The mechanism of calcium transport in mitochondria isolated from the marine mussel, Mytilus edulis (L.)

Isolated mussel mitochondria produced a less pronounced transient stimulation of respiration upon the addition of Ca²⁺ in a reaction medium containing Pi and a slower rate of Ca²⁺ transport compared to rat liver mitochondria. The initial rates of Ca²⁺ transport in the absence of Pi were more similar and both types of mitochondria possessed a sigmoidal relationship between the initial rate of Ca²⁺ transport and the free Ca²⁺ concentration $\text{(‘Km’ ? 5μM)}$. Ruthenium red produced an equal maximal inhibition of the initial rate of Ca²⁺ transport in both types of mitochondria but mussel mitochondria were rather more resistant to the inhibitor. The major difference found was that approximately 15 nmoles La³⁺ mg protein^?1 was required to produce maximal inhibition of the initial rate of Ca²⁺ transport in mussel mitochondria compared to approximately 1.0 nmole La³⁺ mg protein^?1 in rat liver mitochondria. It is concluded that mussel mitochondria possess a comparable Ca²⁺ transporter to vertebrate mitochondria and possible reasons for resistance to La³⁺ are discussed.     

Effects of moderate and severe iron deficiency chlorosis on fruit yield, appearance and composition in pear (Pyrus communis L.) and peach (Prunus persica (L.) Batsch)

The effects of different levels of Fe-deficiency chlorosis on the fruit yield, appearance and composition of pear and peach trees grown in field orchards have been studied. The major effect of Fe deficiency in both species was a large yield reduction, even when chlorosis was moderate, associated to decreases in fruit tree load. Fruit size increased with moderate chlorosis in both species and decreased with severe chlorosis in peach. In peach, moderate or severe chlorosis affected uniformly all branches, leading to firmer fruits with higher acidity, total phenolics and carboxylates. This indicates a delayed maturity that can be attributed to a low C-availability for fruits. In Fe-deficient pear trees, the majority of fruits (98%) were on non-chlorotic or moderately chlorotic branches, and fruits were less green and firm with an increased sugars/acids ratio. This indicates an advanced fruit maturity that can be attributed to an increased C-availability for fruits. All chlorosis levels increased within-tree variation in fruit appearance.     

Experimental test of biodeposition and ammonium excretion from blue mussels (Mytilus edulis) on eelgrass (Zostera marina) performance

Blue mussels and eelgrass have been found to coexist in many locations. However, knowledge of the interactions between these species is limited. Two experiments were conducted in the laboratory, a “Deposit” and an “Epiphyte” experiment. The Deposit experiment examined possible effects of increasing load of blue mussel (Mytilus edulis) biodeposits on sediment biogeochemistry and eelgrass (Zostera marina) performance. Z. marina mesocosms received normal or high loads of mussel biodeposits (Normal and High), while no biodeposits were added to the Control. High dosage had overall negative effects on Z. marina, which was reflected as lower leaf numbers and biomass and accumulation of elemental sulphur in rhizomes. The sediment biogeochemical conditions were altered, as the mussel biodeposits enhanced sulphate reduction rates and increased sulphide concentrations in the porewater, which may result in sulphide invasion and reduced growth of Z. marina.In the Epiphyte experiment effects of mussel excretion, with particular emphasis on ammonium, on the growth of Z. marina and their epiphytes were examined. A thick cover of epiphytes developed on Z. marina growing together with M. edulis, and the relative growth rate was reduced with 20% compared to plants from control without mussels. Overall the experiments showed negative effects on Z. marina growing together with M. edulis, thereby supporting a preceding field study by Vinther et al. [Vinther, H.F., Laursen, J.S., Holmer, M. 2008. Negative effects of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds in Flensborg fjord, Denmark. Est. Coast Shelf. Sci. 77, 91-103.].     

Seasonal changes in flesh weight and biochemical composition of mussels (Mytilus edulis L.) in the Conwy Estuary,North Wales

Sublittoral Mytilus edulis L. from natural mussel beds of the Conwy Estuary fishery exhibited an annual cycle of dry flesh weight, biochemical composition, and caloric value during 1971–1974.Mean percentage values of the main components of dry flesh, with seasonal extremes in parentheses, were: protein 58.7 (46.4–73.1), carbohydrates 22.5 (4.1–36.7), lipids 7.0 (3.9–9.6), and ash 11.8 (8.8–17.2). The mean caloric values of dry flesh were 5.57 kcal/g ash-free and 4.92 kcal/g ashinclusive.Individual dry flesh weight was highest in summer and autumn, when protein and carbohydrate were maximal, and decreased through the winter to a post-spawning minimum in spring. Weight loss in winter resulted from rapid utilization of carbohydrate (glycogen) reserves and a depletion of both protein and lipid content. It is considered likely that mussels were then stressed by food shortage at the time when metabolic demands, due to gametogenesis, were highest.During the six main fishing months, October to March, the average weight of dry flesh fell by 30–50 % and caloric content by 35–45 %. The likelihood of similar losses in cultivated mussel stocks is indicated and the need for comparable information in fishery management is emphasized. The extent to which predators compensate for these seasonal changes in prey quality also requires examination.     

Effects of temperature,salinity and aerial exposure on predation and lysosomal stability of the dogwhelk Thais (Nucella) lapillus (L.)

The ingestion and absorption rate of standard length Thais lapillus (L.) stepwise-acclimated to constant temperature-salinity conditions and preying on Mytilus edulis (L.) varied directly with environmental salinity at 10, 15 and 20°C. Dogwhelk ingestion and absorption rates indicate that cold torpor existed at 5°C and heat stress was evident at 20°C. The feeding cycle duration was significantly longer for dogwhelks acclimated to 20%. S than in those acclimated to 30%. S at 10°C even though no significant difference existed between the two groups of snails in the drilling and ingestion or postfeeding phases of the cycle. Ingestive conditioning of dogwhelks to mussels occurred; the duration of the drilling and ingestion and total feeding cycle declined as a function of the number of mussels consumed by a snail. Dogwhelks of all sizes prey on a wide length range of mussels and there is also a high degree of variability in the ingestion rate of snails as a function of their size. A prominent feature of the lack of a relationship between dogwhelk ingestion rate and snail size was that the percentage of nonfeeding snails increased at low salinity and temperature extremes. Digestive-tubule cell lysosomal stability was tested as an index of digestive capability and animal condition; in stepwise-acclimated dogwhelks, it correlated well with their ingestion and absorption rates. The ingestion rate of dogwhelks acclimated to 30%. S and subjected to a 30?17.5?30%. S semidiurnal pattern of fluctuating salinity for 21 days was significantly lower than for snails maintained at 30%. S; however, snails acclimated to 17.5%. S and exposed to the same pattern of fluctuating salinity fed at a higher rate than snails maintained at 17.5%. S. Aerial exposure of snails maintained at 30%. S and 10°C water temperature resulted in an ingestion rate 2.1 times faster than for snails constantly submerged suggesting that tidal emersion is not always stressful to intertidal carnivores. The postfeeding phase of the feeding cycle was shortened in dogwhelks subjected to aerial exposure. Although significant variation occurred in digestive-tubule cell lysosomal stability during the first cycle of fluctuating salinity, the variability had declined significantly by Day 21. This observation suggests that digestive tubule lysosomal stability becomes adapted to a fluctuating osmotic environment, although the initial changes in lysosomal stability are probably related to intralysosomal protein catabolism and production of amino acids for intracellular osmoregulation. Variations in the osmotic environment of T. lapillus have resulted in unexpected outcomes with respect to their ingestion rate under conditions of fluctuating salinity and aerial exposure.     

Effects of salinity on the respiration and heart rate of the common mussel, Mytilus edulis L., and the black chiton, Katherina tunicata (Wood)

The rate of oxygen consumption of stepwise acclimated Mytilus edulis L. increased linearly from 30 to 10‰ salinity (S) while that of Katherina tunicata (Wood) was not significantly different between 10 and 30‰ S. Heart rate was 21–22 and 17–18 beats m^?1 in Mytilus edulis and Katherina tunicata, respectively, and no difference was found in the heart rate of either species acclimated stepwise to 10, 20 or 30‰ S. The average oxygen consumption rate of Mytilus edulis exposed to 12 h, 30-10-30 and 10-30-10‰ S cycles of fluctuating salinity was significantly lower than the respective control rate: there was a similar response during the 30-10-30‰ S cycle in Katherina tunicata. The respiration rate of Mytilus edulis and Katherina tunicata declined as salinity deviated from the control salinity and increased as salinity returned to the control salinity. The rate of oxygen consumption by K. tunicata varied directly with the ambient salinity during the 10-30-10‰ S cycle. The average heart rate of Mytilus edulis was significantly lower during cyclic changes in salinity than at the respective control salinities; a similar relationship existed for Katherina tunicata during the 10-30-10‰ S cycle. Heart rate of Mytilus edulis varied in a parallel manner with oxygen consumption during both cycles. Katherina tunicata heart rate was relatively constant and could not be fitted to a regression line during the 10-30-10‰ S cycle. The normalized heart rate increased to 113% of control at 10‰ S of the 30-10-30‰ S cycle and returned to the control rate by 12 h. The oxygen consumption and heart rate of these two species are not directly coupled to regulation of water volume because different responses are observed with respect to salinity although there is poor water volume regulation in both species.     

Effects of reserpine on reproduction and serotonin immunoreactivity in the stable fly Stomoxys calcitrans (L.)

Biogenic amines are known to play critical roles in key insect behaviors such as feeding and reproduction. This study documents the effects of reserpine on mating and egg-laying behaviors of the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), which is one of the most significant biting fly pests affecting cattle. Two sperm staining techniques were adapted successfully to reveal the morphology of stable fly sperm, for the first time, and determine successful mating in females through the assessment of sperm transfer. This approach was also applied to assess sperm transfer by males treated with different doses of reserpine. Mating or sperm transfer did not occur in flies during the first 3 days after emergence. Thereafter, the percentage of females that mated increased with age. Reserpine treatment of males reduced sperm transfer in a dose-dependent manner. Older males were more sensitive to reserpine treatment than younger flies. Reserpine treatment of 5 days old females reduced the number of eggs laid, but had no effect on egg-hatching rates. Results of immunoreactivity (IR) experiments indicated that serotonin in the neuronal processes innervating male testes was completely depleted by reserpine within 5 h after treatment. This effect was transient as the serotonin immunoreactive signal was recovered in 33.3% of the males at 1 day post-treatment and in 94.4% of the flies at 3 days post-treatment. The results of this study concur with previous findings in other insect species and extend our knowledge of the critical roles biogenic amines play in mating and oviposition behaviors of the stable fly. The work could provide a foundation to further characterize the specific roles of individual biogenic amines and their receptors in stable fly reproduction.     

The impact of iron plaque on La and Nd uptake and translocation in rice (Oryza sativa L.)

The effect of root surface iron plaque formation on the uptake, transfer and accumulation of La and Nd in the rice root system was evaluated by using solution cultures. The results showed that La and Nd pollution stress inhibit formation of rice root surface iron plaques. The amount of La and Nd absorbed by the rice root surface iron plaque rose with the increase of La and Nd solution concentrations. Iron plaque formation on the rice root surface significantly decreases the La and Nd concentrations in rice roots and shoots. At growth solution La concentrations of 0.1, 0.5, and 1.0 mmol.L^? 1, concentrations of La in rice roots with induced iron plaques decreased by 17.1%, 37.4%, and 31.2%, respectively, and concentrations of La in rice shoots decreased by 43.9%, 60.6%, and 27.0%, respectively, when compared to plants with non-induced iron plaques. Also, with Nd solution concentrations of 0.1, 0.5, and 1.0 mmol.L^? 1, the Nd concentrations in rice roots and shoots of plants with induced iron plaques decreased by 21.0–31.7% and 22.7–47.5%, respectively when compared to plants with non-induced iron plaques. Iron plaque formation on the rice root surface affects the accumulation and transfer of La and Nd in rice roots. Accumulation of La and Nd was greater in rice roots than in rice shoots regardless of whether the plants had induced or non-induced iron plaques. Transfer coefficients of iron plague on rice root surface and root system under La treatments were both higher than those under Nd treatment. For rice roots and iron plaques on the root surface, the enrichment coefficient in the La treatment group was less than that in the Nd treatment group, while for rice shoots, the enrichment coefficient in the La treatment group was greater than that in the Nd treatment group. Clearly, the mechanisms governing the effect of iron plaque on La and Nd uptake and transfer in the rice root system are rather complicated.     

Orientated growth of Membranipora membranacea (L.) on the thallus of Saccorhiza polyschides (Lightf.) Batt.

Orientated growth is described in colonies of Membranipora membranacea (L.) growing on the large brown seaweed Saccorhiza polyschides (Lightf.) Batt. On average, 60% of the growth of the colonies was directed proximally along the long axis of the plant, irrespective of the region of the plant on which the colonies were growing or their proximity to its primary meristem. These results seem to rule out the possibility that orientated growth in Membranipora is a response to an age dependent polarity in the host plant, since the tissue ages in opposite directions in the lamina and stipe yet the growth of Membranipora is orientated in the same direction on both. The possibility that directional growth in this species may be a rheopositive response is discussed.     

The ecology of Mytilus edulis L. in exposed rocky intertidal communities

Information is given to show that Mytilus edulis L. is an important component of exposed rocky coast communities of the Western Hemisphere. It is abundant on the exposed coast of Washington State with a potential distribution extending from + 10.6 ft ( + 3.2 m) down to at least 10 m depth: it is not continuous along this entire gradient. It dominates a band from +10.6 ft down to +9.6 ft ( + 3.2 to + 2.9 m) tidal height where it usually intergrades with its congener M. californianus Conrad. Its upper limit appears to be determined by desiccation stress and the lower probably by competition and or predation.In the mid-intertidal zone, from + 5.6 to + 9.6 ft ( + 1.7 to 2.9 m), where M. californianus is dominant, M. edulis occurs in patches of cleared space which usually form in the M. californianus bed matrix in winter months. Here, it acts as an opportunistic species by colonizing quickly and growing rapidly to reproductive size. It is preyed upon by Thais spp. which prefer it to Mytilus californianus and eventually is eliminated from these patches. It also occurs, sometimes abundantly, in tufts of the red alga Endocladia muricata (Postels & Ruprect) J. Agardh at high and mid-intertidal heights.In low intertidal and subtidal regions, to ≈ 10 m depth, Mytulis edulis can be found in refuges of filamentous or intricately arranged substrata which generally offer protection from predation. These are represented by a wide variety of forms such as hydroids. bryozoans, filamentous algae, coralline algae, and kelp with convoluted holdfasts or complex stipes.     

Regeneration of the penis in Balanus balanoides (L.)

In Balanus balanoides (L.) the penis is ‘lost’ each autumn. The regeneration of the penis is described. The primordium contains mesenchyme. The pedicel structures develop early as thickened areas of the exoskeleton and give rise to the characteristic structural features of the mature pedicel. Tissue differentiation begins in the pedicel and later extends to the penis proper which becomes annulated. The ductus eventually opens by a terminal invagination of the exoskeleton.     

Cardiac and branchial physiology associated with copper accumulation and detoxication in the mytilid mussel Perna viridis (L.)

Acute, sublethal, copper exposures induced bimodal physiological responses in the mytilid mussel Perna viridis. Whole animal studies revealed that copper increased heart rate (mild tachycardia) whilst clearance rates and hence gill cilia were simultaneously inhibited. The inhibitory bioamine dopamine reversed tachycardia, indicating that elevated heart rates were due to nervous (serotonergic) stimulation of the myocytes. The excitatory bioamine 5-hydroxytryptamine failed to reverse copper-induced inhibition of clearance rates, suggesting that mechanical damage or blockage of the cilia rather than overt neurotoxicity was impairing the function of the gill. The digestive diverticula was the major copper-accumulating organ although rapid metal exocytosis was evident when individuals were allowed to depurate in uncontaminated seawater. Waste products are expelled from the digestive diverticula into the intestine and as the rectum passes through the heart, elevated rates of ventricular contraction may facilitate egestion of metal-rich faeces. Elevated cardiac activity during exposure to copper may serve to increase ventricular pulsatile pressure on the rectum for the expulsion of metal-rich faecal inclusions (coproliths) derived from the digestive diverticula lysosomes. This study describes a relationship between the heart, alimentary canal and digestive diverticula lysosomes as a pathway for metal detoxication in mytilid mussels.     

Cryopreservation of the Mediterranean mussel (Mytilus galloprovincialis) spermatozoa

The effects of cryoprotectants, cooling rate and freezing on the mussel Mytilus galloprovincialis sperm were evaluated. At the end of each step of the experimental protocol, motility and fertilization ability of sperm were analyzed, compared to fresh semen. Five cryoprotectants were tested in their toxicity level: dimethylsulfoxide, ethylene glycol, 1-2 propylene glycol at 5%, 7%, 10%, 15% and 20% concentration; glycerol and methanol at concentration of 5%, 7% and 10%. The incubation times were 10, 20 and 30 min at 20 ± 1 °C. Only dimethylsulfoxide, ethylene glycol and 1-2 propylene glycol at 5%, 7% and 10% were chosen for the following pre-freezing step. Five adaptation/chilling rates were analyzed: 10 min at 20 ± 1, −2, −1, −0.5 and −0.25 °C/min and the last one was used for testing the best freezing procedure among seven gradients. Particularly, two rapid rates, three slow rates and two double step rates were conducted.Thawing results showed that M. galloprovincialis sperm are very sensitive to rapid pre-freezing and freezing protocols and only a slow procedure assured good motility and fertilization percentages.     

Geographical variation in leucine aminopeptidase in Mytilus edulis L. From the Irish coasts

Phenotypic variation in leucine aminopeptidase has been demonstrated in Mytilus edulis L. from twelve localities in Ireland. It is proposed that one locus with three common and two rare alleles is responsible for one group of variants. The frequencies of the common alleles are significantly correlated with the relative amount of wave action (exposure) at the sites investigated. M. edulis seems to exhibit an above average amount of genetic variation thereby paralleling the variations in growth rate, shell morphology, filtration rate, and certain kinetic parameters previously recorded amongst individuals of this species. In view of the apparently close correlation between genotype and environmental conditions and since genotype in other species is known to control survival and growth rate, genetic studies of the kind described here could clearly have important implications for the commercial mussel fishery.     

Effects of hypoxia and body size on the oxygen consumption of the bivalve Arctica islandica (L.)

The relationship between oxygen consumption and body weight has been examined in Arctica islandica (L.).Large Arctica exhibit a high degree of respiratory independence under hypoxic conditions; like other species studied, respiratory independence increases markedly with increasing body size. Respiratory independence can also be modified by temperature and physiological condition and it is concluded that the division of species per se into oxygen regulators and oxygen conformers is not merited. These terms describe only the extremes of what is a variable capacity to maintain respiratory independence during hypoxia.     

Dormancy of Medicago marina (L.) seed

Medicago marina (L.) is a Mediterranean species whose seeds show strong dormancy that prevents germination. We used an integrated approach of physiological analyses and proteomics to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, we evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at −20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay. The ABA content of germinated and non-germinated mature (control) and treated seeds was determined. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signalling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications.     

In vitro characterization of the Ac locus in white clover (Trifolium repens L.)

Microsomal fractions from developing shoots of adult white clover plants (of genotype AcAc) and cotyledons of dark germinated clover seedlings can synthesize 2-hydroxy-2-methylpropanenitrile and 2-hydroxy-2-methylbutanenitrile, the aglycone precursors of the cyanogenic glucosides, linamarin and lotaustralin, from various precursors in the presence of NADPH. l-Valine, 2-methylpropanal oxime, and 2-methylpropanenitrile are converted to 2-hydroxy-2-methylpropanenitrile and are detected as cyanide and acetone. l-Isoleucine and 2-methylbutanal oxime are converted to 2-hydroxy-2-methylbutanenitrile and are detected as cyanide and 2-butanone. At least two steps in these conversions are missing in microsomes from plants of genotype acac.     

Effects of selection criteria on yield stability in chickpea (Cicer arietinum L.)

Summary Selection in the F₃ generation for seed yield, fruiting branches/plant, effective pods/plant, and seed index (100-seed weight) was carried out in two chickpea crosses. Sixty F₅ lines (15 lines/selection criterion) along with check variety were evaluated for seed yield in three distinct environments. The effects of selection criteria on yield stability was examined using linear regression approach and genotype-grouping technique. There were no differences between selection criteria for linear yield responses of F₅ lines to different environments. Within all four selection criteria the lines showed similar linear responses. The non-linear component was relatively higher for lines selected for effective pods and seed index than lines selected for yield and fruiting branches. On the basis of mean yield and coefficient of variation across environments, the seed index was the least effective selection criterion for developing high yielding and stable lines. When the results of stability parameters and genotype-grouping technique were considered together, selection for yield and fruiting branches was highly effective for isolating stable and high yielding lines.