Anatomical location and sex ratio of gastrointestinal trichostrongylids in sheep in the Region of Murcia

Entre 1998 y 2001 se estudiaron un total de 181 ovejas sacrifi cadas en un matadero de Cartagena (Murcia). El contenido del abomaso y del intestino delgado se recogió y se procesó con objeto de recontar e identifi car los tricostrongílidos encontrados. Se contabilizaron 156.889 nematodos en 158 ovejas parasitadas; de ellos, 103.076 localizados en el abomaso y 53.813 en el intestino delgado. En ambas localizaciones el número de hembras superó al de machos, siendo la proporción entre sexos de 1,57 en el abomaso y de 1,98 en el intestino delgado. Se identifi caron trece especies, ocho de ellas en hábitats no comunes: Teladorsagia circumcincta, T. trifurcata, Marshallagia marshalli, Trichostrongylus vitrinus, T. colubriformis, T. axei, Nematodirus spathiger y N. fi licollis en ambos órganos; T. davtiani, M. occidentalis y H. contortus tan solo en el abomaso y T. capricola y N. abnormalis únicamente en el intestino delgado

Comparing production-biomass ratios of benthos and suprabenthos in macrofaunal marine crustaceans

Using available data from the literature, we compared the productionbiomass ratios (P/B) between the suprabenthic (= hyperbenthic) and the benthic (infaunaepifauna) species within the group of the macrofaunal marine crustaceans. This data set consists of 91 P/B estimates (26 for suprabenthos and 65 for infaunaepifauna) for 49 different species. Suprabenthic crustacean P/B was significantly higher than P/B of benthic crustacean (post-hoc Scheffé test; one-way analysis of covariance, ANCOVA; p < 103) and also of other (noncrustacean) benthic invertebrate (p < 104). Predictive multilinear regression (MLR) analysis for macrofaunal marine crustaceans showed P/B to depend significantly on mean annual temperature (T) and mean individual weight (W) (R2 = 0.367). Adding the variable swimming capacity increased goodness-of-fit to R2 = 0.528. The higher P/B of suprabenthic (= swimming) macrofauna in comparison with that of the benthic compartment seems to be related to the most apparent feature of the suprabenthos, its swimming capacity. The high P/Bs reported for suprabenthic species indicate how a nontrivial part of benthic production can be ignored if suprabenthos is not well sampled, therefore biasing the models of energy flow generated for trophic webs

Segregation models

Many antigen receptors of the immune system belong to the family of multichain immune recognition receptors (MIRRs). Binding of ligand (antigen) to MIRR results in receptor phosphorylation, triggering downstream signaling pathways and cellular activation. How ligand binding induces this phosphorylation is not yet understood. In this Chapter, we discuss two models exploring the possibility that kinases and phosphatases are intermingled on the cell surface. Thus, in resting state, MIRR phosphorylation is counteracted by dephosphorylation. Upon ligand binding, phosphatases are removed from the vicinity of the MIRR and kinases, such that phosphorylated MIRRs can accumulate (segregation models). In the first model, clustering of MIRRs by multivalent ligand leads to their concentration in lipid rafts where kinases, but not phosphatases, are localized. The second model takes into account that the MIRR-ligand pair needs dose apposition of the two cell membranes, in cases where ligand is presented by an antigen-presenting cell. The intermembrane distance is too small to accommodate transmembrane phosphatases, which possess large ectodomains. Thus, phosphatases become spatially separated from the MIRRs and kinases (kinetic-segregation model)

The role of Antarctic sea ice in global climate change

Taking a distinct interdisciplinary focus, a critical view is presented of the current state of research concerning Antarctic sea-ice/atmosphere/ocean interaction and its effect on climate on the interannual timescale, with particular regard to anthropogenic global warming. Sea-ice formation, morphology, thickness, extent, seasonality and distribution are introduced as vital factors in climatic feedbacks. Sea-ice / atmosphere interaction is next discussed, emphasizing its meteorological and topographical influences and the effects of and on polar cyclonic activity. This leads on to the central theme of sea ice in global climate change, which contains critiques of sea-ice climatic feedbacks, current findings on the representation of these feedbacks in global climatic models, and to what extent they are corroborated by observational evidence. Sea-ice/ocean interaction is particularly important. This is discussed with special reference to polynyas and leads, and the use of suitably coupled sea-ice/ocean models. A brief review of several possible climatic forcing factors is presented, which most highly rates a postulated ENSO-Antarctic sea-ice link. Sea-ice/atmosphere/ocean models need to be validated by adequate observations, both from satellites and ground based. In particular, models developed in the Arctic, where the observational network allows more reasonable validation, can be applied to the Antarctic in suitably modified form so as to account for unique features of the Antarctic cryosphere. Benefits in climatic modelling will be gained by treating Antarctic sea ice as a fully coupled component of global climate