Using stable isotope analysis with telemetry or mark-recapture data to identify fish movement and foraging

Information about animal movements has often been inferred from stable isotope analysis (SIA), but is dependent on animals assimilating site-specific isotopic signatures via diet. This potential weakness in ecological interpretation can be overcome by using other investigative tools that provide precise information about individual movement patterns. In this paper, we demonstrate the value of combining SIA with telemetry or mark-recapture data from trapping, electrofishing and remote detection of individuals to study the movement and feeding ecology of fishes in different habitats. In a fjord lake system in Newfoundland, Canada, juvenile Atlantic salmon delayed downstream migration (smolts) or actively moved into a large lake (parr) where they foraged for periods reflecting different life history strategies. In the Miramichi River (New Brunswick, Canada), SIA provided evidence of distinct foraging habitats (tributary versus large river). By tracking fish implanted with passive integrated transponder (PIT) tags, we distinguished between movements related to foraging versus seeking cool water refugia during high temperature events. Finally, site fidelity and limited mobility of slimy sculpin, a small benthic fish, was established where δ¹³C in muscle tissue showed a progressive enrichment downstream and where a median displacement of <10 m was estimated for sculpin tagged with PIT tags. Technological improvements have permitted non-destructive tissue sampling of wild fishes for SIA, and the tagging and remote detection of animals smaller than was previously possible. These advancements and the combination of investigative tools promise new insights into animal ecology.     

Erythrocyte spectrin is an E2 ubiquitin conjugating enzyme

The involvement of red blood cell spectrin in the ubiquitination process was studied. Spectrin was found to form two ubiquitin-associated derivatives, a DTT-sensitive ubiquitin adduct and a DTT-insensitive conjugate, characteristic intermediate and final products of the ubiquitination reaction cascade. In addition to spectrin and ubiquitin, ubiquitin-activating enzyme (E1) and ATP were necessary and sufficient to form both the spectrin-ubiquitin adduct and conjugate. No exogenous ubiquitin-conjugating (E2) or ligase (E3) activities were required, suggesting that erythrocyte spectrin is an E2 ubiquitin-conjugating enzyme able to target itself. Both ubiquitin adduct and conjugate were linked to the alpha subunit of spectrin, suggesting that the ubiquitin-conjugating (UBC) domain and its target regions reside on the same subunit.     

Small Tails Tell Tall Tales – Intra-Individual Variation in the Stable Isotope Values of Fish Fin

Background

Fish fin is a widely used, non-lethal sample material in studies using stable isotopes to assess the ecology of fishes. However, fish fin is composed of two distinct tissues (ray and membrane) which may have different stable isotope values and are not homogeneously distributed within a fin. As such, estimates of the stable isotope values of a fish may vary according to the section of fin sampled.

Methods

To assess the magnitude of this variation, we analysed carbon (δ ¹³C), nitrogen (δ ¹⁵N), hydrogen (δ ²H) and oxygen (δ ¹⁸O) stable isotopes of caudal fin from juvenile, riverine stages of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). Individual fins were sub-sectioned into tip, mid and base, of which a further subset were divided into ray and membrane.

Findings

Isotope variation between fin sections, evident in all four elements, was primarily related to differences between ray and membrane. Base sections were¹³C depleted relative to tip (~ 1 ‰) with equivalent variation evident between ray and membrane. A similar trend was evident in δ ²H, though the degree of variation was far greater (~ 10 ‰). Base and ray sections were ¹⁸O enriched (~ 2 ‰) relative to tip and membrane, respectively. Ray and membrane sections displayed longitudinal variation in ¹⁵N mirroring that of composite fin (~ 1 ‰), indicating that variation in¹⁵N values was likely related to ontogenetic variation.

Conclusions

To account for the effects of intra-fin variability in stable isotope analyses we suggest that researchers sampling fish fin, in increasing priority, 1) also analyse muscle (or liver) tissue from a subsample of fish to calibrate their data, or 2) standardize sampling by selecting tissue only from the extreme tip of a fin, or 3) homogenize fins prior to analysis.     

Ethnobotanical plant uses in the KwaNibela Peninsula, St Lucia, South Africa

Ethnobotanical field studies were conducted for the first time in the KwaNibela Peninsula of southern Maputaland, KwaZulu-Natal, to document indigenous knowledge about useful plants. The vernacular names and uses of 82 plant species were recorded and compared to published Zulu and Swazi knowledge. Medicines for skin disorders, toothache, wounds, worms, chest and throat ailments, infertility and purgatives are still commonly used. Superstition and divination play a major role in the traditional knowledge system of the people of KwaNibela with 24 plants used for this purpose. Three KwaNibela medicinal plants (Erythroxylum delagoense, Putterlickia verrucosa, and Teclea natalensis) appear to be new records, not previously reported in the general scientific literature. The list also includes 61 novel uses of plants and another 15 new variations on known (published) uses. Ten previously unpublished vernacular names are presented, together with an additional 19 new variants of known names. These new additions to the scientific literature confirm that indigenous knowledge in KwaZulu-Natal is not yet completely recorded.     

Role of φ29 connector channel loops in late-stage DNA packaging

Double-stranded DNA bacteriophages and their eukaryotic virus counterparts have 12-fold head-tail connector assemblages embedded at a unique capsid vertex. This vertex is the site of assembly of the DNA packaging motor, and the connector has a central channel through which viral DNA passes during genome packaging and subsequent host infection. Crystal structures of connectors from different phages reveal either disordered residues or structured loops that project into the connector channel. Given the proximity to the translocating DNA substrate, these loops have been proposed to play a role in DNA packaging. Previous models have proposed structural motions in either the packaging ATPase or the connector channel loops as the driving force that translocates the DNA into the prohead. Here, we mutate the channel loops of the Bacillus subtilis bacteriophage φ29 connector and show that these loops have no active role in translocation of DNA. Instead, they appear to have an essential function near the end of packaging, acting to retain the packaged DNA in the head in preparation for motor detachment and subsequent tail assembly and virion completion.     

The distribution and habitats of crossbills Loxia spp. in Britain, with special reference to the Scottish Crossbill Loxia scotica

A study was carried out, primarily in northern Scotland, to relate bill and wing measurements to diagnostic calls of crossbill species, and thereby use the calls to describe the distributions and habitats of the different species. Bill depth and wing length measurements from museum specimens and live‐trapped birds were used to describe the size categories. Almost all measurements of crossbills from England were similar to measurements of Common Crossbills from Fennoscandia. Museum specimens showed that crossbills in northern Scotland between 1822 and 1990 were a combination of Common Crossbills, birds which were intermediate between Common and Parrot Crossbills (Scottish Crossbills), and perhaps a few Parrot Crossbills. However, catches of crossbills between 1995 and 2000 showed that Parrot Crossbills (based on bill and wing measurements) were present at some sites in the Highlands. Recordings of flight calls and excitement calls of birds of known bill sizes allowed a classification of crossbills according to call types. Four different flight calls (referred to here as types 1–4) and five excitement calls (types A–E) were recognized. A sample of small‐billed birds, thereby identified as Common Crossbills, indicated that there were three groups of Common Crossbills: those giving type 1 flight calls and type A excitement calls (1A), type 2 flight calls and type B excitement calls (2B), and type 4 flight calls and type E excitement calls (4E). Large‐billed birds identified as Parrot Crossbills gave mainly type 2 flight calls and type D excitement calls. Birds with intermediate bill depths (Scottish Crossbills) gave type 3 flight calls and type C excitement calls. Distributions based on calls showed that 1A Common Crossbills were widespread in Scotland but the other types of Common Crossbill were rare. Parrot Crossbills were found in a few localities in the Highlands, and Scottish Crossbills (defined as those giving type 3 flight calls and type C excitement calls) were restricted to the northern and eastern Highlands. Scottish Crossbills and 1A Common Crossbills had overlapping distributions, and overlapped greatly in the types of forests they used between January and March when the Scots Pine cones were still closed. However, Scottish Crossbills were more frequently associated with stands containing Scots Pine compared with Common Crossbills.     

A comparison of urinary mercury between children with autism spectrum disorders and control children

Background

Urinary mercury concentrations are used in research exploring mercury exposure. Some theorists have proposed that autism is caused by mercury toxicity. We set out to test whether mercury concentrations in the urine of children with autism were significantly increased or decreased compared to controls or siblings.

Methods

Blinded cohort analyses were carried out on the urine of 56 children with autism spectrum disorders (ASD) compared to their siblings (n = 42) and a control sample of children without ASD in mainstream (n = 121) and special schools (n = 34).

Results

There were no statistically significant differences in creatinine levels, in uncorrected urinary mercury levels or in levels of mercury corrected for creatinine, whether or not the analysis is controlled for age, gender and amalgam fillings.

Conclusions

This study lends no support for the hypothesis of differences in urinary mercury excretion in children with autism compared to other groups. Some of the results, however, do suggest further research in the area may be warranted to replicate this in a larger group and with clear measurement of potential confounding factors.