To be a Juvenile and Not to be a Larva: An Attempt to Synthesize

The question - when does a fish becomes a juvenile - might seem strange to some, and even totally worthless, mainly to those fish and fishery biologists who designate all the small ontogenetic stages of fishes by the banal term fry (for a commentary on this unfortunate term, see Balon 1990). Despite this, a group of predominantly younger scientists met at a workshop in Bratislava to exchange views on this topic. Ontogeny is a process during which one event is related to another and everything is related to everything else. Therefore, besides the title subject, the participants of the workshop discussed also such topics as fish metamorphosis, whether the larva period begins with hatching or with the onset of exogenous feeding, and eventually, whether fish ontogeny is saltatory or otherwise.     

Channel properties of template assembled alamethicin tetramers.

The multiple conductance levels displayed by the antibiotic alamethicin in planar lipid bilayers is explained by a dynamic 'barrel-stave' model, the conducting pore resulting from the aggregation of up to ten helical amphipathic helical monomers. However, the precise assignment of an oligomerization state to a particular single-channel conductance substate is far from being experimentally clear. In addition, it could be useful to tailor a given channel geometry to selectively allow the permeation of solutes with different molecular sizes, whilst retaining a high voltage-dependence. To control the aggregation state of the channel, the TASP (template assembled synthetic proteins) strategy was applied to synthesize structurally defined oligomers, i.e. dimer, trimer, tetramer. The modulation of conductance properties of three alamethicin tetramers with the length and flexibility of the linkers of the 'open' or linear template is described. It is shown that the introduction of an alanine between the contiguous lysines to which are tethered C-terminally modified alamethicin helical monomers stabilizes the open channel states, whereas the alanine substitution by Pro-Gly, a reverse beta-turn promoting motif, increases voltage-dependence and leads to single-channel conductance values more in line with the expected ones from a tetrameric bundle.     

Microbiome resilience of Amazonian forests: Agroforest divergence to bacteria and secondary forest succession convergence to fungi

An alarming and increasing deforestation rate threatens Amazon tropical ecosystems and subsequent degradation due to frequent fires. Agroforestry systems (AFS) may offer a sustainable alternative, reportedly mimicking the plant–soil interactions of the natural mature forest (MF). However, the role of microbial community in tropical AFS remains largely unknown. This knowledge is crucial for evaluating the sustainability of AFS and practices given the key role of microbes in the aboveground–belowground interactions. The current study, by comparing different AFS and successions of secondary and MFs, showed that AFS fostered distinct groups of bacterial community, diverging from the MFs, likely a result of management practices while secondary forests converged to the same soil microbiome found in the MF, by favoring the same groups of fungi. Model simulations reveal that AFS would require profound changes in aboveground biomass and in soil factors to reach the same microbiome found in MFs. In summary, AFS practices did not result in ecosystems mimicking natural forest plant–soil interactions but rather reshaped the ecosystem to a completely different relation between aboveground biomass, soil abiotic properties, and the soil microbiome.     

Comet assay of fresh and cryopreserved bull spermatozoa

In this study, we describe DNA fragmentation of fresh and cryopreserved bull spermatozoa using the comet assay. Cryopreservation caused a significant but low (3.8%) decrease in the percentage of DNA in the comet head and an increase (5.3%) in the tail length. Our results suggest that in addition to motility and viability, low levels of DNA fragmentation after cryopreservation is a characteristic of bull spermatozoa and can be a part of remarkable cryoresistance of bull spermatozoa.     

Molecular study of the Cardamine maritima group (Brassicaceae) from the Balkan and Apennine Peninsulas based on amplified fragment length polymorphism

The amphi-Adriatic region, and especially the Western Balkan Peninsula, belongs to the most important biodiversity hotspots in the temperate region. Nevertheless, detailed phylogeographic and molecular systematic studies in the Western Balkan are rare due to sporadic sampling in regions, where access has been, until recently, restricted by war. The Cardamine maritima group, which is the focus of this study, comprises not only the currently recognised species C. maritima and C. monteluccii, but also other taxa, which have been rendered to synonymy by most of the national floras and checklists. Molecular data acquired by the amplified fragment length polymorphism method showed a clear pattern within the group. Italian populations of C. monteluccii are well separated from Balkan taxa. In a step forward from previous taxonomic confusion surrounding Balkan populations, the present study confirms that five allopatric units—each with a clearly delimited and a rather restricted distribution range—can be easily recognised here. They correspond to C. fialae, C. serbica, C. rupestris, and two genetically distant and allopatric units within C. maritima. While individual taxa gained high bootstrap support in the neighbour-joining tree, there is low support for the internal nodes and it is hard to infer any relationships among taxa based on this information. The majority of Balkan populations of the C. maritima group exhibit features of genetic variability that enable us to hypothesise that these populations are relic ones.     

The Sensory Canal Systems of the Living Coelacanth, Latimeria Chalumnae: A New Instalment

Entire sensory canal systems of the coelacanth, Latimeria chalumnae, are described: not only the course of principal canals with their primary and secondary collaterals, but also the course and branches of the pit-line and reticular canals. The number of pores on the left side of the head were found to be 296 in an early (yolksac) embryo, 321 in a late term fetus, 485 in a juvenile, and 2974 in adults. This means that in latimeria most of the lateral-line canal system develop after parturition. Pit lines of the living coelacanth are not rows of superficial neuromasts but canals covered by a thin epidermis like in other sensory canals of the lateral line. These pit-line canals, however, have a very specific structure and branching pattern: the medial dorsal pit-line canal is connected by fine branches on top of the head. The infra-dentary pit-line canal connects via these branches with canals deep inside the bones. Several fine and richly branched canaliculi of unknown function radiate from each quadratojugal pit-line canal. The gular plate pit-line canal has superficially branching arms as well as connections to numerous deeper canals inside the bone. These canals consist of fine branches that in turn lead to and open on the ventral surface of the gular plates as small pores. The system is reminiscent of the reticular (pore) canal system known only from some fossil agnathans and fishes. Thus latimeria combines the reticular system of ancient vertebrates with the lateral-line system of modern fishes. The significance of this gular (possibly electro-sensory) system for feeding by the coelacanth will be discussed.