Advertisement Call Variation in the Golden Rocket Frog (Anomaloglossus beebei): Evidence for Individual Distinctiveness

Individual distinctiveness in acoustic signals can allow receivers to respond appropriately to different individuals. The aim of this research was to examine signal variation and to investigate the relative importance of different acoustic properties for coding individual distinctiveness in the advertisement calls of male golden rocket frogs (Anomaloglossus beebei). We examined patterns of within‐individual and among‐individual variability in 760 advertisement calls of 40 males as well as repeatability in 16 additional males that were recorded on two different occasions. We examined eight call properties, and all properties exhibited significant among‐individual variation and moderate to high repeatability across days. We employed discriminant function analysis to examine individual distinctiveness statistically. These analyses assigned 79% of calls to the correct individual. Fine temporal properties, including pulse duration, pulse rate, and pulse interval, as well as the spectral property of dominant frequency, contributed most toward discrimination among individuals. These results indicate that individual male golden rocket frogs can be distinguished statistically by their advertisement calls. We use these findings to evaluate results of previous playback studies in A. beebei and to generate testable predictions regarding the potential for specific call properties to function in mate selection and social recognition.     

Short-interfering RNA-mediated Lck knockdown results in augmented downstream T cell responses

The Src family kinase Lck is essential for T cell Ag receptor-mediated signaling. In this study, we report the effects of acute elimination of Lck in Jurkat TAg and primary T cells using RNA interference mediated by short-interfering RNAs. In cells with Lck knockdown (kd), proximal TCR signaling was strongly suppressed as indicated by reduced zeta-chain phosphorylation and intracellular calcium mobilization. However, we observed sustained and elevated phosphorylation of ERK1/2 in Lck kd cells 30 min to 2 h after stimulation. Downstream effects on immune function as determined by activation of a NFAT-AP-1 reporter, and TCR/CD28-stimulated IL-2 secretion were strongly augmented in Jurkat and primary T cells, respectively. As expected, overexpression of SHP-1 in Jurkat cells inhibited TCR-induced NFAT-AP-1 activation, but this effect could be overcome by simultaneous kd of Lck. Furthermore, acute elimination of Lck also suppressed TCR-mediated activation of SHP-1, suggesting the possible role of SHP-1 in a negative feedback loop originating from Lck. This report underscores Lck as an important mediator of proximal TCR signaling, but also indicates a suppressive role on downstream immune function.     

Clustering of adhesion receptors following exposure of insect blood cells to foreign surfaces

Cell-mediated immune responses of insects involve interactions of two main classes of blood cells (hemocytes) known as granular cells and plasmatocytes. In response to a foreign surface, these hemocytes suddenly transform from circulating, non-adherent cells to cells that interact and adhere to each other and the foreign surface. This report presents evidence that during this adhesive transformation the extracellular matrix (ECM) proteins lacunin and a ligand for peanut agglutinin (PNA) lectin are released by granular cells and bind to surfaces of both granular cells and plasmatocytes. ECM protein co-localizes on cell surfaces with the adhesive receptors integrin and neuroglian, a member of the immunoglobulin superfamily. The ECM protein(s) secreted by granular cells are hypothesized to interact with adhesion receptors such as neuroglian and integrin by cross linking and clustering them on hemocyte surfaces. This clustering of receptors is known to enhance the adhesiveness (avidity) of interacting mammalian immune cells. The formation of ring-shaped clusters of these adhesion receptors on surfaces of insect immune cells represents an evolutionary antecedent of the mammalian immunological synapse.     

The impact of severely damaged cells in cytogenetic research.

In a large multilaboratory cytogenetic study of interlaboratory variations using 4 dose levels of triethylenemelamine and a control, a severely damaged cell was operationally defined as a cell which contained at least 10 aberrations of any type. A review of this study suggested that the use of this definition introduced a bias in the measurement and interpretation of results for the other cytogenetic categories studied. As a result, the original severely damaged cells were carefully reanalyzed to investigate the characteristics of this bias and to seek procedures to minimize or eliminate it. Results characterize this bias and demonstrate that when a severely damaged cell is defined as one containing at least 20 aberrations and those aberrations in the remaining non-severely damaged cells are classified by specific type, the bias is significantly reduced and chromosome analysis can be improved as a test system.     

Lung mediated auditory contrast enhancement improves the Signal-to-noise ratio for communication in frogs

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Male green frogs lower the pitch of acoustic signals in defense of territories: a possible dishonest signal of size?

In responses to broadcasts of conspecific advertisement calls,male green frogs (Rana clamitans) lower the dominant frequencyof their calls. Because dominant frequency is negatively correlatedwith male body size in green frogs, frequency alteration providesa means of potentially exaggerating size during territorialcontests. In field playback experiments, we broadcast syntheticstimuli representing small, medium, or large intruders to territorialresidents. We tested the hypotheses that males use frequency alteration to provide honest signals of their size or theirsize-independent fighting ability, or to dishonestly signalsize. Dominant frequency did not better predict male size inresponse calls than in unsolicited calls. The magnitude offrequency alteration was not related to body size, general condition, or an indirect measure of fighting ability. Thus,males did not use frequency alteration to provide honest informationabout body size or size-independent fighting ability. However,males significantly increased their apparent size by producinglower frequency calls. Small males produced relatively lowerfrequency calls in response to the large-male stimulus (comparedto the small-male and medium-male stimuli), but large malesdid not. Further, the magnitudes of frequency alteration weresignificantly greater in responses to the large-male stimulus,primarily because small males responded with a greater decreasein frequency to the large-male stimulus than to the small-maleand medium-male stimuli. These results support several predictions of the dishonest signal hypothesis and suggest that dishonestymay be a conditional strategy used by small males.     

Differential Metabolite Profiles during Fruit Development in High-Yielding Oil Palm Mesocarp

To better understand lipid biosynthesis in oil palm mesocarp, in particular the differences in gene regulation leading to and including de novo fatty acid biosynthesis, a multi-platform metabolomics technology was used to profile mesocarp metabolites during six critical stages of fruit development in comparatively high- and low-yielding oil palm populations. Significantly higher amino acid levels preceding lipid biosynthesis and nucleosides during lipid biosynthesis were observed in a higher yielding commercial palm population. Levels of metabolites involved in glycolysis revealed interesting divergence of flux towards glycerol-3-phosphate, while carbon utilization differences in the TCA cycle were proven by an increase in malic acid/citric acid ratio. Apart from insights into the regulation of enhanced lipid production in oil palm, these results provide potentially useful metabolite yield markers and genes of interest for use in breeding programmes.     

A Novel Glucagon-Related Peptide (GCRP) and Its Receptor GCRPR Account for Coevolution of Their Family Members in Vertebrates

The glucagon (GCG) peptide family consists of GCG, glucagon-like peptide 1 (GLP1), and GLP2, which are derived from a common GCG precursor, and the glucose-dependent insulinotropic polypeptide (GIP). These peptides interact with cognate receptors, GCGR, GLP1R, GLP2R, and GIPR, which belong to the secretin-like G protein-coupled receptor (GPCR) family. We used bioinformatics to identify genes encoding a novel GCG-related peptide (GCRP) and its cognate receptor, GCRPR. The GCRP and GCRPR genes were found in representative tetrapod taxa such as anole lizard, chicken, and Xenopus, and in teleosts including medaka, fugu, tetraodon, and stickleback. However, they were not present in mammals and zebrafish. Phylogenetic and genome synteny analyses showed that GCRP emerged through two rounds of whole genome duplication (2R) during early vertebrate evolution. GCRPR appears to have arisen by local tandem gene duplications from a common ancestor of GCRPR, GCGR, and GLP2R after 2R. Biochemical ligand-receptor interaction analyses revealed that GCRP had the highest affinity for GCRPR in comparison to other GCGR family members. Stimulation of chicken, Xenopus, and medaka GCRPRs activated Gα_s-mediated signaling. In contrast to chicken and Xenopus GCRPRs, medaka GCRPR also induced Gα_q/11-mediated signaling. Chimeric peptides and receptors showed that the K¹⁶M¹⁷K¹⁸ and G¹⁶Q¹⁷A¹⁸ motifs in GCRP and GLP1, respectively, may at least in part contribute to specific recognition of their cognate receptors through interaction with the receptor core domain. In conclusion, we present novel data demonstrating that GCRP and GCRPR evolved through gene/genome duplications followed by specific modifications that conferred selective recognition to this ligand-receptor pair.     

Short Amplexus Duration in a Territorial Anuran: A Possible Adaptation in Response to Male-Male Competition

Mating duration is a reproductive behaviour that can impact fertilization efficiency and offspring number. Previous studies of factors influencing the evolution of mating duration have focused on the potential role of internal sperm competition as an underlying source of selection; most of these studies have been on invertebrates. For vertebrates with external fertilization, such as fishes and frogs, the sources of selection acting on mating duration remain largely unknown due, in part, to the difficulty of observing complete mating behaviours in natural conditions. In this field study, we monitored breeding activity in a population of the territorial olive frog, Rana adenopleura, to identify factors that affect the duration of amplexus. Compared with most other frogs, amplexus was short, lasting less than 11 min on average, which included about 8 min of pre-oviposition activity followed by 3 min of oviposition. We evaluated the relationship between amplexus duration and seven variables: male body size, male condition, operational sex ratio (OSR), population size, clutch size, territory size, and the coverage of submerged vegetation in a male’s territory. We also investigated the influence of these same variables, along with amplexus duration, on fertilization rate. Amplexus duration was positively related with clutch size and the degree of male-bias in the nightly OSR. Fertilization rate was directly related to male body size and inversely related to amplexus duration. Agonistic interactions between males in amplexus and intruding, unpaired males were frequent. These interactions often resulted in mating failure, prolonged amplexus duration, and reduced fertilization rates. Together, the pattern of our findings indicates short amplexus duration in this species may be an adaptive reproductive strategy whereby males attempt to reduce the risks of mating and fertilization failures and territory loss resulting from male-male competition.