Energy storage during the transition from endogenous to exogenous feeding in Australian redclaw crayfish Cherax quadricarinatus (Von Martens, 1898)

Summary

The Australian redclaw crayfish Cherax quadricarinatus hatches at an advanced stage. Two post-hatching stages rely on yolk reserves before the organism becomes a juvenile. After a juvenile appears, the yolk is depleted and young crayfish might spend a few days among female pleopods before starting to feed independently. During this phase, the juvenile organism needs alternative energy sources. Offspring from three females were analyzed with histological and histochemical techniques, from hatching until reaching the 2-week juvenile stage, to trace digestive system development and internal organ lipid and glycogen accumulation. Neutral lipids are stored in specialized cells of the hepatopancreatic tissue until the juvenile stage is reached. An increasing rate of accumulation was found. Glycogen was stored in hepatopancreas and tail muscle cells until post-embryo II, and no increasing or decreasing rate was found in storage functions.     

The K+/H+ antiporter LeNHX2 increases salt tolerance by improving K+ homeostasis in transgenic tomato

The endosomal LeNHX2 ion transporter exchanges H⁺ with K⁺ and, to lesser extent, Na⁺. Here, we investigated the response to NaCl supply and K⁺ deprivation in transgenic tomato (Solanum lycopersicum L.) overexpressing LeNHX2 and show that transformed tomato plants grew better in saline conditions than untransformed controls, whereas in the absence of K⁺ the opposite was found. Analysis of mineral composition showed a higher K⁺ content in roots, shoots and xylem sap of transgenic plants and no differences in Na⁺ content between transgenic and untransformed plants grown either in the presence or the absence of 120 mm NaCl. Transgenic plants showed higher Na⁺/H⁺ and, above all, K⁺/H⁺ transport activity in root intracellular membrane vesicles. Under K⁺ limiting conditions, transgenic plants enhanced root expression of the high‐affinity K⁺ uptake system HAK5 compared to untransformed controls. Furthermore, tomato overexpressing LeNHX2 showed twofold higher K⁺ depletion rates and half cytosolic K⁺ activity than untransformed controls. Under NaCl stress, transgenic plants showed higher uptake velocity for K⁺ and lower cytosolic K⁺ activity than untransformed plants. These results indicate the fundamental role of K⁺ homeostasis in the better performance of LeNHX2 overexpressing tomato under NaCl stress.     

Molecular data illuminate cryptic nudibranch species: the evolution of the Scyllaeidae (Nudibranchia: Dendronotina) with a revision of Notobryon

Scyllaeidae represents a small clade of dendronotoid nudibranchs. Notobryon wardi Odhner, 1936, has been reported to occur in tropical oceans from the Indo‐Pacific and eastern Pacific to temperate South Africa. The systematics of Notobryon has not been reviewed using modern systematic tools. Here, specimens of Notobryon were examined from the eastern Pacific, the Indo‐Pacific, and from temperate South Africa. Additionally, representatives of Scyllaea and Crosslandia were studied. Scyllaeidae was found to be monophyletic. Notobryon was also found to be monophyletic and is the sister group to Crosslandia plus Scyllaea. The molecular data also clearly indicate that within Notobryon, at least three distinct species are present, two of which are here described. Genetic distance data indicate that eastern Pacific and South African exemplars are 10–23% divergent from Indo‐Pacific exemplars of Notobryon wardi. Scyllaea pelagica has been regarded as a single, circumtropical species. Our molecular studies clearly indicate that the Atlantic and Indo‐Pacific populations are distinct and we resurrect Scyllaea fulva Quoy & Gaimard, 1824 for the Indo‐Pacific species. Our morphological studies clearly corroborate our molecular findings and differences in morphology distinguish closely related species. Different species clearly have distinct penial morphology. These studies clearly reinforce the view that eastern Pacific, Indo‐Pacific, and temperate biotas consist largely of distinct faunas, with only a minor degree of faunal overlap. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 165 , 311–336.     

Comparative analysis of leaf angle and sclerophylly of Aspidosperma quebracho‐blanco on a water deficit gradient

Abstract Aspidosperma quebracho‐blanco is found throughout the Chaco (17°?33°S) in Argentina, and it is the dominant tree species in the arid Chaco. Under the hypothesis that morpho‐physiological features of A. quebracho‐blanco change as a function of its geographical position on a water deficit gradient, it was predicted that with increasing water stress, leaf angles (specifically horizontal) would be greater and mean values of the leaf mass per area would increase. These leaf characteristics were compared at three points on a water deficit gradient extending from the humid Chaco through semi‐arid Chaco to the arid Chaco of Argentina (south‐west to north‐east rainfall gradient, from 350 to 1200 mm annual mean precipitation). Twig and leaf positions were modified and water potentials were measured at the highest heating hour of the day at a site of the arid Chaco. Daily and seasonal water potential variations of untreated twigs were also observed. Leaf angle modification towards horizontal produced more negative twig water potentials with respect to those of leaves in non‐horizontal positions. The comparison of the three sites along the gradient showed contrasting patterns of leaf‐angle frequency distribution of adults. In Chancaní (mean annual temperature: 18–24°C, mean annual precipitation: 450 mm, arid) there was a higher frequency of angles near 90° for non‐pendulous and about 270° for pendulous trees. Leaf angles in Copo (semi‐arid) and Chaco National Park (mean annual temperature: 20–23°C, mean annual precipitation: 1300 mm humid) were widely distributed with higher frequency towards the angles near 0° and 180°. This sclerophyllous tree species showed plasticity in its leaf traits along the precipitation gradient. Plasticity in leaf mass per area and leaf position enables plants to develop efficiently in contrasting environmental conditions of humidity and aridity.     

Effects of livestock breed and grazing pressure on ground‐dwelling arthropods in Cantabrian heathlands

Abstract 1. The effects of different goat breeds and grazing pressures on epigeal arachnids (Lycosidae and Opiliones) and ground beetles (Carabidae) were assessed in a heath–gorse shrubland located in the north of the Iberian Peninsula. Three treatments (low grazing pressure with Cashmere breed, high grazing pressure with Cashmere breed, and high grazing pressure with local Celtiberic breed) with three replicates of each treatment were allocated randomly to nine plots. 2. Arthropod fauna abundance, diversity, and species richness were estimated using pitfall trapping over 3 years (2003, 2004, and 2005). Vegetation cover, composition, and height were assessed along transects and above‐ground plant biomass was sampled in quadrats. 3. Lower grazing pressure led to lower herbaceous cover and higher heather cover than high grazing pressure. Overall, it did not enhance arthropod diversity or abundance, but the abundance and species richness of carabids, and abundance of lycosids like Pardosa pullata, were higher under high stocking rates, whereas Opiliones were favoured by the low stocking rates. Although it has been assumed that traditional breeds enhance biodiversity, the present study found no significant differences for both arthropod fauna and vegetation between the goat breeds. 4. Arthropod–vegetation relationships were examined by constrained ordination. Fauna assemblages followed a gradient from closed canopy shrubland areas, in the lowest grazing pressure, to grassier open canopy areas resulting from higher grazing pressure, revealing the importance of grazing management as a driver of arthropod community structure of the heathland.     

Ozone‐induced reductions in below‐ground biomass: an anatomical approach in potato

Potato plants were grown in open‐top chambers under three ozone concentrations during two complete cropping seasons (93 and 77 d in 2004 and 2005, respectively). The effects of chronic exposure to ozone on leaf anatomy, cell ultrastructure and crop yield were studied. Severe cell damage was found, even at ambient ozone levels, mainly affecting the spongy parenchyma and areas near the stomata. Damage to the cell wall caused loss of cell contact, and loss of turgor pressure due to tonoplast disintegration, contributed to cell collapse. Phloem sieve plates were obstructed by callose accumulation, and damaged mesophyll cells increased their starch stores. Tuber yield fell sharply (24–44%), due to the biggest tubers becoming smaller, which affected commercial yield. These anatomical findings show the mechanisms of ozone effect on assimilate partitioning, and thus crop yield decrease, in potato. Further implications of ozone causing reductions in below‐ground biomass are also discussed.     

Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes?

1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long‐term limnological data set to document changes in the food‐web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L^?1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents from ricefields. 3. Chlorophyll a concentration was reduced by half (annual mean of 180 μg L^?1). Cyanobacteria abundance remained high but its composition changed towards smaller species, both filamentous and chroococcal forms. 4. Cladocera abundance increased and reached peaks twice a year (December to March and July to September). After nutrient reduction, short‐term clear‐water phases (up to 5 weeks) occurred during February to March in several years, concomitant with annual flushing of the lake and lower fish densities. The abundance of Cladocera in winter contrasted with the spring peaks observed in northern restored shallow lakes. The zooplankton to phytoplankton biomass ratio remained lower than in northern temperate shallow lakes, probably because of fish predation on zooplankton. 5. Improvement of the water quality of Lake Albufera remained insufficient to counteract littoral reed regression or improve underwater light allowing submerged plants re‐colonise the lake. 6. Sewage diversion from Lake Albufera impacted the food web through the plankton, but higher trophic levels, such as fish and waterfowl, were affected to a lesser degree. Although the fish species present in the lake are mainly omnivorous, long‐term data on commercial fish captures indicated that fish communities changed in response to nutrient level and trophic structure as has been observed in restored shallow lakes at northern latitudes. 7. Phosphorus concentrations produced similar phytoplankton biomass in Lake Albufera as in more northern shallow lakes with abundant planktivorous fish and small zooplankton. However, in Lake Albufera, high average concentrations were maintained throughout the year. Overall, results suggest that nutrient control may be a greater priority in eutrophicated warm shallow lakes than in similar lakes at higher latitudes.     

RELATIONSHIP BETWEEN TASTE AND CHEWING PATTERNS OF VISCO-ELASTIC MODEL FOODS

The jaw movements and muscular activity of masticatory muscles of five assessors, having bitterness thresholds about 8 μM quinine in water, were monitored throughout chewing of similar strength gelatin gels containing 0, 40, 70 or 100 μM quinine. Gel bitterness ratings were not related to sensory texture which was 78kN/m² by shear test. On average, 100 μM quinine gels were as bitter as 7 to 30 μM quinine in water, depending on the assessor. Chewing patterns were not affected by concentration of quinine in the gels. During mastication of acceptable gels, there appears to be no feedback from taste to the motor control of mastication. In gels of the same consistency and the same concentration of quinine, assessors who chewed more rated higher for bitterness. The implications for mimicking mastication by machine and the training of assessors for solid foods are discussed.