Blanchard's cricket frog (Acris crepitans blanchardi) morphological abnormalities in southeast Michigan.
One Blanchard's cricket frog (Acris crepitans blanchardi) lacking the left eye and orbit was found by Smith and Powell in Missouri in 1973 (1983). McCallum and Trauth examined museum specimens of A. crepitans at the Arkansas State University Museum of Zoology and Herpetology Collection and noted an increase in abnormality frequency from 1957 to 2000, with an overall abnormality rate of 7.10% (104 out of 1,464 frogs) (2003).Gray recorded rates of abnormalities in northern cricket frog (Acris crepitans) populations in Illinois, and found that only 0.39% of frogs collected from 1968 to 1971 were abnormal (2000). Gray noted only seven confirmed developmental abnormalities among 10,000 specimens. Resampling of these populations in 1998 indicated no increase in the rate of abnormalities, with continued low rates of deformities. Additional studies by Beasley et al. in Illinois in 1994 found one adult male with an extra forelimb and 4.6% of adults examined had intersex gonads (a form of hermaprhoditism) (2005). Lastly, Reeder et al. reported that 2.7% of cricket frogs collected in Illinois in 1993, 1994, and 1995 were intersex individuals (1998).
Blackburn (unpublished) found an overall malformation during the 1999 and 2000 seasons of 4.4% (36 out of 813 frogs) in cricket frog populations in east-central Indiana. Missing limbs, limb segments, or digits comprised the majority (83.3%; 30 out of 36) of these malformations, and the rest were underdeveloped or missing eyes (13.9%; 5 out of 36) and extra limbs (2.8%; 1 out of 36).
No other studies have previously been done on deformity rates of Acris in southeast Michigan. As part of exploration of a translocation of a population of Blanchard's cricket frogs, Acris crepitans blanchardi, a Michigan Species of Special Concern, we surveyed populations in four locations in southeast Michigan from May to August 2004 and May to August 2005. These sites include Ford Lake Park, Ypsilanti; Lakewood Farms, Ypsilanti; Ives Road Fen, Tecumseh; Port Huron State Game Area, Port Huron. During this work, we found only one deformed adult frog in the field (Figure 1, Ford Lake park), missing a hind foot, in June 2004 out of 17 frogs found at Ypsilanti sites (four from Lakewood Farms and 13 from Ford Lake). No deformities were seen among the 62 adult frogs captured in Ives Road Fen in 2004 and 2005. We also found one adult frog out of five surveyed in Port Huron in 2005 with a swollen thigh, but that could have been due to an elastomer injection (Figure 2).
Our source population of cricket frogs for the translocation experiment came from a wetland in Ypsilanti, Michigan that was slated for development. Collection efforts began on August 4, 2004, and ended on October 20, 2004, during our first season. We captured mostly juveniles and tadpoles and a few adults. All animals were moved to the Detroit Zoological Institute where they were quarantined while full health assessments were conducted on the population and release sites selected. A total of 1010 cricket frogs and tadpoles were removed from the site in 2004 (176 tadpoles, 829 young of year, and 5 adults). We collected 57 additional adults from April 22, 2005 to June 13, 2005 and released these animals immediately at the Port Huron State Game Area. No deformities were found in the 2005 release group.
All 834 juvenile and adult frogs collected from Lakewood Farms and released in fall 2004 were checked for deformities and measured and photographed if any abnormalities were observed. No abnormalities were seen in the five collected adults. Eleven juveniles were noted to have some kind of gross morphological deformity, mostly involving missing hind limbs. All mortalities that occurred during the quarantine period (70 total) were preserved and checked for deformities. Of these preserved animals, four deformities could be identified. Fifteen of the 829 juveniles collected had some type of deformity (1.8%). This rate is comparable to the roughly 1% rate of deformities that other investigators have accepted as a background level of frog abnormalities and within the range observed for Acris in the Midwest (Hoppe 2005).
These deformities included four missing or deformed hind limbs (Figure 3), four curled toes, one missing left eye (Figure 4), one extra hind limb, and one missing three toes on the left front limb. Some abnormalities could be due to predation attempts, or stress and injuries from capture and transport. One animal had a third hind limb and was submitted for analysis for trematodes, a possible cause of extra hindlimbs, but showed no signs of trematodes at the limb base at the time of necropsy (Sessions and Ruth 1990). While this result does not rule out trematodes as a possible cause of this deformity, it is unlikely that trematode infection accounts for most of the abnormalities seen in this population, as only one individual had extra hind limbs. No animals were dissected to identify deformities of the mouth or internal organs and no tadpoles were assessed for mouthpart abnormalities or other deformities.
Prior to release, a randomly selected subset of the population (n = 270) was weighed, measured, and photographed. The deformed animals were smaller (average SVL = 15.60 mm and average weight was 0.43 g), than the measured subpopulation (average SVL of 17.28 mm and average weight was 0.54 g).
The low rate of morphological abnormalities in cricket frog populations suggests that deformities are not a significant contributing factor to the decline of this species in the Midwest.
Literature Cited
Beasley, V.R., S.A. Faeh, B. Wikoff, C. Staehle, J. Eisold, D. Nichols, R.Cole, A.M. Schotthoefer, M. Greenwell, and L.E. Brown. 2005. Risk Factors and Declines in Northern Cricket Frogs (Acris crepitans). In Amphibian Declines: The Conservation Status of United States Species, edited by M.L. Lannoo, 75-86. Berkeley, CA: University of California Press.
Gray, R.H. 2000. Historic occurrence of malformations in the cricket frog Acris crepitans in Illinois. Transactions of the Illinois Academy of Sciences 93:279-284.
Hoppe, D.M. 2005. Malformed Frogs in Minnesota: History and Interspecific Differences. In Amphibian Declines: The Conservation Status of United States Species, edited by M.L. Lannoo, 103-108. Berkeley, CA: University of California Press.
McCallum, M.L., and S.E. Trauth. 2003. A forty-three year museum study of northern cricket frog (Acris crepitans) abnormalities in Arkansas: Upward trends and distributions. Journal of Wildlife Diseases 39:522-528.
Reeder, A.L., G.L. Foley, D.K. Nichols, L.G. Hansen, B. Wikoff, S. Faeh, J. Eisold, M.B. Wheeler, R. Warner, J.E. Murphy, and V.R. Beasley. 1998. Forms and Prevalence of Intersexuality and Effects of Environmental Contaminants on Sexuality in Cricket Frogs (Acris crepitans). Environmental Health Perspectives 106: 261-266.
Sessions, S.K. and S.B. Ruth. 1990. Explanations for naturally occurring supernumerary limbs in amphibians. Journal of Experimental Zoology 254: 38-47.
Smith, D.D. and R. Powell. 1983 Life history notes: Acris crepitans blanchardi (Blanchard's cricket frog). Anomalies Herpetological Review 14: 118-119.
Ariana Rickard, School of Natural Resources and Environment, University of Michigan, 440 Church Street, Ann Arbor, M148109
Edythe Sonntag, National Amphibian Conservation Center, Detroit Zoological Institute, 8450 West Ten Mile Road, Royal Oak, Michigan 48068-0039, USA [email protected]
Ariana Rickard is a M.S. candidate in the Resource Ecology and Management program at the School of Natural Resources at the University of Michigan in Ann Arbor and is currently studying wetlands restoration and amphibian reintroduction programs.
Edythe Sonntag is presently working on her PhD at Michigan State University in the Department of Fisheries and Wildlife. Her research area is amphibian conservation locally and regionally while mainly focusing on the Blanchard's cricket frog decline in Michigan. She can be contacted at [email protected]
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| Author: | Rickard, Ariana; Sonntag, Edythe |
|---|---|
| Publication: | Endangered Species Update |
| Geographic Code: | 1USA |
| Date: | Oct 1, 2006 |
| Words: | 1252 |
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