Intraspecific variation in limblessness in vertebrates: a unique example of microevolution

Many species of arboreal marine snails in the genus Littoraria are polymorphic for shell colour, with morphs that correspond in both colour and frequency to those predominant in the habitat. Although the combined effects of selection for crypsis and apostasy have been suggested as the most likely reasons for this, they have not been demonstrated directly in the field. We investigated whether two parasitoid flies, Sarcophaga megafilosia and Sarcophaga meiofilosia, select for crypsis in Littoraria filosa . It was possible to compare the proportions that matched and did not match the background between samples of live and dead snails because the shells of individuals killed by these parasitoids, within which the larva and pupa develop, remain attached to the substratum. This comparison was necessary because these snails frequently move among different coloured microhabitats, which will tend to obscure any effect of selection for crypsis if only live individuals are censused. The method appeared reliable since there was no change in background colour and very little loss of shells between larviposition and emergence of flies. S. megafilosia killed a significantly greater than expected proportion of snails that did not match their background. In contrast, there was no evidence of selective attack by S. meiofilosia. These results are discussed in relation to previous work on polymorphisms in Littoraria species. We also suggest that the role of parasitoid insects as selective agents contributing to the maintenance of colour polymorphisms in terrestrial molluscs may have been overlooked.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77, 367−377.     

The interaction of taste and heat on the biting response of the tsetse fly Glossina fuscipes fuscipes

Abstract.Tsetse flies probe more on a heated surface with a trace of uric acid than on one without. Uric acid is one of the components of human sweat and it elicits spike responses from taste hairs on the flies' legs. In this paper it is examined how heat from the surface and taste interact to affect the biting behaviour of Glossina fuscipes fuscipes Newstead 1910 (Diptera: Glossinidae) over successive days of food deprivation. The biting behaviour consists of bouts of probing, both ambulatory and stationary, intercalated with short hops of flight. The number of bouts increases over successive days, whereas the average bout duration does not. Although uric acid alone could not induce the flies to probe, in combination with surface heat it affected the flies greatly. Average bout duration was two‐fold that on a heated surface not treated with uric acid. The frequency of bouts was not affected by uric acid. These experiments and auxiliary ones on mechanoreceptive input and odours lead to the insight that the factors which affect biting behaviour can be viewed as a hierarchy. The hierarchy extends from those that affect the onset of biting to those that affect its course.     

Microsatellite markers in Carica papaya L.: isolation,characterization and transferability to Vasconcellea species

A dinucleotide microsatellite‐enriched genomic library was obtained from Carica papaya L. Sixty‐nine microsatellites were evaluated on three genotypes of C. papaya and seven species of the neighbour genus Vasconcellea. Among them, 45 markers were characterized on a sample of 29 accessions of C. papaya from the Caribbean region and 11 accessions of Vasconcellea from the Andes of Colombia and Ecuador. Twenty‐four gave polymorphism in C. papaya and only four among the seven species of Vasconcellea, confirming the divergence between both genera.     

Will European soil-monitoring networks be able to detect changes in topsoil organic carbon content?

Within the United Nations Framework Convention on Climate Change, articles 3.3 and 3.4 stipulate that some voluntary activities leading to an additional carbon (C) sequestration in soils could be accounted as C sinks in national greenhouse gas inventories. These additional C stocks should be verifiable. In this work, we assess the feasibility of verifying the effects of changes in land use or management practice on soil organic carbon (SOC), by comparing minimum detectable changes in SOC concentration for existing European networks suitable for soil monitoring. Among the tested scenarios, the minimum detectable changes differed considerably among the soil-monitoring networks (SMNs). Considerable effort would be necessary for some member states to reach acceptable levels of minimum detectable change for C sequestration accounting. For SOC, a time interval of about 10 years would enable the detection of some simulated large changes in most European countries. In almost all cases, the minimum detectable change in SOC stocks remains greater than annual greenhouse gases emissions. Therefore, it is unlikely that SMNs could be used for annual national C accounting. However, the importance of organic C in soil functions, and as an indicator of soil condition and trends, underlines the importance of establishing effective national SMNs.     

Survival of dried eukaryotes (anhydrobiotes) after exposure to very high temperatures

Organisms that tolerate essentially complete dehydration are said to be in anhydrobiosis, and can be referred to as anhydrobiotes. Those organisms are of great ecological and medical importance, but also provide models for the study of a variety of biological phenomena. We examined the tolerance of selected eukaryotic anhydrobiotes to high temperatures using slow (∼4 °C min⁻¹) and rapid (∼100 °C min⁻¹) heating to 110, 120, 130, and 140 °C. Test organisms were then either returned to storage temperatures close to 22 °C (preheating), or held at those high temperatures for an additional 10 min. Some anhydrobiotes survived slow heating to 130 °C, whereas rapid heating led to a dramatic reduction in survival. None of these organisms encounter anywhere near these high temperatures in nature, so tolerance is not an obvious result of adaptation to current or recent conditions. We speculate that tolerance could have been achieved during the much earlier evolution of these organisms, and has been retained up to the present.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 15–22.     

Ribosomal DNA Sequence of Nucleospora salmonis Hedrick, Groff and Baxa, 1991 (Microsporea: Enterocytozoonidae): Implications for Phylogeny and Nomenclature

ABSTRACT. Rules of zoological nomenclature, morphological data, and robosomal DNA sequence data support the validity of the genus Nucleospora , and its placement in the family Enterocytozoonidae. Although Nucleospora exhibits most of the distinguishing morophological characteristics of the family Enterocytozoonidae Cali and Owne, 1990, the distinctively different hosts (fish and humans, respectively) and sites of development (the nuclei of immature blood cells and the cytoplasm of enterocutes) supprot the placement Nucleospora and Enterocytozoon into separate genera. Ribosomal DNA sequence comparisons between Nucleospora salmonis and Enterocytozoon bieneusi showed 19.8% genetic divergece in the large and small subunit regions. Although more inter- and intrageneric divergence between the two species is sufficiently larg to deter suppression of the genus Nucleospora as a junior synonym of Enterocytozoon. A polymerase chain reaction test for the detection of N. salmonis in chinook salmon ( Oncorhynchus tshawytscha ), based on N. salmonis -specific ribosomal DNA sequence, is described.     

Involvement of the hyperglycemic neurohormone family in the control of reproduction in decapod crustaceans

Summary

In the last few years, (bio)chemical and molecular biological studies have shown that several members of the hyperglycemic hormone family are present in different molecular forms. In vivo and in vitro bioassays revealed that some of these isoforms also play a role in the control of reproduction in decapod crustaceans. This communication gives a review of the cytological aspects of the eyestalk X-organ sinus gland complex, responsible for the synthesis, storage and release of these neuropeptides, and the molecular and functional aspects of those members involved in the control of reproduction. Finally, the role of the hyperglycemic hormone family in the regulation of reproduction in the female lobster is described as an example of the (possible) interactions of the members of the hyperglycemic hormone family with other (neuro)endocrine factors in the reproductive process of crustaceans.     

Intraspecific variation in the postcranial skeleton morphology in African clariids: a case study of extreme phenotypic plasticity

Taxonomic relationships within the Clariidae, especially within the anguilliform species, are currently ambiguous due to the lack of a reliable structure of valid generic and specific characteristics. Based on the information available, it is difficult to properly diagnose the different elongated genera and species; this is due in part to a high degree of variability of certain traits generally considered to be important taxonomically. For example, the caudal skeleton is often considered to be an important diagnostic trait. However, the degree of phenotypic plasticity has not hitherto been adequately assessed. This paper deals with interspecific variation of the caudal skeleton of Clarias gariepinus , Platyallabes tihoni , Platyclarias machadoi , Gymnallabes typus , Channallabes apus and Dolichallabes microphthalmus . The caudal skeleton of C. apus is studied, using specimens from three regions in Gabon. Hypural fusions and haemal and neural spines show most variation. The observed morphological variation appears to be geographically independent, in contrast to other morphological features such as vertebrae.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 437–446.     

Projecting future N2O emissions from agricultural soils in Belgium

This study analyses the spatial and temporal variability of N₂O emissions from the agricultural soils of Belgium. Annual N₂O emission rates are estimated with two statistical models, MCROPS and MGRASS, which take account of the impact of changes in land use, climate, and nitrogen‐fertilization rate. The models are used to simulate the temporal trend of N₂O emissions between 1990 and 2050 for a 10′ latitude and longitude grid. The results are also aggregated to the regional and national scale to facilitate comparison with other studies and national inventories. Changes in climate and land use are derived from the quantitative scenarios developed by the ATEAM project based on the Intergovernmental Panel on Climate Change‐Special Report on Emissions Scenarios (IPCC‐SRES) storylines. The average N₂O flux for Belgium was estimated to be 8.6 × 10⁶ kg N₂O‐N yr⁻¹ (STD = 2.1 × 10⁶ kg N₂O‐N yr⁻¹) for the period 1990–2000. Fluxes estimated for a single year (1996) give a reasonable agreement with published results at the national and regional scales for the same year. The scenario‐based simulations of future N₂O emissions show the strong influence of land‐use change. The scenarios A1FI, B1 and B2 produce similar results between 2001 and 2050 with a national emission rate in 2050 of 11.9 × 10⁶ kg N₂O‐N yr⁻¹. The A2 scenario, however, is very sensitive to the reduction in agricultural land areas (−14% compared with the 1990 baseline), which results in a reduced emission rate in 2050 of 8.3 × 10⁶ kg N₂O‐N yr⁻¹. Neither the climatic change scenarios nor the reduction in nitrogen fertilization rate could explain these results leading to the conclusion that N₂O emissions from Belgian agricultural soils will be more markedly affected by changes in agricultural land areas.