Diet and food selection in the endemic Hawaiian amphidromous goby, Sicyopterus stimpsoni (Pisces: Gobiidae)

Synopsis The ecological role of Sicyopterus stimpsoni as a nearly exclusive algal grazer in Hawaiian streams is established through gut content analysis of 192 fish from Wainiha River on the northern island of Kaua'i. Algae in three phyla (Chlorophyta, Cyanophyta, and Chrysophyta) were found to be the primary components of the fish's diet (94.62% of dry biomass). Aquatic insect immatures (primarily Chironomidae) accounted for most of the remaining food biomass (5.37%). Poorly developed gill rakers and high gut-to-length ratios provide evidence for adaptation to herbivory and morphological separation of S. stimpsoni from sympatric gobiods. Interspecific competition for the green alga, Cladophora sp., is suggested as an important feature of biotic interactions among native stream fishes but is mitigated by interspecific differences in food preference and utilization. A Category V hurricane which devastated the island in September 1992 provided a fortuitous opportunity to study disturbance influences on benthic food resources in the stream. Disturbance regimes influenced food selection of S. stimpsoni by altering the abundance and composition of stream algae. Rapid adjustment of S. stimpsoni to changes occurring in algal resource abundance illustrates its superb adaptation to life in a swift-water environment subjected to periodic flood-induced disturbance.     

Diel changes of larval drift among amphidromous gobies in Japan, especially Rhinogobius brunneus

Larvae of amphidromous gobies migrate to the sea as passive drift. In order to identify the diel drift pattern (DDP) of each species, we conducted 24 hour collections in different sections ofthree rivers. The DDPs ofdifferent species at each sampling station were almost identical, but the DDP of each species varied among stations, depending on the topographical features of water-courses. Downstream migration occurred throughout the day in steep water-courses while it was nocturnal with a peak in number soon after sunset in gentle gradients in the plain and was also nocturnal with a small amount of day time drifting between the two gradients. It is suggested that the larvae drifting from the upper parts of the river in daytime halted their migration in a pool with low flow rate until twilight.     

The survival of <Emphasis Type="Italic">Sicyopterus stimpsoni</Emphasis>, an endemic amphidromous Hawaiian gobiid fish,relies on the hydrological cycles of streams: evidence from changes in algal composition of diet through growth stages fish

Gut contents of larval, juvenile, and adult specimens of the Hawaiian gobiid fish Sicyopterus stimpsoni were examined to catalog the algal flora ingested by this species. The developmental stages of S. stimpsoni examined represented hallmark points in the fish’s life cycle corresponding with major migratory and metamorphic transitions. The algal flora was dominated by diatom species and shifted from taxa representative of a marine, planktonic community in larval fish to a freshwater, benthic community in juvenile and adult fish. This change in diet corresponds with the migration of larval fish to freshwater streams just prior to juvenile development in which rapid modification in mouth anatomy makes ingestion of planktonic algal species difficult. Benthic diatoms from juvenile and adult fish assemblages represented multiple genera that live in a narrow set of environmental conditions. These algae grow during a specific period in the development of the benthic algal community in Hawaiian streams. This suggests a highly specialized dietary behavior that depends heavily on continually restarting the benthic algal successional pattern, which appears to be regulated by the hydrological cycles of streams on the island.     

Salmon lice, Lepeophtheirus salmonis, infestation as a causal agent of premature return to rivers and estuaries by sea trout, Salmo trutta, juveniles

A field experiment conducted in the River Lønningdalselven in spring 1992 supports the hypothesis that salmon lice, Lepeophtheirus salmonis, infestations may cause premature return of sea trout, Salmo trutta, juveniles, either to estuaries or to rivers. When lice infested (exposed) and uninfested (control) sea trout juveniles (post smolts) were released simultaneously into the sea, exposed fish returned to the estuarine area earlier compared with controls. Within the following two days, exposed sea trout migrated further into freshwater. At that time they were infested with a median of 62.5 lice, dominated by chalimus larvae and late juveniles. Exposed sea trout suffered from an osmoregulatory failure in sea water and this is considered one reason for infested fish returning to brackish water. While only a few control fish returned to the estuary on the day of release, some more returned to freshwater the following four days. During this time they had become heavily infested with copepodids, and carried a median of 150.0 lice. It is suggested that physiological stress and high infection pressure in the sea results in sea trout juveniles returning to estuaries and freshwater.     

The migratory behaviour of North Sea plaice: Currents, clocks and clues

Water currents are a dominant feature of the open sea and often play an important part in the life cycle of the fish that live there. For over three decades, a focus of research at Lowestoft has been the role of tidal water currents as a part of wider understanding of the population dynamics of plaice (Pleuronectes platessa) in the North Sea. Increasingly sophisticated telemetry methods have been developed and used, initially to describe the migratory behaviour of individual fish, and latterly to describe the spatial dynamics of whole populations. Here, the authors review cues and clues for environmental transport at different life stages, with a critical evaluation of the facultative use of selective tidal stream transport in relation to water current speed. The clues that trigger movement into mid-water by adult fish are reconsidered in light of new findings. Finally, the orientation capabilities of plaice, together with evidence of repeat migrations and spawning site fidelity were examined.     

Regulation of cell contraction and membrane ruffling by distinct signals in migratory cells.

Cell migration and wound contraction requires assembly of actin into a functional myosin motor unit capable of generating force. However, cell migration also involves formation of actin-containing membrane ruffles. Evidence is provided that actin-myosin assembly and membrane ruffling are regulated by distinct signaling pathways in the migratory cell. Interaction of cells with extracellular matrix proteins or cytokines promote cell migration through activation of the MAP kinases ERK1 and ERK2 as well as the molecular coupling of the adaptor proteins p130CAS and c-CrkII. ERK signaling is independent of CAS/Crk coupling and regulates myosin light chain phosphorylation leading to actin-myosin assembly during cell migration and cell-mediated contraction of a collagen matrix. In contrast, membrane ruffling, but not cell contraction, requires Rac GTPase activity and the formation of a CAS/Crk complex that functions in the context of the Rac activating protein DOCK180. Thus, during cell migration ERK and CAS/Crk coupling operate as components of distinct signaling pathways that control actin assembly into myosin motors and membrane ruffles, respectively.     

Relative ventricular weight of wild Atlantic salmon parr in relation to sex, gonad maturation and migratory activity

Relative ventricular weight (RVW, ventricular weight/body weight · 100) was measured for five groups of Atlantic salmon parr from the Girnock Burn in Scotland. The mean RVW was: mature males, 0.087; immature resident males, 0.054; immature resident females, 0.056; immature migrant males, 0.056; immature migrant females, 0.053. For a group of mature male parr from the R. Nith, Galloway, Scotland, the mean RVW was 0.108. There were no significant differences in the RVW between groups of immature fish. The RVW of each group of mature male parr was significantly greater than those of each, group of immature parr. Condition indices (weight/length³) were closely similar between all groups of parr. The functional significance of plasticity in ventricular weight is discussed in relation to life histories of Atlantic salmon.     

Increased connexin 43 expression improves the migratory and proliferative ability of H9c2 cells by Wnt-3a overexpression

The change of connexin 43 (Cx43) expression and the biological behaviors of Cx43 in rat heart cell line H9c2, expressing Wnt-3a (wingless-type MMTV integration site family, member 3A) were evaluated in the present study. Plasmid pcDNA3.1/Wnt-3a was constructed and transferred into H9c2 cells. The cell model Wnt-3a~ -H9c2 steadily expressing Wnt-3a was obtained. Compared with H9c2 and pcDNA3.1-H9c2 cells, the expression of Cx43 in Wnt-3a~ -H9c2 cells was clearly increased, the proliferation of Wnt-3a~ -H9c2 cells was significantly changed, and cell migration abilities were also improved (P<0.05). In comparison with H9c2 and pcDNA3.1-H9c2 cells, the G_2 phase of the cell cycle increased by 11% in Wnt-3a~ -H9c2 cells. Thus, Wnt-3a overexpression is associated with an increase in Cx43 expression and altered migratory and proliferative activity in H9c2 cells. Cx43 might be one of the downstream target genes regulated by Wnt-3a.     

Use of light and inorganic carbon acquisition by two morphotypes of Zostera noltii Hornem

The affinity for dissolved inorganic carbon (DIC) and the mechanisms to use HCO₃⁻ as a source of DIC for photosynthesis were investigated in two morphotypes of Zostera noltii Hornem. Both morphotypes were collected at Ria Formosa lagoon (Southern Portugal) at two different levels in the intertidal. Affinity for DIC at saturating photon fluence rate (PFR), estimated as photosynthetic conductance for CO₂ (g_p(CO2)), was reduced by 75% in the Z. noltii plants adapted to shade conditions (lower intertidal) in comparison to the sun morphotype (45×10⁻⁶ and 182×10⁻⁶ m s⁻¹, respectively), indicating that the plants acclimated to sun conditions (higher intertidal) had a higher capacity to use HCO₃⁻ as DIC source for photosynthesis. Since external carbonic anhydrase activity was negligible and a large inhibitory effect was produced by Tris buffer addition, this HCO₃⁻ use was attributed to the operation of H⁺ ATPases creating low pH zones in periplasmic space. The photosynthetic CO₂-flux supported for this mechanism was calculated to be 53 μmol O₂ m⁻² s⁻¹ in sun morphotype, about 80% out of maximum photosynthesis rate. In order to determine the possible photosynthetic energy cost of the HCO₃⁻ use, the effect of decreasing light on photosynthetic rates and g_p(CO2) was estimated. Photosynthetic conductance decreased in both morphotypes at non-saturating PFR. This dependence of g_p(CO2) on PFR indicated the existence of a positive interactive effect between DIC and PFR which was more pronounced in the shade morphotype since the ascending slope of O₂ evolution vs. PFR curves at limiting PFRs was reduced from 7.2 to 2.3 mmol O₂ mol photon⁻¹ at 4 and 0.5 mol m⁻³ of DIC, respectively.     

Migration,clogging, and carbon source release of nano emulsified vegetable oil in porous media,evaluated by column experiments

To effectively solve the problem of aquifer clogging in the process of in situ bioremediation of groundwater pollution by micron emulsified vegetable oil (Micron EVO), Nano emulsified vegetable oil (Nano EVO) was prepared to replace conventional micron EVO, and three one-dimensional laboratory columns packed with medium or fine sands were conducted to simulate migration, clogging, and carbon source release of EVO in porous media. Column experiment results show that micron and nano EVO resulted in a 20.40% and 3.20% reduction in permeability of medium sand, respectively. Correspondingly, the interception of micron and nano EVO in medium sand were 28.51% and 20.15%, respectively. Obviously, EVO interception is an important reason for permeability loss, and reducing EVO droplet size can effectively alleviate permeability loss in porous media. The COD ratios (dissolved COD/total COD) of micron and nano EVO in medium sand were 87.61% and 61.95%, respectively. The release effect of nano EVO was better than that of micron EVO. Effective longevity of micron and nano EVO were 243.17 d and 98.80 d, respectively. The effect of fine sand media on EVO indicated nano EVO can be used in a finer granular media, and its longevity can also be extended in this media.     

Integrin-dependent neuroblastoma cell adhesion and migration on laminin is regulated by expression levels of two enzymes in the O-mannosyl-linked glycosylation pathway, PomGnT1 and GnT-Vb

O-mannosyl-linked glycans constitute a third of all brain O-linked glycoproteins, and yet very little is understood about their functions. Several congenital muscular dystrophies with central nervous system defects are caused by genetic disruptions in glycosyltransferases responsible for the synthesis of O-mannosyl glycans. The glycosyltransferase GnT-Vb, also known as GnT-IX, is expressed abundantly in the brain and testis and is proposed to be the enzyme that branches O-mannosyl-linked glycans. In this study, we show in a human neuronal model that GnT-Vb expression enhances neurite outgrowth on laminin. GnT-Vb has been shown to perform both N-linked and O-mannosyl-linked glycosylation. To determine if the effect on neurite outgrowth was due to N-linked or O-mannosyl-linked glycosylation by GnT-Vb we suppressed the expression of glycosyltransferases important for the elongation of both N-linked and O-mannosyl-linked glycans using RNA interference. Our results suggest that GnT-Vb and PomGnT1, enzymes involved in the O-mannosyl glycosylation pathway, play an active role in modulating integrin and laminin-dependent adhesion and migration of human neuronal cells.     

Descriptive morphology of the eggs,larvae, and juveniles of two cyprinid fishes belonging to the <Emphasis Type="Italic">Zacco temminckii</Emphasis> species' group

 Embryonic, larval, and juvenile development of two cyprinid species belonging to the Zacco temminckii species' group, Z. temminckii (Temminck and Schlegel) and Zacco sp. (type A), are described and compared with each other from laboratory-reared and wild specimens. The eggs of both species were closely similar except in diameter [1.92–2.20 mm in Z. temminckii vs. 1.60–1.75 mm in Z. sp. (type A)], being demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk, and no oil globule. Hatching occurred 40–53 h after fertilization in Z. temminckii and after 47–60 h in Z. sp. (type A). The newly hatched larvae of both species [4.9–5.3 mm in body length (BL) in Z. temminckii and 3.5–4.8 mm BL in Z. sp. (type A)] also resembled each other, having a large transparent pear-shaped yolk and lacking body pigmentation. Myomere counts of Z. temminckii and Z. sp. (type A) larvae and juveniles were 24–27 + 14–17 = 41–42 and 23–27 + 14–17 = 40–41, respectively. The yolk was completely absorbed at 8.3 mm BL in Z. temminckii and at 6.6 mm BL in Z. sp. (type A). Notochord flexion was initiated and completed at 7.8 mm BL and 8.2 mm BL in Z. temminckii and at 6.3 mm BL and 6.6 mm BL in Z. sp. (type A), respectively. Aggregate numbers of all fin rays were completed at 17 mm BL in Z. temminckii and 13 mm BL in Z. sp. (type A). Although the morphology of larvae and juveniles of both species was very similar, differences in body length of each developmental stage, the duration and process of disappearance of the adipose finfold, the anal fin ray counts, and pigmentation on the lateral body surface were clearly recognized. Received: August 10, 2001 / Revised: March 14, 2002 / Accepted: March 27, 2002     

Impairment of VEGF-A-stimulated lamellipodial extensions and motility of vascular endothelial cells by chondromodulin-I, a cartilage-derived angiogenesis inhibitor

Chondromodulin-I (ChM-I) is a cartilage-derived angiogenesis inhibitor that has been identified as inhibitory to the growth activity of vascular endothelial cells. In our present study, we demonstrate the anti-angiogenic activity of recombinant human ChM-I (rhChM-I) in mouse corneal angiogenesis and examine its action. We focus on the VEGF-A-induced migration of vascular endothelial cells, a critical regulatory step in angiogenesis. In a modified Boyden chamber assay, nanomolar concentrations of rhChM-I inhibited the chemotactic migration of human umbilical vein endothelial cells (HUVECs) induced by VEGF-A as well as by FGF-2 and IGF-I. The ChM-I action was found to be endothelial cell-specific and independent of cell adhesions. Time-lapse analysis further revealed that rhChM-I markedly reduces VEGF-A-stimulated motility of HUVECs and causes frequent alterations of the moving front due to the appearance of multiple transient protrusions. This action involved the inhibition of cell spreading and the disrupted reorganization of the actin cytoskeleton upon VEGF-A stimulation. Consistent with these observations, rhChM-I was found to significantly reduce the activity of Rac1/Cdc42 during cell spreading, and the VEGF-A-induced Rac1 activity but not its basal activity in quiescent cells. Taken together, our present data suggest that ChM-I impairs the VEGF-A-stimulated motility of endothelial cells by destabilizing lamellipodial extensions.     

Rapid repression of vacuolar invertase in mungbean hypocotyl segments and regulation by sucrose, auxin and light

Two previously unrecorded endogenous cytokinin metabolites,6-[2-(-D-glucopyranosyloxy)benzylamino]purine and6-[2-(-D-glucopyranosyloxy)benzylamino]-2-methylthiopurine, wereidentified, together with 6-benzylamino-9--D-glucopyranosylpurine(BAP9G),from Chenopodium rubrum cells, grown autotrophically insuspension culture. The new metabolites belong to the aromatic class ofcytokinins, in which an aromatic side chain is attached at theN⁶-position of the adenine species. The identification was performedby capillary-liquid chromatography/frit-fast atom bombardment - massspectrometry (LC/FAB MS) after pre-column derivatisation and the structuralelucidation was confirmed by organic synthesis. Cytokinin activity of thecompounds was tested in an Amaranthus bioassay. Theendogenous synthesis of the identified compounds was verified byin vivo deuterium labelling of the analysed cytokininspecies, thereby for the first time providing absolute evidence for theendogenous origin of these compounds.     

Antialgal, antibacterial and antifungal activity of two metabolites produced and excreted by cyanobacteria during growth

The antimicrobial activity of two cyanobacterial exometabolites, norharmane (9H-pyrido(3,4-b)indole) and 4,4'-dihydroxybiphenyl, was determined in suspension assays. Good anticyanobacterial activities (concentrations of 8-80 microg ml(-1)) and moderate antibacterial (16-160 microg ml(-1)) and antifungal (32-40 microg ml(-1)) activities were found for both compounds. The natural function as allelopathic chemicals and a possible applicability as antifouling agents or leads for the development of new antifouling chemicals are discussed.