The embryonic development of attached and isolated eggs of Carcinus maenas

Eggs of the shore crab, Carcinus maenas, were reared in the laboratory both attached to and in isolation from the female. With continuous agitation the isolated eggs showed better survival and faster embryonic development than attached eggs under comparable conditions. Embryonic development was successful at temperatures from 11 to 25°C. and for attached eggs the development time decreased with temperature according to the equation: D = 20326 (T + 3.3)^?2.09. At all temperatures development was slower than for a comparable study at Plymouth by Wear [8]. Isolated eggs were reared under a wide range of salinities, and appreciable survival beyond the prezoea occurred from 26‰ to 39‰.     

Effects of salinity variations on the rates of photosynthesis and respiration of the juvenile giant clam (Tridacna gigas,Bivalvia, Cardiidae)

Giant clams are in symbiotic relationship with the photosynthesizing zooxanthellae and dwell in the shallow coral reefs of the Indo-Pacific region where they may be exposed to fluctuating salinities during high levels of precipitation. This study evaluated the effects of reduced salinities (18, 25, and 35‰ as control) on the rates of photosynthesis and respiration in juvenile Tridacna gigas for 14 days. At 18‰, total mortality was recorded after day 4, so no photosynthetic measurements were subsequently conducted for this treatment. However, results showed no significant differences in the photosynthetic rates among treatments. Respiration rates were significantly increased at both low salinities resulting in low P_g/R ratios. After 14 days of exposure, photosynthetic parameters at 25‰ were not significantly different from the control which suggests that juvenile T. gigas may be able to acclimate to osmotic stress and adjust its photophysiology following reductions in salinity of up to 25‰.     

Growth and Toxigenesis of the Chrysomonad Prymnesium parvum as a Function of Salinity*

SYNOPSIS The euryhaline chrysomonad Prymnesium parvum (Carter) was grown in artificial (ASW) and natural sea water (NSW) media at salinities 1.3-33.3 ‰, and constant illumination. Low salinities (< 10‰) increased the doubling time (DT) and induced higher levels of protein and nucleic acids. DT was lowest for cells in ASW at 25 ‰ and NSW 17.9 ‰. The protein content was more variable. RNA content was lowest for cells at ca. 10 ‰. The DNA content was lowest for cells in 10‰ ASW and 11‰ NSW. Generally, the cells grew faster in NSW but had less protein and RNA than cells in ASW. The highest hemolytic content was in cells grown at 22.8 ‰ ASW or NSW. Glycerol enhanced growth rate and toxin synthesis within 24 hr of addition to the cells. Hemolysis was inhibited by high pH's. A membrane fraction containing ca. 20% of the hemolysin was isolated by density gradient centrifugation.     

Influence of salinity and cadmium on capsule strength in Pacific herring eggs

Eggs of Pacific herring (Clupea pallasi) were incubated at 5°C in salinities of 5, 20, and 35‰, and in cadmium concentrations of 0.05, 0.1, 1, 5, and 10 ppm (20‰ S). Bursting pressures of eggs in the eight groups were measured throughout incubation. In general, bursting pressures rose to a primary maximum after fertilization, declined, rose to a secondary maximum, then declined again toward hatching. Rate of attainment of the primary maximum was related to salinity of the incubation medium. Bursting pressures at the primary and secondary maxima reached final values of about 1300 and 700 g, respectively, in incubation salinities at and above 20‰. Corresponding egg volumes were greatest in low salinities (5‰) and near minimum values in salinities of 20‰ or greater (35‰). Cadmium in the incubation medium delayed attainment of primary maximum bursting pressures and primary and secondary maxima were reduced to 200–350 g at Cd concentrations near 1 ppm. Egg volumes also decreased with increased Cd concentration. It appears that Ca⁺⁺/Cd⁺⁺ ratios, depending on salinity and Cd levels in the incubation medium, influence the properties of both the jelly coat and the capsule of herring eggs. Changes in the properties of these layers could make the eggs more susceptible to mechanical damage, particularly at combinations of higher (?1 ppm) Cd concentration and lower (?20 ‰) salinities.     

The effect of salinity on larval survival and development in the sea urchin Echinometra lucunter

Summary

Reductions in salinity can have adverse effects on larval development and larval survival in some invertebrate taxa but not others. Salinity tolerance of larvae may be particularly important in echinoderms because they are both poor ion regulators and stenohaline. I examined the effect of six levels of salinity (15, 18, 21, 24, 27 and 33 PSU) on survival and rate of development of larvae in the subtropical sea urchin Echinometra lucunter. In the short-term, mortality rate was significantly lower in 33 PSU than in all other salinities except 27 PSU, and it was significantly greater in 15 and 18 PSU than in all higher salinities. In the long-term, daily and cumulative mortality were significantly greater in 15 PSU than in most other salinities over 11 days of development (except for cumulative mortality in 18 PSU). They were significantly greater in 18 PSU than in 21 PSU or 33 PSU over a period of 13 days. Furthermore, daily mortality was significantly greater in 18 PSU than in 24 PSU or 27 PSU at 13 d after fertilization. Daily and cumulative mortality were significantly lower in 33 PSU than in 21, 24 or 27 PSU over a period of 17 days. Although in the control (33 PSU) 75% of larvae completed development to the 8-arm stage at 35 d, no larvae developed further than the 4-arm stage in 18, 21, 24 or 27 PSU; in 15 PSU, ~60% of larvae did not develop further than swimming blastulae. Since prolonged exposure to salinities as high as 27 PSU (frequently recorded in the adult habitat) can result in great larval losses, adaptive behaviours that prevent larvae from entering water layers of low salinity will enhance their chance for survival.     

Population Growth of Six Iranian Brachionus Rotifer Strains in Response to Salinity and Food Type

Intrinsic rates of population increase (r) were evaluated as a measure of population dynamics of four strains of Brachionus plicatilis and two strains of B. urceolaris from Iran in response to different salinities and feeding algae. Each rotifer strain was cultured at four salinities: 5, 20, 25 and 30‰ and fed with two microalgal species: Chlorella vulgaris and Nannochloropsis oculata. Salinity of 5‰ was critical for all the examined strains, at which r was at minimum and was different from the other salinities (P < 0.05). For B. plicatilis strains, the maximum r was observed in those fed on Chlorella at salinities of 10 and 30‰ (64 ± 0.01 day⁻¹). While, in B. urceolaris, maximum r was for Nannochloropsis fed rotifers at salinity of 20‰ (0.69 ± 0.01 day⁻¹). Maximum final population density (FD) was obtained for a strain of B. urceolaris fed on Nannochloropsis at 20‰ (329.3 ± 10.9 ind.mL⁻¹). FD was relatively lower in B. plicatilis strains among all examined salinities. ANOVA showed the significant effect of salinity and rotifer strain, and algae × rotifer strain on both r and FD, and salinity × rotifer × algae on FD (P < 0.05). (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Salinity and oxygen tolerances of eggs and larvae of Hawaiian striped mullet,Mugil cephalus L.*

Salinity and oxygen tolerances of eggs and larvae of Hawaiian striped mullet (Mugil cephalus L.) were studied. Optimal salinities for eggs incubated at 19.5-20.5°C were 30–32‰. Maximum larval survival occurred within the salinity range of 26–28‰. Significant decreases in egg survival occurred with eggs incubated in mean oxygen concentrations below 5.0 p.p.m. and for larvae held in mean oxygen concentrations below 5.4 p.p.m. The results are discussed in terms of spawning sites and the effects of oxygen saturation values on fish eggs and larvae.     

A model evaluating the contribution of environmental factors to the production of resting eggs in the rotifer Brachionus plicatilis

The production of resting eggs by the rotifer Brachionus plicatilis was tested at four salinities (9, 18, 27 and 36\%) and six concentrations of the alga Chlorella stigmatophora (0.25, 0.5, 1.0, 2.0, 4.0 and 6.0 × 10⁶ cells ml^–1). The results indicated that resting eggs were produced only at two salinities (9\% and 18\%) and that their number was affected by the amount of food provided. A model consisting of two generalized linear sub-models was built to evaluate the contribution of each of the tested food concentrations at the two salinities. The sub-models were used to distinguish between two different components of resting egg production: one related to the presence or absence of resting egg production, and the other to the number of resting eggs produced, given that production had occurred. Besides indicating the best combination of salinity and food concentration for obtaining large numbers of resting eggs, they revealed the contribution of internal population factors that were not controlled in the course of the experiment. The model identified the positive contribution of the relative number of females to males, and the negative association between high rotifer densities and the production of resting eggs. The results of the present study help in defining the optimal conditions for mass production of resting eggs, which are of potential importance in aquaculture.Deceased, September 1991.     

Salinitätspräferenzen bei Glasaalen und jungen Gelbaalen(Anguilla anguilla)

Preference experiments have been carried out on elvers and young eels in order to assess locomotory responses to different salinity conditions. Employing different test apparatus it was established that elvers preferred fresh water to water of 18 ‰ and 36 ‰ S. There was no significant difference between responses to water of 18 ‰ and 36 ‰ S. When young yellow eels were offered different salinities (fresh water, 18 ‰ and 36 ‰ S) in tubes, a preference for water of 18 ‰ S was noted. This preference was not influenced by the different salinities in which the eels had previously been kept.     

Effects of emergence date and maternal size on egg development and sizes of eggs and first-instar nymphs of a semelparous aquatic insect

We examined whether or not sizes of eggs and offspring were related to emergence date or maternal size in a semelparous aquatic insect (the burrowing mayfly, Hexagenia) in which parental care is lacking and oviposited eggs are passively dispersed. We quantified the size of males and female imagos over the emergence span at a site on the Detroit River, Canada, and investigated relationships between emergence date and female size and (1) egg size and (2) size of first-instar nymphs. Although size of female imagos (H. limbata and H. rigida combined) declined significantly (P<0.025) over the emergence season, there was no significant relationship between body length and emergence date for males of either species. Males were significantly (P<0.001) smaller than females. H. limbata eggs, subsampled from three individuals from each of three size classes of female imagos collected on seven sampling dates, were measured using video image analysis. Eggs (n=100) oviposited by each of 63 H. limbata imagos were inspected daily for hatching. Newly hatched nymphs were removed, counted and measured. Egg size (P<0.001) and size of first-instar nymphs (P<0.001) varied significantly with emergence date, but not maternal size. The largest eggs and newly hatched nymphs occurred at peak emergence of adults. The synchronous release of larger (faster-sinking) eggs may result in reduced predation. Plasticity in egg development time and egg and nymph size may account for the ability of this taxon to recover from episodes of massive population reduction. Received: 12 March 1996 / Accepted: 24 February 1997     

GROWTH RESPONSES TO SALINITY VARIATION IN FOUR ARCTIC ICE DIATOMS1,2

During spring, extensive blooms of microalgae grow on the underside of arctic sea ice. The brownish, algal layer penetrates ca. 2 cm into the bottom surface of the ice and the algae are potentially exposed to very high salinities. Four diatom species, Melosira juergensii Ag., Porosira glacialis (Grun.) Jørg., Navicula transitans var. derasa (Grun.) Cleve, and Coscinodiscus lacustris Grun., isolated from, sea ice samples taken from the Beaufort and Chukchi seas near Barrow, Alaska, were grown at 11 salinities ranging from 5 to 70‰ at 5 C under constant illumination. All of the species grew at 5‰ except N. transitans whose lower growth limit was 15‰. Growth was high over a broad range of salinities, but none of the species grew at salinities above 60‰. These diatom species appear to be well suited to tolerate the salinities in the brine pockets near the bottom of annual arctic sea ice where they are found. High brine-cell salinity, however, may limit the upward, penetration of ice algae into the bottom of sea ice.     

Spawning habits and embryonic development of the banded lampeye killifish Aplocheilichthys spilauchen (Duméril 1861) in ex situ fresh and brackish water environments

Aside from ornamental uses, there is growing interest in using killifishes for a multiplicity of purposes including baitfish and mosquito biocontrol. This experiment explored the spawning habits and embryonic development of the banded lampeye, Aplocheilichthys spilauchen in ex situ freshwater (0.04‰) and brackish water (5.01‰) to ascertain the captive breeding prospects for mosquito control in areas where they occur. Significantly higher number of eggs were laid in the brackish water than the freshwater (X² = 1613.0, P < 0.05), and black mop was the most preferred spawning substrate, followed by green, blue and white mops. Microscopic monitoring of embryos revealed that cleavage occurred within the first 30 min after fertilization, organogenesis commenced on average in the 25th hour and hatching in approximately 230 h. Although freshwater eggs were relatively bigger than brackish water eggs and certain embryonic developmental stages occurred faster in the freshwater than brackish water, these differences were overall not significant and had no effects on the development and hatching. The observed outcome that A. spilauchen can be optimally propagated with black mops in brackish water offers a significant step in its use for the mosquito biocontrol programme, as well as other potential uses not yet explored.     

Ionregulation in juvenile swordspine snook (Centropomus ensiferus,Poey, 1860) in relation to environmental salinity

Ninety‐nine swordspine snook Centropomus ensiferus (9.80 ± 0.3 g, mean ± SE) were studied in order to evaluate the influence of salinity on physiological properties under rearing conditions. Growth performance, survival rates, and ion concentrations (Na⁺, K⁺, Cl^?) as well proximal composition were measured over 76 days. Fish were exposed to three experimental salinities (0, 10, 20 ‰ , three replicates per treatment) and maintained in plastic tanks with a recirculation system equipped with flow‐through aquaria pumps (533 L per tank). Fish were fed twice daily to apparent satiation; at the end of the experiment the weight of fish kept in 10 ‰ was higher than that of fish kept in 0 and 20 ‰ , however no significant differences (P > 0.05) were observed among the experimental salinities. Survival was significantly lower in 10 ‰ salinity than in fish kept in 20 and 0 ‰ salinities. No significant differences (P > 0.05) were found in the Condition factor (K), specific growth rate (SGR), or in plasma Na⁺, K⁺, or Cl^? concentrations among treatments. Salinities also did not affect body composition (P > 0.05), but were significantly lower (P < 0.05) than at the start of the experiment. However, towards the end of the experiment a large accumulation of visceral fat in fish farmed in the three salinities (VFI > 4%) was observed. Water quality was within the optimum range (T: 28.7 ± 0.1°C; O2: 5.6 ± 0.1 mg L^?1; ammonia: 0.2 mg L^?1) for the growth of swordspine snook. Data indicates that C. ensiferus is an ionoregulator fish and able to cultivate successfully in various osmotic conditions, and in turn, maintain high levels of survival in captivity.     

Effect of elevated temperature on osmotic and ionic regulation in a salt-tolerant caddisfly from Death Valley,California

The effects of temperature (8–10 or 20°C) on regulation of haemolymph osmotic and ionic concentrations were investigated over a range of salinities (0–25‰) in fifth-instar larvae of the Death Valley caddisfly Limnephilus assimilis. At low temperatures, levels of chloride and sodium in the haemolymph are regulated over a wide range of salinities corresponding to the salinities at which larvae occur in nature and at which they can complete development into adults. In contrast, haemolymph osmolality is constant at low salinities (<14‰) but approaches conformity with the medium at higher salinities. High temperature reduces the larva's ability to maintain low chloride concentrations in its haemolymph and also leads to a reduction in haemolymph osmotic pressure; thus, at high temperatures ions account for more of the haemolymph osmotic concentration than at low temperatures. These data suggest that the absence of larvae from thermal pools and from all Death Valley waters in summer can be explained by the effects of high water temperatures on hydromineral regulation.     

The effects of repeated early deprivation on ultrasonic vocalizations and ontogenetic development in mandarin vole pups

Early deprivation is popularly used in rodent models as an early life social stress to investigate and determine the factors that affect the development of the brain and behavior. Ultrasonic calls made by pups play an important role in parental–pup interactions during the neonatal period. However, whether repeated early deprivation affects the properties of ultrasonic vocalizations (USVs) produced by mandarin vole (Microtus mandarinus) pups, and whether ontogenetic development is subsequently affected, remains unclear. Here we measured USVs and developmental parameters in mandarin vole pups deprived of their parents and littermates for 3 h per day (ED, which is significantly different from 5 min isolation used to induce USVs) and another pup group developed under normal nest conditions (PC). Repeated measures analysis indicated that the number of USVs from ED pups was significantly lower than those from PC pups during the postnatal period (p < 0.05). The pulse durations of ED pups were longer than those of PC pups at two (p < 0.001) and five days of age (p < 0.05), but shorter at 14 days of age (p < 0.001). Compared with PC pups, the frequency range of the ED pups was wider at 18–45 kHZ, variable during the first week, smaller and narrower at 18–30 kHZ at eight and 11 days of age, and became stable similar to PC pups at 25 kHZ after 14 days of age. ED also reduced pup body weight significantly and resulted in earlier eye opening compared with PC pups (p < 0.001). A positive relationship was also found between USV emissions and levels of parental care received by pups. It appears that pup USVs are an important age-dependent behavioral phenotype and an effective communicative method between parents and offspring. Prolonged parental and littermate deprivation (ED) may alter USVs emitted by pups and then ontogenetic development and parental care. Mandarin voles show USV properties similar to socially monogamous rodents and this add further support to the hypothesis that species with different social systems produce different patterns of ultrasonic vocalizations. USVs, ontogenetic development and parental care are closely associated.     

Artificial incubation of trumpeter swan eggs: Selected factors affecting hatchability

Eggs collected from captive trumpeter swans (Cygnus buccinator) in 1993 (n = 33) and 1994 (n = 42) were artificially incubated with careful monitoring to identify factors contributing to the low hatch success reported by the Ontario Trumpeter Swan Restoration Program. Fertility was > 80% in both years, whereas hatch success of fertile eggs was 14.3% (n = 4) of 28 eggs in 1993 and 37.1% (n = 13) of 35 eggs in 1994. Necropsy of non‐viable eggs indicated a high incidence of embryonic mortality during early and late incubation. Early embryonic mortality was associated with egg storage times exceeding 7 days (P < 0.05) and bacterial contamination of eggs (P < 0.01). Late mortality was associated with (P < 0.001) increased weight loss during incubation period and may have resulted from incubator temperature and humidity fluctuations. We established patterns of weight loss for eggs and determined that hatched eggs lost 11–15% of initial mass and that weight loss >15% resulted in embryo mortality. Results from this study indicate that collection and handling of eggs before incubation and precise control of the incubator environment are critical to hatchability of eggs. Zoo Biol 18:403–414, 1999. © 1999 Wiley‐Liss, Inc.     

Growth,salinity tolerance and extracellular carbohydrate yield of Prasinocladus marinus (Cienk.) Waern (class prasinophyceae)

Growth of Prasinocladus marinus (Cienk.) Waern was maximal in media of 35‰ salinity, showing a five-fold increase over a 7-day period. At lower salinities (10–27.5‰) growth varied between 55–90% and at 45‰ was 85% of that in ‘normal’ sea water. Yield of extracellular carbohydrate was higher than in ‘normal’ sea water in lowered salinities and at 45‰ over a 42-day period. Larger quantities of extracellular carbohydrate were obtained at all stages of growth in media of 15‰, compared with those of 35‰ and 45‰. Whilst growth forms were markedly different at low salinities, DNA measurements indicated that similar quantities of cell material were present. Mannitol and glucose were the principal carbohydrates identified in intracellular material, and glucose in the extracellular products. Chloroplast pigment synthesis appears unaffected by growth at 15‰, 35‰, and 45‰.     

Salinity tolerance and osmoregulatory ability of Galaxias maculatus (Jenyns) (Pisces, Salmoniformes, Galaxiidae)

The salinity tolerance and osmoregulatory ability of Galaxias maculatus were investigated. In the field this species has been recorded from salinities of less than 1‰ to 49‰. In the laboratory, upper L.D.⁵⁰ salinity values of 62‰ after gradual acclimation and 45‰ after direct transfer were established. Within the salinity range of its field occurrence the species is a powerful osmoregulator, being able both to hypo- and hyper-osmoregulate.     

Changes in plasma osmolality and Na+/K+ ATPase activity of juvenile obscure puffer Takifugu obscurus following salinity challenge

The osmoregulatory capabilities of 6-month-old juvenile obscure puffer Takifugu obscurus, transferred directly from fresh water to different salinities (0‰, freshwater control; 10‰; 20‰ and 30‰), were studied over an 8-day period. After transfer, plasma osmolality of the fish at 30‰ was significantly higher than those at all other salinities throughout the experiment. The Na⁺/K⁺ ATPase activity in the gills of the fish treated with various salinities increased significantly, peaking at 48 h, then decreased gradually to the control level at 192 h. Similar fluctuation trends of the Na⁺/K⁺ ATPase activity were observed in the kidneys. Modified Gaussian model provided accurate fits for the time-course changes in the Na⁺/K⁺ ATPase activities after abrupt salinity challenge. The results demonstrated that obscure puffer has strong capacity to tolerate abrupt salinity changes and can osmoregulate well over a wide range of salinities even in juvenile stage.