Cane Toads (Rhinella marina) Research Writing Assignment (Research Paper Sample)

Cane Toads (Rhinella marina)
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Cane Toads (Rhinella marina)
Introduction
Cane toads are rough, and tough organisms that belong to the kingdom Animalia, phylum Chordata, class Amphibia, Order Anura, family Bufonidae, genus rhinella and its specific name is Marina. Even though Cane toad belongs to the order Anura which includes other types of frogs, it has exceptional features that differentiate it from other members of its family. It has a high ability to adapt to many places with different climatic conditions, but it is more dominant in Australia where it has minimal predators because of its poisonous nature. They have a gigantic body frame that makes them relatives heavier than members of the class Amphibia. They have a dry, warty skin which is rough and makes them appear dull in nature (Crossland, Brown, & Shine, 2011). They usually move by making small steps because of their relatively heavy weight that hinders them from jumping very high like other members of the class Amphibia. Its ability to reproduce and multiply rapidly is favored by its mode of feeding which is unique to members of its class because it feeds on its prey, independent of whether it is dead or alive. Their length for a normal fully grown cane toad range from 10 cm to 15 cm but mostly it is summarized to be about 6 inches long. However, the largest ever length recorded for a cane toad is 10 inches in length.
The cane toad is always referred to as an ancient species of the genius rhinella. The various scientific research studied argue that the present-day cane toad highly resembles the features of a fossil toad that was discovered in a deposit of floodplain. Rhinella marina has poisonous glands all over its dry, warty skin that makes it appear as if it has many pimples all over its skin though their under-body part appears like a white stretched canvas tent and had no poisonous glands. Their tadpoles are the most poisonous because of their tendency to release toxic chemicals when a predator feeds on them. Their unique feeding habit that involves eating every matter including the living and nonliving objects in a relatively large amount has made them more important to the people of the Caribbean island (Heise-Pavlov, & Longway, 2011). They highly prefer the cane toad in their farms to act as a pest control measure thus increasing their agricultural yield. Taxonomists derived the common name for cane toad from the cane beetle which is the dormant prey for the cane toad. Previously cane toad was preferred for pest control measures, and it was introduced in many regions especially the Caribbean island. However, today cane toad has turned to be a major concern in the agricultural sector. The cane toad has invasively concurred the agricultural sector as a serious pest that is causing the pest control department a lot of time and money.
Description
Rhinella marina is a gigantic heavy frog with the female toad being slightly longer than the male toads. An adult toad usually measures 6 inches in length though there was an incident where a very big cane toad was discovered, and it measured almost 10 inches in length. Their diversity is such that the big and heavy toads occupy the low populated regions with few human activities. They have a lifespan of between 10 -15 years for those inhabiting the forest or wild, but in some special cases, they can live longer than 15 years because there was a discovery that revealed a toad that lived for over 30 years of age. The body skin of the toad is dry, warty, and dull with many pores giving the skin a rough appearance (Hernández, Sernia, & Bradley, 2012). Depending on the nature of their surrounding they can be grey, red-yellow, olive brown or yellowish with varied patterns including trips or patched. They have a parotid gland around their eye region. Their toes are webbed in nature with protrusion of the fingers. A young, immature toad is characterized by a dark skin which is usually smooth compared to the skin of a fully grown adult toad which is usually dry and very rough. The young toads approaching the adult stage are relatively less poisonous compared to a tadpole or an adult toad. The tadpoles are minor and completely black in color. They are completely aquatic occupying the bottom layer of rivers and streams adding up to the benthic population in an aquatic system. The tadpoles range from 1 cm to 2.5 cm long. They always have a big spherical head with a small tail protrusion.
Ecology, Behavior and Life History
From the specific name, marina it is evident that the cane toad is associated with marine or aquatic life especially the tadpoles which breath through gills thus they cannot survive outside a water body. However, a fully matured adult rhinellla is a completely terrestrial organism which will only be found in fresh water bodies such as streams and rivers during its breeding time. Scientific research argues that a tadpole can tolerate a maximum salt concentration of about 14% - 18%. However recently researchers found some cane tadpole in sea waters with a salinity content of 28%. The cane toads are associated with woodlands and grassland regions though in the regions that have been modified by human activities they tend to occupy the swampy area such as the drainage systems and gardens (Lever, 2001). In the wild, the toads can occupy the subtropical forest though their activities are usually hindered by the foliage in the region.
The life cycle of a cane toad starts from an egg which is usually in the form of string covered with a protective mucoid layer and are laid in water bodies away from predators. A female toad lay over 10000 eggs at a go and can be stretched to a length of over 60 feet. The eggs are black in color covered with a jelly-like layer with a diameter of 1.8 mm. The rate at which the eggs will produce a tadpole will depend on variation in temperature. The toad poles eggs hatch within two days after fertilization by the male toad though the time may differ depending on the atmospheric temperature condition. The eggs hatch into many minute tadpoles that form in groups or cluster after ten days to 2 months the tadpoles enters the juvenile stage of its development. The eggs of a cane toad will successfully hatch into tadpoles without interference from animals because both the eggs and the tadpoles are poisonous thus they will never be feed on with any predator. Once the eggs hatch into tadpoles, they move and grow faster, but when they are about to enter the juvenile stage, the growth rate decreases drastically. Biologists argue that the tadpole usually has a higher growth rate because that is the only means of survival to evade their enemies and also overcome competition in the ecosystem. When the tadpole reaches the juvenile or intermediate stage, they lose their toxicity, and their skin becomes smooth and dark. As thy continue to grow, they develop a parotid gland near their eye region. The parotoid gland is what contains the poisonous bufotoxin which is usually a defensive measure from their enemies.
The rate at which the juvenile cane toad will attain its sexual maturity will depend on its strategic geographical location. For instance, a cane toad in new guinea will attain its sexual maturity at a length of 7cm while in Panama sexual maturity is attained at the length of 9cm. The pattern of breeding depends on the climatic conditions, for example, the rate at which the toads breed in the tropical region is higher than the rate of breeding in the subtropical regions where their breeding is favored only during the warmer seasons. The cane toads have a higher tolerance to climatic conditions because of their high critical thermal maximum which allows them to go into exile for a very long time.
Diet
The cane toad literally hunts for their prey which they trace with their high visualization power. At times the toad makes use of its sense of smell to trace for food. They have a wide diversity of prey to choose from because they consume both plants and small animals and insects.
Defenses
An adult cane toad has a dry, rough skin with parotoid glands which produces bufotoxin which is a very toxic chemical. The chemical is secreted from the glands when the toad is frightened or when it notices any danger. The chemical is toxic to the human being, domestic and wild animals. Studies on drug classify bufotein chemical under class one drugs meaning that its effect resembles that of heroin according to the Australian law (Morrison, Strahl-Heldreth, & Clark-Price, 2016). The clinical sign and symptoms that the chemical imposes in a human being include mild hallucinations that may last for a while or forever depending on the dosage of the toxin. Getting in touch with the chemical especially when the chemical is introduced into the digestive system of an animal apart from the toad, then there are chances of critical illness or even death of an individual. The cane toad usually inflates its lungs as it puffs up; thus it bulges off the ground to appear big to scare away the enemies.
Predators
Despite of its poisonous nature, they are still some potential predators that have a mechanism of neutralizing the toxin thus they can hunt and feed on the cane toad. Some of the potential predators include various species of snake such as the anulata, some catfish species which feed on the eggs and the tadpole of the cane toad. There is also the black rat, water monitor tawny frogmouth and some of the Australian crows.
Distribution
The toad is originally native to the United States of America where their population is spread along the Rio Grande valley all through to the central Amazon. They are also found in some of the continental islands within the vicinity of America. They are mostly populated in the tropical regions, but some are also found in the semiarid regions. The population of cane toad is highe...