Seagrass ecosystem multifunctionality under the rise of a flagship marine megaherbivore

Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well-recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing-induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality.     

Staining with Fluorescein Diacetate Correlates with Hepatocyte Function

To establish the importance of fluorescein diacetate (FDA) as a viability stain for cultured hepatocytes. we hypothesized that FDA staining would correlate positively with hepatocyte viability and function. Mixtures of live and dead cells were stained with FDA and scanned by flow cytometry. A close correlation was observed between the live cell fraction and percent viability as determined by FDA staining (R² = 0.962). Hepatocytes were also sorted into low fluorescence and high fluorescence groups. Both albumin production and lidocaine metabolism (P-450 activity) were significantly increased in the high fluorescence group compared to the low fluorescence group. An automated, fluorescence-activated assay was useful for rapid assessment of hepatocyte viability. In addition. the intensity of green fluorescence following staining with FDA correlated well with two specific measures of hepatocyte function.     

Targeting of superantigens

The bacterial superantigen staphylococcal enterotoxin A (SEA) is an extremely potent activator of T lymphocytes when presented on MHC class II antigens. In order to induce T lymphocytes to reject a tumor, we substituted the specificity of SEA for MHC class II molecules with specificity for tumor cells by combining SEA with a MAb recognizing colon carcinomas. Chemical conjugates or recombinant fusion proteins of the MAb C215 and SEA retained excellent antigen binding properties whereas the binding to MHC class II was markedly reduced. The hybrid proteins directed SEA responsive T cells to tumors with specificity determined by the specificity of the MAb. Significant tumor cell killing was obtained at picomolar concentrations of the hybrid proteins and was the result of direct cell mediated by cytotoxicity as well as production of tumoricidal cytokines by T cells. Targeting of superantigens represents a novel approach to specific immunomodulation and deserves further study as a potential therapy for malignant disease.     

Morphological phylogenetics of theAsteraceae-Asteroideae,with notes on character evolution

The relationships within theAsteraceae-Asteroideae are scrutinized by means of cladistic analyses of morphological and chemical data. New data are presented, and novel interpretations of features previously used in cladistic analyses are made. Examples are insertion of anther filaments in the corolla, and morphology of disc floret styles, respectively. The results include a polyphyletic or paraphyleticInuleae s. l., and a paraphyleticHeliantheae s.l. in which theEupatorieae constantly form a subclade. Comparisons are made with previous cladistic analyses of morphological data, and those acquired from molecular data. Speculations about the evolution of certain organs are presented.     

The Effect of Transport Stress on Plasma Levels of Catecholamines,Cortisol, Corticosteroid-Binding Globulin,Blood Cell Count,and Lymphocyte Proliferation in Pigs

The effect of transport stress on the plasma levels of catecholamines, Cortisol, and corticosteroid-binding globulin were studied in 6 gilts. To assess the effect on immune status, white blood cells were also counted and the cell-mediated immunity was estimated. The adrenaline level increased significantly during transport, from a basal mean level of 0.03 ng/ml to a plateau level of 0.11 to 0.12 ng/ml. The noradrenaline level fluctuated, but not constantly, during transport. The mean plasma Cortisol level before loading was approximately 40 nmol/1 and rose immediately after the start of transport to 70 nmol/1 (p< 0.05) and to 87 nmol/1 (p< 0.01) within 10 and 30 min, respectively. After unloading the Cortisol level rapidly decreased and a minimum level was seen 4 h after the transport, whereafter the diurnal rhythm was resumed. The plasma corticosteroid-binding globulin level increased nonsignificantly during the day of transport, from 25 nmol/1 to a level of 34 nmol/1, and it continued to increase until a plateau level was reached on the second day after transportation. The total white blood cell number increased significantly (from 13.7 to 15.5 × 109 cells/1), the number of lymphocytes decreased significantly (from 8.4 to 7.0 × 109 cells/1), and the number of polymorphonuclear neutrophils increased significantly (from 4.3 to 7.2 × 109 cells/1) during transport. No significant variation in the proliferation response was seen in the whole blood cell cultures. The main results were the significant signs of simultaneous activity of both the adrenal cortex and the adrenal medulla during transport.     

THE MARINE DINOFLAGELLATE ALEXANDRIUM OSTENFELDII: PARALYTIC SHELLFISH TOXIN CONCENTRATION,COMPOSITION, AND TOXICITY TO A TINTINNID CILIATE1

The composition of paralytic shellfish toxins in the marine dinoflagellate Alexandrium ostenfeldii (Paulsen) Balech et Tangen grown in unialgal culture was determined by high-performance liquid chromatography. The toxin profile revealed that the low-potency sulfamate toxin B₂ was dominant (90 molar % of total toxins), but small amounts of the weakly toxic 21-N-sulfocarbamoyl derivatives C₁₊₂ and trace amounts of the carbamate toxins GTX₂ and GTX₃ were also present. The mammalian toxicity was confirmed by a modification of the conventional AOAC mouse bioassay (0.6–1.4 pg STX_eq· cell^-1). The acute toxicity to a potential predator, the tintinnid ciliate Favella ehrenbergi (Clap, et Lach.) Jörg., was also investigated. The ciliate was able to graze on A. ostenfeldii when the cell concentration of the dinoflagellate was low (<2000 cells · mL^-1). At higher concentrations the ciliate was affected by exudates (presumably PSP toxins) that induced backward swimming followed by swelling and lysis of the cell. Fluorescence microscopy of calcofluor-stained cells was employed as an easy and rapid method to identify this and other thecate dinoflagellates.     

Omphalina foliacea, a new basidiolichen from America

A relatively large Leptogium -like lichen overgrowing mosses in wet paramos has been discovered in the northern Andes and Costa Rica. It has, however, a green photobiont and basidiomycete hyphae. No fruitbodies have been observed, only asexual reproduction by fragmentation of the fragile thallus and by goniocysts formed on the ecorticate lower surface. Some aspects of the taxonomy of Omphalina are briefly discussed.     

Synthesis and AT2 receptor-binding properties of angiotensin II analogues.

The present study investigates the importance of the amino acid side chains in the octapeptide angiotensin II (Ang II) for binding to the AT2 receptor. A Gly scan was performed where each amino acid in Ang II was substituted one-by-one with glycine. The resulting set of peptides was tested for affinity to the AT2 receptor (porcine myometrial membranes). For a comparison, the peptides were also tested for affinity to the AT1 receptor (rat liver membranes). Only the substitution of Arg2 reduced affinity to the AT2 receptor considerably (92-fold when compared with Ang II). For the other Gly-substituted analogues the affinity to the AT2 receptor was only moderately affected. To further investigate the role of the Arg2 side chain for receptor binding, we synthesized some N-terminally modified Ang II analogues. According to these studies a positive charge in the N-terminal end of angiotensin III [Ang II (2-8)] is not required for high AT2 receptor affinity but seems to be more important in Ang II. With respect to the AT1 receptor, [Gly2]Ang II and [Gly8]Ang II lacked binding affinity (Ki > 10 microM). Replacement of the Val3 or Ile5 residues with Gly produced only a slight decrease in affinity. Interestingly, substitution of Tyr4 or His6, which are known to be very important for AT1 receptor binding, resulted in only 48 and 14 times reduction in affinity, respectively.     

POPULATION STRUCTURE IN AN INSHORE CETACEAN REVEALED BY MICROSATELLITE AND mtDNA ANALYSIS: BOTTLENOSE DOLPHINS (TURSIOPS SP.) IN SHARK BAY, WESTERN AUSTRALIA

We examined population substructure of bottlenose dolphins ( Tursiops sp). in Shark Bay, Western Australia, using 10 highly polymorphic microsatellite loci, and mitochondrial DNA (mtDNA). For microsatellite analysis, 302 different animals were sampled from seven localities throughout the bay. Analysis of genetic differentiation between sampling localities showed a significant correlation between the number of migrants ( Nm ) calculated from F _ST, R _ST and private alleles, and distance between localities–a pattern of isolation-by-distance. For mtDNA, 220 individuals from all seven localities were sequenced for a 351 base pair fragment of the control region, resulting in eight haplotypes, with two distinct clusters of haplotypes. Values of F _ST and (φ)_ST for mtDNA yielded statistically significant differences, mostly between localities that were not adjacent to each other, suggesting female gene flow over a scale larger than the sampled localities. We also observed a significant correlation between the number of female migrants calculated from F _ST and φ_ST and the distance of sampling localities. Our results indicate that dispersal in female dolphins in Shark Bay is more restricted than that of males.