Foraging Rules for Group Feeders: Area Copying Depends upon Food Density in Shoaling Goldfish

The decision rules governing forage area copying behaviour were investigated in shoaling fish. Shoaling goldfish were offered two equal food patches, one of which was adjacent to an equal-sized shoal feeding behind a transparent barrier. When food was low, goldfish foraged according to an area copying rule, but under high and zero food area copying disappeared. Only under high food density did equal numbers of fish feed at both sites as predicted by foraging theory. Under zero food the fish were less certain about where to forage. Precise visual cues from feeding fish were required: non-feeders did not attract area copiers. Furthermore, area copying was task-dependent since it reappeared strongly if fish were not able to forage on patches like their fellows. Control experiments eliminated an increase in group size for anti-predator advantage as an explanation. Two sequential decisions: to stay or move, and to join or leave may explain the results, which are not accommodated by simple optimality models. These decisions may be based on a comparison of current food intake with the anticipation of a higher reward by foraging socially.     

Vocal Discrimination in Mate Guarding Male Australian Sea Lions: Familiarity Breeds Contempt

The vocal characteristics of a species can be immensely diverse, and can significantly impact animal social interactions. The social structure of a species may vary with geographical variation in call characteristics. The ability of pinnipeds (true seals, fur seals, sea lions and walrus) to distinguish between conspecifics may assist male reproductive strategies, particularly mate acquisition. We assessed the ability of mate guarding Australian sea lion (Neophoca cinerea) males to discriminate local from foreign males’ barks recorded from a geographically distant breeding colony. Bark characteristics were significantly different between colonies, with barks produced by males from the Lewis Island breeding colony higher pitched and longer in both duration and interval duration than barks produced by males on Kangaroo Island. Mate guarding males displayed inter‐colony discrimination of barks, with a significantly stronger response to barks from local males than to those of males from a colony approx. 180 km away. Local males’ barks were apparently considered a greater threat than barks from unfamiliar males. We propose that discrimination of acoustic characteristics may facilitate reproductive isolation in this species that may lead to an ethological–acoustic barrier between breeding colonies, and subsequent genetic isolation.     

Rapid Onset of Maternal Vocal Recognition in a Colonially Breeding Mammal,the Australian Sea Lion

Background

In many gregarious mammals, mothers and offspring have developed the abilities to recognise each other using acoustic signals. Such capacity may develop at different rates after birth/parturition, varying between species and between the participants, i.e., mothers and young. Differences in selective pressures between species, and between mothers and offspring, are likely to drive the timing of the onset of mother-young recognition. We tested the ability of Australian sea lion mothers to identify their offspring by vocalisation, and examined the onset of this behaviour in these females. We hypothesise that a rapid onset of recognition may reflect an adaptation to a colonial lifestyle.

Principal Findings

In a playback study maternal responses to own pup and non-filial vocalisations were compared at 12, 24 and every subsequent 24 hours until the females'' first departure post-partum. Mothers showed a clear ability to recognise their pup''s voice by 48 hours of age. At 24 hours mothers called more, at 48 hours they called sooner and at 72 hours they looked sooner in response to their own pup''s vocalisations compared to those of non-filial pups.

Conclusions

We demonstrate that Australian sea lion females can vocally identify offspring within two days of birth and before mothers leave to forage post-partum. We suggest that this rapid onset is a result of selection pressures imposed by a colonial lifestyle and may be seen in other colonial vertebrates. This is the first demonstration of the timing of the onset of maternal vocal recognition in a pinniped species.     

Biochemical isolation and purification of ovulation-inducing factor (OIF) in seminal plasma of llamas

Background  

The objective of the present study was to isolate and purify the protein fraction(s) of llama seminal plasma responsible for the ovulation-inducing effect of the ejaculate.     

Schizophrenia susceptibility pathway neuregulin 1-ErbB4 suppresses Src upregulation of NMDA receptors

Hypofunction of the N-methyl D-aspartate subtype of glutamate receptor (NMDAR) is hypothesized to be a mechanism underlying cognitive dysfunction in individuals with schizophrenia. For the schizophrenia-linked genes NRG1 and ERBB4, NMDAR hypofunction is thus considered a key detrimental consequence of the excessive NRG1-ErbB4 signaling found in people with schizophrenia. However, we show here that neuregulin 1β-ErbB4 (NRG1β-ErbB4) signaling does not cause general hypofunction of NMDARs. Rather, we find that, in the hippocampus and prefrontal cortex, NRG1β-ErbB4 signaling suppresses the enhancement of synaptic NMDAR currents by the nonreceptor tyrosine kinase Src. NRG1β-ErbB4 signaling prevented induction of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses and suppressed Src-dependent enhancement of NMDAR responses during theta-burst stimulation. Moreover, NRG1β-ErbB4 signaling prevented theta burst-induced phosphorylation of GluN2B by inhibiting Src kinase activity. We propose that NRG1-ErbB4 signaling participates in cognitive dysfunction in schizophrenia by aberrantly suppressing Src-mediated enhancement of synaptic NMDAR function.     

Back-to-the-future: a fresh policy initiative for fisheries and a restoration ecology for ocean ecosystems

'Back-to-the-future' (BTF) is an integrative approach to a restoration ecology of the oceans that attempts to solve the fisheries crisis. To this end, it harnesses the latest understanding of ecosystem processes developments in whole ecosystem simulation modelling, and insight into the human dimension of fisheries management. BTF includes new methods for describing past ecosystems, designing fisheries that meet criteria for sustainability and responsibility, and evaluating the costs and benefits of fisheries in restored ecosystems. Evaluation of alternative policy choices, involving trade-offs between conservation and economic values, employs a range of economic, social and ecological measures. Automated searches maximize values of objective functions, and the methodology includes analyses of model parameter uncertainty. Participatory workshops attempt to maximize compliance by fostering a sense of ownership among all stakeholders. Some challenges that have still to be met include improving methods for quantitatively describing the past, reducing uncertainty in ecosystem simulation techniques and in making policy choices robust against climate change. Critical issues include whether past ecosystems make viable policy goals, and whether desirable goals may be reached from today's ecosystem. Examples from case studies in British Columbia, Newfoundland and elsewhere are presented.     

Phosphorylation and chronic agonist treatment atypically modulate GABAB receptor cell surface stability

GABA(B) receptors are heterodimeric G protein-coupled receptors that mediate slow synaptic inhibition in the central nervous system. The dynamic control of the cell surface stability of GABA(B) receptors is likely to be of fundamental importance in the modulation of receptor signaling. Presently, however, this process is poorly understood. Here we demonstrate that GABA(B) receptors are remarkably stable at the plasma membrane showing little basal endocytosis in cultured cortical and hippocampal neurons. In addition, we show that exposure to baclofen, a well characterized GABA(B) receptor agonist, fails to enhance GABA(B) receptor endocytosis. Lack of receptor internalization in neurons correlates with an absence of agonist-induced phosphorylation and lack of arrestin recruitment in heterologous systems. We also demonstrate that chronic exposure to baclofen selectively promotes endocytosis-independent GABA(B) receptor degradation. The effect of baclofen can be attenuated by activation of cAMP-dependent protein kinase or co-stimulation of beta-adrenergic receptors. Furthermore, we show that increased degradation rates are correlated with reduced receptor phosphorylation at serine 892 in GABA(B)R2. Our results support a model in which GABA(B)R2 phosphorylation specifically stabilizes surface GABA(B) receptors in neurons. We propose that signaling pathways that regulate cAMP levels in neurons may have profound effects on the tonic synaptic inhibition by modulating the availability of GABA(B) receptors.     

The bacterial cytochrome cbb3 oxidases

Cytochrome cbb(3) oxidases are found almost exclusively in Proteobacteria, and represent a distinctive class of proton-pumping respiratory heme-copper oxidases (HCO) that lack many of the key structural features that contribute to the reaction cycle of the intensely studied mitochondrial cytochrome c oxidase (CcO). Expression of cytochrome cbb(3) oxidase allows human pathogens to colonise anoxic tissues and agronomically important diazotrophs to sustain N(2) fixation. We review recent progress in the biochemical characterisation of these distinctive oxidases that lays the foundation for understanding the basis of their proposed high affinity for oxygen, an apparent degeneracy in their electron input pathways and whether or not they acquired the ability to pump protons independently of other HCOs.     

Differential Expression of Immune Response Genes in Steller Sea Lions (Eumetopias jubatus): An Indicator of Ecosystem Health?

Characterization of the polygenic and polymorphic features of the Steller sea lion major histocompatibility complex (MHC) provides an ideal window for evaluating immunologic vigor of the population and identifying emergence of new genotypes that reflect ecosystem pressures. MHC genotyping can be used to measure the potential immunologic vigor of a population. However, since ecosystem-induced changes to MHC genotype can be slow to emerge, measurement of differential expression of these genes can potentially provide real-time evidence of immunologic perturbations. MHC DRB genes were cloned and sequenced using peripheral blood mononuclear leukocytes derived from 10 Steller sea lions from Southeast Alaska, Prince William Sound, and the Aleutian Islands. Nine unique DRB gene sequences were represented in each of 10 animals. MHC DRB gene expression was measured in a subset of six sea lions. Although DRB in genomic DNA was identical in all individuals, relative levels of expressed DRB mRNA was highly variable. Selective suppression of MHC DRB genes could be indicative of geographically disparate environmental pressures, thereby serving as an immediate and sensitive indicator of population and ecosystem health.