Francis L. Rose

Detection of salmonellae in different turtle species within a headwater spring ecosystem.

Sediments and water from the slough arm of Spring Lake, the headwaters of the San Marcos River, Texas, USA, as well as swabs from biofilms on carapaces and from the cloacae of 18 common musk turtles (Sternotherus odoratus), 21 red-eared sliders (Trachemys scripta elegans), nine Texas river cooters (Pseudemys texana), one snapping turtle (Chelydra serpentina serpentina), and three Guadalupe spiny soft-shell turtles (Apalone spinifera guadalupensis), caught at the same site, were analyzed for salmonellae by culture and molecular techniques. Although enrichment cultures from sediment and water samples were negative for salmonellae in polymerase chain reaction (PCR)–based analyses, this technique detected salmonellae in the enrichments from both carapaces and cloacae of 11 musk turtles (61%), eight red-eared sliders (38%), and the snapping turtle. Salmo-nellae could also be detected in the enrichments from the carapaces of two additional red-eared sliders and two Texas river cooters; the remaining samples were negative. Further characterization of isolates obtained from the enrichment cultures of seven selected individuals that represented all turtle species with salmonellae confirmed the presence of Salmonella enterica subspecies enterica, with serovars Rubislaw, Newport, Gaminara, and Thompson identified. These results demonstrate the presence of different strains of potentially human pathogenic salmonellae naturally occurring on several turtle species with different life histories even within supposedly pristine environments.

Measured and Predicted Egg Volume of Pseudemys texana with Comments on Turtle Egg Shape

The relationship between egg size (length, width, mass), female body size, and clutch size has been investigated in a variety of reptiles (Ferguson et al., 1982; Congdon and Gibbons, 1985; Bjorndal and Carr, 1989; Ford and Seigel, 1989; Deeming and Ferguson, 1990; Iverson and Ewert, 1991). In spite of this attention, little has been written regarding egg shape and volume and those factors that egg shape and volume might reflect. Turtle eggs are described as being spheres, ellipsoids, or bicones. As a general rule, chelonids, chelydrids, trionychids, and larger tortoises produce round, hard-shelled eggs. Most members of other groups produce some form of an elongated, symmetrical egg. (For reviews of turtle egg biology see Ewert, 1979 and Moll, 1979.) Phylogenetic considerations were given to egg shape and hardness by Iverson and Ewert (1991). Elongated eggs provide greater volume without increasing the short-side diameter beyond presumed morphological constraints; e.g., diameter of pelvic canal (Congdon and Gibbons, 1987) or carapace-plastron exit port (Rose and Judd, 1991). Increased egg volume could add significantly to energy and nutrient storage capacity, resulting in a hatchling with greater fitness (Sinervo, 1990). Large egg or hatchling size would be balanced against negative pressures of reduced reproductive output (Smith and Fretwell, 1974) or restrictions imposed on reproductive product exiting the female (Congdon and Gibbons, 1985). It is surprising, then, that so few workers have addressed the issue of egg volume in turtles (Iverson and Ewert, 1991), especially as it might relate to egg shape. Pseudemys texana, a recently elevated taxon (Ward, 1984), is an emydine turtle that inhabits Texas streams, rivers, and ponds. Information regarding its general biology and reproductive characteristics are scarce despite the fact that this turtle might be the most conspicuous vertebrate in many aquatic systems in Texas. Several fish hatchery ponds and the adjacent San Marcos River on the Southwest Texas State University campus, Hays County, are excellent habitats for this species and females frequently are observed constructing nests during spring and early summer months. Eggs available to us provided an opportunity to evaluate egg shape-volume relationships of a common, relatively unknown, aquatic turtle. We used 14 eggs, selected from two clutches that were laid on 21 May 1994. Each egg was washed, dried and frozen. Upon thawing, we measured length (long axis) and width (short axis) to the nearest mm using Mitutoyo digimatic calipers. Mass was determined to the nearest 0.01 gram with an electronic Mettler BasBal scale. All linear measurements were recorded in mil-

Seasonal and ontogenetic changes in the sex ratio of a population of stinkpots (Kinosternidae: Sternotherus odoratus)

Abstract Current hypotheses suggest that many of the biased sex ratios reported for turtle populations are the result of sampling errors, such as improper sex determination, collection bias, and behavioral differences between the sexes. This study was performed to assess whether the observed sex ratio of a population of stinkpots (Sternotherus odoratus) was an artifact of sampling biases. A total of 989 stinkpots (637 males, 352 females) was captured from 1996 through 2000 at Spring Lake, Aquarena Center, Hays County, Texas. The overall sex ratio based on all census techniques was significantly male-biased (1.8M:1F). The sex ratio changed across size classes. Data from a bimonthly trapping experiment from May 1999 through May 2000, in which hoop traps baited with either a food source or a mature female stinkpot, reinforced the view that the observed sex ratio in this population is inherently skewed, and not an artifact of sampling techniques.

Detection of Salmonellae in Captive and Free-Ranging Turtles Using Enrichment Culture and Polymerase Chain Reaction

Abstract Information on the importance of captive turtles as sources of human Salmonella infections is well established; however, data on the potential of free-ranging turtles as carriers of salmonellae are scarce and contradictory. We combined traditional culture techniques and molecular tools to analyze swabs obtained from the cloacae and from different body parts of captive and free-ranging turtles for salmonellae. Salmonellae were detected in 50% of captive turtles (N = 10). A similar percentage of detection (51%) was obtained for salmonellae in free-ranging turtles from the Rio Grande (N = 80) with six sites at Big Bend National Park, Texas, and one site at Elephant Butte Reservoir, New Mexico, analyzed. Here, 46% of Trachemys gaigeae (N = 36), 56% of Apalone spinifera (N = 43), and the only individual of Chrysemys picta were positive for salmonellae. These percentages of detection of salmonellae in turtles were independent of the location of the sampling in the Rio Grande, the species and the gender of the turtles. Although individuals of captive turtles testing positive for salmonellae were generally positive for all body parts tested (i.e., the cloacae, the carapace, the ventral base of the left rear leg, underneath one or more of the claws on the front feet, and the ventral base of the tail), individuals of free-ranging turtles testing positive for salmonellae were often positive for only one or two body parts. Our results demonstrate that salmonellae are prevalent in high rates in both captive and free-ranging turtles.

Cutaneous mastocytomas in the neotenic caudate amphibians Ambystoma mexicanum (axolotl) and Ambystoma tigrinum (tiger salamander)

Abstract Spontaneous mastocytomas studied in 18 axolotls (Ambystoma mexicanum) and six tiger salamanders (Ambystoma tigrinum) were gray-white, uni- to multilobular cutaneous protrusions from 2 mm to 2 cm in diameter. Tumors were moderately cellular unencapsulated masses that usually infiltrated the dermis and hypodermis with the destruction of intervening tissues. Some tumors were invading superficial bundles of the underlying skeletal muscle. Tumors consisted of mitotically active cells derived from a single lineage but showing a range of differentiation. Immature cells had nearly smooth to lightly cleft or folded basophilic nuclei bordered by a band of cytoplasm with few cytoplasmic processes and containing a few small uniform eccentric granules. Mature cells had basophilic nuclei with deep clefts or folds and abundant eosinophilic cytoplasm with multiple long intertwining cytoplasmic extensions packed with metachromatic granules. The axolotls were old individuals from an inbred laboratory colony. The tiger salamanders were wild animals from a single polluted pond. They could have been old and inbred. Both groups were neotenic. These are the first mastocytomas discovered in cold-blooded animals.

Egg Production by the Texas Tortoise, Gopherus berlandieri, in Southern Texas

. 1922. The amphibians and reptiles of the Sierra Nevada de Santa Marta, Colombia. Univ. Michigan Mus. Zool. Misc. Publ. 8:1-69. SAVAGE, J. M. 1987. Systematics and distribution of the Mexican and Central American rainfrogs of the Eleutherodactylus gollmeri group (Amphibia: Leptodactylidae). Fieldiana Zool., N. S. 33:1-57. , AND W. R. HEYER. 1967. Variation and dis. The amphibians and reptiles of the tribution in the treefrog genus Phyllomedusa in Costa Rica, Central America. Beitr. Neotrop. Fauna 5: 111-131.

Annual Frequency of Clutches of Pseudemys texana and Trachemys scripta at the Headwaters of the San Marcos River in Texas

Abstract I observed 215 nesting events of Pseudemys texana (134) and Trachemys scripta (81) from 25 April to 14 July 2008 on a golf course in Hays County, Texas. For P. texana, 111 (82.8%) nested one time, 21 (15.7%) nested twice, and 2 (1.5%) nested three times. For T. scripta, 53 (65.4%) nested one time, 24 (29.6%) nested twice, 3 nested three times (3.7%), and 1 nested four times (1.2%). Both species had an internesting interval of ca. 30 days between first and second clutches. Subsequent internesting intervals were shorter but samples were not sufficient to address whether this was fortuitous. On their first attempt, 82% of P. texana and 78% of T. scripta completed nesting. Nesting was diurnal with most activity occurring before noon. Neither distance to nesting site from water nor number of days from the first nesting event to the next nesting event varied with length of plastron.

Taxonomic Status of Acris Gryllus Paludicola: In Search of the Pink Frog

Abstract Acris gryllus paludicola, the Coastal Cricket Frog, was described from Sabine Pass, Jefferson County, Texas, by L. W. Burger, P. W. Smith, and H. M. Smith in 1949. Additional specimens have not been reported or examined in the literature. At the time of its description, the association with Acris gryllus was parsimonious with the then-current understanding of the taxonomic position of the two species within the genus, A. gryllus and Acris crepitans. All subspecies within the genus were described within four years of each other, and all were subspecies of A. gryllus. The Coastal Cricket Frog is currently treated as a subspecies of A. crepitans but without an explicit treatment resolving its species level affinity. Seven individuals found on 19 May 2005 near the type locality are relatively smooth skinned; have reduced, or lack, anal warts; and retain ill-defined postfemoral striping; vocalizing males have pink-rose colored vocal pouches. Phenotypic comparison of the seven specimens fails to eliminate their inclusion in the species A. gryllus. Concurrent mtDNA sequence comparisons with A. gryllus from Florida and a series of A. crepitans from Texas confirm that the Coastal Cricket Frog is nested within the A. crepitans clade distinct from A. gryllus. We conclude that the original description of the “pink” frog is supported by examination of living specimens and have no evidence indicating that its subspecific status within A. crepitans should be questioned. Recent work within this genus has highlighted the need for an exhaustive study of the variation it presents rangewide.

Use of Space by Western Cottonmouths (Agkistrodon piscivorus) Inhabiting a Variable–Flow Stream

Abstract In central Texas, western cottonmouths (Agkistrodon piscivorus) inhabit small, low-productivity limestone streams characterized by variability in seasonal flows. An 11-year study of western cottonmouths was conducted at Honey Creek, a spring-fed stream flowing 3.2 km to its confluence with the Guadalupe River, Comal County, to determine how this predator used space in this narrow, linear, and dynamic system. During 57 searches along the 1,564-m study area, 39 sexually mature, 14 subadults, and 4 juvenile snakes were marked. Rates of recapture did not differ between sexes, but females outnumbered males (2.3∶1) and adults were recaptured more frequently than juveniles. Distances between captures were less than predicted if distributions were random, and distances did not vary with number of times captured or time between captures.

Morphology of an inland population of the keeled earless lizard (Holbrookia propinqua)

Abstract We studied the morphological characters of the keeled earless lizard, Holbrookia propinqua, in Guadalupe County, Texas, near its type locality (Wilson County, Texas) and at the northern extension of its range. Adults of this population were similar to those of other mainland populations but significantly smaller than adults of coastal island populations. Juveniles of the population in Guadalupe County and a coastal population showed no significant differences in size. Tail length of males did not differ among mainland populations but differed significantly from those of the island populations.