The green salamander (Aneides aeneus) is a species of lungless
salamander in the family
Plethodontidae.[2] It and the
Hickory Nut Gorge green salamander (A. caryaensis) are the only currently-described members of the
genusAneides that inhabit any areas in the eastern half of United States (all other Aneides salamanders are found west of the
Mississippi River). Rarely seen in the field,[3] the green salamander is an extremely habitat-specific
species that is seldom found away from its preferred surroundings: moist, shaded rock crevices. Green salamanders have one of the most specialized niches of any other salamander. [4]
Description and taxonomy
The green salamanders scientific name is Aneides aeneus. The name, Aneides, is Greek for “lacking form or shape”, in reference to their flattened, elongated bodies. The species epithet, aeneus, is Latin, meaning bronze or copper, and refers to their dorsal coloration.[5] The green salamander is small and notably flat. Green, lichen-like blotches against a darker dorsum make Aneides aeneus the only salamander in
North America with green markings.[3]A. aeneus possesses squared toe-tips, large, conspicuous eyes, and a light blue to yellow ventral surface. The square toe-tips, as well as a prehensile tail, are morphological adaptations that help the salamander with climbing.[6] Adults range from 8–12 cm (3 to 5 in) with 14 to 15 costal grooves.[7]
Aeneus was formerly considered the only species of the Aneidesgenus found in the Eastern
United States. However, some claimed that there could be up to four different species of Aneides between the
Cumberland Plateau and Blue Ridge Escarpment populations.[8] A 2019 study found several A. aeneus populations to represent distinct taxonomic groups, supporting the presence of a possible
species complex. At least one was found to represent a distinct species in its own right, the
Hickory Nut Gorge green salamander (A. caryaensis). The subgenus Castaneides was created to contain all eastern species of Aneides, with caryaensis being the most
basal member of the complex. Castaneides diverged from the Aneides hardii lineage between 27.2 and 32.3 million years ago.[9]
Members of Castaneides are the only
salamanders in
North America with green markings. Due also to their hyper-specific
habitat, they are almost unmistakable when found in the field.[9]
Aneides aeneus is an extreme
habitat specialist.[11][12] This species of Aneides is found almost exclusively in an environment following these guild-lines: A. aeneus prefers the crevices of rocks on the sides of cliffs or other outcroppings. Most crevices in which A. aeneus is observed, there is little to no sun light allowed in. This shade may be due to either vegetation outside of the crevice or outcroppings above the crevice.[7] While a number of instances of Aneides aeneus observations in
arboreal situations have occurred,[7] most of these instances are in trees either adjacent to rock outcroppings and cliffs, or the specimen in question was located underneath the bark of the tree. Habitat preferences shift seasonally, with trees serving as the primary habitat from May to September, and research suggest that green salamanders are more abundant in habitat at lower elevations with south-facing slopes. [13]
Males are extremely territorial toward other salamanders and would-be predators when disturbed or presented with any manner of threat.[14] Cupp observed aggressive behavior in 45 of 49 instances where a male was placed within an artificial territory of another. Such a high level of
aggression is rare in salamanders,[14] and is observed in few other
species, though hardly to the degree as observed in A. aeneus. This aggressive behavior, although in different forms, can also be observed in
brooding of the female A. aeneus over her eggs.[7] While the male A. aeneus will attack would-be invaders with such actions as butting, snapping, biting or snout-pressing,[14] females will often snap at objects placed within the breeding crevice or near the eggs she guards.
Annual cycle
Breeding period
Aneides aeneus has been observed to begin its period of sex and
courtship in late May to early June. For Aneides aeneus, the male will enter the breeding crevices and await the arrival of females.[7] These specialized crevices are considered the basis of a green salamander's territory, as they are defended by an individual throughout the breeding season. [15]Once a male and female meet, the courtship begins. Like some salamanders of genus Plethodon, A. aeneus begins courtship with the female straddling the base of the male's tail.[16] In this position, and with periodic nudging and encouragement from the male, the two will traverse a small circle within the rock crevice. After some time in this dance, the male will deposit a spermatophore[16] upon the ground and the female, still straddling the base of the male, eventually makes her way to it and “scoops” it up by lateral undulations and slow movements of the base of the tail of the female.[16]
Eggs are laid soon after courtship. The female A. aeneus lies on her back within the rock crevice, her ventral surface pressed against the ceiling. Egg-laying often takes a period of 20 to 30 hours, where the female will apply an adhesive substance to the surface of the rock, followed by a single egg. Clutches of eggs average 15-25 eggs. The female will stay with the eggs, usually wrapping her body around the cluster or at least pressed against it, guarding them for the entirety of development. When presented with a foreign object, be it a wire, stick, or a wandering insect, the female will attack, eating the invader if possible. Female A. aeneus are not known to feed during brooding. Individuals taken from their eggs had their stomachs and small intestines examined and were all found to be completely empty in Gordon's study in 1971. This guarding period usually lasts 3 months, where the eggs hatch in September.[7]
Dispersal and aggregation
Eggs of Aneides aeneus hatch throughout the month of September.[7]Aneides aeneus is a direct developing
salamander, which means it does not have a larval stage and develops to its adult phase within the egg. Juvenile A. aeneus emerge from the eggs resembling their parents, and will likely leave the crevice in which they were born within 2 months.[7] Following the hatching of their young, the female A. aeneus no longer shows the hyper-aggressiveness expressed during guarding. In fact, it has been observed that the females will do little to stop the collection or otherwise disturbance of her brood after they have hatched from the eggs. Newborn A. aeneus almost always leave the crevice in which they were born and do not return.[7]
Hibernation
A period in the annual cycle of Aneides aeneus called the pre-hibernation aggregation takes place in which A. aeneus will disperse from the breeding crevices. It is during this period, throughout the month of November, that most specimens of A. aeneus can be observed wandering over and between rock crevices.[7] Following this dispersal, it is thought that A. aeneus ventures deep within the interconnected crevices of the cliffs and rock outcroppings to
hibernate.[7] Attempts were made to find A. aeneus underground, beneath logs, within rotten logs, under rocks and under tree bark, but not a single specimen was produced.[7]
Post-hibernation aggregation and dispersal
Aneides aeneus emerges from
hibernation around the month of May. During this period, A. aeneus is observed wandering about the rock crevices and outcroppings, often during light rains at night.
Conservation
Efforts aimed towards the conservation of such a secretive
organism are proving complicated. While the fact that Aneides aeneus is such a habitat-specific
salamander results in more vulnerability to
habitat destruction, the cliffs and outcroppings it has chosen are relatively safe from harm. It has been speculated that A. aeneus inhabited the ancient
chestnut forest that covered a large percentage of the
Great Smoky Mountains National Park.[8] It is not known whether or not A. aeneus utilized these trees more or less than its currently preferred habitat, but it is certainly a possibility. When inhabiting arboreal habitats studies have found that green salamanders prefer hardwood trees to conifers.[17] Green salamanders have been negatively impacted by habitat loss, climate change, disease, and overcollection[18] In
Indiana, the green salamander is listed as an
endangered species.[19] Green Salamanders are listed as "imperiled" in Georgia and North Carolina as well as "critically imperiled" in South Carolina.[18]
^Frost, Darrel R. (2013).
"Aneides aeneus (Cope and Packard, 1881)". Amphibian Species of the World 5.6, an Online Reference. American Museum of Natural History. Retrieved 26 October 2013.
^
abConant, Roger et al. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin Company, Singapore. 1998.
^Corser, J.D (2001). "Decline of disjunct green salamander (Aneides aeneus) populaitons in the southern Appalachians". Biological Conservation.
^Soto, K. M., McKee, R. K., and Newman, J. C. 2021. Conservation Action Plan: Green Salamander (Aneides aeneus) Species Complex. Southeast Partners in Amphibian and Reptile Conservation
^
abcdefghijklGordon, Robert E. A Contribution to the Life History and Ecology of the Plethodontid Salamander Aneides aeneus. American Midland Naturalist. Vol. 47, No. 3 (May 1952), pp. 666-701.
^
abDobb, Kenneth C. The Amphibians of Great Smoky Mountains National Park. University of Tennessee Press, Knoxville, TN. 2004.
^Snyder, D.H. The Green Salamander Aneides aeneus in Tennessee and Kentucky, With Comments on the Carolina's Blue Ridge Populations. Journal of the Tennessee Academy of Science 66, 1991, pp. 165–169.
^John, R. R. (2019). "Overnight movements of Green Salamanders (Aneides aeneus) in Northern Alabama". Journal of Herpetology.
^Gordon, Robert E. and Smith, Richard L. Notes on the Life History of the Salamander Aneides aeneus. Copeia. American Society of Ichthyologists and Herpetologists
Vol. 1949, No. 3 (September 15, 1949), pp. 173-175.
^Soto, K. M., McKee, R. K., and Newman, J. C. 2021. Conservation Action Plan: Green Salamander (Aneides aeneus) Species Complex. Southeast Partners in Amphibian and Reptile Conservation
^
abcCupp, Paul V. Jr. Territoriality in the Green Salamander, Aneides aeneus. Copeia. American Society of Ichthyologists and Herpetologists. Vol. 1980, No. 3 (September 6, 1980), pp. 463-468.
^Rossell, C. Reed, Jr., et al. "Nest Success and Attributes of Brood Crevices Selected by Green Salamanders (Aneides aeneus) on the Blue Ridge Escarpment." The American Midland Naturalist, vol. 181, no. 1, Jan. 2019, pp. 40+. Gale Academic OneFile, link.gale.com/apps/doc/A574177910/AONE?u=clemsonu_main&sid=bookmark-AONE&xid=7654ddff. Accessed 19 Feb. 2024.
^
abcCupp, Paul V. Jr. Fall Courtship of the Green Salamander, Aneides aeneus
Herpetologica. Herpetologists' League. Vol. 27, No. 3 (September 1971), pp. 308-310.