Temperate marine protected area provides recruitment subsidies to local fisheries.

The utility of marine protected areas (MPAs) as a means of protecting exploited species and conserving biodiversity within MPA boundaries is supported by strong empirical evidence. However, the potential contribution of MPAs to fished populations beyond their boundaries is still highly controversial; empirical measures are scarce and modelling studies have produced a range of predictions, including both positive and negative effects. Using a combination of genetic parentage and relatedness analysis, we measured larval subsidies to local fisheries replenishment for Australasian snapper (Chrysophrys auratus: Sparidae) from a small (5.2 km2), well-established, temperate, coastal MPA in northern New Zealand. Adult snapper within the MPA contributed an estimated 10.6% (95% CI: 5.5-18.1%) of newly settled juveniles to surrounding areas (approx. 400 km2), with no decreasing trend in contributions up to 40 km away. Biophysical modelling of larval dispersal matched experimental data, showing larvae produced inside the MPA dispersed over a comparable distance. These results demonstrate that temperate MPAs have the potential to provide recruitment subsidies at magnitudes and spatial scales relevant to fisheries management. The validated biophysical model provides a cost-efficient opportunity to generalize these findings to other locations and climate conditions, and potentially informs the design of MPA networks for enhancing fisheries management.

Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species.

Soundscapes provide a new tool for the study of fish communities. Bigeyes (Pempheris adspersa) are nocturnal planktivorous reef fish, feed in loose shoals and are soniferous. These vocalisations have been suggested to be contact calls to maintain group cohesion, however direct evidence for this is absent, despite the fact that contact calls are well documented for many other vertebrates, including marine mammals. For fish, direct evidence for group cohesion signals is restricted to the use of visual and hydrodynamic cues. In support of adding vocalisation as a contributing cue, our laboratory experiments show that bigeyes significantly increased group cohesion when exposed to recordings of ambient reef sound at higher sound levels while also decreasing vocalisations. These patterns of behaviour are consistent with acoustic masking. When exposed to playback of conspecific vocalisations, the group cohesion and vocalisation rates of bigeyes both significantly increased. These results provide the first direct experimental support for the hypotheses that vocalisations are used as contact calls to maintain group cohesion in fishes, making fish the evolutionarily oldest vertebrate group in which this phenomenon has been observed, and adding a new dimension to the interpretation of nocturnal reef soundscapes.

Potential Competitive Dynamics of Acoustic Ecology.

The top predators in coastal marine ecosystems, such as whales, dolphins, seabirds, and large predatory fishes (including sharks), may compete with each other to exploit food aggregations. Finding these patchy food sources and being first to a food patch could provide a significant competitive advantage. Our hypothesis is that food patches have specific sound signatures that marine predators could detect and that acoustic sources and animal sensory capabilities may contribute to competition dynamics. Preliminary analysis shows that diving gannets have a distinct spectral signature between 80 and 200 Hz, which falls within the hearing sensitivity of large pelagic fishes. Therefore, we suggest that diving birds may contribute to the sound signatures of food aggregations, linking competition dynamics both above and below the water surface.

Unilateral ablation of trunk superficial neuromasts increases directional instability during steady swimming in the yellowtail kingfish Seriola lalandi.

Detailed swimming kinematics of the yellowtail kingfish Seriola lalandi were investigated after unilateral ablation of superficial neuromasts (SNs). Most kinematic variables, such as tail-beat frequency, stride length, caudal fin-beat amplitude and propulsive wavelength, were unaffected but lateral amplitude at the tip of the snout (A0 ) was significantly increased in SN-disrupted fish compared with sham-operated controls. In addition, the orientation of caudal fin-tip relative to the overall swimming direction of SN-disrupted fish was significantly deflected (two-fold) in comparison with sham-operated control fish. In some fish, SN disruption also led to a phase distortion of the propulsive body-wave. These changes would be expected to increase both hydrodynamic drag and thrust production which is consistent with the finding that SN-disrupted fish had to generate significantly greater thrust power when swimming at ≥1·3 fork lengths (LF ) s(-1) . In particular, hydrodynamic drag would increase as a result of any increase in rotational (yaw) perturbation and sideways slip resulting from the sensory disturbance. In conclusion, unilateral SN ablation produced directional instability of steady swimming and altered propulsive movements, suggesting a role for sensory feedback in correcting yaw and slip disturbances to maintain efficient locomotion.

A novel hearing specialization in the New Zealand bigeye, Pempheris adspersa.

The New Zealand bigeye, Pempheris adspersa, is a nocturnal planktivore and has recently been found to be an active sound producer. The rostral end of the swim bladder lies adjacent to Baudelot's ligament which spans between the bulla and the cleithrum bone of the pectoral girdle. The aim of this study was to use the auditory evoked potential technique to physiologically test the possibility that this structure provides an enhanced sensitivity to sound pressure in the bigeye. At 100 Hz, bigeye had hearing sensitivity similar to that of goldfish (species with a mechanical connection between the swim bladder and the inner ear mediated by the Weberian ossicles) and were much more sensitive than other teleosts without ancillary hearing structures. Severing Baudelot's ligament bilaterally resulted in a marked decrease in hearing sensitivity, as did swim bladder puncture or lateral line blockage. These results show that bigeye have an enhanced sensitivity to sound pressure and provide experimental evidence that the functional basis of this sensitivity represents a novel hearing specialization in fish involving the swim bladder, Baudelot's ligament and the lateral line.

A proposed mechanism for the observed ontogenetic improvement in the hearing ability of hapuka (Polyprion oxygeneios).

Swim bladder extensions and hearing ability were examined in the temperate reef fish Polyprion oxygeneios (hapuka). Using the auditory evoked potential (AEP) technique, hearing thresholds were determined in four age-classes of hapuka, from larvae to juveniles. The youngest age-class had poor hearing abilities, with lowest thresholds of 132 dB re 1 µPa, and a narrow auditory bandwidth (100-800 Hz). Hearing ability improved significantly throughout the remainder of their first year, including decreases in thresholds of up to 27 dB, and an increase in auditory bandwidth (up to 1,000 Hz). Magnetic resonance imaging (MRI) was used to investigate structural mechanisms that may account for this ontogenetic improvement in hearing. These showed rostral extensions of the swim bladder developing early in the juvenile stage, and extending with increasing age closer to the otic capsule. It is suggested that this indirect connection between the swim bladder and the otic capsule could impart pressure sensitivity closer to the inner ear, accounting for the increase in sensitivity seen during development, although further investigation of older fish is required for conclusive evidence. The improvement in hearing ability in hapuka could be potentially related to a unique life history of extended pelagic durations up to 4 years.

The feeding response of Pseudophycas barbata to multisensory prey cues in a low light environment.

The nocturnal southern bastard cod Pseudophycis barbata was found to utilize chemo- and mechanosensory systems when hunting for prey under low light conditions. The sensory system used depended on whether prey produced a hydrodynamic signal.

Sensory integration in the hydrodynamic world of rainbow trout.

Water movements, of both abiotic and biotic origin, provide a wealth of information for fishes. They detect these water movements by arrays of hydrodynamic sensors located on the surface of the body as superficial neuromasts and embedded in subdermal lateral line canals. Recently, the anatomical dichotomy between superficial and canal neuromasts has been matched by demonstrations of a corresponding functional dichotomy. Superficial neuromasts are sensitive to water flows over the surface of the fish and are the sub-modality that participates in orientation to water currents, a behaviour known as rheotaxis. The canal neuromasts are sensitive to water vibration and it is this sub-modality that determines the localization of artificial prey. Recently, however, it has been shown that the complex behaviour of natural prey capture in the dark requires input from both lateral line sensory submodalities and here we show that the ability of trout to hold station behind a stationary object in fast flowing water also requires integration of information from both sub-modalities.

Responses of anterior lateral line afferent neurones to water flow.

The mechanoreceptive lateral line system detects hydrodynamic stimuli and plays an important role in a number of types of fish behaviour, including orientation to water currents. The lateral line is composed of hair cell receptor organs called neuromasts that occur as superficial neuromasts on the surface of the skin or canal neuromasts located in subepidermal canals. Both are innervated by primary afferents of the lateral line nerves. Although there have been extensive studies of the response properties of lateral line afferents to vibrating sources, their response to water flow has not been reported. In this study, we recorded extracellularly from anterior lateral line afferents in the New Zealand long-fin eel Anguilla dieffenbachii while stimulating the eel with unidirectional water flows at 0.5-4 cm s(-)(1). Of the afferents, 80 % were flow-sensitive to varying degrees, the response magnitude increasing with flow rate. Flow-sensitive fibres gave non-adapting tonic responses, indicating that these fibres detect absolute flow velocity. Further studies are needed to confirm whether flow-sensitive and flow-insensitive fibres correlate with superficial and canal neuromasts, respectively.

The murine Fhit locus: isolation, characterization, and expression in normal and tumor cells.

The murine Fhit locus maps near the centromere nu proximal Ptprg locus on mouse chromosome 14. The cDNA sequence and structure are similar to those of the human gene, with exons 5-9 encoding the protein. The predominant mRNA in the tissues and cell lines tested was an alternatively spliced form missing exon 3. Most murine cell lines tested, including lines established from normal mouse embryos and tumors, expressed very low or undetectable levels of Fhit mRNA. Most normal mouse tissues expressed wild-type Fhit mRNA, whereas approximately 40% of murine lung carcinomas expressed wild-type and aberrant Fhit RT-PCR products that lacked various exons. Several tumorigenic mouse cell lines exhibited homozygous deletions of Fhit exons. We conclude that the murine Fhit gene, like its human counterpart, is a target of alterations involved in murine carcinogenesis.

AbdB-like Hox proteins stabilize DNA binding by the Meis1 homeodomain proteins.

Recent studies show that Hox homeodomain proteins from paralog groups 1 to 10 gain DNA binding specificity and affinity through cooperative binding with the divergent homeodomain protein Pbx1. However, the AbdB-like Hox proteins from paralogs 11, 12, and 13 do not interact with Pbx1a, raising the possibility of different protein partners. The Meis1 homeobox gene has 44% identity to Pbx within the homeodomain and was identified as a common site of viral integration in myeloid leukemias arising in BXH-2 mice. These integrations result in constitutive activation of Meis1. Furthermore, the Hoxa-9 gene is frequently activated by viral integration in the same BXH-2 leukemias, suggesting a biological synergy between these two distinct classes of homeodomain proteins in causing malignant transformation. We now show that the Hoxa-9 protein physically interacts with Meis1 proteins by forming heterodimeric binding complexes on a DNA target containing a Meis1 site (TGACAG) and an AbdB-like Hox site (TTTTACGAC). Hox proteins from the other AbdB-like paralogs, Hoxa-10, Hoxa-11, Hoxd-12, and Hoxb-13, also form DNA binding complexes with Meis1b, while Hox proteins from other paralogs do not appear to interact with Meis1 proteins. DNA binding complexes formed by Meis1 with Hox proteins dissociate much more slowly than DNA complexes with Meis1 alone, suggesting that Hox proteins stabilize the interactions of Meis1 proteins with their DNA targets.

Reln(rl-Alb2), an allele of reeler isolated from a chlorambucil screen, is due to an IAP insertion with exon skipping.

The reeler Albany2 mutation (Reln(rl-Alb2) in the mouse is an allele of reeler isolated during a chlorambucil mutagenesis screen. Homozygous animals had drastically reduced concentrations of reelin mRNA, in which an 85-nt exon was absent. At the genomic level, the mutation was shown to be due to an intracisternal A-particle insertion leading to exon skipping. This appears to be the first observation of retrotransposon insertion during chlorambucil mutagenesis.

Identification of a conserved family of Meis1-related homeobox genes.

Meis1 locus was isolated as a common site of viral integration involved in myeloid leukemia in BXH-2 mice. Meis1 encodes a novel homeobox protein belonging to the TALE (three amino acid loop extension) family of homeodomain-containing proteins. The homeodomain of Meis1 is the only known motif within the entire 390-amino-acid protein. Southern blot analyses using the Meis1 homeodomain as a probe revealed the existence family of Meis1-related genes (Mrgs) in several diverged species. In addition, the 3' untranslated region (UTR) Meis1 was remarkably conserved in evolution. To gain a further understanding of the role Meis1 plays in leukemia and development, as well as to identify conserved regions of the protein that might reveal function, we cloned and characterized Mrgs from the mouse and human genomes. We report the sequence of Mrg1 and MRG2 as well as their chromosomal locations in murine and human genomes. Both Mrgs share a high degree of sequence identity with the protein coding region of Meis1. We have also cloned the Xenopus laevis ortholog of (XMeis1). Sequence comparison of the murine and Xenopus clones reveals that Meis1 is highly conserved throughout its coding sequence as well as the 3' UTR. Finally, comparison of Meis1 and the closely related Mrgs to known homeoproteins suggests that Meis1 represents a new subfamily of TALE homeobox genes.

Structure and function of the vertebrate magnetic sense.

Some vertebrates can navigate over long distances using the Earth's magnetic field, but the sensory system that they use to do so has remained a mystery. Here we describe the key components of a magnetic sense underpinning this navigational ability in a single species, the rainbow trout (Oncorhynchus mykiss). We report behavioural and electrophysiological responses to magnetic fields and identify an area in the nose of the trout where candidate magnetoreceptor cells are located. We have tracked the sensory pathway from these newly identified candidate magnetoreceptor cells to the brain and associated the system with a learned response to magnetic fields.

High-resolution genetic map and YAC contig around the mouse neurological locus reeler.

Mutations at the recessive reeler locus (rl) on mouse Chromosome (Chr) 5 result in abnormal development of multiple central nervous system components, including the cerebral and cerebellar cortices. These abnormalities are characterized by highly disorganized laminar structures thought to have arisen from a post-migration failure of neuronal organization events that are probably mediated through cell-cell interactions. As a result of a mutagenesis scheme designed to generate visible recessive mutations induced by the drug chlorambucil, we had previously recovered a new allele of the reeler locus (rlAlb) that is likely to involve a deletion based on the known mechanisms of chlorambucil action. We have constructed a high-resolution genetic map from two intercrosses segregating this allele. Our first cross, in which the mutation was outcrossed to the 101 strain prior to intercrossing, consisted of 196 meioses and resulted in the positioning of four loci proximal to rl, with D5Mit1 being the closest (2.6 +/- 1.1 cM). The second cross consisted of intercrossing rl heterozygotes derived from an outcross to the C57BL/6 strain. A total of 318 mice (636 meioses) gave rise to a panel of 41 recombinants, which were used to map a total of 14 loci within a 6.4-cM interval bounded by D5Mit1 and the En-2 gene. A yeast artificial chromosome contig consisting of clones containing two of these loci, D5Mit72 (located 0.31 cM distal to rl), and D5Mit61 (no recombinants with rl), has been assembled and is being used to locate the rl gene.

GABA, muscarinic cholinergic, excitatory amino acid, neurotensin and opiate binding sites in the octavolateralis column and cerebellum of the skate Raja nasuta (Pisces: Rajidae).

As part of a study of signal processing in the electro- and mechanosensory systems we have screened the octavolateralis column of the skate for GABAA, muscarinic cholinergic, excitatory amino acid, neurotensin and opiate binding sites using autoradiography following in vitro labelling of cryostat sections with tritiated ligands. The presence and distribution of these binding sites is compared between the octavolateralis column and the corpus cerebellum. GABAA binding sites were located in high concentrations in the granule cell regions of the cerebellum and octaval columns, with much lower concentrations in the Purkinje cell layer of the corpus cerebellum. Little or no labelling was evident in all molecular layer areas. Displacement studies using the discriminating ligand CL218,872 indicated that the GABAA binding sites were predominantly of the GABAA/benzodiazepine Type II variety. M1 muscarinic cholinergic binding sites were found in high concentrations in all granule cell areas and in lower concentrations in the molecular layer of the octavolateralis column, with an absence of labelling in the molecular layer of the corpus cerebellum. Kainic acid and AMPA binding sites were present in very high concentrations in all molecular layer areas. Glutamate binding was present in the molecular layer of the octavolateralis column and in some restricted regions of the dorsal granular ridge, whereas phencyclidine binding sites were sparse or absent. Neurotensin binding sites were strongly present in all granule cell areas and evident in the molecular layer of the octavolateralis column. There was evidence for opiate binding sites in the molecular layer of both the dorsal and medial octavolateralis nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

An adaptive filter that cancels self-induced noise in the electrosensory and lateral line mechanosensory systems of fish.

In lateral line and electrosensory systems of fish, the animal's own movements create unwanted stimulation that could interfere with the detection of biologically important signals. Here we report that an adaptive filter in the medullary nuclei of both senses suppresses self-stimulation. Second-order electrosensory neurons in an elasmobranch fish and mechanosensory neurons in a teleost fish learn to cancel the effects of stimuli that are presented coupled to the fish's movements. A model is proposed for how the adaptive filter is realized by the cerebellar-like circuits of the hindbrain nuclei in these senses.