Protein variation in wild Atlantic salmon, with particular reference to southern Ireland

The extent of genetic variation in wild Atlantic salmon parr, Sulmo salur L., from river systems in Ireland, Iceland and eastern Canada, was investigated using starch gel electrophoresis. Within Ireland, seven polymorphic enzyme loci ( sAAT-4 *, GPI-1 *, IDDH-1 *, IDDH-2 *, IDHP-3 *, MDH-3 * and mMEP-2 *) were screened in nine different rivers and nine tributaries from the River Blackwater. Significant heterogeneity in gene frequencies occurred between riverine samples and between samples from tributaries of the River Blackwater. Variation between tributaries was as great as between rivers elsewhere in the country. Levels of population differentiation were comparable to those found in other regions throughout the range of the species, and temporal stability in gene frequencies was apparent when the results were compared with previously published data. Screening of riverine samples from Iceland and eastern Canada (Newfoundland and New Brunswick) allowed the Irish results to be considered in a broader context. Irish salmon cluster in the western European group, to which may be added Icelandic populations. Salmon from eastern Canada show a high level of genetic distinctiveness from the European group.     

Characterization of some East African Theileria species isolates by isoenzyme analysis, with particular reference to T. parva

Eight different isolates of Theileria parva and one isolate of T. taurotragi, in the form of intra-lymphocytic schizonts and/or purified piroplasms, were subjected to isoenzyme analysis for 24 enzymes by both isoelectric focusing in agarose and electrophoresis in starch gel. Twelve enzymes distinguished between T. parva and T. taurotragi; five enzymes (HK, GPI, PEP1, LDH and SOD) showed variations within T. parva. The metabolism of the host cell was affected by schizont infection, which masked intraspecific variations. Piroplasms were of more potential value for characterization of T. parva.     

Prevalence of a single fish-pathogenic Saprolegnia sp. clone in Finland and Sweden

Thirty-one isolates of Saprolegnia sp., most originating from infected salmon or trout, were characterised genetically and physiologically. The majority (6 of 31) of the isolates from several widely separated geographical locations was found to be genetically almost identical as assessed by RAPD-PCR. The remaining isolates belonged to 3 different groups with 1 to 3 representatives each. It is suggested that the first group of isolates represents a virulent form of the organism that has been widely spread by clonal propagation. The ability to repeated zoospore emergence, as an alternative to direct germination, seems to characterise specific Saprolegnia genotypes that may have adapted to certain hosts.     

Revision of the genus Elaphostrongylus Cameron (Nematoda, Metastrongyloidea) with particular reference to species of the genus occurring in Norwegian cervids

The three species of the genus Elaphostrongylus occurring in Norway. namely, E. cervi, E. rangiferi and E. alces from Cervus elaphus, Rangijer tarandus and Alces alces respectively are redescribed and figured using light and scanning electron microscopical techniques. The taxonomic status of the three species is reviewed and their validity confirmed.     

A taxonomic revision of the pipunculid fly genus Chalarus Walker, with particular reference to the European fauna

Twenty-one species of Chalarus Walker are described from Europe, 11 of them new. The puparial remains of 15 species are described. Type material of all previously described Chalarus species except C. velutinus (Macquart, 1835) was examined. The status of C. holosericeus (Meigen, 1824) is revised, and exiguus (Haliday, 1833) is confirmed as a valid species. Lectotypes are designated for C. holosericeus and C. spurius (Fallén, 1816). Five species-groups are tentatively proposed. Separate keys to females and males are given. The status of Chalarus species described from outside Europe is discussed, and two of these, C. kamijoi Morakote, in Morakote & Hirashima (1990) and C. konishii Morakote, in Morakote & Hirashima (1990), are synonymized with fimbriatus Coe and exiguus (Haliday) respectively. The functional significance of some taxonomic characters, particularly of the eyes and ovipositor, is discussed.     

Communication during aggressive interactions with particular reference to variation in choice of behaviour

Communication during aggressive interactions is discussed and defined primarily on the basis of functional considerations. A distinction is made between communication due to choice of action and communication due to performance of a given choice of action. Most attention is directed to choice of behaviour. Two models are developed to show that there are no arguments of general validity against communication through choice of behaviour or signalling as has been claimed. The first model is built on variation in fighting ability only and shows that choice of signal can carry information both about intentions (use of local strategy) and fighting ability. The second model which is based on the war of attrition with random rewards instead considers variation in subjective resource value. It shows that signalling of local strategy can be stable. It is concluded that evolutionary stability of communication through choice of behaviour is due to variation among animals in the utility of showing different behaviour patterns whereas communication by performance is due to a not easily removed relationship between the performance of a certain behaviour pattern and the factor communicated.     

A taxonomic study of thePoa macrocalyx complex,with particular reference to the populations in eastern Hokkaido

An attempt was made to investigate some populations of thePoa macrocalyx complex in eastern Hokkaido in relation to the taxonomy of this complex. Individual specimens preserved in TI, KYO and TNS were also studied. Chromosome counts of 2n=42 were obtained in the majority of a total of 84 collections, and counts of 2n=63 (incl. ca. 63), ca. 70 and 84 were also made in a few collections. High percentages of viable pollen were observed. The morphological features which were designated by previous authors to be significant in separatingPoa sachalinensis fromP. macrocalyx and in discriminating between the varieties ofP. macrocalyx were critically examined with emphasis on the observations of infra-population variation. It was confirmed that (1) the populations of thePoa macrocalyx complex in eastern Hokkaido are greatly variable morphologically and are also in a dynamic state cytogenetically, (2) plants of this complex in eastern Hokkaido belong to one and the same species,P. macrocalyx, and the varietiesfallax, scabriflora andtatewakiana may be merely morphs, and (3) some plants which are somewhat different from the plants in eastern Hokkaido with respect to glume features are distributed in Sakhalin, and northern and central Hokkaido. Some problems which should be subjected to further studies are pointed out.     

Seasonal variation in insect abundance among three Australian rain forests,with particular reference to phytophagous types

Monthly sweep net and light trap samples were used to examine seasonal changes in the abundance of insects in subtropical, warm and cool temperate rain forest in New South Wales. Maximum insect abundance, especially of phytophages, coincided with leaf flushing in the canopy trees. Cool temperate insect numbers were highest during the month just following the beech leaf flush, a rapid and synchronous growth event. Conversely, numbers of subtropical insects fluctuated over a longer period, in a pattern similar to the continuous growth of leaves that occurred throughout spring and summer there. The warm temperate was intermediate in its vegetation growth phenology and insect patterns. Rainforest insect abundance varied both temporally and spatially.     

Wound healing in the liver with particular reference to stem cells.

The efficiency of liver regeneration in response to the loss of hepatocytes is widely acknowledged, and this is usually accomplished by the triggering of normally proliferatively quiescent hepatocytes into the cell cycle. However, when regeneration is defective, tortuous ductular structures, initially continuous with the biliary tree, proliferate and migrate into the surrounding hepatocyte parenchyma. In humans, these biliary cells have variously been referred to as ductular structures, neoductules and neocholangioles, and have been observed in many forms of chronic liver disease, including cancer. In experimental animals, similar ductal cells are usually called oval cells, and their association with impaired regeneration has led to the conclusion that they are the progeny of facultative stem cells. Oval cells are of considerable biological interest as they may represent a target population for hepatic carcinogens, and they may also be useful vehicles for ex vivo gene therapy for the correction of inborn errors of metabolism. This review proposes that the liver harbours stem cells that are located in the biliary epithelium, that oval cells are the progeny of these stem cells, and that these cells can undergo massive expansion in their numbers before differentiating into hepatocytes. This is a conditional process that only occurs when the regenerative capacity of hepatocytes is overwhelmed, and thus, unlike the intestinal epithelium, the liver is not behaving as a classical, continually renewing, stem cell-fed lineage. We focus on the biliary network, not merely as a conduit for bile, but also as a cell compartment with the ability to proliferate under appropriate conditions and give rise to fully differentiated hepatocytes and other cell types.     

Esterase isozyme variation in theEragrostis curvula complex (Poaceae)

The biosystematic relationships of the apomictic complexEragrostis curvula s. lato, is investigated by disc electrophoresis of seed extracts to obtain esterase patterns of 23 accessions representing the morphological variants of this complex: curvula, conferta, robusta, chloromelas and lehmanniana. The zymograms thus obtained were classified into four groups on the basis of the presence of certain bands taken as characteristic and constant markers. Within each group variations were found in strict accordance with the morphological and cytogenetic data available on the complex. Cluster analysis showed similarity levels between the strains studied, representing different genomic groups. The esterase pattern proved useful as an additional criterion for identifying the individual taxa making up the complex and for evaluating their reciprocal relationships.