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The blue-spotted salamander (Ambystoma laterale) is a mole salamander native to the Great Lakes states and northeastern United States, and parts of Ontario and Quebec in Canada. Their range is known to extend to James Bay to the north, and southeastern Manitoba to the west. Blue-spotted salamanders include unisexual lineages that can reproduce without fertilization (gynogenesis).
Description
Blue-spotted salamanders are between in length, of which the tail comprises 40%. Generally, males are slightly smaller than their female counterparts. Their skin is bluish-black, with characteristic blue and white flecks on its back, and bluish-white spots on the sides of its body and tail. They have elongated bodies. The vent is typically black, which contrasts with the paler belly. Larvae that have transformed may have yellow splotches; these turn blue once the individual becomes terrestrial. Occasionally, a melanistic individual may be found in the wild.
They have long toes: four on the front feet and five on the hind feet. Typically, specimens will have 12–14 costal grooves. Males tend to be smaller than females, though they have longer, flattened tails.
Blue-spotted salamanders are nocturnal, staying underground during the day and coming out at night to find food.
Habitat
Blue-spotted salamanders are primarily found in moist, deciduous hardwood forests and swampy woodlands with sandy soil, Underbrush, leaf litter, rocks and logs are commonly used for shelter. Studies are beginning to show that habitat selection may also be affected by factors such as light pollution and chemical hues. Blue spotted salamanders are facing habitat loss.
Reproduction
Blue-spotted salamanders mate through the depositing and collecting of a spermatophore. A spermatophore is a packet of sperm that is deposited by the male. Reproduction is initiated by the male by taking hold of the female and rubbing her head with his chin. The female's eggs can be fertilized by the sperm in the spermatophore, but she must be in close proximity to the spermatophore. The male will try to position her so she is close enough that this can happen.
Eggs are laid in small agglomerations attached to twigs, rocks or plants at the edge of a woodland pond or ditch. Clutches average a dozen eggs, and females may lay up to 500 eggs yearly. Males and females first mate when two years old. Breeding occurs in early spring near vernal pools.
Eggs take about one month to hatch. At hatching, larvae have a well-developed mouth and eyes, as well as external gills and broad tail fins. The unisexual females often look like blue-spotted salamanders but have hybrid genomes Usually the eggs then discard the sperm genome and develop asexually (i.e., gynogenesis, with premeiotic doubling); however, they may incorporate the genome from the sperm into the resulting offspring.
In the northern portion of the blue-spotted salamander's geographic range, there is an area where this species interacts with a unisexual population of salamanders. The unisexual population of salamanders interacts with the blue-spotted salamanders to initiate reproduction, as the unisexual species is, for the most part, female. This interaction can be somewhat detrimental to blue-spotted salamander population because genes of the unisexual population are being promoted, creating competition between the two groups.
Pure-diploid blue-spotted salamanders (A. laterale) are among the rarest amphibians in the northeastern United States.
Relationship with Tremblay's salamander
Female Tremblay's salamanders (Ambystoma tremblayi) breed with male blue-spotted salamanders from March to April. Eggs are laid singly or in small masses of 6 to 10 eggs on debris at pond bottom. The males' chromosome contribution only stimulates the egg's development; its genetic material is ignored.
Defense
Blue-spotted salamanders have several defense mechanisms. The blue spots on the salamander's back and tail make it difficult for predators to clearly see the salamander. Blue-spotted salamanders also have specialized glands on their tails that secrete a milky substance which is harmful to predators. Having a large tail is also advantageous for a salamander as it can use its tail to shield its body from a predator. The large tail covered in a toxic substance would be the first part of the salamander that comes in contact with a predator's mouth, hopefully causing the predator to drop the salamander.