Serological Cross-Reactivity to Rat Anti H-Y Antiserum in the Female European Eel (Anguilla anguilla)

Anti H-Y antiserum, raised in highly inbred Lewis rats, was absorbed with gonadal cells from European eels of both sexes. It was found that rat anti H-Y antiserum cross-reacts with gonadal cells from the eel ovary but not with eel testicular cells. From these results it is suggested that in the European eel, the female is the heterogametic sex.     

Rapid moult among palaearctic passerines in West Africa- an adaptation to the oncoming dry season?

Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides , Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.     

Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest: extending observations beyond the first year

Limitations in available techniques to separate autotrophic (root) and soil heterotrophic respiration have hampered the understanding of forest C cycling. The former is here defined as respiration by roots, their associated mycorrhizal fungi and other micro‐organisms in the rhizosphere directly dependent on labile C compounds leaked from roots. In order to separate the autotrophic and heterotrophic components of soil respiration, all Scots pine trees in 900 m² plots were girdled to instantaneously terminate the supply of current photosynthates from the tree canopy to roots. Högberg et al. (Nature 411, 789–792, 2001) reported that autotrophic activity contributed up to 56% of total soil respiration during the first summer of this experiment. They also found that mobilization of stored starch (and likely also sugars) in roots after girdling caused an increased apparent heterotrophic respiration on girdled plots. Herein a transient increase in the δ¹³C of soil CO₂ efflux after girdling, thought to be due to decomposition of ¹³C‐enriched ectomycorrhizal mycelium and root starch and sugar reserves, is reported. In the second year after girdling, when starch reserves of girdled tree roots were exhausted, calculated root respiration increased up to 65% of total soil CO₂ efflux. It is suggested that this estimate of its contribution to soil respiration is more precise than the previous based on one year of observation. Heterotrophic respiration declined in response to a 20‐day‐long 6 °C decline in soil temperature during the second summer, whereas root respiration did not decline. This did not support the idea that root respiration should be more sensitive to variations in soil temperature. It is suggested that above‐ground photosynthetic activity and allocation patterns of recent photosynthates to roots should be considered in models of responses of forest C balances to global climate change.     

Interaction of Kinetin and Indoleacetic Acid in the Avena Straight-Growth Test

Kinetin has a stimulating effect in the Avena straight-growth test. The action of different concentrations of kinetin, 2.5 × 10^?7, 2.5 × 10^?6 and 2.5 × 10^?5M, in combination with different concentrations of IAA was studied in this test. It was shown that the effect of low IAA concentrations, 0.25 × 10^?7 and 1 × 10^?7M, was strongly enhanced by the addition of all the kinetin concentrations investigated. The effect of the highest IAA concentrations, 25 × 10^?7 and 100 × 10^?7M, on the other hand, was inhibited relatively strongly by the highest employed concentration of kinetin. The results are explained as due to a kinetin-produced increase of auxin in the coleoptile segment, which in combination with low IAA concentrations can lead to a growth stimulation and with high IAA concentrations to a growth inhibition. Since kinetin in purification and chromatography of auxin can partly follow IAA, thereby affecting the quantitative yield, it is emphasized that, prior to the test, auxin extracts containing cytokinins should be freed from the latter by, for example, gel filtration or paper electrophoresis.     

Cosmine resorption structures on three osteolepid jaws and their biological significance

Cosmine resorption structures on three osteolepid jaws provide evidence for two different types of resorption process, one superficial and one initially internal. The superficial process starts in the pore canal openings. and the internal probably in the dentine pulp cavities or other cavities within the cosminc. Different stages of the superficial process that have previously not been recorded can he seen. Their positions show that superficial resorption may start in a few centers, from which it may spread in all directions but at different rates in different directions. There is no observable correspondence between the occurrence of resorption and the growth of the dermal bones along their sutures. Thus, the primary reason for resorption is not to allow marginal growth of the dermal bones. □ Cosmine resorption, osteolepids, Middle Devonian.     

Neuromuscular Systems in Molluscs

Molluscs have become increasingly popular in the study of centralneural mechanisms. More recently, there have been attempts torelate activity in central neurons with behavior in animalsof this phylum. The latter studies necessitate an understandingof the effectors of such behaviors. This requires not only informationabout the neuromuscular junction, but also an awareness of thecapabilities of the muscles themselves. Therefore, we have discussedsome structural and related functional characteristics of molluscanmuscle. We suggest that invertebrate mucles might be comparedon three scales: the amount of myofilament organization, theamount of vesicular specialization and organization, and theamount of paramyosin. We have considered some characteristicsof the widely-studied sustained contraction, known as "catch."Finally, we have discussed the neuromuscular junction—thetypes of junctions, the multiplicity of innervation, and someaspects of pharmacology. The results of such a study indicatedmany areas in which further research is essential before wecan understand behavior in terms of activity in the centralnervous system.     

Nitrogenase Activity in Relation to Intracellular Organisms in Sphagnum Mosses

Electron microscopic studies of Sphagnum lindbergii (Schimp.) and S. riparium (Ångstr.) have revealed the presence of intracellular organisms such as blue-green algae, green algae, bacteria and fungi. Nitrogenase activities of these Sphagnum mosses were found to be related mainly to the presence of intracellular Nostoc filaments. The appearance of nitrogen-fixing blue-green algae within bryophytes is thus not restricted to liverworts. The association is likely to be of ecological importance as it seems to occur in very acid habitats generally lacking blue-green algae. Possible interrelations between the moss, the blue-green algae and different types of bacteria are discussed.