Regional specialization for an optomotor response in the honeybee compound eye

ABSTRACT. The optomotor head-turning response of the honeybee ( Apis mellifera ) to a horizontally moving stripe pattern was analysed after occlusion of specific regions of the compound eye. The dorsal half of the eye and the medial region appear to be irrelevant to this behavioural reflex. Occlusion of the ventrolateral portion of the eye, however, even with the remainder of the eye unoccluded, rendered the optomotor system blind. The optomotor response was found to be mediated by an area roughly equal to one-fifth of the total eye surface with some redundancy in the system, since occlusion of at least half of the zone did not significantly impair the response. These results support the hypothesis of physically separate visual subsystems in the bee eye which are adapted for different functions.     

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.     

Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia)

Molecular analyses are transforming our understanding of the evolution of scleractinian corals and conflict with traditional classification, which is based on skeletal morphology. A new classification system, which integrates molecular and morphological data, is essential for documenting patterns of biodiversity and establishing priorities for marine conservation, as well as providing the morphological characters needed for linking present‐day corals with fossil species. The present monograph is the first in a series whose goal is to develop such an integrated system. It addresses the taxonomic relationships of 55 Recent zooxanthellate genera (one new) in seven families (one new), which were previously assigned to the suborder Faviina (eight genera are transferred to incertae sedis). The present monograph has two objectives. First, we introduce the higher‐level classification system for the 46 genera whose relationships are clear. Second, we formally revise the taxonomy of those corals belonging to the newly discovered family‐level clade (restricted today to the western Atlantic and Caribbean regions); this revised family Mussidae consists of ten genera (one of which is new) and 26 species that were previously assigned to the ‘traditional’ families Faviidae and Mussidae. To guide in discovering morphologic characters diagnostic of higher‐level taxa, we mapped a total of 38 morphologic characters [19 macromorphology, eight micromorphology, 11 microstructure] onto a molecular tree consisting of 67 species [22 Indo‐Pacific and seven Atlantic species in the traditional family Faviidae; 13 Indo‐Pacific and ten Atlantic species in the traditional family Mussidae; 13 species in the traditional families Merulinidae (5), Pectiniidae (7), and Trachyphylliidae (1); two Atlantic species of traditional Montastraea], and trace character histories using parsimony. To evaluate the overall effectiveness of morphological data in phylogeny reconstruction, we performed morphology‐based phylogenetic analyses using 27 (80 states) of the 38 characters, and compared morphological trees with molecular trees. The results of the ancestral state reconstructions revealed extensive homoplasy in almost all morphological characters. Family‐ and subfamily‐level molecular clades [previously identified as XVII?XXI] are best distinguished on the basis of the shapes of septal teeth and corresponding microstructure. The newly revised family Mussidae (XXI) has septal teeth with regular pointed tips (a symplesiomorphy) and a stout blocky appearance. It has two subfamilies, Mussinae and Faviinae. The subfamily Mussinae is distinguished by spine‐shaped teeth and widely spaced costoseptal clusters of calcification centres. The subfamily Faviinae is distinguished by blocky, pointed tricorne or paddle‐shaped teeth with elliptical bases, transverse structures such as carinae that cross the septal plane, and well‐developed aligned granules. Defining diagnostic characters for the broader data set is more challenging. In analyses of taxonomic subsets of the data set that were defined by clade, morphological phylogenetic analyses clearly distinguished the families Mussidae (XXI) and Lobophylliidae (XIX), as well as the two subfamilies of Mussidae (Mussinae, Faviinae), with one exception (Homophyllia australis). However, analyses of the entire 67‐species data set distinguished the family Lobophylliidae (XIX), but not the Merulinidae (XVII) and not the newly defined Mussidae (XXI), although the subfamily Mussinae was recovered as monophyletic. Some lower‐level relationships within the Merulinidae (XVII) agree with molecular results, but this particular family is especially problematic and requires additional molecular and morphological study. Future work including fossils will not only allow estimation of divergence times but also facilitate examination of the relationship between these divergences and changes in the environment and biogeography. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. Zoological Journal of the Linnean Society, 2012, 166 , 465–529.     

Initiation of Procambial Strands in Leaf Primordia of Bread Wheat, Triticum aestivum L

In Triticum aestivum L. the median and lateral procambial strandsserving the primordia originate independently and in isolationfrom the vascular system of the rest of the plant. The medianstrand is initiated first, followed by a succession of lateralstrands during the next four or so plastochrones. The medianand first lateral strands have their point of origin in theaxis, in the disc of insertion of the primordium. The laterlaterals are initiated up in the primordium. Once initiatedthe procambial strands extend from their point of origin bothacropetally and basipetally, the latter extension eventuallylinking them to strands associated with older leaves. It wouldappear that the materials necessary for the growth of the apicaldome and of the first four leaf primordia are supplied by generaldiffusion and not via direct vascular connexions with the restof the plant.     

Effect on predatory performance of the presence of prey after moulting in the water stick insect, Ranatra linearis

ABSTRACT. During the first 4h following moulting, Ranatra linearis L. (Heteroptera, Nepidae) perform numerous claw and femur foreleg movements, but do not then catch any prey (e.g. Daphnia ). The frequency of these movements depends on the presence of potential prey, and is significantly higher in the presence of potential prey items than in their absence. The presence or absence of prey during these four post-moult hours influenced subsequent performance. Ranatra moulting in the absence of prey showed later a lower catching success and a smaller proportion of complex predatory movements at all stages of development than did Ranatra moulting in the presence of prey, all other factors being similar. The importance of this deficit resulting from depriving Ranatra of the presence of prey during the post-moult period is discussed.     

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.     

Simultaneous Transmission of Three Stable Genotypes in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

REPLICATION of the double stranded DNA genomes of bacteria takes place by a semi-conservative mechanism¹, but although autoradiographic studies have confirmed that eukaryotic DNA is replicated semi-conservatively^2,3, our lack of knowledge about the structure of the eukaryotic chromosome means that this finding does not prove that the conserved unit is a single polynucleotide strand of DNA. Indirect information supporting the hypothesis that the conserved unit consisted of a single polydeoxyribonucleotide strand has accumulated from transmission studies in chemical mutation experiments. Two phenotypic classes of mutants are readily distinguishable as a result of chemical mutagenesis; mosaic (fractional) mutants and complete (whole body) mutants. Mutation studies assume that the treated gametes contain one DNA polymer per chromosome and that the polymer is made up of two complementary nucleotide strands. With chemical mutagens (excluding acridine dyes) it is probable that only one of the two complementary strands would be chemically altered⁴. Following fertilization, DNA replication occurs, fixing both the mutational event and its complementary wild type site. The zygote will possess a mutation which will be phenotypically expressed in the adult fly depending on the early morphogenic movements in the fly's development. Assuming that only one strand is altered, the two cell lines would contain a mutant genotype and a wild type genotype. Two genotypically mutant cell lines would arise if two mutational events occur in the opposing polydeoxyribonucleotide strands within the same genie region. In this case, there would be no genotypically wild type cells in the embryo.