Dispersion and settlement of two sympatric sculpins of the genus Gymnocanthus

Larval dispersion rather than adult migration generally leads to the worldwide expansion of fishes. Species of the genus Gymnocanthus have expanded geographically while undergoing allopatric speciation. Of this genus, while Gymnocanthus tricuspis inhabits the Arctic Ocean and surrounding area, G. herzensteini and G. intermedius occur around northern Japan. Larval early life histories of G. herzensteini and G. intermedius from northern Japan and G. tricuspis from Unalaska Island were investigated to estimate their dispersal potential during larval stages. The larval and juvenile abundances of G. herzensteini and G. intermedius were highest in May in shallow sandy bottoms below 7 m in depth, and the body sizes were 9.7–34.6 mm notochord length (NL) and/or standard length (SL) in G. herzensteini and 8.4–46.7 mm NL and/or SL in G. intermedius. Two egg masses of G. tricuspis (1.92 ± 0.08 mm in diameter) and hatched larvae (6.20 ± 0.19 mm NL) were collected in March. Compared with other sculpins in previous studies, the body sizes of G. herzensteini and G. intermedius at hatch are large and at settlement are small, while both hatch and settlement sizes of G. tricuspis are much larger. Counting micro-increments between the hatch check and settlement marks in G. herzensteini and G. intermedius demonstrated that the pelagic larval durations for 2 weeks with an immature body suggests that these species cannot disperse widely during the pelagic phase, while pelagic larvae of Arctic species such as G. tricuspis with long pelagic larval durations could disperse.     

Use of the lateral line for feeding in two Lake Baikal sculpins

Batrachocottus baicalensis , endemic to Lake Baikal, Russia, has wider lateral line canals than Paracottus kneri , which also inhabits Siberian streams. In quiet water B. baicalensis responded to amphipods at a greater distance than did P. kneri. Batrachocottus baicalensis also moves less often from search positions than does P. kneri . Fish responded to faster moving prey at a greater distance than slower prey. They also responded to a greater distance to prey moving more parallel to the fish's body surface. In an artificial stream B. baicalensis responded only to prey that touched them whilst P. kneri responded to both swimming prey and prey that contacted them. It is argued that B. baicalensis is primarily an ambush predator that is a habitat specialist and P. kneri is a cruising predator that visits many habitats.     

Phylogenetics of the marine sculpins (Teleostei: Cottidae) of the North American Pacific Coast

With 92 species along the North American Pacific Coast, marine sculpins represent the most species-rich radiation of fishes in this region. I used the mitochondrial cytochrome b gene and the nuclear ribosomal S7 intron for 99 species (76 North American, 19 Asian, and four North Atlantic) to produce the most complete phylogenetic hypothesis yet generated for this assemblage. Maximum likelihood and Bayesian analyses produced highly similar tree topologies. While many previously proposed groupings based on morphology are recovered, the molecular data suggest that a number of genera are para- or polyphyletic. However, this analysis supports the monophyly of one large clade that is found exclusively along the North American Pacific Coast (Chitonotous–Ruscarius–Artedius–Orthonopius–Clinocottus–Leiocottus–Oligocottus). Some sibling species have disjunct ranges, suggesting allopatric speciation. However, many other sibling species have largely overlapping ranges, and repeated habitat shifts appear to have facilitated diversification.     

A method for analyzing non-Newtonian blood viscosity data in low shear rates

Viscosity measurements were made using a coaxial rotating cylinder viscometer for blood having various volume fractions of red cells. A method is described for analyzing non-Newtonian blood viscosity in low shear rates by taking account of an increase or a decrease in size of red cell aggregates induced by shear. Our results are compared with empirical formulae presented by Scott Blair, Weaver-Evans-Walder and Thurston.     

Effects of extracellular environments on the motility of spermatozoa in several marine sculpins with internal gametic association

• 1.1. The motility of spermatozoa in several marine sculpins, which exhibit a special reproductive manner of the internal gametic association, was measured in various artificial solutions, ovarian fluid and seminal plasma.
• 2.2. In the elkhorn sculpin, Alcichthys alcicornis, spermatozoa showed high motility in solutions of 300 to 400 mOsm/kg, containing sodium ion, with pH higher than 7.5, which coincided with the nature of ovarian fluid of the fish.
• 3.3. Spermatozoa of sunrise sculpin, Pseudoblennius cottoides, and elegant sculpin, Bero elegans, were motile at osmolalities isotonic to the ovarian fluid but not at osmolalities higher than 500 and 800 mOsm/kg, respectively, indicating that the gametic association in these fish is carried out exclusively in their ovaries.
• 4.4. Spermatozoa of littledragon sculpin, Blepsias cirrhosus, were motile at osmolalities higher than 300 mOsm/kg, but not in sea water, suggesting an internal gametic association to occur in this species of sculpins.
• 5.5. The results indicate that spermatozoa of the marine sculpins with the internal gametic association show their motility in environmental conditions appropriate to respective reproductive modes.

     

On temperature factor and the effect of viscosity on blood temperature in the arteries

A mathematical theory which could be used to explain a clinical observation in some sickle-cell anemia patients is proposed. It is shown that if the energy stored in the elastic walls of the artery of such a patient is accompanied by thermal effects, then the existence of a local hot spot on the body of a sickle-cell anemia patient could be due to shock formation even when the viscosity of the blood is zero. On the other hand, if the energy stored is not accompanied by thermal effects, then a jump in the temperature can only occur if the viscosity is not zero. We give the location of such a jump in the temperature and the time of its occurrence in both cases.     

Methane oxidation potential in the water column of two diverse coastal marine sites

Methane oxidation in the water column was investigated at two nearshore marine environments with relatively high concentrations of dissolved methane. In the northern Gulf of Mexico, high methane oxidation rates were observed at the pycnocline, with the highest oxidation rate corresponding to the most negative bacterial ¹³C values. These low isotopic values occurred during the winter when overall bacterial productivity was low, suggesting that at this time of the year, methanotrophs in the Gulf could make up a significant portion of the overall bacterial assemblage. Although methane oxidation also occurred during more productive times (i.e., summer), the isotopic signal of methane oxidation was not observed in the bacterial biomass because of the higher overall bacterial productivity. The other site, Cape Lookout Bight, NC, is a small marine embayment where methane is produced in the organic-rich sediments. No measurable rates of methane oxidation in the water column occurred, and no anomalously low ¹³C values of the bacterioplankton were measured. In both environments, methane production and oxidation appear to be spatially coupled, occurring at/near the pycnocline in the northern Gulf of Mexico and at the sediment-water interface at Cape Lookout Bight, NC.     

Evaluation of two cold thermoregulatory models for prediction of core temperature during exercise in cold water.

Cold thermoregulatory models (CTM) have primarily been developed to predict core temperature (T(core)) responses during sedentary immersion. Few studies have examined their efficacy to predict T(core) during exercise cold exposure. The purpose of this study was to compare observed T(core) responses during exercise in cold water with the predicted T(core) from a three-cylinder (3-CTM) and a six-cylinder (6-CTM) model, adjusted to include heat production from exercise. A matrix of two metabolic rates (0.44 and 0.88 m/s walking), two water temperatures (10 and 15 degrees C), and two immersion depths (chest and waist) were used to elicit different rates of T(core) changes. Root mean square deviation (RMSD) and nonparametric Bland-Altman tests were used to test for acceptable model predictions. Using the RMSD criterion, the 3-CTM did not fit the observed data in any trial, whereas the 6-CTM fit the data (RMSD less than standard deviation) in four of eight trials. In general, the 3-CTM predicted a rapid decline in core temperature followed by a plateau. For the 6-CTM, the predicted T(core) appeared relatively tight during the early part of immersion, but was much lower during the latter portions of immersion, accounting for the nonagreement between RMSD and SD values. The 6-CTM was rerun with no adjustment for exercise metabolism, and core temperature and heat loss predictions were tighter. In summary, this study demonstrated that both thermoregulatory models designed for sedentary cold exposure, currently, cannot be extended for use during partial immersion exercise in cold water. Algorithms need to be developed to better predict heat loss during exercise in cold water.     

Seasonal cycles in total chemical composition of two Lake Baikal benthic-pelagic sculpins (Cottocomephorus, Cottoidei)

Annual cycles in chemical composition of the body, liver, gonads, red and white muscles were determined for two medium fat sculpins, Cottocomephorus grewingki and C. inermis , endemic to Lake Baikal. Their total lipid content ranged from 3 to 9% during the year. The content of defatted dry substance was 14–17%, similar to the protein content of the other Baikalian cottoid fishes. The prespawning period was characterized by a positive lipid and protein balance in both species. In C. grewingki the liver performed largely a metabolic function, whereas in C. inermis it served also as a storage site for lipid reserves. During spawning, total body lipids of females of both species showed a two- to threefold decrease. Males of C. grewingki guarding nests deplete greatly their total body lipids, which decrease seven- to ninefold by the time of larval hatching in comparison with the prespawning period, and constitute 1–2%. After spawning, lipid reserves of C. grewingki were quickly restored to the initial level (from about 3 to 9%) and maintained during the long sexual maturation period. In C. inermis total body lipids increased only twofold in comparison to those observed during the spawning period.     

Feeding ecology of two planktonic sculpins, Comephorus baicalensis and Comephorus dybowskii (Comephoridae), in Lake Baikal

Planktonic sculpins (Comephorus baicalensis and Comephorus dybowskii) are endemic to Lake Baikal, and their migration behavior is characterized by their strange movements, which occur only vertically. We investigated their detailed food sources at each growth stage by stable isotope analyses in combination with stomach content analysis. At all growth stages, both fishes and amphipods were the main diet for C. baicalensis, whereas amphipods alone were the main diet for C. dybowskii. Our results indicate that the relationship between the two species shifts from a competitive interaction to a predator–prey interaction with the growth stages of C. baicalensis.     

Thermoregulation during cold water immersion is unimpaired by low muscle glycogen levels

This investigation studied the importance of muscle glycogen levels for body temperature regulation during cold stress. Physiological responses of eight euglycemic males were measured while they rested in cold (18 degrees C, stirred) water on two separate occasions. The trials followed a 3-day program of diet and exercise manipulation designed to produce either high (HMG) or low (LMG) preimmersion glycogen levels in the muscles of the legs, arms, and upper torso. Preimmersion vastus lateralis muscle glycogen concentrations were lower during the LMG trial (144 +/- 14 mmol glucose/kg dry tissue) than the HMG trial (543 +/- 53 mmol glucose/kg dry tissue). There were no significant differences between the two trials in shivering as reflected by aerobic metabolic rate or in the amount of body cooling as reflected by changes in rectal temperature during the immersions. Postimmersion muscle glycogen levels remained unchanged from preimmersion levels in both trials. Small but significant increases in plasma glucose and lactate concentration occurred during both immersions. Plasma glycerol increased during immersion in the LMG trial but not in the HMG trial. Plasma free fatty acid concentration increased during both immersion trials, but the change was apparent sooner in the LMG immersion. It was concluded that thermoregulatory responses of moderately lean and fatter individuals exposed to cold stress were not impaired by a substantial reduction in the muscle glycogen levels of several major skeletal muscle groups. Furthermore, the data suggest that, depending on the intensity of shivering, other metabolic substrates are available to enable muscle glycogen to be spared.     

Variation in the fatty acid profiles of two cold water diatoms grown under different temperature,light, and nutrient regimes

There is a growing demand for marine omega-3 fatty acids (FAs) that is produced in high amounts by some microalgae. Here we determined the FA profiles of two cold water adapted diatoms, Chaetoceros wighamii and Thalassiosira baltica. The cultures were acclimated to different temperatures (3, 7, 11, 15, and 19 °C) and irradiance (20, 40, 130, and 450 μmol photons m^?2 s^?1) and the FA profiles were determined in exponential and stationary growth phases, the latter induced by different nutrient limitation (N, P, and Si). The maximum growth rate was obtained by both species at 11 °C, ≥ 130 μmol photons m^?2 s^?1 and was 0.8 day^?1 and 0.6 day^?1 for C. wighamii and T. baltica, respectively. Both species contained relatively high amounts of eicosapentaenoic acid (EPA). Thalassiosira baltica accumulated maximally ~ 30 mg EPA g^?1 ash-free dry weight (AFDW) under Si-limitation. The content of docosahexaenoic acid (DHA) was lower, reaching up to 4 mg DHA g^?1 AFDW in T. baltica. The concentration of EPA correlated positively with the chlorophyll a:carbon ratio, suggesting that it is bound to membranes in the photosynthetic apparatus and the EPA content in T. baltica was high enough to consider it as a potent candidate for cultivation under cold (< 15 °C) conditions. Covering a wide range of environmental conditions, the strongest differentiation in FA profiles was observed between the species with the growth phase/nutrient limitation pattern as the second most important driver of the FA composition.

     

Integrating low water potential seed hydration with other treatments to improve cold tolerance

Matriconditioning improved the performance of pepper, tomato, sweet corn, snap bean, table beet, sugar beet and watermelon seeds in early field plantings at suboptimal temperatures (averaged over 10 d after planting) ranging from 12 to 18 °C. Reduction in the time to 50% (T(50)) emergence in conditioned seeds ranged from 0·6 d in watermelon to 3·3 d in pepper and improvement in emergence from 10% in sugar beet to 30% in table beet. Further improvement in emergence occurred by inclusion of pesticides and/or gibberellin during conditioning. A 4 d conditioning of pepper at 25 °C was superior to 7 d conditioning at 15 °C in seeds germinated at 15 °C on filter paper, but 15 °C conditioning was superior in improving percentage emergence in early field plantings. Tomato seeds conditioned at 15 or 25 °C performed equally well in the field. A 2 d conditioning was superior to 1 d conditioning in improving the performance of supersweet sweet corn cultivars grown in a growth chamber at 10/20 °C. The water uptake rate in the presence of Micro-Cel E during matriconditioning of sweet corn seeds was slower than when the seeds were exposed to the same amount of water in absence of the carrier. Electrolyte leakage was greater in supersweet 'Challenger' sweet corn seeds carrying the sh(2) gene compared to the sugary type sweet corn 'More', and in both cases matriconditioning reduced the leakage. Lettuce seeds matriconditioned for 24 h had higher 1-aminocyclopropane-l-carboxylic acid (ACC) content, developed greater ACC oxidase activity and performed better at 10 °C (germinated earlier and had higher percentage germination) than the untreated seeds. Matriconditioning appears to bring about beneficial physical, physiological and biochemical changes that seemingly improve embryo growth potential and tolerance to low temperatures.