus polystictus. We found traces of seasonal variation in the SCG Tp, but this could not be assessed in the LG. Tp from the LG was much higher (29 – 34.3 °C) than from the SCG (22.5-30.9 °C). Values for the accuracy of thermoregulation (db) and thermal quality of the environment (de) indices from the LG were consistently higher than from the SCG. However, the efficiency of thermoregulation (E) was higher when calculated from the SCG. Tp estimates were wider than most that have been obtained from other snake species, suggesting that C. polystictus is eurythermic. The Blowin Demers and Weatherhead index was nearly identical in both gradients. Results from the LG indicated that C. polystictus is an inaccurate and inefficient thermoregulator, due to the higher temperatures chosen in this environment. In contrast, results from the SCG suggested that it is a highly accurate and active thermoregulator. We suggest that the LG could represent a stressful environment for snakes, and, as a consequence, they might select higher temperatures to increase anti-predatory performance at the expense of less efficient thermoregulation. Generally, a thermal gradient that more accurately replicates the natural habitat of snake species should reduce stress and result in more robust estimates of thermoregulatory variables.

Venom Ontogeny in the Mexican Lance-Headed Rattlesnake (Crotalus polystictus).

As trophic adaptations, rattlesnake venoms can vary in composition depending on several intrinsic and extrinsic factors. Ontogenetic changes in venom composition have been documented for numerous species, but little is known of the potential age-related changes in many rattlesnake species found in México. In the current study, venom samples collected from adult and neonate Crotalus polystictus from Estado de México were subjected to enzymatic and electrophoretic analyses, toxicity assays (LD50), and MALDI-TOF mass spectrometry, and a pooled sample of adult venom was analyzed by shotgun proteomics. Electrophoretic profiles of adult males and females were quite similar, and only minor sex-based variation was noted. However, distinct differences were observed between venoms from adult females and their neonate offspring. Several prominent bands, including P-I and P-III snake venom metalloproteinases (SVMPs) and disintegrins (confirmed by MS/MS) were present in adult venoms and absent/greatly reduced in neonate venoms. Age-dependent differences in SVMP, kallikrein-like, phospholipase A2 (PLA2), and L-amino acid oxidase (LAAO) activity levels were confirmed by enzymatic activity assays, and like many other rattlesnake species, venoms from adult snakes have higher SVMP activity than neonate venoms. Conversely, PLA2 activity was approximately 2.5 × greater in venoms from neonates, likely contributing to the increased toxicity (neonate venom LD50 = 4.5 μg/g) towards non-Swiss albino mice when compared to adult venoms (LD50 = 5.5 μg/g). Thrombin-like (TLE) and phosphodiesterase activities did not vary significantly with age. A significant effect of sex (between adult male and adult female venoms) was also observed for SVMP, TLE, and LAAO activities. Analysis of pooled adult venom by LC-MS/MS identified 14 toxin protein families, dominated by bradykinin-inhibitory peptides, SVMPs (P-I, P-II and P-III), disintegrins, PLA2s, C-type-lectins, CRiSPs, serine proteinases, and LAAOs (96% of total venom proteins). Neonate and adult C. polystictus in this population consume almost exclusively mammals, suggesting that age-based differences in composition are related to physical differences in prey (e.g., surface-to-volume ratio differences) rather than taxonomic differences between prey. Venoms from adult C. polystictus fit a Type I pattern (high SVMP activity, lower toxicity), which is characteristic of many larger-bodied rattlesnakes of North America.

Primer registro de crotalus polystictus (squamata: viperidae) en el área natural protegida sierra de Quila, Jalisco, México

Crotalus polystictus es Una serpiente de cascabel endémica de México. Se considera bajo protección especial de acuerdo a la NOM-059-2010-SEMARNAT. Crotalus polystictus fue registrada por primera vez en el área Natural protegida Sierra de Quila, Jalisco. Este registro se encuentra a por lo mneos 31 km al noroeste del punto más cercano de su distribución conocida.

Análise preliminar revela baixos níveis de diversidade na estrutura filogeográfica da cascavel mexicana Crotalus polystictus (Serpentes: Viperidae).

Se investigaron las relaciones matrilineales entre poblaciones de la serpiente de cascabel Mexicana cabeza de lanza (Crotalus polystictus), esta especie se distribuye en valles que presentan elevaciones altas de la meseta del sur de México. Se analizó un fragmento mitocondrial de la ATPasa 8 y 6, los genes (589 pares de bases) revelaron bajos niveles de diversidad genética, con poco polimorfismo nucleótico entre la muestra geográfica analizada. La poca divergencia (1.0%) intraespecífica encontrada en los genes de la ATPasa 8 y 6 en C. polystictus contrastan con los fuertes porcentajes de divergencia (~1.0–14.1%) que han sido observados dentro de otros linajes de serpientes de cascabel mexicanas que habitan elevaciones altas. La variación intraespecífica es observadacomúnmente en especies de cascabel que se distribuyen en elevaciones menores y que presentan una distribución amplia (por ejemplo, C. tigris). Proponemos que la baja diversidad genética encontrada en C. polystictus comparada con la diversidad registrada en otras serpientes de cascabel que habitan elevaciones altas, se debe a diferencias ecológicas que han dado como resultado una respuesta evolutiva diferente en esta especie a los eventos climáticos del Pleistoceno. Nuestros resultados de una aparente baja diversidad genética en C. polystictus son un fuerte soporte para hacer un llamadoa la importancia de realizar iniciativas de conservación para proteger praderas con elevaciones altas en el centro de México.

Sexual differences in head form and diet in a population of Mexican lance-headed rattlesnakes, Crotalus polystictus

Sexual dimorphism of phenotypic traits associated with resource use is common in animals, and may result from niche divergence between sexes. Snakes have become widely used in studies of the ecological basis of sexual dimorphism because they are gape-limited predators and their head morphology is likely to be a direct indicator of the size and shape of prey consumed. We examined sexual dimorphism of body size and head morphology, as well as sexual differences in diet, in a population of Mexican lance-headed rattlesnakes, Crotalus polystictus, from the State of Mexico, Mexico. The maximum snout–vent length of males was greater than that of females by 21%. Males had relatively larger heads, and differed from females in head shape after removing the effects of head size. In addition, male rattlesnakes showed positive allometry in head shape: head width was amplified, whereas snout length was truncated with increased head size. By contrast, our data did not provide clear evidence of allometry in head shape of females. Adults of both males and females ate predominately mice and voles; however, males also consumed a greater proportion of larger mammalian species, and fewer small prey species. The differences in diet correspond with dimorphism in head morphology, and provide evidence of intersexual niche divergence in the study population. However, because the sexes overlapped greatly in diet, we hypothesize that diet and head dimorphisms in C. polystictus are likely related to different selection pressures in each sex arising from pre-existing body size differences rather than from character displacement for reducing intersexual competition. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 633–640.

Reproductive ecology of female Mexican lance‐headed rattlesnakes

Our understanding of snake biology is heavily biased towards species and populations occurring at higher latitudes. In particular, little information is available concerning the biology of the numerous species of Mexican rattlesnakes. We studied the reproductive ecology of female Mexican lance-headed rattlesnakes Crotalus polystictus in a montane (c. 2500 m a.s.l.) valley of the Rio Lerma, in the Mexican state of México. We collected data from 162 different females and 203 litters over 4 years (2004–2007). Parturition coincided with summer monsoon rains, with the majority of females giving birth in late June and early July. Larger females and females gestating larger litters typically gave birth earlier in the summer than did smaller females and females gestating smaller litters. Some females matured rapidly; 26 females reproduced as 3-year olds, 17 as 2-year olds and a single female reproduced at 1 year of age. Females commonly reproduced in consecutive years. Litter size and mean neonate size increased with maternal body length; however, the relative clutch mass did not vary with female size. The mean litter size was 7.3 neonates (range 3–15), and the mean neonate body length (snout–vent length) and mass were 198 mm and 8.7 g. Neonate size varied less than did other litter characteristics. Rapid maturity, frequent reproduction and synchronization of parturition with seasonal precipitation are consistent with previously observed patterns of snake reproduction at lower latitudes.

Cannibalism of nonviable offspring by postparturient Mexican lance-headed rattlesnakes, Crotalus polystictus

Female vertebrates frequently ingest undeveloped ova and stillborn offspring. Two hypotheses have been proposed to interpret this behaviour: (1) it is a form of parental care, and (2) it recycles otherwise wasted energy, facilitating maternal recovery. Our study of Mexican lance-headed rattlesnakes provides the first quantitative description of cannibalism by postparturient rattlesnakes. We collected gravid females during June–July of 2004–2007 in central México, recording 239 litters from 190 females. Production of nonviable offspring was common (48% of litters). Most females (68%) ate some or all nonviable offspring, consuming an average of 11% of postpartum mass. Females consumed undeveloped ova and stillborn neonates in similar proportions. To evaluate factors that influenced the decision to cannibalize we used logistic regression. The best model included four predictive variables: (1) parturition date; (2) proportion of nonviable offspring mass per litter; (3) maternal investment index; and (4) snout–vent length (SVL). All variables exerted a positive effect on maternal cannibalism, although SVL was only a marginally significant predictor. Consumption of nonviable offspring confers energetic benefits to emaciated postparturient females. Energetic benefits are greatest when a large proportion of a litter is nonviable, while the pressure to cannibalize is greatest when late parturition shortens the time available to forage before the next reproductive event. Our results demonstrate the importance of maternal cannibalism in rattlesnakes, and suggest stronger support for the maternal recovery hypothesis than for the parental care hypothesis.

Comparative enzymatic study of HPLC-fractionated Crotalus venoms

1. 1. Ten venoms of the genus Crotalus ( Crotalus adamanteus, Crotalus atrox, Crotalus durissus durissus, Crotalus horridus horridus, Crotalus lepidus, Crotalus polystictus, Crotalus molossus molossus, Crotalus pusillus, Crotalus scutulatus scutulatus, venom B, and Crotalus viridis lutosus) were fractionated using HPLC anion and cation exchange chromatography. 2. 2. HPLC venom fractions were tested for hemorrhagic, hemolytic, and proteolytic activities. 3. 3. Crude Virginia opossum ( Didelphis virginiana) serum neutralized the hemorrhagic activity of HPLC fractions.

Envenomation by the Mexican lance-headed rattlesnake Crotalus polystictus: a case report

—A case of envenomation by the Mexican lance-headed rattlesnake, Crotalus polystictus, resulted in local swelling and muscle fasciculation, which abated after i.v. antivenin and an area of necrosis healed. A mild thrombocytopenia and hypofibrinogenemia with elevation of fibrin split products was noted.