Lethal and sublethal behavioural responses of saline water beetles to acute heat and osmotic stress

1. As species' physiological breadth determines their potential to deal with environmental changes, and influences individuals' survival and the persistence of populations, information about lethal and sublethal responses could be fundamental for conservation purposes. 2. We used a standard experimental approach to explore mortality and behavioural avoidance responses (i.e. flight and emersion from the water) to a combination of acute heat and osmotic stress on six species of saline water beetles (belonging to Enochrus, Nebrioporus, and Ochthebius genera). 3. Heat stress affected survival and behavioural responses in all of the species, whereas osmotic stress and the interaction between both stressors only showed significant effects for the Ochthebius genus. Behavioural and survival patterns were highly interrelated across the stress gradients. The Enochrus and Nebrioporus studied species showed maximum avoidance activity at 35–40 °C, and a short (< 30 min) exposure to 45 °C was lethal. Ochthebius species were the most heat tolerant and displayed increasing behavioural responses with increasing temperature. In the Nebrioporus and Ochthebius genera, the species occupying lotic, more environmentally stable habitats, showed greater mortality, and avoidance responses were higher or initiated at lower stress thresholds than lentic species. In contrast, both Enochrus species displayed a similar mortality, and the lentic species E. bicolor emerged and flew more than the lotic E. falcarius, in concordance with its higher dispersal capacity. 4. Avoidance responses could provide interesting information about species' physiological amplitudes as a complement to lethal responses. The lotic species here studied showed narrower physiological amplitude (i.e. N. baeticus and O. glaber) or lower dispersal ability (i.e. E. falcarius) than their lentic relatives; both traits could result in a higher vulnerability of lotic species to thermal habitat changes.     

Ecological assessment of an intermittent Mediterranean river using community structure and function: evaluating the role of different organism groups

1. Reliable lotic ecological monitoring requires knowledge of river typology, environmental factors, the effect of stressors known here as ‘pressures’ and appropriate indicators of anthropogenically induced change. We sampled benthic macroinvertebrate, fish, bird and macrophyte communities along an intermittent Mediterranean river and analysed community structure (relative abundance) and function (metrics) relative to environmental and pressure gradients in order to identify suitable indicator group(s) for future monitoring and mitigation programmes. 2. Principal components analysis revealed that scale‐dependent longitudinal differences in valley form separated narrower higher lying sites and tributaries with good quality habitats from more open degraded sites lower down the river continuum on a small floodplain and large scale pressures describing changes in land use related to agriculture with associated physical bankside and channel impacts. 3. Forward selection of variables in redundancy analysis (RDA) showed that reach scale environmental variables were selected more frequently than pressure variables for each organism group. Altitude and pH were highly redundant within and between groups, indicating essentially longitudinal structural and functional distribution patterns. Redundancy was far lower between selected pressure variables, but single or no pressure variables were retained for some organism groups indicating poor association of functional data, in particular, with the identified pressures. All RDA results indicated a longitudinal pH gradient, highlighting the combined effect of multiple environmental and pressure based mechanisms on organism groups. 4. Large, mobile organisms such as fish and birds provided a reliable link between organism structure and function, environmental factors and physical disturbance of the channel, bankside and wider river corridor. Benthic macroinvertebrate and macrophyte structural data revealed distribution patterns in relation to water velocity, a key parameter for developing appropriate compensation measures. 5. Results clearly show the importance of assessing patterns of both functional and structural change across multiple organism groups in order to identify typologically appropriate links with complex environmental and pressure gradients and develop and implement appropriate monitoring systems.     

The Molecular Ecology of Fundulus heteroclitus Hemoglobin-Oxygen Affinity

Animals faced with environmental perturbations must adapt orface extinction. The respiratory complex, specifically hemoglobins,is perhaps the best system to study such adaptation becauseit exists at the organism—environment interface. Fishare particularly useful models because they respond directlyto such environmental variables as temperature, oxygen, pH,carbon dioxide, and salinity. Our experiments have addressedthe molecular, cellular, and physiological mechanisms employedby fish to maintain respiratory homeostasis in the wake of changingtemperature and oxygen. Immediate, intermediate, and long-termadaptation can only be understood when the hemoglobin's ligandbinding properties and the cellular and hormonal regulationof various ligands are considered simultaneously. We describea detailed thermodynamic model for the binding of oxygen, protons,and organic phosphates to hemoglobin; discuss the role of multiplehemoglobins; and present evidence for physiological and geneticregulation of hemoglobin's major allosteric modifiers in responseto environmental stress in the mummichog, Fundulus heteroclitus     

Biochemical Changes in Cultures of Nectria galligena during the Autolytic Phase of Growth

Some biochemical changes occurring in cultures of Nectria galligenaduring its autolytic phase of growth have been investigated.In nitrate-grown and autolysed cultures of this fungus the degreeof autolysis amounted to 57 per cent. The amount of myceliallipids decreased continuously with the age of the culture. Totalmycelial nitrogen did not substantially change within the first50 days of autolysis. The constancy in the amount of bound aminoacids released from mycelium of Nectria galligena strongly suggeststhat mycelial protein are not affected by autolysis.     

Laticifers in Euphorbiaceae–a conspectus

Laticifers in Euphorbiaceae–a conspectus. Despite the multitude of references on laticifers in Euphorbiaceae, much of the work concentrated on economically important, and often highly specialized genera, particularly Euphorbia and Hevea, the evolution of the laticifer in the family is poorly understood. In this paper, laticifers, in a representative sample of genera of Euphorbiaceae, are investigated with respect to morphology and distribution. This information is supplemented with a review of existing literature. It seems probable that the articulated and non-articulated types are not as divergent as commonly supposed, since both may undergo intrusive growth, although more ontogenetic studies are needed to clarify the relationship between them.     

Phylogeny of Veneroidea (Mollusca: Bivalvia) based on morphology and molecules

The largest Recent family of Bivalvia, the marine Veneridae with approximately 800 species, comprises one of the least understood and most poorly defined molluscan taxa, despite including some of the most economically important and abundant bivalves, for example quahog, Pismo clams, and Manila clams. A review of previous phylogenetic analyses including the superfamily Veneroidea (Veneridae, Petricolidae, Glauconomidae, Turtoniidae, Neoleptonidae) and within the Veneridae shows minimal taxon sampling leading to weak conclusions and few supported synapomorphies. New phylogenetic analyses on 114 taxa tested the monophyly of Veneroidea, Veneridae, and 17 nominal venerid subfamilies, using morphological (conchological, anatomical) data and molecular sequences from mitochondrial (16S, cytochrome oxidase I) and nuclear (28S, histone 3) genes. Morphological analyses using 45 exemplar taxa and 23 traditional characters were highly homoplastic and failed to reconstruct traditional veneroid classification. Full morphological analyses (31 characters) supported the monophyly of Veneroidea and Veneridae but only when certain taxa were excluded, revealing analytical difficulties caused by a suite of characters associated with neotenous or miniaturized morphology. Molecular analyses resulted in substantially higher clade consistency. The combined molecular data set resulted in significant support for a particular topology. The monophyly of Veneridae was supported only when Petricolidae and Turtoniidae were subsumed, and recognized as members with derived or neotenous morphologies, respectively. Morphological character mapping on molecular trees retained a high level of homoplasy, but revealed synapomorphies for major branch points and supported six subfamily groups (Dosiniinae, Gemminae, Samarangiinae, Sunettinae, Tapetinae, combined Chioninae + Venerinae). Glauconomidae and Neoleptonidae are provisionally maintained in Veneroidea pending further study; Petricolinae and Turtoniinae are placed in Veneridae. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 148 , 439–521.