Egg extrusion as a kepone-clearance route in the blue crab,Callinectes sapidus

The concentration of Kepone in extruded egg masses and the backfin muscles of the blue crab,Callinectes sapidus, collected from seven stations in the lower James River and lower Chesapeake Bay was determined. Crabs from the lower James River were generally more contaminated than those from the lower Chesapeake Bay. Extruded eggs contain approximately three times more Kepone than backfin muscle. Egg extrusion is concluded to be a major route of Kepone clearance from female blue crabs.     

Aliens like us?

Simon Conway Morris explains that as and when (and indeed if) we meet the extraterrestrials, they will look eerily like us.     

Constraints on the origin of mafic alkaline volcanics and included xenoliths from Oberon,New South Wales,Australia

Basanites and alkali basalts from Oberon, NSW, Australia contain variable abundances of small Cr-diopside lherzolite xenoliths. Despite a limited range in (metamorphic) textures and modal mineralogy, there is significant variation in mineral chemistry. Mineral thermometric data applied to the geotherm of O'Reilly and Griffin (1985) suggests equilibration over a narrow pressure interval corresponding to depths of 30–45 km. These data show that significant compositional variations exist over a small depth interval in the subcontinental mantle.Basaltic host rocks show near-primary chemical characteristics. Mildly and strongly incompatible element (i.e. D< 1 and D1 respectively) concentrations have been used to constrain the modal amounts of clinopyroxene and garnet in a presumed garnet peridotite mantle source. Estimated proportions of (ol+opx)=73%; cpx=16%; gar= 11% closely resemble source compositions for other basaltic rocks of eastern Australia. Batch partial melting of this source in the range F=9.5–15% applied to the available REE data suggests the source is enriched relative to chondrite 8–10 × La, 2.1–2.4 × Tb and 2.5–3.7 × Yb.     

Conodont palaeobiology: recent progress and unsolved problems

The fossilized soft-parts of conodonts are extraordinarily rare; excluding dubious and refuted examples, only 10 specimens are known. Nine come from the Lower Carboniferous of Granton, Scotland, and represent at least two genera with complex polygnathacean apparatuses. The soft-parts include well-defined myotomal segmentation and a probable notochord, thus strongly suggesting affinity with the chordates. The tenth specimen, from the Lower Silurian of Waukesha, Wisconsin, bears a simpler apparatus of panderodontid conodont elements. The soft-parts are very poorly preserved, but appear to be unlike those of the Granton specimens. In both occurrences the conodont apparatus appears well adapted for grasping and biting, supporting earlier suggestions that conodont elements acted as teeth. Many conodonts were probably predators or scavengers, but other feeding modes are not necessarily excluded. Other aspects of conodont palaeobiology reviewed here include mode of life and possible migration, reproduction and genetics, and palaeopathology. All these topics rely almost exclusively on the study of conodont elements, and many problems of conodont palaeobiology await further research.     

The ability of a field population of diatoms to discriminate between phosphate and arsenate

Dissolved inorganic arsenic and phosphate levels present in an enclosed experimental ecosystem have been studied during the course of a natural spring diatom bloom. Whilst phosphate levels dropped rapidly to almost zero as the bloom developed, arsenic levels remained constant even when arsenate levels exceeded the dissolved phosphate. Certain diatom species (Thalassiosira spp., Chaetoceras spp. and Skeletonema costatum) therefore appear to be capable of discriminating, either by uptake or excretion, between phosphate and arsenate. The implications of such findings are discussed.     

Metamorphism and metamorphic K–Ar ages of the Mesozoic accretionary complex in Northland, New Zealand

Abstract A southwest dipping Mesozoic accretionary complex, which consists of tectonically imbricated turbiditic mudstone and sandstone, hemipelagic siliceous mudstone, and bedded cherts and basaltic rocks of pelagic origin, is exposed in northern North Island, New Zealand. Interpillow limestone is sometimes contained in the basaltic rocks. The grade of subduction‐related metamorphism increases from northeast to southwest, indicating an inverted metamorphic gradient dip. Three metamorphic facies are recognized largely on the basis of mineral parageneses in sedimentary and basaltic rocks: zeolite, prehnite‐pumpellyite and pumpellyite‐actinolite. From the apparent interplanar spacing d₀₀₂ data for carbonaceous material, which range from 3.642 to 3.564 Å, the highest grade of metamorphism is considered to have attained only the lowermost grade of the pumpellyite‐actinolite facies for which the highest temperature may be approximately 300°C. Metamorphic white mica K–Ar ages are reported for magnetic separates and <2 µm hydraulic elutriation separates from 27 pelitic and semipelitic samples. The age data obtained from elutriation separates are approximately 8 m.y. younger, on average, than those from magnetic separates. The age difference is attributed to the possible admixture of nonequilibrated detrital white mica in the magnetic separates, and the age of the elutriation separates is considered to be the age of metamorphism. If the concept, based on fossil evidence, of the subdivision of the Northland accretionary complex into north and south units is accepted, then the peak age of metamorphism in the north unit is likely to be 180–130 Ma; that is, earliest Middle Jurassic to early Early Cretaceous, whereas that in the south unit is 150–130 Ma; that is, late Late Jurassic to early Early Cretaceous. The age cluster for the north unit correlates with that of the Chrystalls Beach–Taieri Mouth section (uncertain terrane), while the age cluster for the south unit is older than that of the Younger Torlesse Subterrane in the Wellington area, and may be comparable with that of the Nelson and Marlborough areas (Caples and Waipapa terranes).