Applying new tools to cephalopod trophic dynamics and ecology: perspectives from the Southern Ocean Cephalopod Workshop, February 2–3, 2006

A two day workshop on Southern Ocean cephalopods was held in Hobart, Tasmania, Australia prior to the triennial 2006 Cephalopod International Advisory Council (CIAC) symposium. The workshop provided a second international forum to present the current state of research and new directions since the last Southern Ocean cephalopod meeting held in 1993. A major focus of the workshop was trophic ecology and the use of a variety of tools that can be applied in Southern Ocean trophic studies for both cephalopod and predator researchers. New tools that are being used as trophic indicators and tracers in food chain pathways include stable isotope, heavy metal and fatty acid signature analysis. Progress is also being made on understanding squid population dynamics in relation to other key components of the ecosystem by incorporating squid data in ecosystem models. Genetic barcoding is now of great value to fish taxonomy as well as other groups and it is expected that a cephalopod barcoding initiative will be an important tool for cephalopod taxonomy. There is a current initiative to produce a new cephalopod beak identification guide to assist predator biologists in identifying cephalopod prey items. There were also general discussions on specific taxonomic issues, Southern Ocean Cephalopod paralarvae and parasites, and suggestions for future CIAC workshop topics.     

Human colonization of the central territory of Argentina: design matrix models and craniometric evidence

In this study we test several hypotheses about the peopling of the central territory of Argentina, archaeologically known as Sierras Centrales, by testing the association between four alternative models of the peopling of the area and cranial morphological variation through distance and matrix correlation analyses. Our results show that the ancient inhabitants of Sierras Centrales demonstrated close morphological similarities with the Patagonian and Tierra del Fuego populations. Moreover, the correlation and partial correlation analyses suggest that the peopling of the Sierras Centrales most likely took place as a migratory wave proceeding from the present area of Northeastern Argentina, and continued southward to Patagonia and Tierra del Fuego.     

Plasmid encoded neurotoxin genes in Clostridium botulinum serotype A subtypes

Clostridium botulinum, an important pathogen of humans and animals, produces botulinum neurotoxin (BoNT), the most poisonous toxin known. We have determined by pulsed-field gel electrophoresis (PFGE) and Southern hybridizations that the genes encoding BoNTs in strains Loch Maree (subtype A3) and 657Ba (type B and subtype A4) are located on large (approximately 280 kb) plasmids. This is the first demonstration of plasmid-borne neurotoxin genes in Clostridium botulinum serotypes A and B. The finding of BoNT type A and B genes on extrachromosomal elements has important implications for the evolution of neurotoxigenicity in clostridia including the origin, expression, and lateral transfer of botulinum neurotoxin genes.     

Water chemistry and nutrient budgets in an undisturbed evergreen rainforest of southern Chile

In a pristine evergreen rainforest of Nothofagus betuloides, located at the Cordillera de los Andes in southern Chile (41 °S), concentrations and fluxes of nutrients in bulk precipitation, cloud water, throughfall water, stemflow water, soil infiltration and percolation water and runoff water were measured. The main objectives of this study were to investigate canopy-soil-atmosphere interactions and to calculate input-output budgets. From May 1999 till April 2000, the experimental watershed received 8121 mm water (86% incident precipitation, 14% cloud water), of which the canopy intercepted 16%. Runoff water volume amounted 9527 mm. Bulk deposition of inorganic (DIN) and organic (DON) nitrogen amounted 3.6 kg ha^–1 year^–1 and 8.2 kg ha^–1 year^–1 respectively. Occult deposition (clouds + fog) contributes for 40% to the atmospheric nitrogen input (bulk + occult deposition) of the forest. An important part of the atmospheric ammonium deposition is retained within the canopy or converted to nitrate or organic nitrogen by epiphytic bacteria or lichens. Also the export of inorganic (0.9 kg ha^–1 year^–1) and organic (5.2 kg ha^–1 year^–1) nitrogen via runoff is lower than the input to the forest floor via throughfall and stemflow water (3.2 kg DIN ha–1 year^–1 and 5.6 kg DON ha^–1 year^–1). The low concentrations of NO ₃ ^– and NH ₄ ⁺ under the rooting depth suggest an effective biological immobilization by vegetation and soil microflora. Dry deposition and foliar leaching of base cations (K⁺, Ca²⁺, Mg²⁺) was estimated using a canopy budget model. Bulk deposition accounted for about 50% of the total atmospheric input. Calculated dry and occult deposition are both of equal value (about 25%). Foliar leaching of K⁺, Ca²⁺, and Mg²⁺ accounted for 45%, 38% and 6% of throughfall deposition respectively. On an annual basis, the experimental watershed was a net source for Na⁺, Ca²⁺ and Mg²⁺.     

New ionic targets of 3,3′,5′-triiodothyronine at the plasma membrane of rat Sertoli cells

The functions of Sertoli cells, which structurally and functionally support ongoing spermatogenesis, are effectively modulated by thyroid hormones, amongst other molecules. We investigated the mechanism of action of rT₃ on calcium (⁴⁵Ca²⁺) uptake in Sertoli cells by means of in vitro acute incubation. In addition, we performed electrophysiological recordings of potassium efflux in order to understand the cell repolarization, coupled to the calcium uptake triggered by rT₃. Our results indicate that rT₃ induces nongenomic responses, as a rapid activation of whole-cell potassium currents in response to rT₃ occurred in <5 min in Sertoli cells. In addition, the rT₃ metabolite, T₂, also exerted a rapid effect on calcium uptake in immature rat testis and in Sertoli cells. rT₃ also modulated calcium uptake, which occurred within seconds via the action of selective ionic channels and the Na⁺/K⁺ ATPase pump. The rapid response of rT₃ is essentially triggered by calcium uptake and cell repolarization, which appear to mediate the secretory functions of Sertoli cells.     

Scavenging in Antarctica: Intense variation between sites and seasons in shallow benthic necrophagy

The response of scavengers to a feeding cue at Adelaide Island, West Antarctic Peninsula was investigated using a baited video camera system. Fourteen experimental deployments, each lasting 72 h were conducted at two contrasting sites during the winter and summer of 2005. The rate of bait consumption varied between sites but not between seasons, and was low in comparison with studies at lower latitudes and greater depths. At the Hangar Cove site, the nemertean Parborlasia corrugatus was out-competed at the bait and displaced by the lysianassid amphipod Cheirmedon femoratus during winter. However, C. femoratus did not feed on the bait during summer, allowing P. corrugatus to monopolise the feeding opportunity. At the South Cove site the asteroid Odontaster validus dominated the bait in both seasons but sporadic feeding by the nototheniid fish Notothenia coriiceps considerably affected consumption rates during two of the six deployments. Scavengers were attracted to the bait in very high numbers and opportunistic necrophagy seems to be a successful strategy in an environment that is intensely disturbed by ice.     

Analysis of <Emphasis Type="Italic">Acropora muricata</Emphasis> Calmodulin (<Emphasis Type="Italic">CaM</Emphasis>) Indicates That Scleractinian Corals Possess the Ancestral Exon/Intron Organization of the Eumetazoan <Emphasis Type="Italic">CaM</Emphasis> Gene

Calmodulin (CaM), belonging to the tropinin C (TnC) superfamily, is one of the calcium-binding proteins that are highly conserved in their protein and gene structure. Based on the structure comparison among published vertebrate and invertebrate CaM, it is proposed that the ancestral form of eumetazoan CaM genes should have five exons and four introns (four-intron hypothesis). In this study, we determined the gene structure of CaM in the coral Acropora muricata, an anthozoan cnidarian representing the basal position in animal evolution. A CaM clone was isolated from a cDNA library constructed from the spawned eggs of A. muricata. This clone was composed of 908 nucleotides, including 162 base pairs (bp) of 5′-untranslated region (UTR), 296 bp of 3′-UTR, and an open reading frame 450 bp in length. The deduced amino acid indicated that the Acropora CaM protein is identical to that of the actiniarian, Metridinium senile, and has four putative calcium-binding domains highly similar to those of other vertebrate or invertebrate CaMs. Southern blot analysis revealed that Acropora CaM is a putative single-copy gene in the nuclear genome. Genomic sequencing showed that Acropora CaM was composed of five exons and four introns, with intron II not corresponding to any region in the actiniarian CaM gene, which possesses only four exons and three introns. Our results highlight that the coral CaM gene isolated from A. muricata has four introns at the predicted positions of the early metazoan CaM gene organization, providing the first evidence from the basal eumetazoan phylum to support the four-intron hypothesis.     

Spatio-temporal organization of intracellular ATP content and oscillation patterns in response to blue light byPhysarum polycephalum

Summary Phototactic responses in a giant amoeboid cell ofPhysarum plasmodium were studied both by analyzing intracellular ATP content and by applying image processing for recording oscillatory changes in thickness with use of a microcomputer. The ATP content fluctuated and deviated from the initial level upon exposure to light with varying wavelength from 400 to 600 nm. The maximum decrease in the integrated value dt with T=9 minutes occurred at the wavelength 450 nm. The ATP in a migrating plasmodium distributed twice as high in the front as in the rear. This polar pattern became unstable, and a new wavy pattern appeared by stimulating a local frontal part with blue light. In a concentrically extending plasmodium, peripheral and inside regions oscillated in opposite phase to each other. When part of this organism was exposed to light, stimulated and unslimulated regions began to oscillate in opposite phase, and phase waves propagated inward the stimulated region. And the protoplasm there became thinner, the strongest avoidance reaction occurring to 450 nm light as in ATP response. Phototactic behavior inPhysarum is discussed in terms of bifurcation in spatio-temporal organization appearing in a self-organizing system.     

Early Holocene human remains from the Argentinean Pampas: Additional evidence for distinctive cranial morphology of early South Americans

The cranial morphology of Early Holocene American human samples is characterized by a long and narrow cranial vault, whereas more recent samples exhibit a shorter and wider cranial vault. Two hypotheses have been proposed to account for the morphological differences between early and late‐American samples: (a) the migratory hypothesis that suggests that the morphological variation between early and late American samples was the result of a variable number of migratory waves; and (b) the local diversification hypothesis, that is, the morphological differences between early and late American samples were mainly generated by local, random (genetic drift), and nonrandom factors (selection and phenotypic plasticity). We present the first craniometric study of three early skulls from the Argentinean Pampas, dated ～8,000 cal. years BP (Arroyo Seco 2, Chocorí, and La Tigra), and one associated with mega‐faunal remains (Fontezuelas skull). In addition, we studied several Late Holocene samples. We show that the skulls from the Argentinean Pampas are morphologically similar to other Early Holocene American skulls (i.e., Lagoa Santa from Brazil, Tequendama, Checua, and Aguazuque from Colombia, Lauricocha from Peru, and early Mexicans) that exhibit long and narrow cranial vaults. These samples differ from the Late Holocene American samples that exhibit a shorter and wider cranial vault. Our results underscore the important differences in cranial morphology between early and late‐American samples. However, we emphasize the need for further studies to discuss alternative hypotheses regarding such differences. Am J Phys Anthropol 143:298–305, 2010. © 2010 Wiley‐Liss, Inc.     

The Nutrient Status of Mgazana,a Warm Temperate Mangrove Estuary in the Transkei,Eastern Cape,South Africa

Mgazana, a rural southern African mangrove system, was visited monthly from August, 1995 to February, 1997 to collect water samples for nutrient analysis. Surface and bottom samples were taken during spring low tide at seven stations along the estuary and the following physico-chemical parameters measured: river flow, temperature, salinity, oxygen, transparency, ammonia, nitrite, nitrate, phosphate, inorganic carbon (IC), organic carbon (OC), total carbon (TC), soluble nitrogen (SN), particulate nitrogen (PN) and total nitrogen (TN). Using correlation matrix analysis and ANOVA, river flow was found to affect estuarine salinity, transparency and stratification, which influenced nutrient dynamics. Significant seasonal (winter and summer) differences were found for temperature, river flow, nitrate, SN, TN, IC and OC. Most nutrients were significantly correlated with river flow showing gradients down the estuary, indicating allochthonous input from the catchment. OC levels within the estuary were high, probably due to autochthonous mangrove leaf-fall processing by the various in-fauna, but high levels measured at the head of the estuary during high river flow suggested additional allochthonous input from coastal forest litter. Conversely, IC was negatively correlated with river flow suggesting that autochthonous faunal and microbial mineralisation of organic matter occurs within creeks, which is then diluted by increased stream-flow. An N:P ratio of 2.7:1 was obtained for this rural mangrove system, which was low compared with Spartina-based East Cape estuaries subject to urban, industrial and agricultural pollution.