Қызыл арқалы саламандр: Өмір сүру ортасы және түрлері

Species of amphibian

The red backed salamander (Plethodon cinereus) is a small, hardy woodland salamander species in the family Plethodontidae. It is also known as the redback salamander, or the northern red backed salamander to distinguish it from the southern red backed salamander (Plethodon serratus). The species inhabits wooded slopes in eastern North America, west to Missouri, south to North Carolina, and north from southern Quebec and the Maritime provinces in Canada to Minnesota. It is one of the most numerous salamanders throughout its range. Red backed salamanders are thus entirely reliant on cutaneous respiration for gas exchange. Permeable skin is susceptible to desiccation and must be kept moist in order to facilitate cutaneous respiration; as a result much of the ecology and behavior of the red backed salamander is restricted by climatic and microclimatic variables, particularly dryness and temperature. The skin of red backed salamanders was found to contain Lysobacter gummosus, an epibiotic bacterium that produces the chemical 2,4 diacetylphloroglucinol and inhibits the growth of certain pathogenic fungi.

Plethodon cinereus exhibits color polymorphism, the common ones being the red striped morph and the lead phase. The "red backed" or "red stripe" variety has a red dorsal stripe that tapers towards the tail, and the darker variety, known as the "lead backed" (or simply "lead") phase, lacks most or all of the red pigmentation. These color morphs are rarer than the red backed, lead backed, and erythristic morphs, but still have been reported with consistency among varying populations of this species. The red backed form is found with greater frequency in colder regions at more northerly latitudes and easterly longitudes throughout its range, whereas the opposite is true of the lead backed form. Standard metabolic rate has also been found to differ between the morphs at certain temperatures, with significantly lower metabolic rates being displayed by the lead backed form at 15 °C; However, more recent research indicates that a plastic response to thermal conditions during development also contributes to color morph determination; in one study, P. cinereus eggs incubated at a higher temperature hatched a greater proportion of lead backed morphs than eggs incubated at a lower temperature. Temperature dependent color morph determination may therefore also potentially influence the spatial distribution of P. cinereus color morphs. The two primary P. cinereus color morphs also differ in diet. Individuals confine themselves to moist microhabitats (beneath rocks, woody debris, etc. as well as beneath the soil) for long periods of time in order to maintain hydration when surface conditions are inhospitably dry or hot, and are only active on the surface to travel, forage, or reproduce for short periods. The duration of surface activity is directly limited by the rate of cutaneous water loss to the environment, which is influenced by environmental variables such as altitude, forest canopy cover, and the amount of recent precipitation. Spatial distributions of the salamander Plethodon cinereus is observed to be seasonal. In spring, Plethodon cinereus are more likely to exist in groups of around 2 to 7 individuals under some object covers such as rocks and wood, than in the other seasons, while the density on the forest floor stays constant. This is because that spatial dispute starts in spring. A study in Blackrock Mountain, Virginia indicates that the mean number of salamanders in each quadrant of 100*100 m varies from 1.6 to 3 in spring compared to 0.8 to 1.8 in summer. A significant increase in the spatial distribution of P. cinereus from spring to summer is thought to be due to intraspecific interference competition. The cover objects on the ground can be a good choice of moisture refuge for P. cinereus during the rainy season. The failure of P. cinereus to forage underground causes them to restrict down to areas under and around the cover objects. Aggression and territoriality under resource, food and shelter limitation are the reasons for the observed spacing. Stress levels of each color phase were estimated by determining the ratio of neutrophil to lymphocyte cells in the blood, and the results suggest stress levels are higher in the lead backed phase than in the red backed phase. This may be a consequence of a higher predation risk experienced in the wild by the lead backed phase, and may also mean lead phase salamanders could be more vulnerable in captivity settings. This allows for essential contact between a female and her eggs in order to ensure their survival, as well as for non attending females and males to explore beyond the home range when under predation pressures, or searching for food or cover, and return to their home range if a more favorable microhabitat is not found. It is necessary to have a visual display in order to elicit the threat posture of P. cinereus, and there will be no obvious aggressive behavior toward conspecifics and heterospecifics if only chemical cues exist. However, P. cinereus will increase time spent in aggressive postures when paired with centipedes but did not show increased aggression when paired with conspecifics. The specific test method was to expose male P. cinereus to four substrate chemical cue treatments separately: control, self, conspecific, or centipede (Scolopocryptops sexspinosus) to determine its behavior in the presence or absence of conspecifics and heterospecific cues reaction.

Males and females of P. cinereus typically establish separate feeding and/or mating territories underneath rocks and logs. However, some red backed salamanders are thought to engage in social monogamy, and may maintain co defended territories throughout their active periods. Breeding occurs in June and July. Females produce from four to 17 eggs in a year. The eggs hatch in 6 to 8 weeks. Not much is known about the dispersal of neonates, although neonates and juveniles are thought to be philopatric. As in many Plethodon species, female red backed salamanders have the ability to store sperm as spermatophore, and have been evidenced in doing so up to eight months prior to the oviposition period in June and July. Sperm or spermatophores are not retained following the oviposition period.

Roads have various negative effects on animal populations. For example, a major source of direct mortality for many species is accidental collisions with moving vehicles. Due to the slow movement of amphibians, it is estimated that the mortality rate of these animals on roads is as high as 10% of the total population each year. From a genetic point of view, roads also reduce gene flow and thus divide animal populations, causing drift and loss of genetic diversity. Eventually, populations separated by roads may become more and more distinct from each other, thus losing the original population. Amongst different sizes of roads, it is known that the interstate highway leads to increased genetic differentiation of Plethodon cinereus by microsatellite examination. Genetic distances between regions on either side of an interstate highway were significantly larger than those between equally spaced quadrants on the same side of the highway. However, plots on smaller roads were not genetically different compared to that in the case of interstate highways. Narrow paved roads reduce the movement of redback salamanders by approximately 25–75% but do not eliminate the dynamic of the population. And the detection of genetic differences across the interstate means that the spread on this road is reduced by well over 25–75%. So there is little gene flow across very large roads, and the P. cinereus population diverges from each other. The indirect effect of smaller roads on genetic population structure is also not a big issue for terrestrial salamanders and is not a direct effect of mortality and habitat change. The observed rate of dispersion in P. cinereus is far less than in most of the animals previously studied. Because P. cinereus have very high population densities, this should reduce the effects of genetic drift in isolated populations. From a conservation standpoint, red backed salamanders are an important research organism because of their behavioral and physiological similarities to many threatened and endangered salamanders.