Temperature and salinity tolerances of larval Californian grunion, Leuresthes tenuis (Ayres): A comparison with gulf grunion, L. Sardina (Jenkins & Evermann)

Temperature and salinity tolerances were determined for larval California grunion, Leuresthes tenuis (Ayres), and compared with previous data for Gulf of California grunion, L. sardina (Jenkins & Evermann). Larvae of similar age and acclimation history showed little interspecific difference in thermal tolerance, as measured by half-hour LT₅₀ values for 20–30 day old late postlarvae acclimated at various temperatures, and by upper and lower incipient lethal temperatures for 18°C-acclimated prolarvae. The upper incipient lethal temperature differed by 1 deg.-C (32°C for L. tenuis, 31°C for L. sardina), while the lower incipient lethal temperature for the 18°C acclimated prolarvae of both species was 7.5°C. L. tenuis larvae were much less euryhaline than L. sardina, with incipient lethal salinities of 4.2–41 %. for prolarvae and 8.6–38 %. for 20-day-old postlarvae; comparable values for L. sardina are 4–67.5 %. and 5–57.5 %. Both species show a decrease in temperature and salinity tolerance with age. The larvae of these disjunct congeners show a significant physiological divergence in euryhalinity but not in overall temperature tolerance. These tolerances are discussed in relation to the respective geographic ranges and behavioral responses of the two species.     

Respiratory and osmoregulatory responses of the hermit crab, Clibanarius vittatus (Bosc), to salinity changes

Intertidal hermit crabs were stepwise acclimated to 10, 20, and 30‰ salinity (S) and 21 ± 1 °C. Hemolymph osmolality, sodium, chloride, and magnesium were isosmotic (isoionic) to ambient sea water at 30‰ and hyperosmotic (hyperionic) at 20 and 10‰ S, while hemolymph potassium was significantly hyperionic in all acclimation salinities. Total body water did not differ significantly at any acclimation salinity. Oxygen uptake rates were higher in summer-than winter-adapted crabs. No salinity effect on oxygen consumption occurred in winter-adapted individuals. Summer-adapted, 30‰ acclimated crabs had a significantly lower oxygen consumption rate than those acclimated 10 and 20‰ S. Crabs exposed to 30 10 30‰ and 10 30 10‰ semidiurnal (12 h) and diurnal (24.8 h) fluctuating salinity regimes showed variable osmoregulatory and respiratory responses. Hemolymph osmolality followed the osmolality of the fluctuating ambient sea water in all cases, but was regulated hyperosmotically. Hemolymph sodium, chloride, and magnesium concentrations were similar to hemolymph osmolality changes. Sodium levels fluctuated the least. Hemolymph potassium was regulated hyperionically during all fluctuation patters, but corresponded to sea water potassium only under diurnal conditions. The osmoregulatory ability of Clibanarius vittatus (Bosc) resembles that reported for several euryhaline brachyuran species. The time course of normalized oxygen consumption rate changed inversely with salinity under semidiurnal and diurnal 10 30 10‰ S fluctuations. Patterns of 30 10 30‰ S cycles had no effect on oxygen consumption rate time course changes. The average hourly oxygen consumption rates during both semidiurnal fluctuations were significantly lower than respective control rates, but no statistical difference was observed under diurnal conditions.     

Respiratory changes in the euryhaline clam, Mulinialateralis (Say), over a range of temperature and salinity combinations

The combined effects of five temperatures (15, 20, 25, 30, and 32 °C) and five salinities (10, 15, 20, 25, and 35%.) on respiratory metabolism in the euryhaline clam, Mulinia lateralis (Say), were determined from polarographic measurements of oxygen consumption. Although both the effects of temperature and salinity were statistically significant as well as their interaction effects, the effect of temperature was greater. Euryhalinity (previously ascribed to M. lateralis based only on its geographical distributions) was reflected physiologically by the few significant differences between respiration rates in various salinities at a given temperature. Significant differences were most often between rates in 20%. and the 10%. or 35%. extremes. Consistently highest rates in 20%. may reflect a salinity preferendum since this salinity was similar to long-term mean habitat salinity.     

Carapace color change in Uca pugilator as a response to temperature

Brachyurid species have various coloration patterns that fluctuate among individuals due to behavioral interactions or a changing environment. In the fiddler crab Uca pugilator, the historical notion is that color change is regulated by circadian rhythms. In this study, color patterns of U. pugilator were affected by changes in temperature; crab carapaces become light in warm temperatures and dark in colder temperatures. The response to temperature occurred within 15 min (often within 5 min of exposure to the treatment), suggesting that temperature may play a key role in color change, and it is activated not through a hormonal pathway, but rather a direct response of the chromatophores. Color change occurred differently between day and night for each sex, which implies that endogenous rhythms are not the sole mechanism for color change in U. pugilator. Both sexes became darker in the cold treatment, however there were differences between the sexes with high temperatures. Females did not show significant coloration changes, while males became significantly lighter and more speckled. Results from this study suggest sex-specific constraints in response to temperature that could be associated to morphological body mass to surface area ratios, as males have large cheliped, which may be involved in thermoregulation. Constraints could also be associated to different diel activities that each sex performs or visual cues associated with mating behaviors.     

Ontogenetic change in the relationship between metabolic rate and body mass in a sea bream Pagrus major (Temminck & Schlegel)

Ontogenetic changes in the relationship between resting rate of oxygen consumption and wet body mass were examined at 20° C with the sea bream Pagrus major ranging from 0.00020 g (weight just after hatching) to 270 g (weight at 530 days old). There was a triphasic relationship between oxygen consumption of an individual fish M (μl min⁻¹) and body mass W (g). During a very early stage (weight 0.00020–0.00025 g), corresponding to the pre-larval stage and with the transitional period to the post-larval stage, there was no substantial change in body mass. The mass–specific metabolic rate M/W (μl g⁻¹ min ¹) showed no clear relationship to body mass as expressed by the equation M/ W =4.86 + 1.47 D , where D is age in days. During the post-larval stage (weight 0.00031–0.005 g), M/W remained almost constant independent of body mass following the expression M = 12.5 W0 .949. During the juvenile and later stages (weight 0.005–270 g), M/ W decreased with increasing body mass following the expression M = 6.3 W ^0.821 which is significantly different from the expression for the post-larval stage ( P < 0.001). Ontogenetic changes in the metabolism-body mass relationship are discussed from the viewpoint of relative growth of organs with different metabolic activities.     

Microbial response to salinity change in Lake Chaka, a hypersaline lake on Tibetan plateau

Previous investigations of the salinity effects on the microbial community composition have largely been limited to dynamic estuaries and coastal solar salterns. In this study, the effects of salinity and mineralogy on microbial community composition was studied by using a 900-cm sediment core collected from a stable, inland hypersaline lake, Lake Chaka, on the Tibetan Plateau, north-western China. This core, spanning a time of 17,000 years, was unique in that it possessed an entire range of salinity from freshwater clays and silty sands at the bottom to gypsum and glauberite in the middle, to halite at the top. Bacterial and archaeal communities were studied along the length of this core using an integrated approach combining mineralogy and geochemistry, molecular microbiology (16S rRNA gene analysis and quantitative polymerase chain reaction), cultivation and lipid biomarker analyses. Systematic changes in microbial community composition were correlated with the salinity gradient, but not with mineralogy. Bacterial community was dominated by the Firmicutes-related environmental sequences and known species (including sulfate-reducing bacteria) in the freshwater sediments at the bottom, but by halophilic and halotolerant Betaproteobacteria and Bacteroidetes in the hypersaline sediments at the top. Succession of proteobacterial groups along the salinity gradient, typically observed in free-living bacterial communities, was not observed in the sediment-associated community. Among Archaea, the Crenarchaeota were predominant in the bottom freshwater sediments, but the halophilic Halobacteriales of the Euryarchaeota was the most important group in the hypersaline sediments. Multiple isolates were obtained along the whole length of the core, and their salinity tolerance was consistent with the geochemical conditions. Iron-reducing bacteria were isolated in the freshwater sediments, which were capable of reducing structural Fe(III) in the Fe(III)-rich clay minerals predominant in the source sediment. These data have important implications for understanding how microorganisms respond to increased salinity in stable, inland water bodies.     

Implications of calcium nutrition on the response of Caesalpinia crista (Fabaceae) to soil salinity

Greenhouse experiments were conducted to assess the effects of supplemental calcium in salinised soil on the response of germination and seedling growth of Caesalpinia crista, L. (Fabaceae). NaCl and CaSO₄·2H₂O were added to the soil and 0:0, !:0, 1:0.25, 1:0.50, 1:0.75, 1:1, 1:1.25, and 1:1.50 Na/Ca ratios were maintained. Salinity significantly retarded the seed germination and seedling growth, but the injurious effects of NaCl on seed germination were ameliorated and seedling growth was restored with calcium supply at the critical level (1:0.50 Na/Ca ratio) to salinised soil. Calcium supply above the critical level further retarded the seed germination and seedling growth due to the increased soil salinity. Salt stress reduced N, P, K and Ca content in plant tissues, but these nutrients were restored by addition of calcium at the critical level to saline soil. The opposite was true for Na⁺. The results are discussed in terms of the beneficial effects of calcium supply on the seedling growth of C. crista grown under saline conditions.     

Changes in the immune response and metabolic fingerprint of the mussel, Mytilus edulis (Linnaeus) in response to lowered salinity and physical stress

Mussels, such as Mytilus edulis, are common keystone species on open coasts and in estuaries and are frequently used in environmental monitoring programmes. Mussels experience a wide range of environmental conditions at these locations, including rapid changes in salinity and physical disturbance (both natural and from aquaculture practices).This paper addressed the hypothesis that reduced salinity will lower mussel blood immune function and influence mussel blood metabolic responses, and that this will in turn increase the susceptibility of mussels to other stresses such as physical disturbance. To test these hypotheses, experiments were conducted in controlled laboratory tank conditions and mussel blood was analysed using a combination of metabolic fingerprinting with FT-IR and immunological assay techniques.Reducing seawater salinity to half that of normal caused a significant reduction in several measures of immune function, including the concentration of haemocytes, percentage of eosinophilic haemocytes and phagocytosis. Mechanical shaking of mussels for 10 min caused a reduction in the level of respiratory burst activity. However, there was no evidence of additive or interactive effects of lowered salinity with shaking on the immune response. Analysis of mussel blood metabolic fingerprints revealed differences in response to half salinity (vs. full salinity) but there were no detectable effects of shaking. Increasing frequency and magnitude of flood events at coastal sites due to climate change could lead to longer, and more frequent, periods of reduced salinity. The potential impact on the immune function of this keystone species within or near estuaries could have knock-on effects on the wider ecosystem including altered nutrient cycling, changes in biodiversity and aquaculture production.     

Phenotypic plasticity in the reef corals Montastraea annularis (Ellis & Solander) and Siderastrea siderea (Ellis & Solander)

Mature colonies of Montastraea annularis (Ellis & Solander) and Siderastrea siderea (Ellis & Solander) were transplanted reciprocally between four reef environments near Discovery Bay, Jamaica. Multivariate analyses of variables describing corallite structures show that colonies of M. annularis change their skeletal morphology after transplantation from that characteristic of their original habitat to that characteristic of the environment to which they were moved. Control colonies of M. annularis, however, retain the morphology characteristic of their original habitat after manipulation. Many colonies of S. siderea similarly altered their morphology after transplantation, but some retained the morphology characteristic of their original habitat. Most control colonies of S. siderea did not change after manipulation. In general, control colonies of S. siderea show more morphologic variation between skeleton deposited before and after manipulation within colonies and also between colonies within populations, than did control colonies of M. annularis.These results indicate that, although M. annularis shows more plasticity than S. siderea. both species have highly plastic phenotypes. A large number of characters describing the architecture of corallites respond to environmental factors such as light intensity, sedimentation rate, water activity, and food availability. The most plastic characters in M. annularis describe coenosteal features and the thickness of thecae. The most plastic characters in S. siderea describe the thicknesses of thecae. septa, and columellae.This study suggests that phenotypic plasticity is an important species attribute in scieractinians and may be a significant mechanism in controlling the distribution and abundance of scleractinians on reefs.     

The growth of Zalerion maritimum (Linder) Anastasiou in response to variation in salinity and temperature

Growth responses of Zalerion maritimum (Linder) Anastasiou to salinity and temperature were measured gravimetrically. F values obtained from a two-way analysis of variance indicated significant (P < 0.0001) salinity, temperature, and interaction effects. A Student-Newman-Keuls multiple-range comparison of mean mycelial dry weights at salinity optima in the temperatures tested showed optimum growth at 20 and 25 °C in 29.7 and 33.0‰, respectively. An alternative quantitation method was developed since cold storage was found to affect inoculum vigor.     

Osteology of Zacco pachycephalus, sensu Jordan & Evermann (1903), with special reference to its systematic position

The skeletal system of Zacco pachycephalus, sensu Jordan & Evermann (1903), is described and compared with that of other related barilines to clarify its systematic position. Osteological characters fall generally into two categories in terms of apomorphic features. The first category is exemplified by autapomorphies such as lower jaw bone shape and the number of branchiostegal rays and hypurals. The latter characters are highly unusual among Cyprinidae. The second category consists of synapomorphies linking Z. pachycephalus and Opsariichthys uncirostris. Specialization of jaw bones for a piscivorous habit is also notable. The quadrate-pterygoid fenestra of Z. pachycephalus and O. uncirostris is considered derived. We conclude that Zacco pachycephalus should be transferred from Zacco to Opsariichthys based on the present osteological analysis.     

Effects of temperature and salinity on yolk utilization in Bairdiella icistia (Jordan & Gilbert) (Pisces: sciaenidae)

The effects of nine different combinations of temperature and salinity on yolk utilization in the eggs and larvae of the sciaenid fish, Bairdiella icistia (Jordan & Gilbert) have been investigated. The rate of yolk absorption was accelerated at higher temperatures, but salinity had only a slight effect. Increased water content resulted in larger yolk sacs at hatching in low salinities and at low temperatures. In all treatments, functional eyes and jaws were formed before the yolk had been completely exhausted. Yolk was utilized most efficiently at the intermediate temperature (24 °C) and lowest salinity (20 %.).     

Respiratory responses to temperature and hypoxia in the nonindigenous Brown Mussel, Perna perna (Bivalvia: Mytilidae), from the Gulf of Mexico

The respiratory responses to increasing temperature and progressive hypoxia were examined relative to temperature acclimation in the nonindigenous, brown mussel, Perna perna (Mytilidae) from the Gulf of Mexico. When oxygen uptake rate (V?_O2) was recorded at near full air O₂ saturation, rate-temperature curves for Texas specimens of P. perna were sigmoidal, V?_O2 generally increasing with increasing temperature but becoming suppressed as temperatures approached 10 and 30 °C, corresponding closely to this species' incipient thermal limits. At each tested temperature, V?_O2 did not differ among individuals acclimated to 15, 20, or 25 °C. Lack of thermal acclimation was also reflected in acclimatory Q₁₀ values>1.0 (range=1.34-2.14) recorded across acclimation groups at test temperatures equivalent to acclimation temperature. Low acute respiratory Q₁₀ values in all acclimation groups across 15-20 °C indicated a limited capacity for thermal regulation of V?_O2 within this temperature range. The ability of P. perna to regulate O₂ uptake with progressive hypoxia was temperature-dependent, increasing from poor O₂ regulation at 10 °C to good regulation at 30 °C. The O₂ regulatory ability of P. perna and other open-water mytilids in declining O₂ concentrations does not greatly differ from that of estuarine heterodont bivalves, suggesting that it is not a major factor preventing open-water species, such as P. perna, from invading estuarine environments. However, P. perna's inability to regulate O₂ uptake at temperatures>25 °C combined with its relatively low upper thermal limit of 30 °C will likely prevent it from establishing permanent estuarine populations on Gulf of Mexico shores.     

Genetic link between Cabeza, a Drosophila homologue of Fused in Sarcoma (FUS), and the EGFR signaling pathway

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that causes progressive muscular weakness. Fused in Sarcoma (FUS) that has been identified in familial ALS is an RNA binding protein that is normally localized in the nucleus. However, its function in vivo is not fully understood. Drosophila has Cabeza (Caz) as a FUS homologue and specific knockdown of Caz in the eye imaginal disc and pupal retina using a GMR-GAL4 driver was here found to induce an abnormal morphology of the adult compound eyes, a rough eye phenotype. This was partially suppressed by expression of the apoptosis inhibitor P35. Knockdown of Caz exerted no apparent effect on differentiation of photoreceptor cells. However, immunostaining with an antibody to Cut that marks cone cells revealed fusion of these and ommatidia of pupal retinae. These results indicate that Caz knockdown induces apoptosis and also inhibits differentiation of cone cells, resulting in abnormal eye morphology in adults. Mutation in EGFR pathway-related genes, such as rhomboid-1, rhomboid-3 and mirror suppressed the rough eye phenotype induced by Caz knockdown. Moreover, the rhomboid-1 mutation rescued the fusion of cone cells and ommatidia observed in Caz knockdown flies. The results suggest that Caz negatively regulates the EGFR signaling pathway required for determination of cone cell fate in Drosophila.     

Ultrastructure of the spermatozoon of the digenean Cricocephalus albus (Kuhl & van Hasselt, 1822) Looss, 1899 (Platyhelminthes, Pronocephaloidea, Pronocephalidae), parasite of “the hawksbill sea turtle” Eretmochelys imbricata (Linnaeus, 1766) in Senegal

The mature spermatozoon of Cricocephalus albus is filiform, tapered at both ends and shows the following features: 2 axonemes of different lengths presenting the 9 + “1” trepaxonematan pattern, 2 bundles of parallel cortical microtubules, a mitochondrion and a nucleus. Nevertheless, the particularity of the spermatozoon of C. albus is its anterior extremity with an apical electron-dense material associated with extramembranar ornamentation, a cytoplasmic dorsolateral expansion and spine-like bodies. To our knowledge, such an anterior extremity of the spermatozoon has not previously been described from a species of the superfamily Pronocephaloidea. Our study provides new data on the mature gamete of C. albus in order to improve our understanding of the pronocephaloidean phylogenetic relationships.     

Movements of bonnetheads, <Emphasis Type="Italic">Sphyrna tiburo</Emphasis>, as a response to salinity change in a Florida estuary

The movement of bonnetheads, Sphyrna tiburo, within an estuarine system on the Gulf of Mexico coast of Florida was examined to define response to salinity change. Shark presence and movements were evaluated by acoustic monitoring and gillnet sampling. Acoustic monitoring data were used to investigate active selection of different zones within the estuary based on differences in salinity among zones. Sharks were monitored for 187 days in 2003 and 217 days in 2004 in salinities ranging from 11.0 to 31.0 ppt in 2003 and 15.8 to 34.6 ppt in 2004. Monitoring data supported the hypothesis that salinity played a role in the distribution and movement of S. tiburo. Catch per unit effort (CPUE) data obtained from gillnet sampling from 1995 to 2004 were examined to determine affinity or avoidance of specific salinities within the study site as calculated using an electivity index. Electivity analysis showed almost no affinity or avoidance for specific salinity values. The difference in results between the CPUE and acoustic monitoring in relation to the potential effects of salinity likely relate to the nature of the data, with acoustic monitoring providing continuous data and CPUE providing snapshot location data. The results of this study suggest that although S. tiburo are collected within a wide range of salinity levels, salinity may affect movement and distribution. Salinity effects may be more pronounced during periods of prolonged and/or large changes in salinity as detected by long-term monitoring.     

Electroantennogram response gradient on the antenna of the European corn borer, Ostrinia nubilalis

The electroantennogram (EAG) response of male moths of the European corn borer (Ostrinia nubilalis) to their two pheromone components, (Z)- and (E)-11-tetradecenyl acetates, were studied. The EAG amplitude of the fast initial phase was approximately proportional to the antennal length. Local EAG responses were obtained along the length of the antenna with multiple electrodes. Response-interaction studies indicated a unique spread of the EAG response in a proximal direction in the antenna. A possible mechanism of the EAG summation was considered. The EAG response characteristic was similar for both (Z)- and (E)-11-tetradecenyl acetate along the length of the antenna.