Host selection by winged summer females of the aphid Sitobion avenae

A total of 55 parthenogenetic lineages of the grain aphid, Sitobion avenae F. were established from single clones collected from winter wheat (agricultural host) and cocksfoot (natural host) at various locations in southern Britain. RAPD-PCR profiles indicated that these lineages consisted of at least 15 genetically distinct clones. Twenty winged individuals (alatae) of known weight were taken from each lineage and presented with a choice of wheat and cocksfoot hosts (with a total leaf area each of 2 cm²) held in petri dishes (laboratory experiments) and flowerpots (field experiments). In both experimental designs host preferences were determined by a ranking of a proportion of counts (limited to -1 +1) of the progeny produced on each host after 5 days. Overall, alatae tended to prefer the agricultural host. However, alatae from individual clones found exclusively on wheat generally had a higher preference for wheat than alatae from individual clones found exclusively on cocksfoot. Wheat-derived lineages (aphid genotypes that were collected on wheat but also present on cocksfoot) showed a significantly greater preference for the agricultural host than the cocksfoot-derived lineages. Individuals from a wheat-derived lineage had significantly higher observed and potential progeny production on wheat than they did on cocksfoot, while individuals from a cocksfoot-derived lineage had significantly higher potential progeny but lower mean progeny weights on wheat. In a second stage, reciprocal host transfer experiments were carried out in the laboratory, i.e. lineages collected from the agricultural host were reared for several generations on the natural host and vice versa prior to being tested for host preference. The preference of the lineages for their host of origin significantly decreased in this second trial, reversing the overall preference trends, while there was little evidence for between-lineage variation in this change in preference. In summary these results indicate weak genotypic but strong environmental influences on alate host preference in S. avenae. This host plant conditioning effect may serve to promote host-based genetic structuring observed in southern British populations of S. avenae.     

A molecular phylogenetic study of the freshwater talitrid amphipod Orchestia cavimana (Crustacea).

In this paper we performed a molecular phylogenetic study of Orchestia cavimana, the sole talitrid amphipod inhabiting beaches of European freshwater lakes and rivers. For that purpose, we have PCR amplified and sequenced regions of the mitochondrial cytochrome oxidase subunit I (COI) gene, basing our analysis on both nucleotide and amino acid sequences and considering also structural classes of the COI enzyme. Phylogenetic analyses were conducted by neighbour-joining (NJ) and maximum-parsimony (MP) methods comparing homologous sequences of talitrids and other Crustacea. In both NJ and MP trees, O. cavimana shows a basal placement with respect to other talitrid amphipods.     

A Commentary on the Need for 3D-Biologically Relevant In Vitro Environments to Investigate Astrocytes and Their Role in Central Nervous System Inflammation

Astrocytes execute essential functions in the healthy CNS, whilst also being implicated as a limitation to functional regeneration and repair after injury. They respond to injury to minimize damage to healthy tissue whilst also attempting to seal the broken blood-brain-barrier, however, they impede recovery if they are persistent and form a permanent scar in the injured brain. As such, it is of great importance to understand the mechanism underlying the astrocytic response to injury, and this understanding is currently limited by the in vitro environments available to scientists. Biomaterials such as nanofibres and hydrogels offer great potential for the development of superior, 3D cell culture environments in which to study astrocyte behavior and phenotype. The implementation of such in vitro environments with a particularly interdisciplinary approach can improve the field’s understanding of astrocytes, their role in central nervous system inflammation, and elucidate potential strategies to achieve functional regeneration.     

Myosin light-chain expression during avian muscle development

Monoclonal antibodies to adult chicken myosin light chains were generated and used to quantitate the types of myosin light-chain (MLC) isoforms expressed during development of the pectoralis major (PM), anterior latissimus dorsi (ALD), and medial adductor (MA) muscles of the chicken. These are muscles which, in the adult, are composed predominantly of fast, slow, and a mixture of fiber types, respectively. Three distinct phases of MLC expression characterized the development of the PM and MA muscles. The first identifiable pase occurred during the period of 5-7 d of incubation in ovo. Extracts of muscles from the pectoral region (which included the presumptive PM muscle) contained only fast MLC isoforms. This period of exclusive fast light-chain synthesis was followed by a phase (8- 12 d of incubation in ovo) in which coexpression of both fast and slow MLC isoforms was apparent in both PM and MA muscles. During the period, the composition of both fast and slow MLC isoforms in the PM and MA muscles was identical. Beginning at day 12 in ovo, the ALD was also subjected to immunochemical analyses. The proportion of fast and slow MLCs in this muscle at day 12 was similar to that present in the other muscles studied. The third development phase of MLC expression began at approximately 12 d of incubation in ovo and encompassed the transition in MLC composition to the isoform patterns incubation in ovo and encompassed the transition in MLC composition to the isoform patterns typical of adult muscle. During this period, the relative proportion of slow MLC rose in both the MA and ALD and fell in the PM. By day 16, the third fast light chain, LC(3f), was apparent in extracts of both the PM and MA. These results show that there is a developmental progression in the expression of MLC in the two avian muscles studied from day 5 in ovo; first, only fast MLCs are accumulated, then both fast and slow MLC isoforms are expressed. Only during the latter third of development in ovo is the final MLC isoform pattern characteristic of a particular muscle type expressed.     

Ontogenetic changes in haemoglobins in roach, Rutilus rutilus (L.) and rudd, Scardinius erythrophthalmus (L.)

The haemoglobins and globins of the roach, Rutilus rutilus (L.) and the rudd, Scardinius erythrophthalmus (L.) have been studied by starch gel electrophoresis. At all stages of development studied, the roach and rudd haemoglobins give a similar electrophoretic pattern, the young fish of about 2 cm standard length possessing three separate haemoglobins, of which two bands only persist in the adult. The evolutionary significance of multiple haemoglobins in fishes is briefly discussed.     

Kurze Mitteilungen

Zusammenfassung Die Schlußfolgerungen, dieStegmann (J. Orn. 109, 1968, p. 441–445) für die verwandtschaftliche Stellung der Flughühner auf Grund seiner eigenen Untersuchungen und an Hand anderer Quellen zieht, werden kommentiert. Es wird gezeigt, daß einige dieser Schlußfolgerungen nur auf morphologischen Merkmalen beruhen und mit den zu anderen Resultaten gelangten ethologischen und physiologischen Untersuchungsergebnissen nicht zu vereinbaren sind. Außerdem erscheint es unwahrscheinlich, daß die Flughühner, deren Ursprung von bodenlebenden Nestflüchtern unbestritten ist, auf dem Umweg über die baum- und felsbewohnenden nesthockenden Tauben erst sekundär wieder zu bodenbewohnenden Nestflüchtern geworden sind. Es gibt kein einziges Flughuhn-Merkmal, das diese Hypothese stützen könnte.     

Ultrastructure of epidermal sensory receptors in Amphibolurus barbatus (Lacertilis: Agamidae)

Summary The histological and ultrastructural organisation of the epidermal sensory organs in Amphibolurus barbatus has been described with respect to their position and possible functions. The sensory organs, located at the scale's edge, are most numerous in scales of the dorsal surface of the head. Most other scales of the body surface have two receptors located laterally to the spine or keel of the scale. In the imbricate scales of the ventral body region, the receptors lie just beneath the reinforced scale lip. Scanning electron microscopy has revealed the surface of the organ to be a crater lacking any surface projections. These sensory organs have a dermal papilla consisting of a nerve plexus and loose connective tissue. The nerve fibres arising from the plexus, pass to the epidermal columnar cells, where some form nerve terminals at the base of the cells, while others pass between them to form nerve terminals embedded in a superficial layer of cuboidal cells. The superficial terminals are held against the overlying keratin by masses of tonofilaments. The keratin is thickened to form a collar around the periphery of the organ but is only about 0.5 m thick immediately above it. Mechanical deformation of the scale's spine or reinforced scale lip may initiate stimulation of the nerve terminals described.