Effects of cyanogenesis in bracken fern (Pteridium aquilinum) on associated insects

Abstract. 1. The relationship between cyanogenesis in bracken fern and the insect fauna feeding on the plant was investigated over a 3 year period. The most common insects between May and July, while cyanide levels were high, were the sawflies Strongylogaster impressata Provancher, S.multicincta Norton, Aneug-menus fzavipes (Norton), the aphid Macrosiphum euphorbiae (Thomas) and a microlepidopteran species of Monochroa .
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds.     

Extracellular superoxide production, viability and redox poise in response to desiccation in recalcitrant Castanea sativa seeds

Reactive oxygen species (ROS) are implicated in seed death following dehydration in desiccation-intolerant 'recalcitrant' seeds. However, it is unknown if and how ROS are produced in the apoplast and if they play a role in stress signalling during desiccation. We studied intracellular damage and extracellular superoxide (O₂^·−) production upon desiccation in Castanea sativa seeds, mechanisms of O₂^·− production and the effect of exogenously supplied ROS. A transient increase in extracellular O₂^·− production by the embryonic axes preceded significant desiccation-induced viability loss. Thereafter, progressively more oxidizing intracellular conditions, as indicated by a significant shift in glutathione half-cell reduction potential, accompanied cell and axis death, coinciding with the disruption of nuclear membranes. Most hydrogen peroxide (H₂O₂)-dependent O₂^·− production was found in a cell wall fraction that contained extracellular peroxidases (ECPOX) with molecular masses of ∼50 kDa. Cinnamic acid was identified as a potential reductant required for ECPOX-mediated O₂^·− production. H₂O₂, applied exogenously to mimic the transient ROS burst at the onset of desiccation, counteracted viability loss of sub-lethally desiccation-stressed seeds and of excised embryonic axes grown in tissue culture. Hence, extracellular ROS produced by embryonic axes appear to be important signalling components involved in wound response, regeneration and growth.     

Can long‐distance migratory birds adjust to the advancement of spring by shortening migration distance? The response of the pied flycatcher to latitudinal photoperiodic variation

Many organisms use day length as a cue for synchronizing their life cycles with seasonal changes in environmental productivity. Under rapid climate change, however, responses to day length may become maladaptive, and photo‐responsive organisms may only be able to evade increasingly unsuitable habitats if they can accommodate to a wide range of photoperiodic conditions. A previous experiment showed that the pied flycatcher, Ficedula hypoleuca, a Palaearctic‐Afrotropical migratory bird, would strongly advance the timing of spring migration and reproductive maturation if it shifted its wintering area from sub‐Saharan Africa to the Mediterranean region. However, it is unknown whether this marked response to latitudinal variation in photoperiodic conditions is continuous over the entire range of potential wintering areas, and if a shortening of migration distance would be an effective mechanism to adjust the timing of migration to rapidly changing climatic conditions. Here, we experimentally show that a moderate northward displacement of the pied flycatcher's current wintering grounds by 10° would result in a clear advancement of the termination of prenuptial moult and the initiation of spring migratory activity and gonadal growth. However, we found no further advancement under conditions simulating higher wintering latitudes, suggesting the existence of a critical photoperiodic threshold or a steep gradual response within a narrow geographical range between 10° and 20° northern latitude. Because habitat conditions in this area are deteriorating rapidly, the potential for pied flycatchers to adjust their life cycle to changing climatic conditions by shortening the migration distance may be limited in the future.     

Rhombognathus auster, a new rhombognathine mite (Acari, Halacaridae) from southern South America

A new species of rhombognathine mites. Rhomhognathus auster , is described. The species lives intcrtidally on the shores of eastern Tierra del Fuego. Judging by the shape of idiosoma. legs and claws, R. auster is presumed to live amongst slender, tubular algae in semi-exposcd and sheltered habitats.     

Molecular markers of phase transition in locusts

The changes accompanying the transition from the gregarious to the solitary phase state in locusts are so drastic that for a long time these phases were considered as distinct species. It was Boris Uvarov who introduced the concept of polyphenism. Decades of research revealed that phase transition implies changes in morphometry, the color of the cuticle, behavior and several aspects of physiology. In particular, in the recent decade, quite a number of molecular studies have been undertaken to uncover phase-related differences. They resulted in novel insights into the role of corazonin, neuroparsins, some protease inhibitors, phenylacetonitrile and so on. The advent of EST-databases of locusts （e.g. Kang et al., 2004） is a most encouraging novel development in physiological and behavioral locust research. Yet, the answer to the most intriguing question, namely whether or not there is a primordial molecular inducer of phase transition, is probably not within reach in the very near future.     

Zur Gattung Bathyhalacarus (Acari, Halacaridae), nebst Beschreibung fünf neuer Arten

Bathyhalacarus was hitherto known from the Pacific only. Now five species have been found in deep sea regions of the Atlantic Ocean. The five species, viz. Bathyhulacarus abyssiculus sp.n., B. ucanthophorus sp.n., B. aculifer sp.n., B. acutus sp.n., and B. atlanticus sp.n. are described. The taxonomic characteristics of the known species are tabulated, and their geographical distribution illustrated.     

Eine neue Actacarus-Art (Acari, Halacaridae) aus dem Bathyal vor der Küste von North Carolina, USA

Actacarus obductus sp.n. is described. The Actacarinae are known from intertidal and shallow subtidal habitats, A. obductus is the first Actacarus species from deeper parts of the ocean. The distribution of the genus Actacarus and a key to known species are given. A. monniotae Krantz is considered to be synonymous with A. bacescui Konnerth-Ionescu.