Liophis miliaris

Common names

South American common names for this species include cobra-d'água (water snake) and cobra-lisa (smooth snake) in Portuguese, and simply culebra (snake) in Spanish.

Taxonomy

Originally described as Coluber miliaris by Carl Linnaeus in 1758, Liophis miliaris is one of more than fifty species in the genus Liophis. The original generic name, Coluber, was indicated to mean "common snake". Liophis miliaris is very polymorphic with a wide range of distribution.

Subspecies

Seven subspecies are recognized, including the nominotypical subspecies.

The subspecific name, merremi is in honor of German herpetologist Blasius Merrem.

Geographic range

Liophis miliaris is found in Brazil, Paraguay, Uruguay, and northeastern Argentina.

Physical characteristics

Liophis miliaris is stout-bodied (muscular) and relatively short-tailed. Tail length/total length ratios vary from 15.0%-19.8% with an average of 18.6.

Adults may attain a total length of about 50 cm (about 20 in).

Dorsally, it is pale olive-brown or yellowish, with each smooth dorsal scale edged with black. Ventrally, it is uniformly yellow.

Feeding

Liophis miliaris feeds on a wide range of prey items. They include amphibians (also, eggs and tadpoles), invertebrates, lizards, fish, birds, and small rodents. However, there is little information on its feeding habits. A study indicated that females with oviductal eggs did not feed, whereas those Liophis miliaris snakes with secondary vitellogenic follicles fed more often than did the non-reproductive females.

Sexual maturity

Sexual maturity is regarded by experts as difficult to determine; however, it can be assessed by the snout-vent length (SVL). Sexual maturity is positively correlated to mean body size. In order to determine the sexual maturity of a Liophis, scientists have determined the diameter of ovarian follicles if seen to be >10 as indicative of sexual maturity in females, as is the presence of oviducal eggs. Males were considered mature if the testes were large and turgid or if the deferent ducts were opaque and convoluted, indicating the presence of sperm. Females in the subspecies populations of Liophis miliaris meremmi and Liophis miliaris orinus were seen to be greater in body size than the males.

Sexual dimorphism

There is sexual dimorphism with respect to size of adult Liophis. Adult females are larger in the subspecies merremi and orinus. They were seen to be larger than the adult males. The sexual dimorphism index was seen to be similar in the geographic areas of the northern coastal Atlantic forest, southern coastal Atlantic forest, northern inland Atlantic forest and southern inland Atlantic forest. This was indicative of no geographic variation in sexual size dimorphism. It is believed that body size may differ either because of local genetic modification or direct phenotypic effect of food availability on the growth rates. In addition to body size, the comparison of head size in Liophis miliaris is seen to show no dimorphism. Head size is considered to be associated with inter-sexual dietary divergence.

Reproductive output

With respect to reproductive output in the northern and southern coast Atlantic forest, and the northern and southern inland forest, the reproductive output recorded for Liophis miliaris orinus and Liophis miliaris merremi were determined via number of eggs, size of eggs, and number of neonates. The mean egg volume in the southern coast Atlantic forest was seen to be the largest of the four regions. The reproductive frequency was lower in the northern coast Atlantic forest than the other regions.

Parasitism

Parasitism is not understood very well in the context of snake ecology. The only inferences that have been made are those with the influence on natural populations. It is thought to be related to the snakes feeding behavior and immunological resistance. Two parasites were discovered in the subspecies orinus and merremi. The first were adults of Ophidiascaris sp. (Nemaotoda) in the stomach. Also Cystacaths of Oligatanthorynchus spira (Acanthocephala) were in the peritoneum. The prevalence found in the four different regions, northern and southern coastal Atlantic forest and northern and southern inland Atlantic forest, were observed in Pizatto's and Marques' study. The lowest prevalence was seen in the northern coastal Atlantic forest. The level of parasite infestation did not differ between the males and females. Female reproductive status was unaffected by the level of infection, nor was the number of eggs she carried. The male reproductive system was unaffected by the level of infestation as well.

Liophis milaris intermedius, a taxonomic error

In 1991, Liophis miliaris intermedius was classified by Henle and Ehrl. However, they made a mistake. It was later discovered by Dixon and Tipton, through various comparisons of body composition, that Liophis miliaris intermedius was actually Liophis reginae.

Habitat

Liophis miliaris is seen in the Atlantic forest of South America, the rainforest in eastern Brazil, and the semideciduous forests in southeastern Brazil.