The spring peeper (Pseudacris crucifer) is a small chorus frog widespread throughout the eastern United States and eastern Canada. It prefers permanent ponds due to its advantage in avoiding predation; however, it is very adaptable with respect to the habitat it can live in. In northern regions, the frog is able to endure below freezing temperatures due to the capacity of its liver to exude and flush the bloodstream with a glucose cryoprotectant which acts both as an anti-freeze in its blood, and allows organs like the heart to enter into a state of protected dormancy. The peeper earned its name from its chirping call, which marks the beginning of spring. Crucifer is derived from the Latin root meaning "cross-bearing", a reference to the cross-like pattern on the spring peeper's dorsal side. These chirping calls are significant for communication in mating as females choose their mates based on the frequency and volume associated with them. Satellite males who do not make any calls also strategically place themselves near those that make louder calls in an attempt to intercept females. Temperature plays a large role in when the spring peeper begins breeding as well as the duration of mating. Warm spells result in a massive increased calling rate.
Description The spring peeper is a tan, grey, or brown frog with a dark cross on its dorsa (thus the Latin name crucifer, meaning cross-bearer), though sometimes the marking may be indistinct. Dark lines can also be found between the eyes and in a crossband on the hindlimbs of P. crucifer. It has a body length between less than 25 mm (0.98 in) to 38 mm (1.5 in) and a mass between 3 and 5 g (0.11 and 0.18 oz). Unlike some other Pseudacris species, P. crucifer does not have white lines on its lips, but its lips may be lighter than its head.
Anatomy and physiology The species has large toe pads for climbing, although it is more at home amid the loose debris of the forest floor. Because of its toepads, the spring peeper was once thought to be more closely related to treefrogs than chorus frogs and was placed in the genus Hyla, but it is now in the genus Pseudacris. The color variations of P. crucifer are mostly tan, brown, yellow, pink, olive green, and gray. All have a slightly pale yellow coloration on the inside of the thighs. Females are lighter-colored, while males are slightly smaller and usually have dark throats. Females have a bulkier abdomen. Skin color of Spring Peepers is also affected by temperature and light. Coloration is dynamic and adaptable in this species. It can be altered quickly, in 15 to 45 minutes, in order to better camouflage from predators. This frog has a vocal sac that expands and deflates like a balloon to create a short and distinct peeping sound. Only males can make this loud high-pitched noise, and they use it to attract mates.
In the female spring peeper, protruding beyond the lower jaw of the frog sits its snout. Through the use of adhesive pads located on the tips of their non-webbed fingers, spring peepers can stick to particular materials. Males and females are differentiated from one another through the darkening of the skin beneath the jaw in males. Males have a body length ranging from 18–30 millimetres (0.71–1.18 in), and females have a body length ranging from 20–35 millimetres (0.79–1.38 in).
Glands and toxins In Pseudacris crucifer males, the blackened pigmentation of the testis affects the seminiferous tubules, the underside of the peritoneum, and the organ itself. The tubules of the testis are surrounded by a pigment layer and a layer of flattened epithelial cells which are located within the surrounding connective tissue. The thickness of an average testis is about 1.10 mm and 2.5 mm in length. The spermatogonia are a cluster of masses jutting out from the tubule lumen. In the late fall, the spermatozoa, located in the seminiferous tubules of the spring peeper, mature and remain there until the spring for breeding. After the seminiferous tubules are emptied, during mating season, the pigmentation of the testis changes from black to a dull grey. In the spring peeper, most of its energy is used during courtship. Higher energetic costs in female spring peepers are associated with gametogenesis, which occurs before breeding. Stored reserves of fat and glycogen contents can be measured early in the reproductive process to determine the amount used in spring peepers and their correlation to body size. Nonpolar lipid and glycogen content in male spring peepers increased with body mass, whereas in females, it decreased or had minimal variation. The fiber triglyceride and glycogen contents of the female spring peeper's liver increased significantly slower than in males as body mass increased. At the beginning of the breeding season, male spring peepers have more significant amounts of bodily lipid content. Therefore, those that are larger are experiencing lower efficiencies in calling. More reserves of glycogen and lipids are required to maintain calling during the season and require additional rationing of reserves to prepare themselves for courtship. In females, there is a positive correlation between their snout length and wet ovary mass, which also correlates to an increase in body size.
Respiratory and circulatory system The bigger, older, and more fit male spring peepers are typically superior callers. These types of males utilize citrate synthase and β-hydroxyacyl CoA dehydrogenase in their muscles at greater levels. Males with higher calling rates also tend to inhibit larger ventricles and greater concentrations of blood hemoglobin; both the large ventricle size and blood hemoglobin concentrations play a significant role in the speed of oxygen consumption, which is intensely linked to the calling rate. When a male spring peeper calls, the sound is made by the contraction of external and internal oblique muscles which subsequently force air out of the lungs, then move through the larynx to the vocal sac. Of the total body weight of male spring peepers, 15% is made up of the trunk muscles – which contain 2% of lipids in the body by volume – and showcase enzymes with mitochondrial markers. Calls that occur at rapid rates result in prominent energetic costs, which is why stored lipids are the source of 90% of energy applied to calling.
… excerpt ends here. Continue reading the full article.
