The quacking frog (Crinia georgiana), also known as the red-thighed froglet due to its legs tending to be bright red, is a species of frog from the Myobatrachidae family and is in a clad with five other species. The frog is well known for the sound it produces which resembles a quack. It has up to 11 notes and can change the notes in their call. It has larger testes compared to other frogs within the genus and has started to be used in experiments. This frog is found in southwest Australia. It is found in ponds, pools, and other moisture filled areas. These frogs engage in polyandry and can result in multiple paternity of its offspring. Additionally, the tadpoles of this species can change the rate they metamorphosize depending on the conditions. The males tend to have larger arm girth and can adopt different mating strategies depending on size. The mating strategy is dependent on male density. The frogs also vary in terms of colour and texture of its skin. The tadpoles are generally golden with transparent tails.
Description
Crinia georgiana is a short or squat froglet that appears flattened and has a large head and short limbs. Characteristic of its family, this frog has long and unwebbed fingers and toes. The dorsal skin can be smooth, but it is usually bumpy or tubercular, while the underside is finely granular. The genus is polymorphic, however, meaning there is great variation in colour and texture of the skin within each species.Barker, J., Grigg, G. C., & Tyler, M. J. (1995). A field guide to Australian frogs. Chipping Norton, NSW: Surrey Beatty & Sons . In addition, some individuals may have a backside with skin folds, while others do not. Its colouring ranges from orange to brown to almost black on its back and may include brown marbling or brown stripes on either side of its back, which aid in camouflage. The belly of males is dirty-grey, while females have a bright white abdomen; both have a white spot at the base of each limb. The groin and anterior and posterior surfaces of the thigh are bright red and the upper eyelids are either red or golden. Its hands are pale in colour. These traits are characteristic of the quacking frog and make it easily distinguishable from other species. Tadpoles are golden in colour and their tail is transparent.
Crinia georgiana is unique compared to other species in the same genus as the testes' mass is significantly larger. This is attributed to extensive levels of sperm competition. The males of this species tend to have an arm girth that is greater than female arm girth. The froglet also has vomerine teeth. It is one of the only frogs within Myobatrachidae that have a variable note number.
Size Females are usually 30–36 mm, while males most often range from 24 to 32 mm, although the smallest calling males can be as small as 20 mm. Although the difference in size between males and females is not significant enough to constitute dimorphism, there is an unusually large variation in size of males in this species, which may be attributed to pressures of sexual selection. When tadpoles hatch, they tend to be 7 mm from snout to tail and can reach 20.5 mm prior to metamorphosis.
Population structure, speciation, and phylogeny
Phylogeny and close relatives There has been debate regarding the placement of species in the Crinia genus. Due to the distinctiveness of Crinia georgiana, the other species within the group were organized as either C. signifera or C. insignifera. C. georgiana does not form a distinct clade from other Crinia species. The sister group of the Crinia clade containing Crinia georgiana is the clade containing C. parinsignifera, with a difference at one branch. The clade contains C. georgiana, C. insignifera, C. glauerti, C. sloanei, C. subinsignifera, and C. pseudinsignifera; this meaning that C. georgiana is a sister taxon to five other Crinia species. The presence of vomerine teeth is one of the features used in the classification and differentiation of Crinia georgiana from other species. Based on calculations from the genetic distance and immunological distance, the divergence of C. signifera to C. georgiana is 6 million years, with the possibility of the divergence occurring due to exploitation of drier habitats.
Etymology Quacking frogs are also called red-thighed froglets. Quacking frogs were first located near Albany; thus, they were named after King George Sound. Habitat and distribution
Habitat Because water is essential to this species, it is confined to areas of the coastal plains and forests where water is abundant particularly in winter, when breeding occurs. It is often found in shallow water near sandstone settlements or in marshy bogs. In addition, the quacking frog is known to live amongst vegetation or in habitats that result from the activity of humans such as agricultural lands and rural gardens where water is likely to be plentiful.
Distribution This froglet is endemic to Australia, and is found only in southwest Western Australia from Gingin in the north, inland to Dumbleyung and east to Cape Le Grand. Most are distributed along the coast, with very few inland due to the necessity of water for survival, especially during breeding, which occurs in water.Davis, R. (1998). Quacking Frog – Crinia georgiana . westernwildlife.com.au
It is estimated that there are more than 50,000 adults currently present with the population size remaining stable or increasing slightly. Crinia georgiana is classified as a popular species.Cogger, H. Crinia georgiana . frogsaustralia.net.au
Conservation status The quacking frog is listed as Least Concern in terms of its conservation status based on its distribution and presumably large population. Its status is not currently determined to be threatened, though habitat loss due to human settlement and development along the coast of Western Australia may later pose a threat. Fortunately, much of its range is coincidentally located in protected areas, which may alleviate the effects of this threat. However, fungal pathogens have been found in some specimens, so disease may endanger their status in the future.
Human interaction From this frog, Crinia angiotensin II was isolated from its skin. Recent research has shown that this hormone can be used on other animals. This results from some research which indicated that the Crinia angiotensin II injected via intracerebroventricular route produces a similar effect to intravenous angiotensin II as it prompted water intake in pigeons. When Crinia angiotensin II was injected intravenously in rats and pigeons, it results in a hypertensive response like that of angiotensin II. This means that Crinia angiotensin II behaves similarly to angiotensin II in that it induces the body to increase blood pressure, body water and sodium content.
Diet and feeding habits In general, the diet of a frog is largely made up of insects, although mites, snails, earthworms, spiders, and other small animals are also consumed. Smaller frogs risk being eaten by larger frogs, as cannibalism is not uncommon. While larger frogs will sometimes feed on fish, it does not appear that this is prevalent among Crinia georgiana. Occasionally, grass, seeds, petals, and other vegetation will be found in the stomachs of frogs, but this is assumed to be accidental. In other words, the frog eats the plants only because other prey was resting on it.
Most frogs catch their prey via a flick of their tongue. The tongue is coated in a sticky secretion, which allows for the adhesion of the prey to the tongue. The catch is then taken into the mouth and swallowed right away, as frogs do not chew their food and many do not even have teeth. Members of Crinia do have vomerine teeth, which are pairs of teeth-like plates on the roof of the mouth that slant inward, but they appear to be rather unimportant. Once the food is in the stomach, the stomach compresses and abdominal muscles aid in digestion and expulsion of waste.Tyler, M. J. (1976). Frogs. Sydney: Collins .
Call The call of the quacking frog, just as its name suggests, is described as closely resembling the quack of a duck. There are usually 1–4 quacks in a sequence, but there can be up to 12 and males will respond to the calls of other males with the same amount of notes. The calls are used to attract females who are ready to mate. The call is distinct and loud,Example of the call (WMA file). frogsaustralia.net.au and these frogs will respond to imitations of their call.
Male Crinia georgiana emit calls that consist of 1-11 notes. However, there is variation in the number of notes that are produced, and this is dependent on stimuli. Using synthetic calls of 2 notes and 4 notes in experiments, it was shown that males match the number of notes. However, in experiments with a 1 note synthetic stimuli, more than 1 note was produced by the male quacking frog. In an experiment where 8 notes of synthetic stimuli were exposed to the male, the male produced less than 8 notes in response. When males of this species are exposed to artificial note stimuli, males alternate the notes that they produce. Additionally, the frogs adjusted the number of notes they produced based on the increase or reduction of the artificial stimuli that was presented. This may be an indication that quacking frogs have a behavior that is meant to minimize the occurrence of call overlap.
Even though they have an array of calls, the calls are categorized as high or low pulse rates. In the C. georgiana, the first note is longer than the other notes that come in succession. However, not all males are able to match the number of notes that they are exposed to precisely, which indicates that there is a form of latency regarding call matching. The number of notes presented in a stimulus was correlated to the latency of the male's response. Human movement in the areas where these frogs inhabit during the day or evening will result in the hiding males to respond with quacks.
Mating Male-male interaction Call matching is present within the species of the quacking frog. Call matching is said to be competitive and is presented as the producing and matching the number and complexity of call(s) between male neighbours. In cases where there are multiple calls that occur, if the time between two consecutive calls is greater than 1.5s apart then the responding male will only respond to the first stimulus and will ignore the second stimulus. Some scientists theorize that the quacking frog has a leader follower relationship due to the presence of long intervals between short advertisement calls and the fact that males usually never interrupt neighbouring male calls. Also, males have never been recorded to produce calls that were distinctively aggressive. A hypothesis that some in the field have is that call matching is a way in which calls are somewhat attractive or equivalent to the neighbouring males but with minimizing energetic cost.
In the male quacking frog, there seems to be an interaction between the size and origin of the population that contributes to variation in the sperm characteristics; this variation indicates that certain males that have specific sperm characteristics within the population use different reproductive strategies.