Effects of constant and cyclic temperatures on the salinity tolerance of the estuarine sandhopper Orchestia chiliensis

The survival of Orchestia chiliensis (Milne Edwards, 1840) was investigated at salinities between 0.3 and 68 and constant or 10 C° cyclic temperatures between 5° and 25° C. Mortality increased with age, temperature and at salinity extremes. Small individuals show little seasonal acclimatisation apart from increased thermal tolerance at the highest exposure temperature. Larger individuals show a lateral shift in the mortality curve to the right in summer, giving increased survival at most salinities. Salinity had less effect on amphipods in cyclic regimes and survival was similar in 5° to 15° C and 10° to 20° C cycles. Mortality of larger individuals was higher in the 15° to 25° C cycle, but seasonal acclimatisation gave increased resistance at all fluctuating temperatures during the summer. Mortality in cyclic temperatures was higher than at similar constant temperatures. O. chiliensis does not actively evade immersion and diel temperature changes of 10 C° represent an important stress factor. This would affect all life stages and influence field populations both in the winter and the summer.     

Larval growth in the estuarine crab Chasmagnathus granulata: the importance of salinity experienced during embryonic development, and the initial larval biomass

The importance of salinity experienced during embryonic development and initial larval biomass on larval growth was studied in the South American estuarine crab Chasmagnathus granulata. Ovigerous females were maintained at three salinities (15, 20, and 32‰) from egg laying to hatching of zoea l. Larvae from all treatments were reared under constant conditions of photoperiod (12∶12), temperature (18°C), and salinity (first instar at 20‰, subsequent instars at 32‰). Biomass was measured as dry weight, carbon, and nitrogen content per individual at egg laying, hatching of zoea l, premoult zoea l, and zoea 4, and in 8-day-old megalopa. From hatching to premoult zoea 4, biomass was higher for larvae from prehatching salinities of 15 and 32‰. There was a significant positive correlation between biomass at hatching and at premoult zoea l and zoea 4. Accumulated biomass during zoeal stages tended to be higher for larvae from broods with higher biomass at hatching, although this trend was not always significant. Zoea 4 either directly metamorphosed to megalopa or moulted to zoea 5, following, respectively, a short or long developmental pathway. The proportion of zoea 4 that followed the long pathway was negatively correlated with biomass of zoeal stages. Biomass at hatching was correlated with biomass of megalopae developed through the short pathway, although it was not correlated with the accumulated biomass at this stage. Megalopae developed through the long pathway (i.e. metamorphosed from zoeae 5) had higher biomass than those from the short pathway. The present results suggest that prehatching salinity and initial egg and larval biomass can be very important for larval growth. Published online: 9 August 2002     

Effect of temperature and salinity on larval development of southern king crab (Lithodes antarcticus)

Larvae of Lithodes antarcticus Jacquinot were reared in October, 1981 from hatching to the glaucothoe stage at 16 temperature/salinity combinations (5.5°; 7.5°; 9.5° and 13.5°C; 26, 29, 32 and 35 S) to determine optimal environmental conditions for larval development. The highest survival percentage was obtained in the culture at 7.5°C and diminished according to temperature increase or decrease. High temperature cultures significantly shorten the larval life duration, but produce large mortalities. At 5.5°C mortality occurred almost exclusively during the moult to glaucothoe stage. Higher survival percentages were obtained as salinity was increased. In the lowest salinity culture (26 S) no zoea reached the post-larvae stage at culture temperatures. The best T/S combination was obtained at 7.5°C and 35 S, with a survival percentage of 29%. The shortest zoeal developments were obtained at 32 S in all culture temperatures. Salinity also affects larvae coloration: there is a pigment concentration on erythrophores, which causes a color decrease.     

Interaction of temperature and salinity on oxygen consumption of the estuarine crab Panopeus herbstii

Marine Biology - The combined effects of temperature and salinity on the rate of oxygen consuption by the estuarine crab Panopeus herbstii Milne-Edwards (Crustacea: Decapoda: Xanthidae) were...     

Effects of copper and cadmium on osmoregulation and oxygen consumption in two species of estuarine crabs

Green crabs (Carcinus maenas) and rock crabs (Cancer irroratus) were exposed to various concentrations of copper as cupric chloride (CuCl₂ · 2 H₂O), and cadmium as cadmium chloride (CdCl₂ · 21/2 H₂O) for 48 h. The exposures were conducted at 5 different salinities. At the end of each exposure period, tests of blood-serum osmolality and gill-tissue oxygen consumption were performed. Copper-exposed crabs exhibited loss of osmoregulatory function with increasing copper concentration until normally hyperosmotic serum became isosmotic with the surrounding medium. Cadmium elevated greencrab serum above its normal hyperosmotic state. Copper had no effect on gill-tissue oxygen consumption; however, cadmium reduced the rate of oxygen consumption in both species tested.     

Synergistic effects of lead,salinity and temperature on embryonic development of the mussel Mytilus galloprovincialis

Combined effects of lead, salinity and temperature on the embryonic development of the mussel Mytilus galloprovincialis Lmk. were studied under laboratory conditions. The basic experimental design was a 4x6 factorial experiment using 4 lead concentrations (100, 250, 500 and 1000 ppb Pb²⁺) and 6 salinity levels (from 25 to 37.5 with 2.5 intervals). These factorial designs were carried out at three constant temperatures (150, 17.50 and 20°C). The statistical analysis indicated that salinity changes have more effect on the embryonic development than temperature. Optimal development was observed at 34.8 and 15.6°C, which is in accordance with observations in the field. The effect of lead was mininal in optimal salinity and temperature conditions. The deleterious effect of lead on the embryonic development was especially conspicuous at 20°C. Since in nature spawning occurs at temperatures inferior to 20°C, lead will probably not drastically decrease the potential recruitment of mussel spat in the littoral populations of the northern Adriatic Sea, where the salinity of the water is relatively stable. Under experimental conditions, lead caused a delay or inhibition of the embryonic development with the occurrence of a large number of abnormal larvae.     

Synergistic effects of salinity,temperature and heavy metals on mortality and osmoregulation in marine and estuarine isopods (Crustacea)

The effects of cadmium (3CdSO₄·8H₂O), zinc (ZnSO₄·7H₂O) and lead [Pb (NO₃)₂] on mortality, and cadmium, zinc and mercury (HgCl₂) on osmoregulation, have been recorded for marine and estuarine species of isopods (Crustacea). The marine species studied were Idotea baltica, I. neglecta, I. emarginata and Eurydice pulchra, which were adapted to 100, 80, 60 and 40% sea water (SW) (100% SW э 34‰ S). The estuarine species used were Jaera albifrons sensu stricto and J. nordmanni, which were adapted to 100, 50, 10 and 1% SW. Both groups of isopods have low mortalities in 100% SW with 10 and 20 ppm of cadmium, zinc and lead, but a decrease in salinity caused an increase in the toxicities of these metals and reduced the LT₅₀ values (time, in hours, to 50% mortality). Mortalities at 10°C were generally higher than those recorded at 5°C. Cadmium had no significant effect on the osmoregulation of I. baltica and I. emarginata in 100 and 80% SW at 5°C, but this metal significantly lowered the blood osmotic concentration of I. neglecta in 80% SW. Zinc did not alter the haemolymph osmotic concentration of I. neglecta in 100 and 80% SW, but significantly lowered the blood osmotic concentration of I. baltica in 100% SW. Cadmium, zinc and mercury also significantly altered the osmoregulatory ability of J. albifrons in dilute saline.     

Effects of the insect growth regulator Dimilin® (TH 6040) on larval development of two estuarine crabs

Effects of Dimilin^® (TH 6040), an insect growth regulator which interferes with the formation of the insect cuticle, were studied on the larval development of Rhithropanopeus harrisii (Gould) and Sesarma reticulatum (Say) (Crustacea: Brachyura). When larvae were exposed to 0.5 (R. harrisii only), 1, 3, 5, 7, and 10 ppb Dimilin from hatching to the first crab stage, survival in both species decreased in relation to increased concentrations of Dimilin. Survival of R. harrisii larvae wa significantly lower at 1 ppb and higher levels compared with control experiments, and in S. reticulatum a significant decrease in survival began at the 3 ppb level. At 10 ppb Dimilin, no larvae survived to the megalopa stage in either of the two species. The results indicate that early stage larvae of R. harrisii are more sensitive to Dimilin than those of S. reticulatum. When R. harrisii larvae were treated with 10 ppb Dimilin during the intermolt period of each of the 4 zoeal stages, nearly all larvae died during molting to the succeeding stage. First zoeal larvae of R. harrisii exposed to 10 ppb Dimilin at various days during the intermolt period were more sensitive to the compound late than early in the period. It is suggested that Dimilin also may interfere with the formation of the cuticle in crab larvae.     

Responses of estuarine crab megalopae to pressure,salinity and light: Implications for flood-tide transport

The megalopal larval stage of many estuarine brachyuran crabs appears to return to adult habitats by undergoing rhythmic vertical migrations which result in saltatory up-estuary transport on flood tides. Larval ascent into the water column during rising tides may be cued by changing hydrologic variables. To test this hypothesis, we investigated the responses of field-caught megalopae of the blue crab Callinectes sapidus and the fiddler crab Uca spp. to constant rates of pressure and salinity change under laboratory conditions. For both genera, pressure changes resulted in increased movement (barokinesis) and upward migration in the test chamber, with C. sapidus megalopae having a lower response threshold (2.8×10^-2 mbar s^-1) than Uca spp. larvae (5×10^-2 mbar s^-1). Similarly, larvae ascended in response to increasing salinity, with C. sapidus larvae being more sensitive. Larvae were negatively phototactic and failed to respond to pressure increases at light levels above 1.0×10¹⁵ and 1.0×10¹³ photons m^-2 s^-1 for C. sapidus and Uca spp. megalopae, respectively. Such responses are thought to explain the low abundances of larvae in the water column during daytime flood tides. Nevertheless, threshold sensitivities to increasing pressure for both genera were above levels experienced during floodtide conditions in the field. Similarly, it is unlikely that increasing salinity is sufficient to induce ascent in Uca spp. postlarvae. However, rates of salinity increase during midflood tide typically reach levels necessary to induce an ascent in C. sapidus megalopae. These results are consistent with the hypothesis that fiddler crab megalopae utilize an endogenous activity rhythm for flood-tide transport, while blue crab megalopae rely upon external cues, especially salinity changes, to time their sojourns in the water column.     

Long-term effects of water-soluble fractions of Kuwait crude oil on the larval and juvenile development of the mud crab Eurypanopeus depressus

Larvae of the mud crab Eurypanopeus depressus (Smith) were reared in various concentrations of the water-soluble fraction of Kuwait crude oil. The 48-h TL_m (median tolerance limit) for Zoea Stage I was approximately 10 ppm total dissolved hydrocarbons and that for Zoea Stage II approximately 17 ppm. Chronic toxicity of more dilute solutions (4.3 and 8.7 ppm) was assessed independently for each larval stage and for subsequent developmental stages through Crab Stage 5. In the group continuously exposed to oil from hatching, there was differential mortality relative to controls in every larval stage and increased duration of intermolt periods was observed at every stage through Crab Stage 5. Mortality in groups not exposed until larvae had reached Zoea Stages III or IV was not greater than controls, suggesting that toxicity to advanced larval stages may be related to accumulation of toxic compounds by the larvae. Neither concentration (4.3 or 8.7 ppm) of crude oil caused increased mortality among juvenile crab stages regardless of the time of initial exposure. Increased occurrence of an extra and morphologically abnormal megalopa stage was associated with exposure to the crude oil. This has not been reported before.Communicated by I. Morris, West Boothbay Harbor     

Influence of food concentration,temperature and salinity on the larval development ofBalanus amphitrite

Influence of food concentration (0.5, 1 and 2 x 10⁵ cell ml^–1 ofSkeletonema costatum), temperature (20 and 30°C) and salinity (15, 25 and 35) on the larval development ofBalanus amphitrite (Cirripedia: Thoracica) was examined. The mortality rate at 20°C was lower than at 30°C in general. Increase in food concentration from 0.5 to 1 x 105 cells ml^–1 improved the survival rate, but this was not evident when food concentration was increased to 2 x 105 cells ml^–1. The results indicate that food availability and temperature jointly determine the energy allocation for metamorphic progress. It was observed that the influence of the tested variables varied with instar. At 20 °C the mean duration of the second instar exceeded 3 d and was much longer than other instar durations. The fourth, fifth and sixth instars and the total naupliar period showed that the effect of different salinities at given food concentrations was negligible at 20°C, while at 30°C there was a marked decrease in duration with increasing salinity.     

Synergistic effects of temperature,salinity and light on the hermatypic coral Montipora verrucosa

Temperature tolerance in the reef coral Montipora verrucosa (Lamarck) is affected by salinity and light. Low salinity reduces ability of the coral to survive shortterm exposure to elevated temperature. High natural light intensity aggravates damage sustained by corals at high temperature. In long-term growth experiments, high light intensity caused substantial loss of zooxanthellar pigment, higher mortality rates, reduced carbon fixation and lowered growth rate at both upper and lower sublethal temperatures Effects of light at optimal temperature were less dramatic. Interactions between physical environmental factors appear to be most important near the limits of tolerance for a given factor. Acclimation capability was indicated, and was influenced by both thermal history and pigmentation state of stressed corals.Contribution No. 543 of the Hawaii Institute of Marine Biology.     

Effects of salinity on the uptake of lead and cadmium by two mangrove species Rhizophora apiculata Bl. and Avicennia alba Bl.

The uptake of lead (Pb) and cadmium (Cd) by Rhizophora apiculata and Avicennia alba under various salinity levels was examined using hydroponic cultivations. After 3 months of exposure at four levels of Pb (0, 0.03, 0.3 and 3 mg·L^?1) and four levels of Cd (0, 0.005; 0.05 and 0.5 mg·L^?1) at different salinities (0, 15 and 30), uptake of the metals was shown to be differently affected by salinity. For uptake of Pb by R. apiculata, the salinity effect was not significant for the leaves and was most significant in the stem, whereas for A. alba, the effect of salinity was significant only in the stem. Uptake of Pb in the roots and stems of both species was similar, but a higher concentration was recorded in the leaves of A. alba. Salinity was shown to affect the uptake of Cd by all tissues of R. apiculata, but most significantly roots. For A. alba, salinity significantly affects the total uptake of Cd, but this is most significant in the roots. The two mangrove species demonstrated different mechanisms of metal distribution into their organs which may be related to different adaptation mechanisms to saline conditions.     

Effects of dieldrin in seawater on the development of two species of crab larvae,Leptodius floridanus and Panopeus herbstii

Some of the effets of dieldrin on the development of two species of crabs, Leptodius floridanus (Rathbun) and Panopeus herbstii (Milne-Edwards), were studied. It was found that the larvae of neither species were able to complete their development at 10 ppb dieldrin or higher in seawater. Groups of L. floridanus larvae reared in 1 ppb dieldrin in seawater had a 15 to 27% higher mortality during development to the postlarval stage than controls. The highest mortality occurred during the first zoeal stage. The time of development to the megalopal stage was as much as 11.4% longer among larvae reared in 1 ppb than among controls. The survival of L. floridanus larvae was not affected by 0.5 ppb dieldrin in seawater. The survival of P. herbstii larvae to the first crab stage was not affected by 1 ppb dieldrin in seawater at 28.5 °C, 30%.S. It was concluded that a comprehensive study of the toxicity of a given pesticide to all stages in the life cycle of a species is necessary to give even an incomplete idea of how the pesticide might affect the animal in its natural environment.     

Interactions between temperature and salinity during brooding on subsequent zoeal development of the mud crab Rhithropanopeus harrisii

Female mud crabs, Rhithropanopeus harrisii, carrying newly extruded eggs, were collected from the Petaluma River (San Francisco Bay Estuarine System, California, USA) in summer 1985, and exposed to factorial combinations of temperature (20°, 25° or 30°C) and salinity (2, 5, 15, 25, or 32%.). Upon hatching, dry weights of 12 to 15 h-old zoeae were determined. Subgroups of the remaining zoeae were transferred from hatching salinities to the salinities listed above and raised until metamorphosis to megalopa. Low salinities reduced zoeal dry weights by as much as 25%. Temperature played a secondary role in reduction of hatching weight of zoeae. Survival of larvae through zoeal development was best when hatching and rearing salinities were the same; in this case, overall survival increased with temperature. Both duration of zoeal development and megalopal dry weights were strongly influenced by temperature and rearing salinity, with only a small contribution from hatching salinity. The influence of hatching salinity was most obvious at extremes of the range tested. These studies indicate that physical conditions during embryogenesis profoundly influence subsequent larval development. Interpretation of experimental approaches to study ecophysiological adaptations of larval stages should not neglect the role of physical conditions during embryogenesis.     

Effects of temperature and salinity on larval development ofNecora puber (Brachyura: Portunidae)

Temperature and salinity affected both length of larval development and mortality inNecora puber collected in the Ría de A Coruña during December 1984 and January 1985. Development time decreased considerably with increased temperature. This decrease was sharper when temperature increased from 15° to 20°C than when it increased from 20° to 25°C. At 35S, average development took 48, 32 and 28 d at 15°, 20° and 25°C, respectively. At the three salinities tested (25, 30 and 35), larval development was completed only at 15°C, at 20°C/30 and 35S, and at 25°C/35S. Development times at 15° and 20°C were highly significantly different at both 35 and 30S (P 0.01). However, there were no significant differences between development times at 20° and 25°C (P > 0.05). Within any one specific temperature series, no significant difference was observed between the salinity values tested (P > 0.05). The duration of each of the five zoeal stages was similar within each and the same temperature/salinity combination, whereas the duration of the megalop was twice as long as any of the zoeal stages. The combination of the lowest temperature (15°C) and the highest salinity (35) tested resulted in the greatest larval survival of 28%. Highest mortality occurred at 25°C, at which temperature development was completed only at 35S. A sharp drop in larval survival was observed in the transition period Zoea V — megalop in all combinations of temperature and salinity tested. Within the limits of tolerance to temperature and salinity, the former effected more pronounced differences in the duration of larval development, while salinity appeared to constitute a limiting factor for survival.     

A response-surface approach to the combined effects of temperature and salinity on the larval development of Adula californiensis (Pelecypoda: Mytilidae). I. Survival and growth of three and fifteen-day old larvae

Laboratory experiments of a factorial design were used to examine the combined effects of temperature and salinity on the survival and growth of early and late-stage larvae of Adula californiensis (Phillippi, 1847). Response-surface curves were generated to predict optimal conditions for survival and growth in order to better understand the successful recruitment of this species within the Yaquina Bay estuary (Oregon, USA). Three-day old cultured larvae were more sensitive to reduced salinity than were 15-day old larvae. However, the 15-day old larvae showed a narrower temperature tolerance than the 3-day old larvae. A. californiensis larvae survived over a wider range of temperatures near optimum salinities than at salinities near their lower tolerance limit, and conversely. Temperature and salinity ranges for maximum survival (10° to 15°C, 31 to 33) were narrower than the ranges which occur within the estuary where the adult populations exist. Larval size did not increase markedly during the 15-day rearing period, and was not greatly affected by temperature or salinity. No statistically significant temperature-salinity interaction was found for either survival or growth.     

Effects of salinity on respiration and nitrogen excretion in two species of echinoderms

The 30-d survival limit of Eupentacta quinquesemita and Strongylocentrotus droebachiensis is 12–13 S. The activity coefficient (1 000/righting time in seconds) of stepwise acclimated sea urchins declined from 16.3 at 30 S to 3.5 at 15 S. Oxygen consumption rates (QO₂) of both species held at 30 S and 13°C were highest in June and lowest in December. During the summer, when environmental salinity is most variable in southeastern Alaska, the QO₂ of both species held at 30, 20 and 15 S varied directly with salinity. Perivisceral fluid PO₂ varied directly with acclimation salinity in sea urchins, but not in sea cucumbers. Perivisceral fluid oxygen content of acclimated sea urchins was significantly lower at 15 and 20 S than at 30 S due to reduced PO₂ and extracellular fluid volume at the lower salinities. The QO₂ of both species varied directly with ambient salinity during a 30-10-30. semidiurnal pattern of fluctuating salinity. No change occurred in the average QO₂ of either species over a 15-30-15. semidiurnal pattern of fluctuating salinity. Sea urchin perivisceral fluid PO₂ declined as ambient salinity fluctuated away from the acclimation salinity in both cycles and increased as ambient salinity returned to the acclimation salinity. Total nitrogen excretion of stepwise acclimated sea cucumbers declined significantly from 30 to 15 S, but there was no salinity effect on total nitrogen excretion in sea urchins. Ammonia excretion varied directly with salinity in stepwise acclimated sea cucumbers (67–96% of total nitrogen excreted), but there was no salinity effect on ammonia excretion (89–95% of total nitrogen excreted) of sea urchins. Urea excretion did not vary with salinity in sea cucumbers (2–4% of total nitrogen excreted) or sea urchins (2–9% of total nitrogen excreted). Primary amines varied inversely with salinity in sea cucumbers (2–30% of total nitrogen excreted), but did not vary with salinity in sea urchins (2–4% of total nitrogen excreted). The oxygen: nitrogen ratio of both species indicated that carbohydrate and/or lipid form the primary catabolic substrate. The O:N ratio did not vary as a function of salinity. Both species are more tolerant to reduced salinity than previously reported, however, rates of oxygen consumption and/or nitrogen excretion are modified by salinity as well as season.     

Reproductive energetics of two species of dorid nudibranchs with planktotrophic and lecithotrophic larval strategies

Onchidoris muricata (Müller) and Adalaria proxima (Alder and Hancock) are sympatric, potentially competing species of dorid nudibranchs, which preferentially graze the cheilostome polyzoan Electra pilosa (L.). O. muricata is small and lays small eggs which hatch as poorly-developed planktotrophic veliger larvae. A. proxima is larger and reproduces by means of larger eggs which hatch, as well-developed lecithotrophic larvae, that can metamorphose within approximately 24 h of release. A. proxima larvae can feed in the plankton, but do not require extrinsic nutrition to undergo complete development. Both species spawn in February–april, and have a strictly annual life-cycle. Comparisons of the calorific content of spawn have shown that A. proxima apportions a greater number of calories to reproduction, but that O. muricata makes a greater relative effort. A. proxima shown considerable individual variability in reproductive effort, which fails to correlate with, body size or rate of spawning. A more deterministic situation applies to O. muricata, because body size and fecundity follow an allometric relationship. It appears that there is a threshold of absolute energy required to support the lecithotrophic larval strategy in nudibranchs, and that this is not attained by the smaller species, O. muricata. A. proxima thus appears to have both reproductive strategies open to it, and to have adopted lecithotrophy in order to offset the unpredictability of energy available for reproduction.Communicated by J. M. Mauchline, Oban     

Entrainment of the larval release rhythm of the crab Rhithropanopeus harrisii (Brachyura: Xanthidae) by cycles in salinity change

Influences of salinity, Na, K, Ca and Mg on Na–K-ATPase activity in the posterior gills of Carcinus maenas (L.) have been investigated with respect to the role of the enzyme in hyperosmotic regulation. K and Mg ions were obligatory for enzyme activity. The dependence on the K concentration can be seen in a saturation curve of the Michaelis-Menten type. Low concentrations of Ca (0.2–3 mM) in the incubation medium strongly inhibited Na–K-ATPase activity. Activities inhibited by Ca could be reactivated to non-inhibited values by the addition of higher amounts of Mg (25 mM). Activity increased along with the salinity of the sea water used as incubation medium up to about 10 S. Here, maximum activity was observed. Further salinity increases of the incubating sea water were inhibitory. Salinity dependence is assumed to be based on Na dependence of the Na-pump. Comparative investigations of the Na–K-ATPase activity and its affinity to sodium in five species of decapod crustaceans indicated that levels of Na–K-ATPase differed in the posterior gills of stenohaline and euryhaline species. The results obtained confirm previous assumptions of a central role of the branchial Na–K-ATPase in hyperosmotic regulation. Properties of the Na–K-ATPase, such as affinity for substrates or dependence on ionic sea water constituents, are kept constant with respect to salinity changes. Modifications due to salinity only concern enzyme amounts especially in the posterior gills. The finding that the Na-pump is localized in basolateral parts of ion-transporting epithelial cells confirms the aforementioned results.