Ultrastructural and immunocytochemical observations of the nervous systems of three macrodasyidan gastrotrichs

The nervous systems of three macrodasyidan gastrotrichs, Dactylopodola baltica, Macrodasys caudatus and Dolichodasys elongatus, were investigated using immunocytochemistry and electron microscopy. Labelling of neural structures against serotonin revealed the presence of two pairs of cerebral cells, a dorsal cerebral connective, and paired ventral nerve cords in D. baltica. In M. caudatus and D. elongatus serotonin immunoreactivity was present in a single pair of dorsal cerebral cells and the ventral nerve cords; the dorsal connective of D. elongatus was also immunoreactive to serotonin and acetylated α‐tubulin. The presence of paired, serotonin‐like immunoreactive cells in D. baltica and other species may represent the plesiomorphic condition in Macrodasyida. The fine structure of the photoreceptors in D. baltica was also investigated to explore the potential ground pattern for eyes in the Macrodasyida. The pigmented photoreceptors of D. baltica contain a unicellular pigment cup, sheath cell and sensory receptor. The pigment cup contains numerous osmiophilic granules that presumably function to shield the eyes from downwelling light in the red part of the spectrum. Projecting into the pigment cup and sheath cell are numerous microvilli from a bipolar sensory cell. A single sensory cell may represent the plesiomorphic condition in Macrodasyida, with multiplication of sensory cells representative of more derived taxa.     

The non-coding RNAs as riboregulators

The non-coding RNAs database (http://biobases.ibch.poznan.pl/ncRNA/) contains currently available data on RNAs, which do not have long open reading frames and act as riboregulators. Non-coding RNAs are involved in the specific recognition of cellular nucleic acid targets through complementary base pairing to control cell growth and differentiation. Some of them are connected with several well known developmental and neuro-behavioral disorders. We have divided them into four groups. This paper is a short introduction to the database and presents its latest, updated edition.     

Effects of latitude, altitude and climate on the habitat and conservation of the endangered butterfly Maculinea arion and its Myrmica ant hosts

Analyses were made of the habitats of the endangered myrmecophilous butterfly, Maculinea arion, and its host ant, Myrmica sabuleti, in five regions, spanning most of the climatic range of the butterfly in west Europe. Near their altitudinal or north latitudinal limits, both species are confined to warm south-facing slopes where the turf is grazed <3 cm tall, but at low altitudes further south, where the summer climate is 4°C warmer, the butterfly and ant inhabit ground with any aspect other than south-facing, and the butterfly is restricted to swards >20 cm tall. Intermediate types of habitat were used in regions with intermediate summer climates. The implications for conservation management are discussed. The fact that M. arion has a narrow niche and occupies very early successional stages near its range-edge makes it difficult to conserve in regions with cool climates. A successful example is described from one site in the UK. During 20 years of intensive management the sward structure was altered from being tall and dense to that predicted as optimal for M. arion at its range-edge. The species of Myrmica changed greatly during this period, with thermophilous ants, including M. sabuleti, supplanting cool-loving non-host species. A population of M. arion now inhabits this site. We predict that the conservation of M. arion will be easier and cheaper to achieve under the warm climates of central lowland Europe where different, less intensive, management is required. © Rapid Science Ltd. 1998     

Trends and variability in spectral diffuse attenuation of coral reef waters

Coral Reefs - Knowledge of water clarity is an essential component of coral reef ecology. While qualitative trends are well known, there are currently few published records of...     

Insularity and adaptation in coupled victim–enemy associations

Employing a mathematical model we show how insularity, genotypic interactions and victim life‐history/demography can influence adaptation in a simple enemy–victim interaction where genotypes migrate between a large source and a smaller, initially unoccupied, isolated habitat. We find that when there are explicit costs to heightened enemy virulence and victim resistance, large/close islands resemble their immigration sources, whereas small and/or distant islands tend to be occupied only by the least defended victims and least virulent enemies. In a model with no explicit cost to genotypic identity, frequencies do not differ on average between source and island. Despite these trends in genotype frequencies, for a range of realistic conditions, both cost and cost‐free genotypic interactions yield an increase in the frequency of resistant encounters as a function of isolation. Moreover, in models with explicit costs, maximal island to island variation in genotypic frequencies is found on islands of intermediate distance from the source. In contrast, the model without explicit costs produces more variable communities, attaining maximum variability in genotypic frequencies at the most isolated islands. We hypothesize that adaptive patterns in mainland–island comparisons may differ substantially from those generated by centre‐periphery comparisons in continental systems.