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1.
Total and fecal coliform bacteria were isolated from the cloaca and feces of the estuarine diamondback terrapin. The majority of samples contained fecal coliforms. Escherichia coli was the predominant fecal coliform species isolated, and members of the genus Salmonella were isolated from 2 of 39 terrapins. Fecal coliform numbers are used to regulate shellfish harvests, and diamondback terrapins inhabit the brackish-water habitats where oyster beds are found; therefore, these findings have implications for the efficacy of current regulatory parameters in shellfishing waters.  相似文献   

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Abstract Understanding phenotypic differentiation among populations of wide-ranging species remains at the core of life-history research, because adaptation to local environmental conditions is expected. For example, when energy resources influence offspring fitness (as in oviparous ectotherms), the egg and hatchling environments are expected to influence selection by acting on the amount of energy allocated to offspring. Here we identify population variation in egg mass, length, width, and volume from diamondback terrapin Malaclemys terrapin eggs collected in Rhode Island (RI), Maryland (MD), and South Carolina (SC). Egg size (mean volume: 7.6, 8.1, and 9.1 cc in RI, MD, and SC, respectively) and clutch size (mean no. eggs: 16.1, 12.2, and 6.0 in RI, MD, and SC, respectively) differed among populations, which indicated that females produce larger clutches with smaller eggs at high latitudes and smaller clutches of larger eggs at lower latitudes. Lipid analyses indicated that eggs from SC contained yolks with a higher proportion of nonpolar lipids than did eggs from MD or RI (mean percentage of nonpolar lipids: 22.3%, 22.5%, and 31.8% in RI, MD, and SC, respectively). Thus, female terrapins in SC are laying larger eggs with increased lipid content to provide more energy for the developing embryo. Interestingly, total triacylglycerol (energetic lipid) was greater in southern populations but occurred in higher proportions in northern populations (total triacylglycerol: 88.0%, 85.4%, and 81.9% in RI, MD, and SC, respectively). This variation in triacylglycerol levels demonstrates the necessity for quantifying each lipid component. These data indicate a difference in reproductive strategy by which females in northern populations invest in higher fecundity with less energetic resources per offspring, whereas females in southern populations invest in larger eggs with considerably greater energy reserves.  相似文献   

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The Diamondback terrapin (Malaclemys terrapin) is a brackish-water turtle species whose populations have been fragmented due to anthropogenic activity such as development of coastal habitat and entrapment in commercial blue crab (Callinectes sapidus) fishing gear. Genetic analyses can improve conservation efforts for the long-term protection of the species. We used microsatellite DNA analysis to investigate levels of gene flow among and genetic variability within 21 geographically separate collections of the species distributed from Massachusetts to Texas. Quantified levels of genetic variability (allelic diversity, genotypic frequencies, and heterozygosity) revealed three zones of genetic discontinuity, resulting in four discrete populations: Northeast Atlantic, Coastal Mid-Atlantic, Florida and Texas/Louisiana. The average number of alleles and expected heterozygosity for the four genetic clusters were NA = 6.54 and HE = 0.050, respectively. However, the geographic boundaries of the populations did not correspond to accepted terrapin subspecies limits. Our results illuminate not only the need to sample terrapins in additional sites, specifically in the southeast, but also the necessity for allowing uninterrupted gene flow among population groupings to preserve current levels of genetic diversity.  相似文献   

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Abstract The laborious process of manual seagrass transplanting has often limited the size of seagrass restoration efforts. This study tested the efficiency of a mechanized planting boat, previously used for transplanting Halodule wrightii, relative to manual transplanting methods for establishing Zostera marina in Chesapeake Bay. Eelgrass planting was conducted at two sites, one each in the Rappahannock and James rivers, in October 2001. The methods were evaluated by three criteria: (1) initial planting success = proportion of attempted planting units (PUs) initially established (number confirmed in sediment by divers/number attempted); (2) survival = proportion of the initially established PUs persisting over 1, 4, and 24 weeks; and (3) efficiency = labor (in person·seconds) invested in each surviving PU. Initial planting success was significantly lower for the planting boat (24 and 56% at the Rappahannock and James sites, respectively) than for manual transplanting (100% at both sites). At the Rappahannock site, survival of initially established PUs declined over time for both methods, but while mean survival was always higher for manually planted rows, differences in survival between methods were not statistically significant. At the James site, survival to 1 and 4 weeks was significantly lower for the machine than for the manual method, but survival to 24 weeks was not significantly different. While the machine was able to attempt PUs faster than the manual method (2.2 s/PU vs. 5.8 s/PU, respectively), this speed was offset by poorer planting success rates, resulting in a much greater total labor investment for each machine‐planted PU that persisted to 24 weeks than for each similarly persisting manually planted PU (40.6 person·seconds/PU and 22.4 person·seconds/PU, respectively, averaged across sites). In summary, those PUs successfully planted by the machine survived similarly to PUs planted by hand, but as a result of poorer initial planting success, the machine required a greater investment of labor and plant donor stock for each PU surviving to 24 weeks. Therefore, in its tested configuration this planting boat is not a significant improvement over the manual method for transplanting eelgrass.  相似文献   

5.
In monoecious plants, gametes can be exchanged in three ways: among unrelated genets (outbreeding), with close relatives (inbreeding), or within individuals (geitonogamous selfing). These different mating systems may have consequences for population demography and fitness. The experiment presented herein used artificial crosses to examine the mating system of Chesapeake Bay, Virginia, USA eelgrass (Zostera marina L; Zosteraceae), a bisexual submerged aquatic plant that can outbreed, inbreed, and self. Genetic data indicate severe heterozygosity deficiencies and patchy genotype distribution in these beds, suggesting that plants therein reproduce primarily by vegetative propagation, autogamy, or geitonogamy. To clarify eelgrass reproductive strategies, flowers from three genetically and geographically distinct beds were hand-pollinated in outbred, inbred, and selfed matings. Fertilization success and seed production, life history stages which contribute greatly to the numeric maintenance of populations, were monitored. We found no evidence that inbreeding had negative consequences for seed production. On the contrary, selfed matings produced seeds significantly more frequently than outcrossed matings and produced significantly larger numbers of seeds than either inbred or outbred matings. These results contrast with patterns for eelgrass in other regions but might be expected for similar populations in which pollen limitation or a short reproductive season renders selfing advantageous.  相似文献   

6.
Seagrass fragments and seeds are important dispersal mechanisms by which individuals can be transported to new habitats. While dispersal distances of these free-floating stages have been recently investigated in some detail, almost nothing is known about how long fragments or seedlings may remain viable in the water-column. This study reports on the results of an experiment in which both mature and seedling life-history stages of the temperate seagrass, Zostera marina L. were successfully maintained hydroponically over a 1-month-period. It is suggested that a potential application of this hydroponic growth approach could be seedling culture for restoration activities.  相似文献   

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Summary Photosynthetic responses of the temperate seagrass, Zostera marina L., were examined by manipulations of photon flux density in an eelgrass bed in Great Harbor, Woods Hole, MA during August 1981. Sun reflectors and light shading screens were placed at shallow (1.3 m) and deep (5.5 m) stations in the eelgrass bed to increase (+35% to +40%) and decrease (-55%) ambient photon flux densities. The portion of the day that light intensities exceeding the light compensation point for Z. marina (H comp) and the light saturation point (H sat) were determined to assess the impact of the reflectors and shades. The H comp and H sat periods at the deep station shading screen were most strongly affected; H comp was reduced by 11% and H sat was reduced by 52%. Light-saturated photosynthetic rates, dark respiration rates, leaf chlorophyll content, chlorophyll a/b, PSUO 2 size, PSU density, leaf area, specific leaf area, leaf turnover times and leaf production rates were determined at the end of three sets of 1- to 2-week experiments. None of the measured parameters were affected by the photon flux density manipulations at the shallow station; however, at the deep station leaf production rates were significantly reduced under the shading screen and chlorophyll a/b ratios were higher at the reflector. These results indicate that adjustment to short-term changes in light regime in Z. marina is largely by leaf production rates. Further, the most dramatic changes in the periods of compensating or saturating photon flux densities had the greatest impact on the measured photosynthetic responses.  相似文献   

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《Aquatic Botany》2007,87(2):147-154
We examined the effects of location (patch edge vs. interior) and shoot density (individual, patchy, continuous) on reproduction in three natural and two transplanted Chesapeake Bay (USA) stands of the submerged marine angiosperm Zostera marina L. (eelgrass; Zosteraceae). There were no edge effects on demographic-based reproductive effort or reproductive output (propagule production), and patch structure (individual, patchy, continuous) alone never accounted for the majority of variability in any metric. Transplant site was the most important predictor of eelgrass reproduction response, and relationships among metrics were predictable within sites. Our results suggest that, in Chesapeake Bay eelgrass, environmental factors acting at a regional scale (km) have a stronger impact on reproductive investment than those at a patch scale (1–10 m). Since tradeoffs between clonal and sexual production are mediated primarily by exogenous environmental factors, site selection may be more critical than transplant configuration for producing self sustaining stands, and achieving long-term restoration success.  相似文献   

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对威海双岛湾大叶藻(Zostera marina L.)种群的有性生殖特性进行了研究。结果表明:该水域中,大叶藻种群于3月下旬或4月上旬进入生殖枝始现期,5月上旬进入始花期,6月下旬进入种子散落高峰期,7月上旬进入生殖枝死亡始期,7月下旬生殖期结束,其有性生殖物候进程与水温密切相关,15℃是其开花适宜水温;生殖枝的侧枝数和扇状聚伞花序数在进入始花期时达到最大,分别为4.4和4.9个·株-1,佛焰苞数和生殖枝高度均在种子散落始期最大,分别为18.6个·株-1和96.2 cm,种子败育率较高,平均为40%,成熟种子产量为44.8粒·株-1;生殖枝密度在始花期时达到最大,为64株·m-2,生殖枝分化率平均仅有12.6%,有性生殖期间营养枝密度和种群总密度的下降幅度超过40%;生殖枝生物量在初果期达到最大(27.9 g·m-2),从始花期至种子散落高峰期平均种群生物量分配格局为地下部38.4%,营养枝52.4%,生殖枝9.2%,生殖分配较低,成熟种子产量为1859粒·m-2。  相似文献   

15.
Seed germination and seedling growth of Zostera marina L. were monitored in the Chesapeake Bay in 1979 and 1980. Harvested seeds were placed in small acrylic tubes at several sites representing the salinity range of Z. marina distribution. Seed germination was observed first in late September and continued through May, with peaks in the fall and spring. The majority of seeds that germinated (66%) did so between December and March when water temperatures ranged from 0–10°C. There was no correlation between sites (different salinity regimes) and frequency of germination rates, indicating that salinity was not a major factor in the germination process in this study. Additional information on seed germination was available for seeds collected in 1977 and 1980 and subsequently monitored for germination at only one site. These data were similar to germination frequency recorded in 1979–1980.Seedling growth was measured from individuals collected from an existing Zostera marina bed. Seedlings were collected from November through May, at which time we could no longer distinguish seedlings from existing vegetative stock. Growth was characterized by the increased length of the primary shoot, number of leaves per shoot and numbers of shoots per plant. Seedling growth was slow during the winter months (water temperature ? 10°C) but rapidly increased in the spring (temperatures > 10°C). The size range of the harvested seedlings indicated that seed germination in the field probably occurred from October through April, corroborating evidence from the seed germination experiments.  相似文献   

16.
The seagrass Zostera marina is widely distributed in coastal regions throughout much of the northern hemisphere, forms the foundation of an important ecological habitat, and is suffering population declines. Studies in the Atlantic and Pacific oceans indicate that the degree of population genetic differentiation is location dependent. San Francisco Bay, California, USA, is a high-current, high-wind environment where rafting of seed-bearing shoots has the potential to enhance genetic connectivity among Z. marina populations. We tested Z. marina from six locations, including one annual population, within the bay to assess population differentiation and to compare levels of within-population genetic diversity. Using 7 microsatellite loci, we found significant differentiation among all populations. The annual population had significantly higher clonal diversity than the others but showed no detectible differences in heterozygosity or allelic richness. There appears to be sufficient input of genetic variation through sexual reproduction or immigration into the perennial populations to prevent significant declines in the number and frequency of alleles. In additional depth comparisons, we found differentiation among deep and shallow portions in 1 of 3 beds evaluated. Genetic drift, sweepstakes recruitment, dispersal limitation, and possibly natural selection may have combined to produce genetic differentiation over a spatial scale of 3-30 km in Z. marina. This implies that the scale of genetic differentiation may be smaller than expected for seagrasses in other locations too. We suggest that populations in close proximity may not be interchangeable for use as restoration material.  相似文献   

17.
Tropical rain forest conservation requires a good understanding of plant–animal interactions. Seed dispersal provides a means for plant seeds to escape competition and density-dependent seed predators and pathogens and to colonize new habitats. This makes the role and effectiveness of frugivorous species in the seed dispersal process an important topic. Northern pigtailed macaques (Macaca leonina) may be effective seed dispersers because they have a diverse diet and process seeds in several ways (swallowing, spitting out, or dropping them). To investigate the seed dispersal effectiveness of a habituated group of pigtailed macaques in Khao Yai National Park, Thailand, we examined seed dispersal quantity (number of fruit species eaten, proportion in the diet, number of feces containing seeds, and number of seeds processed) and quality (processing methods used, seed viability and germination success, habitat type and distance from parent tree for the deposited seeds, and dispersal patterns) via focal and scan sampling, seed collection, and germination tests. We found thousands of seeds per feces, including seeds up to 58 mm in length and from 88 fruit species. Importantly, the macaques dispersed seeds from primary to secondary forests, via swallowing, spitting, and dropping. Of 21 species, the effect of swallowing and spitting was positive for two species (i.e., processed seeds had a higher % germination and % viability than control seeds), neutral for 13 species (no difference in % germination or viability), and negative (processed seeds had lower % germination and viability) for five species. For the final species, the effect was neutral for spat-out seeds but negative for swallowed seeds. We conclude that macaques are effective seed dispersers in both quantitative and qualitative terms and that they are of potential importance for tropical rain forest regeneration.  相似文献   

18.
高等植物大叶藻研究进展及其对海洋沉水生活的适应   总被引:15,自引:0,他引:15  
综述和讨论了目前对海洋沉水植物大叶藻的研究进展 ,主要包括 :(1 )形态解剖结构特点 ,(2 )基本生理研究 ,(3 )耐盐机理 ,(4)生存限制因子 ,(5 )问题与展望。其中着重讨论了大叶藻与海洋沉水生活相适应的一些特点 ,特别是其对海水盐度的适应机理。  相似文献   

19.
We characterized 37 single nucleotide polymorphism (SNP) makers for eelgrass Zostera marina. SNP markers were developed using existing EST (expressed sequence tag)-libraries to locate polymorphic loci and develop primers from the functional expressed genes that are deposited in The ZOSTERA database (V1.2.1). SNP loci were genotyped using a single-base-extension approach which facilitated high-throughput genotyping with minimal optimization time. These markers show a wide range of variability among 25 eelgrass populations and will be useful for population genetic studies including evaluation of population structure, historical demography, and phylogeography. Potential applications include haplotype inference of physically linked SNPs and identification of genes under selection for temperature and desiccation stress.  相似文献   

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