Polyandry and multiple paternities in the threatened Agassiz’s desert tortoise, <Emphasis Type="Italic">Gopherus agassizii</Emphasis>

We used data from 17 to 20 microsatellite markers to investigate the incidence of multiple paternities in wild Agassiz’s desert tortoises, Gopherus agassizii. Neonates were sampled from clutches of eggs laid by wild mothers in nesting enclosures at Edwards Air Force Base and at the Marine Corps Air Ground Combat Center, California. We genotyped 28 clutches from 26 females sampling an average of six neonates per clutch. The number of paternal alleles was used to determine the minimum number of sires for each clutch. Based on conservative criteria requiring evidence from at least two loci to determine multiple paternity, a minimum of 64% of females were polyandrous, while a minimum of 57% of clutches were sired by multiple males. This formed one of the highest incidences of multiple paternities recorded to date in any species of tortoise. The high number of microsatellite loci involved in the analyses allowed detection of multiple paternities in clutches where this may have been missed if fewer loci were used. Our results highlighted the potential pitfalls of quantitatively comparing paternity studies based on differing sampling strategies. Finally, we summarized the conservation implications of the high rate of multiple paternities in this threatened species.     

Reference intervals and physiologic alterations in hematologic and biochemical values of free-ranging desert tortoises in the Mojave Desert

Desert tortoise (Gopherus agassizii) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss, and human and disease-related mortality. Evaluation of hematologic and biochemical responses of desert tortoises to physiologic and environmental factors can facilitate the assessment of stress and disease in tortoises and contribute to management decisions and population recovery. The goal of this study was to obtain and analyze clinical laboratory data from free-ranging desert tortoises at three sites in the Mojave Desert (California, USA) between October 1990 and October 1995, to establish reference intervals, and to develop guidelines for the interpretation of laboratory data under a variety of environmental and physiologic conditions. Body weight, carapace length, and venous blood samples for a complete blood count and clinical chemistry profile were obtained from 98 clinically healthy adult desert tortoises of both sexes at the Desert Tortoise Research Natural area (western Mojave), Goffs (eastern Mojave) and Ivanpah Valley (northeastern Mojave). Samples were obtained four times per year, in winter (February/March), spring (May/June), summer (July/August), and fall (October). Years of near-, above- and below-average rainfall were represented in the 5 yr period. Minimum, maximum and median values, and central 95 percentiles were used as reference intervals and measures of central tendency for tortoises at each site and/or season. Data were analyzed using repeated measures analysis of variance for significant (P < 0.01) variation on the basis of sex, site, season, and interactions between these variables. Significant sex differences were observed for packed cell volume, hemoglobin concentration, aspartate transaminase activity, and cholesterol, triglyceride, calcium, and phosphorus concentrations. Marked seasonal variation was observed in most parameters in conjunction with reproductive cycle, hibernation, or seasonal rainfall. Year-to-year differences and long-term alterations primarily reflected winter rainfall amounts. Site differences were minimal, and largely reflected geographic differences in precipitation patterns, such that results from these studies can be applied to other tortoise populations in environments with known rainfall and forage availability patterns.     

Backbone and partial side chain assignment of the microtubule binding domain of the MAP1B light chain

Microtubule-associated protein 1B (MAP1B) is a classical high molecular mass microtubule-associated protein expressed at high levels in the brain. It confers specific properties to neuronal microtubules and is essential for neuronal differentiation, brain development and synapse maturation. Misexpression of the protein contributes to the development of brain disorders in humans. However, despite numerous reports demonstrating the importance of MAP1B in regulation of the neuronal cytoskeleton during neurite extension and axon guidance, its mechanism of action is still elusive. Here we focus on the intrinsically disordered microtubule binding domain of the light chain of MAP1B. In order to obtain more detailed structural information about this domain we assigned NMR chemical shifts of backbone and aliphatic side chain atoms.     

Reproductive investments of a small,arid zone tortoise Chersobius signatus: Follicle and egg development

We used ultrasonography and radiography to evaluate whether body size (BS), body condition (BC) and environmental factors influenced reproductive investments by Chersobius signatus in September 2000 and from September 2003 to November 2004. Follicle volume increased with increasing BS, BC and rainfall but decreased with increasing temperature. Egg volume averaged 8.8% of body volume, increased allometrically with BS, but was not affected by BC, rainfall or temperature and did not differ between first and second clutches. Most females produced at least one single-egg clutch per year, even when BC was low. Many females produced two, possibly more, clutches but some forfeited reproduction in some years. Females often retained large follicles from one season to the next with 18%–71% carrying pre-ovulatory sized follicles in different times of the year. Increasing temperatures likely influenced timing of first ovulations in August while decreasing water and food availability, linked with high temperatures, possibly terminated ovulations by November. The gravid season was short compared to other winter-rainfall tortoises in South Africa. We propose that the females' small bodies may constrain investments in eggs, resulting in low fecundity, which is countered by producing large hatchlings with high survivorship in an arid habitat.     

Growing and shrinking in the smallest tortoise, <Emphasis Type="Italic">Homopus signatus signatus</Emphasis>: the importance of rain

Climate change models predict that the range of the world’s smallest tortoise, Homopus signatus signatus, will aridify and contract in the next decades. To evaluate the effects of annual variation in rainfall on the growth of H. s. signatus, we recorded annual growth rates of wild individuals from spring 2000 to spring 2004. Juveniles grew faster than did adults, and females grew faster than did males. Growth correlated strongly with the amount of rain that fell during the time just before and within the growth periods. Growth rates were lowest in 2002–2003, when almost no rain fell between September 2002 and August 2003. In this period, more than 54% of the tortoises had negative growth rates for their straight carapace length (SCL), shell height (SH), and shell volume (SV); maximum shrinking for SCL, SH, and SV was 4, 11, and 12%, respectively. The shell of H. s. signatus has some flexibility dorso-ventrally, so a reduction in internal matter due to starvation or dehydration may have caused SH to shrink. Because the length and width of the shell seem more rigid, reversible bone resorption may have contributed to shrinkage, particularly of the shell width and plastron length. Based on growth rates for all years, female H. s. signatus need 11–12 years to mature, approximately twice as long as would be expected allometrically for such a small species. However, if aridification lowers average growth rates to the level of 2002–2003, females would require 30 years to mature. Additionally, aridification would lower average and maximum female size, resulting in smaller eggs and hatchlings. These projected life history responses to aridification heighten the threat posed by the predicted range contraction of this red-listed species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Living with the genetic signature of Miocene induced change: evidence from the phylogeographic structure of the endemic angulate tortoise Chersina angulata

The phylogeographic structure of the monotypic endemic southern African angulate tortoise Chersina angulata was investigated throughout its distribution with the use of partial sequences from three mtDNA loci (COI, cyt b and ND4). Phylogeographic and phylogenetic structuring obtained for the three mtDNA markers were highly congruent and suggested the presence of two genetically distinct, reciprocally monophyletic evolutionary lineages. Group one contained two subclades with haplotypes from the north-western Cape and south-western Cape, respectively, while haplotypes from the southern Cape comprised group two. The two major clades were separated by nine and eight mutational steps for COI and ND4, respectively. Of the three mtDNA gene regions examined, the ND4 partial sequence contained the most phylogenetic signal. Haplotype diversity was generally low and we recovered 34 haplotypes for the 125 animals sequenced for the ND4 subunit. Nested clade analyses performed on the variable ND4 partial sequences suggested the presence of two major refugial areas for this species. The demographic history of the taxon was characterised by range expansion and prolonged historical fragmentation. Divergence time estimates suggest that the temporal and spatial distribution of the taxon was sculpted by changes in temperature and rainfall patterns since the late Miocene. Corroborative evidence from other reptiles is also suggestive of a late Miocene divergence, indicating that this was a major epoch for cladogenesis in southern Africa. Apart from the genetic differences between the two major clades, we also note morphometric and behavioural differences, alluding to the presence of two putative taxa nested within C. angulata.     

Clinical disease and laboratory abnormalities in free-ranging desert tortoises in California (1990-1995)

Desert tortoise (Gopherus agassizii) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss and human and disease-related mortality. Diagnosis of disease in live, free-ranging tortoises is facilitated by evaluation of clinical signs and laboratory test results but may be complicated by seasonal and environmental effects. The goals of this study were: 1) to describe and monitor clinical and laboratory signs of disease in adult, free-ranging desert tortoises at three sites in the Mojave Desert of California (USA) between October 1990 and October 1995; 2) to evaluate associations between clinical signs and hematologic, biochemical, serologic, and microbiologic test results; 3) to characterize disease patterns by site, season, and sex; and 4) to assess the utility of diagnostic tests in predicting morbidity and mortality. Venous blood samples were obtained four times per year from tortoises of both sexes at the Desert Tortoise Research Natural Area (DTNA), Goffs/Fenner Valley, and Ivanpah Valley. Tortoises were given a physical examination, and clinical abnormalities were graded by type and severity. Of 108 tortoises, 68.5% had clinical signs of upper respiratory tract disease consistent with mycoplasmosis at least once during the study period. In addition, 48.1% developed moderate to severe shell lesions consistent with cutaneous dyskeratosis. Ulcerated or plaque-like oral lesions were noted on single occasions in 23% of tortoises at Goffs and 6% of tortoises at Ivanpah. Tortoises with oral lesions were significantly more likely than tortoises without lesions to have positive nasal cultures for Mycoplasma agassizii (P = 0.001) and to be dehydrated (P = 0.0007). Nine tortoises had marked azotemia (blood urea nitrogen [BUN] > 100 mg/dl) or persistent azotemia (BUN 63-76 mg/dl); four of these died, three of which had necropsy confirmation of urinary tract disease. Laboratory tests had low sensitivity but high specificity in assessing morbidity and mortality; there was marked discrepancy between serologic and culture results for M. agassizii. Compared with tortoises at other sites, tortoises at DTNA were more likely to be seropositive for M. agassizii. Tortoises at Goffs were significantly more likely to have moderate to severe shell disease, oral lesions, positive nasal cultures for M. agassizii, and increased plasma aspartate aminotransferase activity. The severe disease prevalence in Goffs tortoises likely contributed to the population decline that occurred during and subsequent to this study.