Variations in Red Snapper oocyte development and spawning in relation to environmental and habitat parameters

Environmental Biology of Fishes - The reproductive biology of Red Snapper, Lutjanus campechanus, is well understood, but there is little information on the impact of environmental, climatic, and...     

Recognition and Response to Native and Novel Predators in the Largespring mosquitofish,Gambusia geiseri

The introduction of predator species into new habitats is an increasingly common consequence of human activities, and the persistence of native prey species depends upon their response to these novel predators. In this study, we examined whether the Largespring mosquitofish, Gambusia geiseri exhibited antipredator behavior and/or an elevation of circulating stress hormones (cortisol) to visual and chemical cues from a native predator, a novel predator, or a non‐predatory control fish. Prey showed the most pronounced antipredator response to the native predator treatment, by moving away from the stimulus, while the prey showed no significant changes in their vertical or horizontal position in response to the novel or non‐predator treatments. We also found no significant difference in water‐borne cortisol release rates following any of the treatments. Our results suggest the prey did not recognize and exhibit antipredator behavior to the novel predator, and we infer that this predator species could be detrimental if it expands into the range of this prey species. Further, our study demonstrates prey may not respond to an invasive predator that is phylogenetically, behaviorally, and morphologically dissimilar from the prey species' native predators.     

A comparison of survey and focal follow methods for estimating individual activity budgets of cetaceans

Activity budget data are essential for determining behavioral responses to physiological and ecological variables. Yet, few studies are available to investigate the robustness, accuracy, and biases of the methods used to estimate activity budgets for cetaceans. In this study, we compare activity budgets of 55 adult female bottlenose dolphins in Shark Bay, Australia derived from two methods: surveys (n = 6,903) and focal follows (n = 1,185, totaling 2,721 h of observation). Activity budgets estimated from survey data differed in all behavioral states compared to focal follow data. However, when controlling for temporal autocorrelation, only time spent socializing and time spent traveling remained disparate between the methods. To control for biases associated with assigning group‐level behavior to individuals, we also compared survey and focal follow activity budgets for lone females. Here we found differences between methods in time spent foraging and traveling regardless of whether we controlled for temporal autocorrelation, which suggests detection biases likely play a role in explaining differences in activity budget estimates between the two methodologies. Our results suggest that surveys are less representative of individual‐level activity budgets, and thus, when individual‐level knowledge about behavior is needed, focal follows are preferred.     

Hyaluronidase Hyal1 Increases Tumor Cell Proliferation and Motility through Accelerated Vesicle Trafficking

Hyaluronan (HA) turnover accelerates metastatic progression of prostate cancer in part by increasing rates of tumor cell proliferation and motility. To determine the mechanism, we overexpressed hyaluronidase 1 (Hyal1) as a fluorescent fusion protein and examined its impact on endocytosis and vesicular trafficking. Overexpression of Hyal1 led to increased rates of internalization of HA and the endocytic recycling marker transferrin. Live imaging of Hyal1, sucrose gradient centrifugation, and specific colocalization of Rab GTPases defined the subcellular distribution of Hyal1 as early and late endosomes, lysosomes, and recycling vesicles. Manipulation of vesicular trafficking by chemical inhibitors or with constitutively active and dominant negative Rab expression constructs caused atypical localization of Hyal1. Using the catalytically inactive point mutant Hyal1-E131Q, we found that enzymatic activity of Hyal1 was necessary for normal localization within the cell as Hyal1-E131Q was mainly detected within the endoplasmic reticulum. Expression of a HA-binding point mutant, Hyal1-Y202F, revealed that secretion of Hyal1 and concurrent reuptake from the extracellular space are critical for rapid HA internalization and cell proliferation. Overall, excess Hyal1 secretion accelerates endocytic vesicle trafficking in a substrate-dependent manner, promoting aggressive tumor cell behavior.     

Gemin5 Binds to the Survival Motor Neuron mRNA to Regulate SMN Expression

Reduced expression of SMN causes spinal muscular atrophy, a severe neurodegenerative disease. Despite the importance of maintaining SMN levels, relatively little is known about the mechanisms by which SMN levels are regulated. We show here that Gemin5, the snRNA-binding protein of the SMN complex, binds directly to the SMN mRNA and regulates SMN expression. Gemin5 binds with high specificity, both in vitro and in vivo, to sequence and structural elements in the SMN mRNA 3′-untranslated region that are reminiscent of the snRNP code to which Gemin5 binds on snRNAs. Reduction of Gemin5 redistributes the SMN mRNA from heavy polysomes to lighter polysomes and monosomes, suggesting that Gemin5 functions as an activator of SMN translation. SMN protein is not stoichiometrically present on the SMN mRNA with Gemin5, but the mRNA-binding activity of Gemin5 is dependent on SMN levels, providing a feedback mechanism for SMN to regulate its own expression via Gemin5. This work both reveals a new autoregulatory pathway governing SMN expression, and identifies a new mechanism through which SMN can modulate specific mRNA expression via Gemin5.     

Prey composition and ontogenetic shift in coastal populations of longnose gar Lepisosteus osseus

Longnose gar Lepisosteus osseus were collected from May 2012 to July 2013 in the Charleston Harbor and Winyah Bay estuaries (SC, U.S.A.). This study examined trends in stomach fullness, described major prey components and their importance in the diet of L. osseus, compared stomach content‐based trophic level estimates with the stable‐isotope‐based proxy: δ¹⁵N and tested for the occurrence of an ontogenetic diet shift using stomach content analysis and stable C and N isotopes (δ¹³C and δ¹⁵N). Dominant prey families were Clupeidae, Sciaenidae, Penaeidae, Fundulidae and Mugilidae, with the highest consumption rates in autumn. Trophic levels calculated using stomach contents did not correspond to δ¹⁵N (P > 0·05). Stomach contents and stable‐isotope signatures indicate ontogenetic prey composition shifts from low trophic level benthic prey (fundulids) to higher trophic level pelagic prey (clupeids) as the fish grow between 400 and 600 mm in standard length. Due to their biomass, abundance and top predator status, L. osseus play a significant ecological role in the estuarine community composition, although this effect has often been overlooked by past researchers and should be considered in future estuarine community studies.     

Genomic correlates of recombination rate and its variability across eight recombination maps in the western honey bee (Apis mellifera L.)

Background

Meiotic recombination has traditionally been explained based on the structural requirement to stabilize homologous chromosome pairs to ensure their proper meiotic segregation. Competing hypotheses seek to explain the emerging findings of significant heterogeneity in recombination rates within and between genomes, but intraspecific comparisons of genome-wide recombination patterns are rare. The honey bee (Apis mellifera) exhibits the highest rate of genomic recombination among multicellular animals with about five cross-over events per chromatid.

Results

Here, we present a comparative analysis of recombination rates across eight genetic linkage maps of the honey bee genome to investigate which genomic sequence features are correlated with recombination rate and with its variation across the eight data sets, ranging in average marker spacing ranging from 1 Mbp to 120 kbp. Overall, we found that GC content explained best the variation in local recombination rate along chromosomes at the analyzed 100 kbp scale. In contrast, variation among the different maps was correlated to the abundance of microsatellites and several specific tri- and tetra-nucleotides.

Conclusions

The combined evidence from eight medium-scale recombination maps of the honey bee genome suggests that recombination rate variation in this highly recombining genome might be due to the DNA configuration instead of distinct sequence motifs. However, more fine-scale analyses are needed. The empirical basis of eight differing genetic maps allowed for robust conclusions about the correlates of the local recombination rates and enabled the study of the relation between DNA features and variability in local recombination rates, which is particularly relevant in the honey bee genome with its exceptionally high recombination rate.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1281-2) contains supplementary material, which is available to authorized users.     

Leptospira immunoglobulin-like protein B (LigB) binding to the C-terminal fibrinogen αC domain inhibits fibrin clot formation, platelet adhesion and aggregation

Leptospira immunoglobulin-like (Lig) proteins including LigA and LigB are adhesins that bind to fibronectin, collagen, laminin and elastin. In addition, Lig proteins are fibrinogen (Fg)-binding proteins, although the physiological role of the Lig-Fg interaction is unclear. In this study, a previously identified Fg-binding region, LigBCen2 (amino acids 1014-1165 of LigB), has been further localized to LigBCen2R, which consists of the partial 11th and entire 12th Ig-like domain (amino acids 1014-1119). LigBCen2R was found to bind to the C-terminal αC domain of Fg (FgαCC; amino acids 392-644 in Fg α chain; isothermal titration calorimetry, K(D) = 0.375 μM; fluorescence spectrometry, K(D) = 0.364 μM). The quenching and blue shift observed for the maximum wavelength intensities of the tryptophan fluorescence spectra for FgαCCY570W upon LigBCen2RW1073C binding suggested an RGD motif close to the sole tryptophan on FgαCCY570W was buried in LigBCen2R upon saturation with FgαCC. A conformational change in LigBCen2R when bound to the FgαCC RGD motif blocked further binding to integrin α(IIb) β3 on platelets, thus preventing their aggregation. LigBCen2R binding to FgαCC reduced clot formation but did not affect plasminogen and tissue-type plasminogen activator interactions with FgαCC. This study is the first to report that a spirochaetal protein binds to the C-terminal αC domain of Fg, which regulates thrombosis and fibrinolysis, and may help explain the pulmonary haemorrhage and thrombocytopenia seen in clinical cases of leptospirosis.