Analysis of primary food sources and trophic relationships of aquatic animals in a mangrove-fringed estuary,Khung Krabaen Bay (Thailand) using dual stable isotope techniques

Stable carbon (¹³C) and nitrogen (¹⁵N) isotopes were used to elucidate primary food sources and trophic relationships of organisms in Khung Krabaen Bay and adjacent offshore waters. The three separate sampling sites were mangroves, inner bay and offshore. The ¹³C values of mangrove leaves were –28.2 to –29.4, seagrass –10.5, macroalgae –14.9 to –18.2, plankton –20.0 to –21.8, benthic detritus –15.1 to –26.3, invertebrates –16.5 to –26.0, and fishes –13.4 to –26.3. The ¹⁵N values of mangrove leaves were 4.3 to 5.7, seagrass 4.3, macroalgae 2.2 to 4.4, plankton 5.7 to 6.4 , benthic detritus 5.1 to 5.3, invertebrates 7.2 to 12.2 , and fishes 6.3 to 15.9. The primary producers had distinct ¹³C values. The ¹³C values of animals collected from mangroves were more negative than those of animals collected far from shore. The primary carbon sources that support food webs clearly depended on location. The contribution of mangroves to food webs was confined only to mangroves, but a mixture of macroalgae and plankton was a major carbon source for organisms in the inner bay area. Offshore organisms clearly derived their carbon through the planktonic food web. The ¹⁵N values of consumers were enriched by 3–4 relative to their diets. The ¹⁵N data suggests that some of aquatic animals had capacity to change their feeding habits according to places and availability of foods and as a result, individuals of the same species could be assigned to different trophic levels at different places.     

Acclimation of the Sea Cucumber Apostichopus japonicus to Decreased Salinity at the Blastula and Gastrula Stages: Its Effect on the Desalination Resistance of Larvae at Subsequent Stages of Development

Apostichopus (= Stichopus) japonicus blastulae and gastrulae were acclimated for 18 h to salinities of 32 (control), 24 and 22 (the lower limit of the range of tolerance), and 20 (below the range of tolerance). Acclimation to 20 resulted in the appearance of teratic larvae, most of which subsequently died. Acclimation to 24, 22, and 20 led to a shift in the range of tolerance of the larvae at further stages of development. With a decrease in salinity, acclimated larvae developed more successfully than unacclimated larvae. Acclimated larvae attained the pentactula stage and settled at a salinity range of 32–20; unacclimated larvae, at 32–22. At different stages of development, acclimated larvae survived greater decreases in salinity than unacclimated larvae. The acclimation effects could be traced up to metamorphosis and settling, i.e., two weeks after the end of the acclimation process.     

Oxygen isotope fractionation during respiration for different temperatures ofT. utilis andE. coli K12

Summary The temperature dependence of the oxygen isotope fractionation factor during respiration has been examined for two different microorganisms, namelyTorulopsis utilis andEscherichia coli K12 representing a yeast and a bacterium, respectively. The investigation covered a temperature range of 18° C, that is from 16° C to 34° C forT. utilis and from 19° C to 37° C forE. coli K12. Within this temperature range the fractionation factor ofT. utilis increases by 0.18; an insignificant change ( _{10° C} = 0.063;r = 0.067), whereas withE. coli K 12 an increase of 1.12; has been observed ( _{10° C} = 0.6;r = 0.55).     

Use of15N/14N rations to evaluate the food source of the mysid,Neomysis intermedia Czerniawsky,in a eutrophic lake in Japan

The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in ¹⁵N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in ¹⁵N was found in the mysid. The annual averages of ¹⁵N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3 (range: 5.7–6.9); POM, 7.9 (5.8–11.8); large sized mysid, 11.6 (7.7–14.3); zooplankton, 12.5 (10.0–16.4); prawn, 13.2 (9.9–15.4); goby, 15.1 (13.8–16.7). The degree of¹⁵N enrichment by the mysid was determined as 3.2 by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of ¹⁵N with about 3 difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.     

Autotrophic carbon sources for heterotrophic bacterioplankton in a floodplain lake of central Amazon

The relative contribution of autotrophic carbon sources (aquatic macrophytes, flooded forest, phytoplankton) for heterotrophic bacterioplankton was evaluated in a floodplain lake of the Central Amazon. Stable carbon isotopes (¹³C) were used as tracers. Values of ¹³C of different autotrophic sources were compared to those of dissolved organic carbon (DOC) and those of bacterially produced CO₂.The percentage of carbon derived from C₄ macrophytes for bacterially produced CO₂ was the highest, on average 89%. The average ¹³C value of CO₂ from bacterial respiration was –18.5 ± 3.3. Considering a fractionation of CO₂ of 3 by bacterial respiration, ¹³C value was –15.5, near C₄ macrophyte ¹³C value (–13.1).The average value of total DOC ¹³C was –26.8 ± 2.4. The percentage of C₄ macrophytes carbon for total DOC was on average 17%. Considering that bacteria consume mainly carbon from macrophytes, the dominance of C₃ plants for total DOC probably reflects a faster consumption of the former source, rather than a major contribution of the latter source.Heterotrophic bacterioplankton in the floodplain may be an important link in the aquatic food web, transferring the carbon from C₄ macrophytes to the consumers.     

Effects of tumor promoters and diacylglycerol on the transdifferentiation of striated muscle cells of the medusa Podocoryne carnea to RF-amide positive nerve cells

Artemia sp (Tuticorin strain) was cultured at a density of 250 individuals 1^–1 at 35, 45, 60, 75 salinity using five combinations of groundnut oil cake, decayed cabbage leaves, single superphosphate and Baker's yeast as feed. Effects on survival, growth, and fecundity were noted.     

Gas exchange and carbon isotope discrimination in lichens: Evidence for interactions between CO2-concentrating mechanisms and diffusion limitation

The characteristics of gas exchange and carbon isotope discrimination were determined for a number of lichen species, representing contrasting associations between fungal (mycobiont) and photosynthetic (photobiont) organism. These parameters were evaluated with regard to the occurrence of any CO₂-concentrating mechanism (CCM) expressed specifically by the green algal (phycobiont) or cyanobacterial (cyanobiont) partner. Carbon isotope discrimination () fell into three categories. The highest , found in lichens comprising a phycobiont plus cyanobacteria limited to pockets in the thallus (known as cephalodia), ranged from 24 to 28, equivalent to a carbon isotope ratio (¹³C) of around -32 to-36 vs. Pee Dee Belemnite (PDB) standard. Further evidence was consistent with CO₂ supply to the carboxylating system entirely mediated by diffusion rather than a CCM, in that thallus CO₂ compensation point and online instantaneous were also high, in the range normally associated with C₃ higher plants. For lichens consisting of phycobiont or cyanobiont alone, organic material formed two distinct ranges around 15 (equivalent to a ¹³C of -23%.). Thallus compensation point and instantaneous were lower in the cyanobiont group, which also showed higher maximum rates of net photosynthesis, whether expressed on the basis of thallus dry weight, chlorophyll content or area. These data provide additional evidence for the activity of a CCM in cyanobiont lichens, which only show photosynthetic activity when reactivated with liquid water. Rates of net CO₂ uptake were lower in both phycobiont associations, but were relatively constant across a wide working range of thallus water contents, usually in parallel with on-line . The phycobiont response was consistent whether photosynthesis had been reactivated with liquid water or water vapour. The effect of diffusion limitation could generally be seen with a 3–4 decrease in instantaneous at the highest water contents. The expression of a CCM in phycobiont algae, although reduced compared with that in cyanobacteria, has already been related to the occurrence of pyrenoids in chloroplasts. In view of the inherent requirement of cyanobacteria for some form of CCM, and the smaller pools of dissolved inorganic carbon (DIC = CO₂ + HCO _inf3 ^su– + CO _inf3 ^su2– ) associated with phycobiont lichens, it appears that characteristics provide a good measure of the magnitude of any CCM, albeit tempered by diffusion limitation at the highest thallus water contents.Abbreviations ANOVA analysis of variance - CCM CO₂-concentrating mechanism - cyanobiont cyanobacterium - DIC CO₂ + HCO _inf3 ^su– + CO _inf3 ^su2– (dissolved inorganic carbon) - photobiont photosynthetic organism present in the association - phycobiont green alga - phycobiont + cephalodia green algae + cyanobacteria in cephalodia - Pmax maximum photosynthetic rate - PPFD photosynthetic photon flux density, 400–700 nm - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - carbon isotope discrimination () - ¹³C carbon isotope ratio () We would like to thank Dr. Enrico Brugnoli (CNR, Porano, Italy) and E.C. Smith (University of Newcastle) for many helpful discussions. Dr. Kristin Palmqvist (Department of Plant Physiology, University of Umeå, Sweden) kindly provided the samples of Peltigera apthosa. In particularly, Cristina Máguas would like to thank to Prof. Fernando Catarino (University of Lisbon) for his support throughout this study. Cristina Máguas has been supported by JNICT-Science Programme studentship (BD/153/90-RN).     

The Reaction of the Starfish Asterias amurensisand Patiria pectinifera (Asteroidea) from Vostok Bay (Sea of Japan) to a Salinity Decrease

The reactions of the starfish Asterias amurensis and Patiria pectinifera that live in Vostok Bay at the salinity of 32–33 to a salinity decrease were studied under laboratory conditions. The lower limits of the desalination tolerance range of A. amurensis and P. pectinifera were, respectively, 24 and 20. A. amurensis proved to be less resistant to desalination. Under experimental conditions, all specimens of this species survived the salinity of 22, while those of P. pectinifera tolerated 18. At the same time, A. amurensis responded more actively than P. pectinifera to unfavorable changes in the environment. Turned to their dorsal side and exposed to a salinity of 16 to 32, the former reverted to the normal position within a shorter time than the latter. Being a more euryhaline species, P. pectinifera endured a salinity decrease to 6 or 8 over, respectively, 21 or 28 h. However, only 30–40% of all specimens could recover locomotory activity 12 or 8.5 h after being placed into water of normal salinity.     

Salinity-temperature tolerance of two closely related triclad species,Dugesia lugubris and D. polychroa (Turbellaria), in relation to their distribution in The Netherlands

The tolerance of adult specimens of Dugesia lugubris and D. polychroa for 13 different chlorinities ranging from 15.0–3.8 and for two temperatures, viz. 4 and 23 °C, was tested.At chlorinities of 7.5 and lower, the survival time of both species was considerably longer than at higher chlorinities (a few hours at 7.5, one to several days at 6.6 and lower concentrations). It is assumed that this is determined by the osmoregulatory capacity of the planarians.It was found that at low chlorinities combined with a high temperature D. polychroa survived longer than D. lugubris, while at the same chlorinities the opposite was true for a low temperature. The effect of temperature on survival at low chlorinities was more drastic for D. lugubris than for D. polychroa.The results correlate with data on the distribution of both species in The Netherlands. Outside areas with an average chlorinity below 2 the two species were rarely found.     

Selective feeding by larval dytiscids (Coleoptera:Dytiscidae) and effects of fish predation on upper littoral zone macroinvertebrate communities of arctic lakes

Carbon and nitrogen stable isotopic data from the primary producers in mangrove ecosystems are needed to investigate trophic links and biogeochemical cycling. Compared with other mangrove species (e.g. Rhizophora mangle) very few measurements have been conducted on the white mangrove, Laguncularia racemosa. The carbon and nitrogen stable isotopic and elemental compositions of L. racemosa were analyzed and compared from Florida and Belize. ¹³C values of L. racemosa from Florida (mean = –26.4) were slightly higher than those from Twin Cays, Belize (mean = -27.4), which may be due to higher salinity in some parts of the Florida site. There was no difference between the ¹⁵N values from L. racemosa from these two sites (Florida mean = 0.6; Belize mean = 0.3), which are indicative of nitrogen derived from nitrogen fixation in a planktonic marine system. However, higher ¹⁵N values from L. racemosa at Man of War Cay in Belize (11.4 and 12.3), which is fertilized by roosting marine birds (14.0), illustrate that L. racemosa can sensitively reflect alternative nitrogen sources. Although the isotopic data could not distinguish between Avicennia germinans, R. mangle and L. racemosa in Belize the L. racemosa had considerably higher C/N ratios (46.5 – 116.1) compared with the Florida samples (42.2 – 76.0) or the other mangrove species. Unlike some previous findings from R. mangle, substrate characteristics (e.g. salinity, NH₄ ⁺, and H₂S) were not related to the isotopic or elemental composition of L. racemosa. ¹³C, ¹⁵N and C/N were analyzed for ecosystem components from L. racemosa habitats at Twin Cays, including other plants (e.g. R. mangle, A. germinans and seagrass), detritus, microbial mats and sediments. Results from mass-balance calculations show that mangrove detritus composes very little of the sediment, which is principally composed of microbial biomass (80 – 90%). Detritus at some sites is also influenced by sources other than that from L. racemosa, including seagrass leaves.     

The gross and amino acid compositions of batch and semi-continuous cultures ofIsochrysis sp. (clone T.ISO),Pavlova lutheri andNannochloropsis oculata

Three species of microalgae commonly used in mariculture —Isochrysis sp. (clone T.ISO) Parke,Pavlova lutheri (Droop) Green andNannochloropsis oculata (Droop) Green — were grown in batch and semicontinuous modes to compare their biochemical composition and production rates.In batch mode, logarithmic-phase cultures of all species had high levels of protein (25.2 to 41.1) and low levels of carbohydrate (7.1 to 10.3) and lipid (8.8 to 14.9). At stationary phase, cultures ofIsochrysis sp. (clone T.ISO) andN. oculata contained significantly less protein (21.8 and 20.3, respectively), all species contained more carbohydrate (14.8 to 30.6), andP. lutheri contained more lipid (16.6). In semi-continuous mode, cultures maintained at late logarithmic-phase contained more carbohydrate,Isochrysis sp. (clone T.ISO) contained less protein, andP. lutheri more lipid than logarithmic-phase batch cultures of the same species. Neither growth phase nor harvest regime affected the amino acid composition of the microalgae significantly. However, the concentration of proline inN. oculata was higher in batch cultures in logarithmic phase (9.4), than in either semi-continuous cultures in logarithmic phase (5.8 to 7.9) or batch cultures in stationary phase (5.6 to 5.9).The production rates from batch and semi-continuous logarithmic-phase cultures were not significantly different for any of the species, and there were only minor differences in the production rates of the species (range 12.4 to 17.1 mg algae dry weight 1^–1 d^–1). The different culture and harvest regimes produced significant differences in the proportions of protein and carbohydrate in the microalgae. Which regime is chosen for culturing these microalgae as food will depend on the nutritional requirements of the animal species being fed.     

Stratification of δ13C values of leaves in Amazonian rain forests

Summary The contribution of soil respiration to the photosynthesis of the shade flora in the Amazon forest was evaluated by measuring the ¹³C values of leaves collected at different levels in two forest communities. Canopy leaves have an average ¹³C of-30.5 in the podsol forest and-28.7 in the laterite forest. Leaves from plants in the lower forest strata have a significantly lower value of-35.2 in the podsol forest and-34.3 in the laterite forest.Mailing address of the first author: Before May 31, 1980: Department of Biological Sciences, Stanford University, Stanford, California 94305 USA. After May 31: Centro de Ecologia, IVIC Aptdo. 1827. Caracas, Venezuela     

Stable carbon isotope signatures of background tropospheric chloromethane and CFC113

Samples of background air were collected in thelower troposphere of the Northern (high Arctic,northern Ontario, Vancouver and Houston) andSouthern (Baring Head, New Zealand) Hemispheresover the period July 1999 until March 2001.These samples were analysed for the stablecarbon isotope ratios of1,1,1-trichlorotrifluoroethane (CFC113) andCH₃Cl using a gaschromatography-continuous flow on-linecombustion isotope ratio mass spectrometrycombination. For CH₃Cl the global averageof the stable carbon isotope ratio is –36.2± 0.3 (error of mean). The average isbased on 78 data points, standard deviation forall measurements is 2.3, and the 90%confidence interval is –35.8 to –36.6.However, the number of data points from theSouthern Hemisphere is rather limited and thusthis observation is not necessarilyrepresentative for the entire SouthernHemisphere. A simple isotopic budget ofCH₃Cl shows the most important parametersneeding to be defined are the kinetic isotopeeffect of CH₃Cl destruction by OH radicalsand the source composition of CH₃Clemitted by the oceans and biomass burning ofC-4 plants. Present budgets of atmosphericCH₃Cl show a significant deficit in thesource strength. We estimate that the averagestable carbon isotope ratio of the additionalCH₃Cl emissions required to balance thebudget is –41.9 ± 7.8. The averageCFC113 isotopic composition based on 38measurements is –23.3 ± 1.6 (error ofmean), = 9.6 with no significantdifference between the hemispheres.     

Stable carbon isotope composition,depth distribution and fate of macroalgae from the Antarctic Peninsula region

Summary Stable carbon isotope composition of macroalgae collected at King George Island (Antarctica) ranged from about -8 to -34. We hypothesize that the ¹³C values are related to the depth distribution: species inhabiting greater depth had much lower values (around-30) compared to species from shallower waters (around -17). Isotopic studies on sediment trap samples from the King George Basin (2,000 m deep) revealed that benthic macroalgae contributed strongly to the total organic carbon pool of the deeper basin waters during austral spring and summer. Fragments of brown macroalgae (Desmarestiales) were detected in microscopical analyses of semi-thin sections of sediment samples from the Bransfield Strait. Possible mechanisms regarding the erosion of benthic macroalgae and their transport to the deeper waters and to the sediment are summarized.     

Short-term changes in carbon-isotope discrimination identify transitions between C3 and C4 carboxylation during Crassulacean acid metabolism

Short-term measurements of instantaneous carbon-isotope discrimination have been determined from mass-spectrometric analyses of CO₂ collected online during gas exchange for the epiphytic bromeliad Tillandsia utriculata L. Using this technique, the isotopic signature of CO₂ exchange for each phase of Crassulacean acid metabolism (CAM) has been characterised. During night-time fixation of CO₂ (Phase I), discrimination () ranged from 4.4 to 6.6, equivalent to an effective carbon-isotope ratio (¹³C) of –12.3 to –14.5 versus Pee Dee Belemnite (PDB). These values reflected the gross photosynthetic balance between net CO₂ uptake and refixation of respiratory CO₂, characteristic of CAM in the Bromeliaceae. When for the relative proportion of external (p _a ) and internal (p _i) CO₂ is taken into account, calculated p _i/p _a decreased during the later part of the dark period from 0.68 to 0.48. Measurements of during Phase II, early in the light period, showed the transition between C₄ and C₃ pathways, with carboxylation being increasingly dominated by ribulose bisphosphate carboxylase (Rubisco) as increased from 10.5 to 21.2 During decarboxylation in the light period (Phase III), CO₂ leaked out of the leaf and the inherent discrimination of Rubisco was expressed. The value of calculated from on-line measurements (64.4) showed that the CO₂ lost was considerably enriched in ¹³C, and this was confirmed by direct analysis of the CO₂ diffusing out into a CO₂-free atmosphere ( ¹³C = + 51.6 versus PDB). Instantaneous discrimination was characteristic of the C₃ pathway during Phase IV (late in the light period), but a reduction in showed an increasing contribution from phosphoenolpyruvate carboxylase. The results from this non-invasive technique confirm the observations that double carboxylation involving both phosphoenolpyruvate carboxylase and Rubisco occurs during the transient phases of CAM (II and IV) in the light period.Abbreviations and Symbols CAM Crassulacean acid metabolism - H⁺ (dawn-dusk) variation in titratable acidity - ¹³C carbonisotope ratio of plant organic material, relative to Pee Dee Belemnite (vs. PDB) - discrimination against ¹³CO₂, - p _i, p _a internal, external partial pressures of CO₂ - Rubisco ribulose1,5-bisphosphate carboxylase - PAR photosynthetically active radiation - PEPCase phosphoenolpyruvate carboxylase We are grateful for financial support in respect of research grants (GR3/5360, GR3/6419) and a studentship awarded by the Natural Environment Research Council, UK.     

Trophic relationships in the nearshore zone of Martel Inlet (King George Island,Antarctica): δ<Superscript>13</Superscript>C stable-isotope analysis

Carbon isotopic composition was used to assess the linkage between three different potential sources of energy and the community in the shallow coastal zone of Martel Inlet. Stable ¹³C ratios ranged from –28.7 for the zooplankton plus phytoplankton to –14.4 for the grazer Nacella concinna. Microphytobenthos (–16.7) was considerably more enriched in ¹³C than were suspended particulate matter (SPM) (–25.6) and macroalgal fragments (–23.6 and –21.1), indicating that stable carbon isotope analysis might be used to discern the relative contribution of these sources of primary production. There is a benthic-pelagic coupling between plankton, benthic suspensivores, the ophiuroid Ophionotus victoriae and the icefish Chaenocephalus aceratus. Benthic grazers such as N. concinna, deposit feeders such as Yoldia eightsi and the nematodes showed a tight coupling with the microphytobenthos and the sediment. Some omnivorous/depositivorous polychaetes, echinoids, amphipods and the fish Notothenia coriiceps showed values close to the ratios of the macroalgal fragments. Benthic carnivores and/or scavengers were generally enriched over suspensivores and depleted in relation to microphytobenthos grazers, showing a considerable overlap in ¹³C values throughout the food web, without any clear coupling with the primary sources of organic matter. The trophic web in the shallow zone of high benthic production and under seasonal ice cover in the Antarctic is more complex than it is in shelf areas, where SPM is the main food source. The soft-bottom community in the shallow zone of Martel Inlet is enriched in ¹³C due to the significant input of carbon from the microphytobenthos and macroalgal fragments.     

Adaptive Responses of the Larvae of Cirripede Barnacle Peltogasterella gracilis to Changes in Seawater Temperature and Salinity

The responses of the larvae of the cirripede barnacle Peltogasterella gracilis (Crustacea: Cirripedia: Rhizocephala) that parasitizes the hermit crab Pagurus pectinatus to different combinations of seawater temperature (25, 22, 20, 16, and 12°C) and salinity (from 34 to 8) were studied in a laboratory. The nauplii of P. gracilis completed the entire cycle of development at 22 to 12°C in a narrow range of salinity (from 34 to 28), which agrees well with the environmental conditions of the crab hosts' habitat. At favorable temperatures (22–20°C) and salinity (34–28), the nauplii reached the cypris stage in 88 ± 2 h, while at 12°C and 34–30, the naupliar development took 156 ± 5 h. The cypris larvae appeared more resistant compared with the nauplii, in terms of changes in both the temperature and salinity of seawater. They actively swam at all experimental temperatures and in the salinity range of 34–18. At temperatures (22–16°C) and salinities (34–24) favorable for the cyprids, their longevity in plankton equaled 6–10 days. Thus, the nauplii of P. gracilis is the more vulnerable stage of development in the life cycle of this parasitic barnacle. The tolerance against changes in environmental factors is due to the adaptive capabilities of parasitic larvae and the environmental conditions in the habitats of its host, a typical marine crustacean. The insignificant parasitization rate of the hermit crab by its rhizocephalan parasite may be explained by the death of the nauplii of P. gracilis, which occurs when they enter to the surface water layer.     

Effects of Desalination and the Detergent Sodium Dodecylsulphate on the Early Development of the Sand Dollar Scaphechinus mirabilis

We studied the effects of reduced water salinity on early ontogenesis in the sea urchin Scapechinus mirabilis. It is shown that the lower limit of salinity tolerance for the embryos and larvae is the salinity of 28. Under the mutual effects of desalination and sodium dodecylsulphate (SDS), an addition of 0.1 mg/l of the detergent to water with a salinity of 28 caused disturbances in the development of the larvae, starting from the stage of blastula. Desalination of the water down to 22 with the presence of SDS exerts significant effects already at the stage of fertilization. The mass death of embryos (73%) was observed at the stage of the first cleavage. The increase in the concentration of SDS up to 1 mg/l in water with a salinity of 28 to 22 caused an increase in the percentage of abnormal embryos and larvae from 40 up to 100%.     

The Effectiveness of the Protection of Embryos and Larvae within Egg Masses of the Gastropod Epheria turritaagainst Changes in Salinity and Desiccation

The effectiveness of the protection of embryos and larvae in egg masses from reduced salinity and desiccation was investigated in the gastropod Epheria turrita, which inhabits the intertidal and upper subtidal zones. Embryos and larvae developing inside egg masses were shown not to be protected against changes in environmental salinity. Viable larvae hatched from egg masses at a salinity of 24–26. However, if free-swimming veliger larvae, rather than egg masses, were transferred to water of reduced salinity, the range of salinity tolerated by the larvae was wider, and its lower limit was 18–20. Egg masses did not protect against desiccation either. A 3-h exposure of egg masses to drying resulted in larval mortality. Larvae hatched from egg masses did not rise to the surface and displayed an early tendency towards gregarious behavior, which apparently enhances their ability to settle on a proper substrate near parental populations.     

Mechanisms of intracellular isosmotic regulation: Fate of14C-labeled serum proteins in the shore crabCarcinus maenas after changed environmental salinity

Summary 1. Two individuals of the common shore crabCarcinus maenas, which had been maintained for 2 months in 11 S, were injected 100 µCi of¹⁴C-glucose and a¹⁴C-amino acid mixture in physiological saline during 5 days. They were the source of a¹⁴C-labeled serum protein, which was injected into the hemocoel of crabs which had been maintained for more than 2 months in 11 S. Six hours after injection the distribution of label and concentrations of serum proteins and free amino acids were investigated in 13 crabs, transferred to 38 S after the injection, and in 13 crabs (controls) which remained in 11 S.2. In crabs transferred from 11 to 38 S, proteolytic processes in serum increased; this was demonstrated by a decrease in serum proteins 6 hours after transfer. This assumption is confirmed by the fact, that¹⁴C-radioactivity in serum originating from serum proteins decreased by 44.4 % within 6 hours after transfer, whereas in controls it decreased by 32.6 %.3. Serum proteins have been metabolized in favour of low molecular intracellular intermediary products, such as amino acids, sugars, and organic acids, all contributing to the new intracellular osmotic pressure. This is shown by a significant increase in radioactivity of low molecular intracellular intermediary products.

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Mechanismen der intrazellulären isosmotischen Regulation: Das Schicksal von¹⁴C-markiertem Serumprotein der StrandkrabbeCarcinus maenas nach einem Wechsel der äußeren Salinität

Kurzfassung Individuen der StrandkrabbeCarcinus maenas, die zwei Monate in 11 S gehalten worden waren, wurden innerhalb von 5 Tagen 100 µCi¹⁴C-Glucose und eines¹⁴C-Aminosäuregemisches in physiologischer Lösung ins Hämocoel injiziert. Diese Tiere dienten als Quelle der benötigten¹⁴C-Serumproteinlösung, die anderen, über 2 Monate in 11 S gehaltenen Strandkrabben ins Hämocoel injiziert wurde. Eine Gruppe dieser Tiere wurde nach der Injektion in 38 S überführt, die Kontrollgruppe verblieb nach der Injektion in 11 S. 6 Stunden später wurden die Konzentrationen von Serumproteinen und freien Aminosäuren sowie die im Serum verbliebene Radioaktivität und die Radioaktivität in den gesamten niedermolekularen Intermediärprodukten bestimmt. Aus der signifikanten Abnahme des Serumproteins und der im Serum verbliebenen Radioaktivität sowie aus einer signifikanten Zunahme der Radioaktivität in den osmotisch aktiven Intermediärprodukten wird geschlossen, daß die intrazelluläre niedermolekulare organische Substanz, die während der Osmoregulation bis zu 100 % vermehrt werden kann, zu einem erheblichen Teil durch proteolytische Vorgänge im Serum der Tiere entsteht.