Tolerance to low oxygen and sulfide in Amphiura filiformis and Ophiura albida (Echinodermata: Ophiuroidea)

The brittle stars Amphiura filiformis (Müller) and Ophiura albida (Forbes) were exposed to different oxygen saturations (100, 10, 5, 3, and <1% oxygen saturation) and to physiological anoxia (<1% oxygen saturation) at different total sulfide concentrations (0, 2, 20, 200 μM). The mortality was followed during experiments and the median survival time (LT₅₀) was determined. The infaunal A. filiformis had a significantly higher tolerance to both hypoxia and sulfide than did the epibenthic O. albida. After exposure to 10% oxygen saturation for a month, only 2.0% A. filiformis and 0% O. albida were dead. In oxygen saturations <1% A. filiformis and O. albida had a LT₅₀ of 7.5 and 2.5 d, respectively. The presence of even very small concentrations of sulfide decreased the survival significantly. Sulfide is shown to be the key factor for the survival of the two species. Received: 11 October 1996 / Accepted: 12 November 1996     

DNA sequence evidence for speciation,paraphyly and a Mesozoic dispersal of cancellothyridid articulate brachiopods

Because the classification of extant and fossil articulate brachiopods is based largely upon shell characters observable in fossils, it identifies morphotaxa whose biological status can, in practice, best be inferred from estimates of genetic divergence. Allozyme polymorphism and restriction fragment length polymorphism of mitochondrial DNA (mtDNA RFLP) have been used to show that nuclear and mitochondrial genetic divergence between samples of the cancellothyridid brachiopods Terebratulina septentrionalis from Canada and T. retusa from Europe is compatible with biological speciation, but the genetic distances obtained were biased by methodological limitations. Here, we report estimates of divergence in 12S rDNA mitochondrial sequences within and between samples of these brachiopods. The sequence-based genetic distance between these samples (5.98ǂ.07% SE) is at least 10 times greater than within them and, since they also differ in a complex life-history trait, their species status is considered to be securely established. Divergence levels between 12S rDNA genes of three other cancellothyridids, T. unguicula from Alaska, T. crossei from near Japan, and Cancellothyris hedleyi from near Australia are higher than between the two North Atlantic species, and the mean nucleotide distance between all these cancellothyrids is similar to the mean distance between species of Littorina (Mollusca: Gastropoda). Sequences of both 12S and 16S genes from cancellothyridids and other short-looped brachiopod species show neither saturation nor lineage-specific rate differences and, when analysed with different outgroups, either separately or together, yield one unexpected, but well-supported, tree with Alaskan T. unguicula basal and C. hedleyi nested within Terebratulina, i.e. these genera are paraphyletic. A geologically dated divergence between Antarctic and New Zealand species of the short-looped brachiopod Liothyrella is used to calibrate the rate of 12S divergence at ca. 0.1% per million years (MY), and this rate is used to infer that T. septentrionalis and T. retusa have been diverging for ca. 60 MY and that they and T. unguicula have been diverging from their last common ancestor for ca. 100 MY. This indicates a Mesozoic origin for the present-day distribution of cancellothyridids and the basal position of T. unguicula suggests a possible North Pacific centre of origin, with separate Atlantic and Pacific radiations. The inclusion of Cancellothyris within Terebratulina also shows that adult shell characters such as umbo, foramen and symphytium shape, whilst probably indispensible for the practical classification of fossils, are not reliable guides to genealogy.     

Tropic attributes of the mudskipper, Periophthalmus barbarus (Gobiidae: Oxudercinae) in the mangrove swamps of Imo River estuary, Nigeria

Aspects of the trophic attributes of the mudskipper,Periophthalmus barbarus occurring in the mangrove swamps of ImoRiver estuary, Nigeria, were investigated during a 12-month period(April, 1992-March, 1993). Feeding intensity increased with size;it was higher in the dry season (November-April) than in the wetseason (May-October); monthly changes in the indices of feedingintensity were significantly correlated. Major food objectscomprised detritus and benthic algae; crustaceans, insects,macrophyte matter and sand grains were minor food objects whilefish, molluscs, Chilopoda, nematodes and fungi were unconsciouslydevoured objects. Diet varied seasonally; algae and sesarmid crabswere generally more in the dry season than during the rains whereasFPOM and fish increased in the wet over dry season. The mudskipperdisplay a high degree of euryphagy and can be considered as ageneralist and an omnivore. The lower trophic status of P. barbarusqualifies it as a good aquaculture candidate. Food richness washigher in big-sized class (BSC) than small-sized class (SSC).Size-based and seasonal variations were not apparent in foodrichness. Diet breadth was higher in the BSC than the SSC; therewas dry season increase in diet breadth.     

Environmental contaminants in prey and tissues of the peregrine falcon in the Big Bend Region, Texas, USA.

Peregrine falcons (Falco peregrinus) have been recorded nesting in Big Bend National Park, Texas, USA and other areas of the Chihuahuan Desert since the early 1900s. From 1993 to 1996, peregrine falcon productivity rates were very low and coincided with periods of low rainfall. However, low productivity also was suspected to be caused by environmental contaminants. To evaluate potential impacts of contaminants on peregrine falcon populations, likely avian and bat prey species were collected during 1994 and 1997 breeding seasons in selected regions of western Texas, primarily in Big Bend National Park. Tissues of three peregrine falcons found injured or dead and feathers of one live fledgling also were analyzed. Overall, mean concentrations of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], a metabolite of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], were low in all prey species except for northern rough-winged swallows (Stelgidopteryx serripennis, mean = 5.1 microg/g ww). Concentrations of mercury and selenium were elevated in some species, up to 2.5 microg/g dw, and 15 microg/g dw, respectively, which upon consumption could seriously affect reproduction of top predators. DDE levels near 5 microg/g ww were detected in carcass of one peregrine falcon found dead but the cause of death was unknown. Mercury, selenium, and DDE to some extent, may be contributing to low reproductive rates of peregrine falcons in the Big Bend region.     

Effect of Climatic Factors on the Growth of Representatives of the Genus Pinus (Pinaceae) under Conditions of Introduction

Four introduced and one aboriginal species of the genus Pinus L. have been studied in the middle taiga subzone of southern Karelia. Significant interspecific differences in the dates of onset, cessation, and peak of the growth of shoots and needles have been revealed. It has been shown that their annual increment depends on the rate of growth, rather than on its duration. The dynamics of shoot and needle growth in introduced and aboriginal species, though largely similar, differ in some respects. These differences reflect species-specific responses to hydrothermal conditions in a certain growing season.     

Trophoblast-like cells sorted from peripheral maternal blood using flow cytometry: A multiparametric study involving transmission electron microscopy and fetal dna amplification

Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.