Description

DESCRIPTION: (A description of species morphology as if you had the amphibian in your hand, typically starting with the snout-vent length, then focusing from the head to the body and extremities)

DIAGNOSIS: (How this species is differentiated from similar species)

Gyrinophilus subterraneus is closely related and sympatric to G. porphyriticus. Gyrinophilus subterraneus can be diagnosed based on its larger size, having a maximum larval snout-vent length of 112 mm (80 mm snout-vent length in G. porphyriticus); smaller eyes, with an eye diameter to snout-vent length ratio of 0.015 - 9.031 (compared to 0.026 - 0.031 in G. porphyritius); greater postorbital head width, with a head width to head length ratio of 0.80 - 1.03 (0.80 - 0.90 in G. porphyriticus); and the presence of two or three irregular rows of pale spots running laterally. Transformed G. subterraneus adult has smaller eyes with a ratio of eye diameter to snout-vent length of 0.023 - 0.031 (0.032 - 0.036 in G. porphyriticus), paler coloration, and indistinct canthus rostralis. Lastly, large larval and transformed adult G. subterraneus lose their sight, showing little or no optomotor response. Gyrinophilus porphyriticus larvae and adults consistently respond to visual stimuli (Besharse and Holsinger 1977).

COLORATION: (In life and/or in preservative)

VARIATION: (if known)

Transformed G. subterraneus have a canthus rostralis, which is a characteristic of Gyrinophilus, but it may be indistinct due to lighter pigmentation (Besharse and Holsinger 1977).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: West Virginia

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (1 records).

Gyrinophilus subterraneus is geographically isolated from all known troglobiotic salamanders except for G. porphyriticus, as it is only known to occur in General Davis Cave in Greenbrier County, West Virginia, United States of America. Other spring and cave habitats in the central Appalachian region only contain populations of G. porphyriticus. The stream that flows in the General Davis Cave originates from a surface stream that flows through the Sinks-of-the-Run Cave to the southeast. The stream depth ranges from 15 to 30 cm, with salamanders having been reported to occur as deep as 1800 m into the cave (Besharse and Holsinger 1977).

Life History, Abundance, Activity, and Special Behaviors
Gyrinophilus subterraneus specimens were found along the mud banks of a stream passage in the cave, with some larvae in the stream. In the cave, G. subterraneus appears to be more abundant than G. porphyriticus (Besharse and Holsinger 1977). Only transformed individuals have shown sexual maturity (Grant et al. 2022). However, large larvae develop mature gonads, suggesting sexual maturity and the evolution of pedogenesis. It is unknown whether large larvae can or have reproduced (Besharse and Holsinger 1977).

Visual ability degenerates before transformation, with large larvae and transformed adults giving little to no response to movements in the visual field (Besharse and Holsinger 1977).

Larva
From one immature male specimen, the snout-vent length is 107 mm and the total length is 177 mm. The snout is slightly longer than it is wide. The snout (13.2 mm) is over twice as wide as it is long (4.9 mm). The eye diameter is 2.4 mm. The eye is sunken with the cornea, which has a diameter of 1 mm, hardly visible from the surface. The forelimbs and hind limbs are of equal length (both 17 mm). Relative finger lengths on the forelimbs are I < IV < II < III, while the relative length of the toes on the hind limbs are I < V < II < IV < III. There are 17 costal grooves between the axilla and groin, and seven between appressed limbs. There are 18 trunk vertebrae (Besharse and Holsinger 1977).

In life, larvae have a brown-pink color, which is darker on the dorsal side than on the ventrum and sides. There is a light gray reticulated pattern that is darker on the dorsum, side, and limbs than on the tail. The ventrum has no reticulations and is light pink in color. The gills are bright red and the rami are lightly pigmented. The coloration in preservative is light gray, being slightly darker on the head and dorsum than on the side and tail. Light, peach-colored spots in two or three irregular rows are present on the sides of the body. Light gray reticulations cover the dorsum, and the ventrum is peach, without any reticulations. In both life and preservative, larger larvae with a snout-vent length over 80 mm also have pale yellow spots on the body in two or three irregular rows between the limbs and dorsally on the proximal area of the tail. These rows converge into one row of close-set spots on the lateral sides of the tail. Many of the spots have a central neuromast (Besharse and Holsinger 1977).

When transforming, the coloration of G. subterraneus is indistinguishable from the large larvae. At maturation, the dark reticulated pattern becomes more distinct while the lateral body spots become less so (Besharse and Holsinger 1977).

Gyrinophilus subterraneus larvae regularly have snout-vent lengths exceeding 100 mm, while those of G. porphyriticus rarely reach 80 mm, especially before metamorphosis. The smallest observed transformed G. subterraneus has a snout-vent length of 96 mm, while the minimum snout-vent length of transformed G. pophyriticus is 69 mm. This suggests that G. subterraneus metamorphosis occurs at a larger body size. Additionally, G. subterraneus larvae reach a wet body weight of over 40 g due to stores of body fat, while the maximum wet body weight for G. porphyriticus is under 20 g. Lastly, large larval and transformed adult G. subterraneus lose their sight, showing little or no optomotor response. Gyrinophilus porphyriticus larvae and adults consistently respond to visual stimuli (Besharse and Holsinger 1977).

Trends and Threats
Gyrinophilus subterraneus is more vulnerable to environmental changes due to its specialized troglobitic adaptations. Other troglobitic salamander species have declined due to urbanization in watershed areas. Karst systems are also susceptible to deforestation, water contamination, and sedimentation, but these have not been observed in General Davis Cave (Grant et al. 2022).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Subtle changes to necessary specialized habitat

Comments

PHYLOGENETIC RELATIONSHIPS:

Gene flow is asymmetric, with greater gene flow occurring from G. porphyriticus to G. subterraneus. This may be due to the larger population of G. subterraneus in the cave, which would make female G. subterraneus individuals less likely to mate with male G. porphyriticus individuals due to chance. There may also be selection against hybrid offspring from G. subterraneus female and G. porphyriticus male crosses (Grant et al. 2022).

ETYMOLOGY (Origin or explanation of scientific name):

This species was featured as news of the week August 1, 2022:

Cave species are often highly endemic and can be especially vulnerable to habitat degradation within and surrounding the cave systems they inhabit. The West Virginia Spring Salamander (Gyrinophilus subterraneus) is only known from a single cave and though it is phenotypically distinct from the more widespread Spring Salamander species complex (Gyrinophilus porphyriticus), its evolutionary history and status as a unique species have been debated for decades. Grant et al. (2022) combine genomic and morphological data to demonstrate that G. subterraneus represent a distinct lineage, and that they occur in sympatry with G. porphyriticus within General Davis Cave. Surprisingly, the team also reports hybridization within the cave with evidence of partial reproductive isolation between the species. Collectively, the results provide strong support for continuing to recognize G. subterraenus as a distinct and unique species, and reveal a compelling study system for understanding how salamanders adapt to cave ecosystems. (Written by Rayna Bell)

References

Besharse, J.C., and Holsinger, J.R. (1977). "Gyrinophilus subterraneus, a New Troglobitic Salamander from Southern West Virginia." Copeia, 4, 624-634. [link]

Grant, E.H.C., Mulder, K.P., Brand, A.B., Chambers, D.B., Wynn, A.H., Capshaw, G., Niemiller, M.L., Phillips, J.G., Jacobs, J.F., Kuchta, S.R., and Bell, R.C. (2022). "Speciation with gene flow in a narrow endemic West Virginia cave salamander (Gyrinophilus subterraneus)." Conserv Genet, 23, 726-744. [link]

Species Account Citation: AmphibiaWeb 2022 Gyrinophilus subterraneus: West Virginia Spring Salamander <https://amphibiaweb.org/species/5814> University of California, Berkeley, CA, USA. Accessed Dec 8, 2022.

Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 8 Dec 2022.

AmphibiaWeb's policy on data use.