Outstripping a Parasite

Moving a planter from atop a rotting stump revealed a California Slender Salamander

With chytrid fungus infections causing large-scale mortality in many amphibian populations, could the California Slender Salamander (Batrachoseps attenuatus) be at risk?  Rolling back downed wood and closely examining the ground beneath often reveals these salamanders coiled and motionless. (Careful replacement of the wood is essential in preserving the ecological communities that are uncovered.)

Inhabitants of chaparral, oak woodlands, and forests, as well as backyards and lots with leaf litter and cover objects, California Slender Salamanders are found throughout the San Francisco Bay Area as far south as Monterey Bay, north along the coast into Southern Oregon, as well as in scattered locations inland. Despite the current range and density of these salamanders, could a chytrid fungus outbreak substantially lower populations, or has this species developed a way of coping with a deleterious infectious organism?

Sara Weinstein, currently a PhD student in the Department of Ecology, Evolution, and Marine Biology at the University of California, Santa Barbara, studied chytrid fungus infection of the California Slender Salamander for her undergraduate honors thesis at the University of California, Berkeley. The work was published in the journal Copeia in 2009.

Through examination of preserved specimens collected earlier, Weinstein determined that amphibian chytrid fungus, Batrachochytrium dendrobatidis, had infected the California Slender Salamander since at least 1973. (Previous to her study, the earliest evidence for amphibian chytrid infection in California was a mountain yellow-legged frog collected in 1975.)

In the case of the California Slender Salamander, amphibian numbers seem stable despite clear evidence of sporadic chytrid disease outbreaks. Chytrid-related mortality of these salamanders occurs mainly during the latter part of the wet season and the months immediately following, from approximately February through May. In contrast, during dry summer conditions that limit fungal growth, it appears that California Slender Salamanders are able to rid themselves of infection through excessive skin shedding and tail loss, essentially removing the parasite faster than it can reproduce.-Anne M. Rosenthal

Stebbins, Robert C. 2003. A Field Guide to Western Reptiles and Amphibians, Third Edition. Houghton Mifflin Company, Boston.

Weinstein, Sara B. 2009. An aquatic disease on a terrestrial salamander: individual and population level effects of the amphibian chytrid fungus, Batrachochytrium dendrobatis, on Batrachoseps attenuatus (Plethodontidae). Copeia No. 4: 653-660.

Seasonal Rhythms of Slender Salamanders

Elongate slender salamanders surface during the rainy season.

Wet weather ambles are the rule for California Sender Salamanders (Batrochoseps attenuatus), one of twenty or so slender salamander species on the Pacific Coast. Like other members of the lungless salamander family, they breathe through skin that must remain moist for oxygen to pass through. In wet coastal areas, California Slender Salamanders may be active year around, but in dryer parts of their range, they retreat underground over the hot, rainless months. 

During the rainy season, California Slender Salamanders are daytime homebodies, remaining under the board, rock, log or other cover object beneath which they reside. On warm, rainy nights, they foray out, but generally within just a few meters of their abodes.

An exception is females heavy with eggs, which may wander farther–during late fall and early winter, sexually mature females lay small strings of eggs in communal nests. One nest, found "in a small depression in damp soil beneath a strip of tin at the northwest corner of Cedar and Spruce streets" in Berkeley, California, was described in the 1939 issue of Copeia by Thomas Paul Malin, Jr. The depression contained "small lumps of earth and a little organic material," in contrast to dry surrounding soil. Besides the female in the act of laying a string of eggs, which were attached to each other by small strands of gelatin, there were three other adult females and a total of 74 eggs in the nest.

Malin measured the eggs to be 6 mm, including a gelatinous capsule, with the "egg proper" 4 mm. His investigations of California Slender Salamanders from the San Francisco Bay Area showed that egg formation began in the ovaries during May, with females carrying an average of about 12 eggs by November, the oviducts "enormously developed...turgid with gelatinous secretions," whereas females taken in December had ovaries with "resting-stage" appearance.

Unlike many salamander species, slender salamanders require neither ponds nor streams for reproduction. Eggs hatch in winter or spring releasing tiny, fully formed salamanders, rather than water-inhabiting tadpoles.

The seasonality of salamander activity and reproduction are reasonably accessible to a sharp observer, but the intricacies of seasonal change within the cells of a salamander are rarely uncovered. A stunning discovery was inclusions of protein crystals within the liver cells of California Slender Salamanders.

Crystal prevalence varied by individual salamander, as well as by season, and indicated high concentrations of protein, possibly a storage form. Note that the crystals are surrounded by membranes of the endoplasmic reticulum where protein synthesis takes place. In the micrograph, these appear as fine wavy lines around the crystals.–Anne M. Rosenthal

Protein crystalline inclusions in California Slender Salamander liver cells. Transmission electron microscopy (TEM) image by Don W. Fawcett.


http://amphibiaweb.org

www.californiaherps.com

Fawcett, Don W. 1981. The Cell. WB Saunders Company. Free web-based copy available: http://www.ascb.org/bioeducate/FawcettTheCell.html

Maslin, Jr., Thomas Paul. 1939. Egg-laying of the slender salamander (Batrachoseps attenuatus). Copeia No. 4: 209-212.

Morey, S. and H. Basey. 1988-1990. California Wildlife Habitat Relationships System, California Slender Salamander. California Department of Fish and Game.

Olson, Deanna H. 2008. Conservation assessment for the California Slender Salamander in Oregon Batrachoseps attenuatus) Version 1.0. U.S.D.A. Forest Service Region 6 and U.S.D.I. Bureau of Land Management Interagency Special Status and Sensitive Species Program.

Stebbins, Robert C. 2003. Western Reptiles and Amphibians, Third Edition. Houghton Mifflin Company, Boston.