Stress Responses in Avian Embryos

The day 13–14 chicken embryo is a useful model for studieson prenatal stress responses. Free dopamine, norepinephrineand epinephrine in its plasma, amniotic and allantoic fluidrespond to a variety of stresses. The allantoic fluid also containsconjugated catecholamines and conjugated steroids. However,a blood/allantois barrier excludes free thyroid hormones andfree steroids, and insulin. On the other hand, the allantoicfluid contains at least 40 amino acids (including six excitatoryamino acids) and related compounds. Most, possibly all, componentsof the allantoic fluid are regulated at specific blood/allantoisand amnion/allantois barriers, and they respond to ethanol stressand metabolite loading differentially. The avian allantois isa depot for important metabolites and messenger substances whichseems to be controlled by as yet unidentified hormones     

CO2 effects on the water budget of grassland microcosm communities

Experimental grassland ecosystems, in microcosms 0.2 m in diameter and with a 0.95 m soil column, varied in their responses to elevated partial pressure of CO₂ (pCO₂) and altered moisture inputs. Ecosystems on moderately fertile sandstone soil and with a typical mix of moderately fast-growing sandstone species, responded to elevated pCO₂ with decreases in mid-season evapotranspiration of nearly 50%. This pattern reversed at the end of the growing season, and sandstone ecosystems under elevated pCO₂ continued active transpiration farther into the summer drought. The sandstone ecosystems appeared to convert mid-season water conservation into increased late-season growth. Effects of increased pCO₂ on ecosystem evapotranspiration were much smaller in ecosystems with very infertile serpentine soil and a diverse mixture of slow-growing serpentine species.     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.     

The structure of the ostracode carapace

The carapace ultrastructure of three Recent [Heterocypris incongruens (Ramdohr), Cypridopsis uidua (Müller), and Conchoecia belgica Müller] and one Cretaceous ostracode species [Cypridea propunctata Sylvester-Bradley] has been studied by means of standard electron microscope techniques. The carapace is shown to be an organic structure divisible into an outer epicuticle, a median exocuticle and an inner endocuticle in the three cypridacean ostracodes examined. In Conchoecia belgica only an outer epicuticle and an inner endocuticle were observed, but this may be due to preservation. The chitin structure of the carapace of calcareous ostracodes is shown to be essentially an interlocking lattice, more coarsely developed in the exocuticle; layered (lamellar) chitin is only present in the selvage and in the connective tissue joining the valves at the hinge. The non-calcareous Conchoecia belgica possesses the layered chitin structure common to other crustaceans and to insects. The relationship of the carapace structure to that present in the decapod and insect exoskeleton is discussed. The technical problems met with during this study are considered in order to outline the difficulties associated with the study of organisms of this size.     

Record Chromosome Number in a Mammal?

CROSS has reported^{1, 2} chromosome complements in rodents ranging up to 2n=84 (in the North American geomyid Geomys breviceps) and 2n=86 (in the heteromyid Dipodomys merriami). Matthey has contested³ this claim; he maintained that in Geomys bursarius 2n =70 or 72 and he doubted whether a higher number had been confirmed. Numbers in the 2n=70 to 80 range have since been reported⁴ in several genera of Canidae and Ursidae. In general, rodent chromosomes fall into the lower group numbers but, among murines, Lophuromys aquillus is reported to have a chromosome complement of 70 (ref. 5) and Cricetomys gambianus one of 78 (ref, 6). In the gerbilline, Meriones shawii, the number can vary up to 78 (ref. 7).     

The ecology and economics of damage to Brassicae by wood-pigeons Columba palumbus

Damage caused by wood-pigeons, Columba palumbus, to spring cabbage and Brussels sprouts was measured during three winters in two areas in the Vale of Evesham, Worcestershire. In one area (experimental) special attempts were made to reduce pigeon damage in addition to the normal efforts of the growers. In the other (control) area no such additional measures were taken. There was slightly more damage in 1969-70, but low market prices made it less important than in 1968-9 or 1970-1. There was no significant difference in any season between the damage in the control and experimental areas. No damage was caused to Brussels-sprout buttons as the birds ate only the tops of the plants; they preferred Brussels sprouts to cabbages and it is likely that the presence of the former helped to reduce the amount of damage to nearby cabbage fields. The amount of damage was not correlated with the amount spent on crop protection; actual damage was not correlated with the grower's estimates in the control area. In the second season a very intensive shooting campaign in the experimental area did not result in less damage, but the movements of local inhabitants and farm workers near a village did afford protection. The significance of the damage in the Vale and elsewhere is assessed in relation to the economics of crop production, the cropping pattern for cabbages and the behaviour and ecology of the wood-pigeon.