North American Pit Viper Research Articles

Annual Cycle of Plasma Testosterone in Male Copperheads,Agkistrodon contortrix(Serpentes, Viperidae): Relationship to Timing of Spermatogenesis, Mating, and Agonistic Behavior

Reproductive cycles of the majority of squamate reptiles remain undescribed. Few studies are available on seasonal patterns of circulating steroid hormones in snakes. The goal of this study was to document the annual cycle of plasma testosterone (T) in male copperheads,Agkistrodon contortrix,a North American pitviper (Serpentes, Viperidae). Two experimental conditions were used in this laboratory study. One condition (repeat-test group) consisted of 10 adult males that were sampled once each month for 11 months. The other condition (single-test groups) consisted of 10 groups each with 5 males (N=50), and each male was tested a single time. The single-test condition was used to evaluate whether or not repeated handling and sampling affected T levels. The study was conducted from February–December, 1992. A well-defined seasonal pattern of plasma T levels was detected; patterns were similar under both experimental conditions with the exception that the repeat-test group had slightly lower levels. Levels of T were lowest (baseline) in April–May, increased in early summer (June), and were highest in late summer (August). Thereafter, T levels declined up to the time of hibernation (early November) and changed little during hibernation (November–January). Upon emergence from hibernation in late winter (February), T levels increased sharply from February to March and then decreased from March to April. The results are discussed in the context of timing of spermatogenesis, mating, and male agonistic behavior.

Intravenous dose-lethality study of American pit viper venoms in mice using standardized methods

An intravenous dose-lethality study of 14 clinically important North and South American pit viper venoms was carried out in mice using standardized, rigorous protocols developed to meet international (WHO) guidelines and US government (FDA) regulations for the development of new treatment products. The study was undertaken in order to establish baseline LD50 values for the ongoing testing of a new crotalid antivenin FAB prepared from sheep immunoglobulin (IgG). The venoms (lyophilized and pooled from juvenile and adult snakes of both sexes) were taken from 10 rattlesnake (nine Crotalus and one Sistrurus) species, two Agkistrodon species, and two Bothrops species. The dose-response data were subjected to probit analysis. Median lethal dose (LD50) values and their 95% confidence limits (CL) were calculated and statistical comparisons between the median potencies were made. The intravenous LD50s (and 95% CL) ranged from a low of 0.13 (0.10–0.15) mg kg–1 for Crotalus durissus terrificus, to a high of 6.32 (5.76–6.94) mg kg–1 for Crotalus horridus horridus. Significant positive rank-order correlations were also found for comparisons between the present LD5Os and published LD5Os for intravenous, intraperitoneal, and subcutaneous administration.

Immunodetection of North American pit viper venoms: Minton, S. A. and Weinstein, S. A.

Immunodetection of North American pit viper venoms: Minton, S. A. and Weinstein, S. A.

An enzyme-linked immunoassay for detection of North American pit viper venoms.

We describe a method for immunodetection of North American pit viper venoms in clinical materials. Antibody-enzyme conjugates prepared against venoms of the western diamondback rattlesnake (Crotalus atrox), Mojave rattlesnake (Crotalus scutulatus), and copperhead (Agkistrodon contortrix) detect homologous venoms in concentrations of 0.1-.01 mcg/ml using a double antibody sandwich technique. Venoms of 10 additional species of U.S. pit vipers were detected in concentrations of 10 mcg/ml or less. Venoms of 4 species could not be detected at levels likely to be encountered in clinical situations. There are extensive cross-reactions between venoms of certain species, hence specific identification of a given venom cannot always be made. Venom usually can be detected at injection sites of experimental animals receiving intramuscular doses of 0.5-1.5 mg of venom but can rarely be detected in urine or plasma specimens. Venom was readily detected in specimens from experimental animals bitten by pit vipers of 6 species. The method is relatively rapid, simple, and inexpensive.

Sexual Selection and Variance in Reproductive Success

Sexual Selection and Variance in Reproductive Success

Treatment of Bites of North American Pit Vipers

Treatment of Bites of North American Pit Vipers

Polyvalent Antivenin in the Treatment of Experimental Snake Venom Poisoning

SummaryThe protective effect of North American polyvalent antivenin was tested against the venoms of eight representative species of North American pit vipers. Mice injected with 2 LD50 of venom were treated by intraperitoneal or subcutaneous injection of 0.1 ml. of antivenin. Significant protection was obtained against the venoms of the San Diego rattlesnake (Crotalus viridis helleri) and the horned rattlesnake (Crotalus cerastes laterorepens). Questionable protection was obtained against the venoms of the timber rattlesnake (Crotalus h. horridus) and the massasauga (Sistrurus c. catenatus). No protection was observed against the venoms of the eastern diamondback rattlesnake (Crotalus adamanteus), the western diamondback rattlesnake (Crotalus atrox), the copperhead (Agkistrodon contortrix mokeson), and the water moccasin (Agkistrodon piscivorus spp.). Intraperitoneal injection of antivenin gave slightly better results than local infiltration of the injured tissue. Antivenin does not prevent local tissue necrosis under these circumstances. Neutralization of the venoms observed here is paraspecific; none of the venoms neutralized are used in the preparation of the antivenin.

The Polyvalency of Crotalidic Antivenins

Summary Those North American pit viper venoms which induce delayed paralysis are strongly neutralized by a monovalent antivenin prepared against a similarly acting venom. It is suggested that this may indicate a distinctive neurotoxic constituent in these venoms. All other North American pit viper venoms are better neutralized by a polyvalent antivenin.

The Polyvalency of Crotalidic Antivenins

Summary An immunizing mixture comprising a small number of rattlesnake venoms produces an antivenin with neutralizing power extending rather widely to venoms of other species of pit viper. Venoms of North American pit vipers form three antigenic groups, as follows: (a) most of the rattlesnake venoms; (b) venoms capable of causing late paralytic symptoms; (c) moccasin venoms. To yield a satisfactory polyvalent antivenin at least one venom from each of these groups must be included in the mixture used for injection of the antivenin-producing animal.

Studies on the Venoms of North American Pit Vipers

Summary This study of the venoms of North American pit vipers brings out the following points: The amount of venom secreted by each species varies directly with the size of the species.There are great differences in the toxicity of venoms from closely related species.The more primitive forms have venoms more toxic to the nerve centers.Species secreting a small amount of venom tend to have more active venoms, while those yielding large amounts have weaker venoms, so that the number of fatal doses in one extraction is more constant than are other factors.The larger species of viper give the largest number of fatal doses per extraction.The danger to man from the bites of pit vipers, varies almost directly with the size of the species.