Spring salamander (Gyrinophilus porphyriticus) COSEWIC assessment and status report: chapter 8

General Biology

Reproduction

Sexual dimorphism of the cloacal gland is described by Sever (1986) while sperm morphology is illustrated in Wortham et al. (1982). Males are relatively longer than females and, through the clear belly skin, the black testes can be distinguished from white eggs (Bishop 1941).

Gyrinophilus porphyriticus reproduces annually in North Carolina (Bruce 1969). Mating occurs in fall with egg deposition the following spring or summer (Bruce 1969 and 1972). Courtship success varies, possibly in relation to the body size of adults (Beachy 1996). Eggs are attached underneath large rocks or logs, in flowing water. The number of eggs varies from 44 to 132 in New York (Bishop 1941). Smaller clutch sizes are reported for southern regions: 9 to 63 in South and North Carolina (Bruce 1972), 87 for a female from North Carolina (Calisaya and Marks 1994), and 44 to 66 in Virginia (Organ 1961). Hatching occurs at the end of the summer (DeGraaf and Rudis 1983) or in the fall (Organ 1961). Development from fertilization to hatching is described by Calisaya and Marks (1994).

Growth and longevity

The larval period is longer than that of any other plethodontid (Hairston 1987; Beachy and Bruce 1992), ranging from 3 to 5 years (Bruce 1980) and even up to 6 years (Resetarits 1995). Larval growth is affected by aquatic habitat condition and predation pressure (Bruce 1978 and 1980; Resetarits 1991 and 1995). Metamorphosed juveniles emerge in spring or summer while sexual maturity is reached a year later (Bishop 1941). In New York, individuals mature sexually at 4 to 5 years old, at a total length of 14 cm (Bishop 1947). Bruce (1969) estimates that females mature sexually at 5 years old. Resetarits (1995) reported sexually immature individuals over 6 years old. This suggests that the spring salamander has one of the most delayed ages at sexual maturity and probably one of the lowest recruitment rates of the Plethodontidae. Longevity is probably over ten years (Tilley 1977; Castenet et al. 1996).

Movements

As for other stream salamanders, movements of larvae and adults probably occur along stream habitats, although this has not been reported specifically for G. porphyriticus (Bruce 1986). Headwater populations may represent a source of colonists for downstream populations following the drift of larvae (Resetarits 1995).

Terrestrial movements should be rare compared to other salamander species (Bruce 1978), although distances traveled have not been reported. Bishop (1941) mentions movements between streams. Barbour (1971) indicates that movements away from a stream usually occur along wet habitats like road ditches. Huheey and Stupka (1967) report many individuals crossing roads during rainy nights in the Great Smoky Mountains. Restricted movements between streams may favor the isolation of populations (Tilley and Scherdtfeger 1981). This may explain the geographical variations and the tendency of sexual isolation among populations and subspecies of G. porphyriticus (Bruce 1978; Beachy 1996) (see Figure 2).

Ecology 

The spring salamander is a predator of other salamanders, of terrestrial and aquatic invertebrates, and of conspecifics (Burton 1976; Resetarits 1995). Larvae forage on the substrate and under cover objects (Resetarits 1991) while adults forage mostly at the stream edges. Intense predation by G. porphyriticus may reduce the availability of food (Culver 1973, 1975) and food shortage would slow larval growth (Resetarits 1991; 1995). In a portion of stream having a high density of spring salamanders, other stream salamanders may be less abundant or be absent (Bonin 1991a, pers. obs.).

The larvae are subjected to predation by trout (Salvelinus fontinalis), which strongly affect distribution and population dynamics (Resetarits 1991 and 1995). Adults avoid predation from trout by using terrestrial habitat. Toxic cutaneous secretions and the red coloration which mimics that of even more toxic species are thought to protect adults from terrestrial predators (Brodie et al. 1979; Brandon and Huheey 1981). The spring salamander is the host of more than a dozen species of helminth parasites (Catalano et al. 1982).

Behavior, physiology and vulnerability

Gyrinophilus porphyriticus is nocturnal, foraging only during rainy nights (Burton and Likens 1975; Burton 1976). It therefore rarely interacts directly with humans. However, it might be intolerant to changes in habitat conditions because of the physiological limits related to lunglessness (Spotila 1972; Feder 1983) and the prolonged larval period (Resetarits 1995). Under natural conditions, the longevity of adults and their relatively large clutch sizes balance larval mortality related to variation in aquatic habitat conditions and predation pressure (Resetarits 1995). The species should have a limited adaptability when changes in the habitat affect adult survival or preclude the aquatic larval development. The vulnerability of the species is illustrated by the specificity of its habitat described above and by the numerous limiting factors listed below.

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