Calorespirometry of developing embryos and yolk-sac larvae of turbot (Scophthalmus maximus)

The rates of oxygen consumption and heat dissipation were simultaneously measured and related to contents of glucose, glycogen and lactate in order to determine whether anaerobic processes contributed significantly to the energy metabolism of developing turbot embryos and larvae. The results suggest that metabolism is fully aerobic between Days 0 and 12 post fertilisation. The data further suggest that glycogen is the sole metabolic fuel during the first 18 to 19 h post fertilisation. After the commencement of epiboly, carbohydrates play an insignificant role in the energy metabolism of the developing embryo and yolk-sac larva.     

Eggs and early larvae of Thrissocles species (Engraulidae: Pisces)

Eggs of Thrissocles species are found in surface plankton in the Ernakulam Channel (Cochin Harbour)during February to May 1967. The eggs hatch within 24 h. Empty egg shells have characteristic apertures, through which the embryos have emerged; yolk is resorbed 36 h after hatching.Larvae (36 to 72 h groups) assemble at the lighted region of the aquaria during day-time and scatter to different levels at night. Larvae older than 72 h show no inclination to assemble as before. All larvae died between 96 and 110 h after hatching. Many batches of eggs were reared in the same medium, and all of them behaved as described. The results indicate that the right type of food was available in the aquaria for larvae up to a period of 72 h. The volume of water also appears to have a bearing upon the survival rate and longevity of the larvae since, in small aquaria, more larvae died at an early stage.     

Effects of pressure,temperature and oxygen on the oxygen consumption rate of the Midwater copepod Gaussia princeps

In this study we assessed the amount of lead accumulated in the body of a grazing mollusc by transfer from its algal food in laboratory experiments, and compared these results with the amounts found in naturally occurring molluscs and seaweed. Near La Jolla, California (USA), where the concentration of lead in seawater is probably less than 0.08 g l^-1, most of the naturally occurring Egregia laevigata contains less than 0.4 g Pb g^-1 wet weight. The total body masses, without shells, of juvenile Haliotis rufescens fed on this seaweed for 3 to 6 months showed similar concentrations. When, however, E. laevigata is placed for 1 to 6 days in seawater to which lead has been added (0.1 or 1.0 mg l^-1) both the seaweed and the abalone subsequently fed with it accumulate proportionally larger amounts of lead. After 6 months, young abalone fed on E. laevigata pretreated with 1.0 mg Pb l^-1 accumulated up to 21 g Pb g^-1 wet weight. This amount of lead had no apparent consequences on the growth or activity of the molluscs. Analyses of 6 different organs from adult abalone showed that the lead was selectively concentrated in the digestive gland. In the foot (muscle tissue), which is the part normally consumed by humans, only negligible amounts were found.     

Yolk utilization and growth to yolk-sac absorption in summer flounder (Paralichthys dentatus) larvae at constant and cyclic temperatures

Rates of development, growth and yolk conversion efficiency were determined in larvae of the summer flounder Paralichtys dentatus at constant temperatures of 21°, 16°, 12° and 5°C and in temperature cycles of 21°–16°, 16°–11°, and 11°–5°C. In constant incubation temperatures, development rate increased with increasing temperature. Larvae reared in the cyclic temperature regimes exhibited development rates intermediate to those at the temperature extremes of the cycle. All larvae reared at 5°C and in the 11°–5°C cycle regime died prior to total yolk-sac absorption. Although development rates were temperature dependent, no significant differences in notochord length ash-free dry weight or yolk utilization efficiency were found at the time of total yolk-sac absorption. The similarity in growth and yolk utilization efficiency for larvae reared under these various temperature regimes suggests that the physiological mechanisms involved are able to compensate for temperature changes encountered in nature.Contribution No. 195 from EPA, Environmental Research Laboratory, Narragansett, Rhode Island 02882, USA     

Effect of temperature on viability and axial muscle development in embryos and yolk sac larvae of the Northeast Arctic cod (Gadus morhua)

Cod (Gadus morhua L.) eggs may develop and hatch within temperatures of −1.5 to 12 °C, but little is known about the effects of very low temperatures on larval characteristics. Eggs of the Northeast Arctic cod (Gadus morhua) were incubated at 1, 5 or 8 °C from Day 1 after fertilisation until hatching, and transferred to 5 °C after hatching. Histological samples of the axial musculature were taken at hatching and 5 d after hatching, and the data on muscle cellularity from these samples were related to survival and hatching, size, developmental data and viability of the yolk sac larvae. All larvae hatched at the same developmental stage. Incubation of eggs at 1 °C produced shorter larvae with a larger yolk sac and more, small deep fibres at hatching than larvae from eggs incubated at 5 or 8 °C. The larval size difference was still present 5 d after hatching, a time at which the larvae from 1 °C-incubated eggs were less developed and less resistant to an acute viability stress test (65 ppt salinity). Although there were no differences between temperature groups in number and size of muscle fibres 5 d after hatching, the deep fibres of the 1 °C-group contained less myofibrils than the two other groups. The phenotype of the larvae at hatching was thus affected within these incubation temperatures. Although all groups were transferred to the same temperature after hatching, the lowest egg incubation temperature (1 °C) still had a negative effect 5 d after hatching, as these larvae were both smaller, less resistant to stress and had less functional muscles at the time of first feeding. Our conclusion is therefore that 1 °C is close to, or below, the lower thermal tolerance limit for normal functional development of Northeast Arctic cod. The results are discussed in relation to larval viability and recruitment of this species in the wild. Received: 4 February 1998 / Accepted: 10 July 1998     

Physiological energetics of developing embryos and yolk-sac larvae of Atlantic cod (Gadus morhua). I. Respiration and nitrogen metabolism

This paper provides the basis for a general model of catabolic metabolism for developing embryos and yolk-sac larvae of Atlantic cod (Gadus morhua L.). Yolk-dependent routine rates of oxygen consumption, ammonia excretion, and accumulation of ammonium ions were related to quantitative changes in contents of glucose, glycogen, lactate, free amino acids, proteins and lipid classes (lipid classes published separately) in order to determine the rate and sequence of catabolic substrate oxidation that occurs with development at 6.0°C, 34.5 S. The stoichiometric relation of the oxygen consumption and total ammonia production to substrate utilisation indicated that during the first 2 to 3 d of development, glycogen was the sole substrate of oxidative metabolism. After formation of the syncytium, free amino acids (75%) together with polar lipids (13%, mainly phosphatidyl choline) and neutral lipids (9%, mainly triacylglycerol) comprised the metabolic fuels of embryonic development. Following hatch (Day 16 post fertilisation), the fuels were free amino acids (32%), polar lipids (20%, mainly phosphatidyl choline), neutral lipids (17%, mainly triacylglycerol) and proteins (31%). Thus, the catabolic metabolism of endogenously feeding Atlantic cod larvae was predominantly fuelled by amino acids (67%) and lipids (32%), while glycogen only accounted for 1% of the total enthalpy dissipated. It is proposed that the above sequence of catabolic substrate oxidation is also generally applicable to other cold-water fishes which spawn eggs that do not contain oil glubules.     

Effects of acute changes in temperature and salinity on the oxygen uptake of larvae of herring (Clupea harengus) and plaice (Pleuronectes platessa)

Routine oxygen uptake (QO₂) by yolk-sac and firstfeeding larvae of herring (Clupea harengus L.) and plaice (Pleuronectes platessa L.) was studied after acute change of temperature (8°, 13°, 18°C) and salinity (5, 12.7, 32, 40). In both species, QO₂ (l mg^-1 dry wt h^-1) of both larval stages increased with increasing temperature. Salinity effect on QO₂ varied: for yolk-sac larvae of both species a lower QO₂ was found at lower combined salinities (5 and 12.7); for feeding larvae a lower QO₂ was observed at 12.7 for both species, possibly due to the relatively smaller size of larvae used at this salinity. For both species, oxygen uptake increased as larvae grew and weight regression coefficients were between 0.74 and 1.33. At 32 S, no difference was found in oxygen consumption between species as a function of temperature.Based on a dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at the University of Stirling, Stirling, Scotland. The work was performed at the Dunstaffnage Marine Research Laboratory, Oban, Scotland     

Food selection by laboratory-reared larvae of the scaled sardine Harengula pensacolae (Pisces,Clupeidae) and the bay anchovy Anchoa mitchilli (Pisces,Engraulidae)

Food selection by laboratory-reared larvae of scaled sardines Harengula pensacolae, and bay anchovies Anchoa mitchilli, was compared. Natural plankton was fed to the larvae during the 22 days following hatching. Food levels in the rearing tanks were maintained at an average of 1,600 to 1,800 potential food organisms per liter. Larvae of both species selected as food copepod nauplii, copepodites, and copepods; initial feeding was on organisms of 50 to 75 body width. Larvae of H. pensacolae averaged 4.2 mm in total length at hatching and those of A. mitchilli about 2.0 mm. H. pensacolae larvae grew about 1.0 mm per day and A. mitchilli 0.70 mm per day. The mean number of food organisms in each digestive tract was greater in H. pensacolae than in A. mitchilli, and the difference in number increased as the larvae grew. Average size of food organisms eaten increased for both species with growth, because of selection by the larvae; the average size of copepodites and copepods in digestive tracts increased at a faste rate in H. pensacolae than A. mitchilli. A. mitchilli longer than 8 mm did not eat copepod nauplii.Contribution No. 170, Bureau of Commercial Fisheries Tropical Atlantic Biological laboratory, Miami, Florida 33149, USA.     

Acute temperature and low dissolved oxygen tolerances of brachyuran crab (Cancer irroratus) larvae

Tolerance limits to acute temperature, and temperature and low dissolved oxygen stresses were determined for 5 zoeal stages and megalops of Cancer irroratus Say. The acute temperature limits for a 120 min exposure were all approximately 29.0°C, with little interstage, variation, while those for 240 min exposure ranged from 27.3° to 28.5°C. More interstage variation was shown when temperature and low dissolved oxygen stress were combined, with low oxygen tolerance decreasing as temperature increased. The first, second, and fourth zoeal stages display similar patterns of response. The third and fifth stages show a similar response, but are different from the former stages. The megalops is relatively insensitive to changes in oxygen concentration with temperature. The larval stages did not show a progressive increase in tolerance to temperature or low dissolved oxygen with development. Tolerance to these factors may be related to size, stage of development and activity level. The larval stages have capacities to tolerate a wider range of these factors than they require in the natural environment.     

Physiological energetics of developing embryos and yolk-sac larvae of Atlantic cod (Gadus morhua). II. Lipid metabolism and enthalpy balance

This paper presents quantitative data for the changes in the contents of total lipids, lipid classes and their associated fatty acids, together with the changes in caloric contents of developing eggs and yolk-sac larvae of Atlantic cod (Gadus morhua L.). During development between Day 0 to 28 post fertilisation, 32% of catabolic metabolism was fuelled by lipids. On a mass-specific basis, polar lipids (mainly phosphatidyl choline) contributed 60%, and neutral lipids (mainly triacyl-glycerol) contributed 40% to this catabolic component, with each class supplying similar amounts of fatty acids as fuel. The fatty acids supplied by phosphatidyl choline were catabolised non-selectively (i.e. in proportion to their presence in the egg), with about half of them being polyunsaturated. However, of the fatty acids esterified in triacylglycerol, the larvae showed an apparent oxidation preference for monoenes over polyunsaturates or saturates. Routine rates of oxygen consumption and ammonia production were related to the caloric contents of the eggs and larvae in order to derive an enthalpy balance equation (of the form P=C+R+E) for an Atlantic cod larva during its period of endogenous nutrition. For the interval of Day 0 to 25 post fertilisation (the period of yolk dependence), integration of the physiological and caloric data revealed that Atlantic cod larvae conserved 53% of yolk enthalpy (C) for growth (P), 42% was dissipated due to metabolism (R) while only 5% was lost via excretion (E).     

Effects of temperature,seawater osmolality and season on oxygen consumption and osmoregulation of the amphipod Gammarus oceanicus

Seasonal variations of oxygen consumption rate, haemolymph osmolality and the concentrations of the inorganic ions potassium and sodium in the haemolymph were measured in the littoral amphipod Gammarus oceanicus collected from the Trondheimsfjorden, Norway in 1987. For each season comparisons were made of amphipods acclimated for 1 wk to 0.5, 4.5, 10.0, 15.0 and 20.0°C, in combination with seawater osmolalities of 100, 500 and 1200 mOsm and to the seawater osmolality corresponding to that of the collecting site. The oxygen consumption rate showed a temperature insensitivity when the amphipods were acclimated to low temperatures in winter and high temperatures in summer. Significant differences were found in oxygen consumption between individuals acclimated to various medium osmolalities, possibly indicating higher energy requirements for osmotic and ionic regulation at low seawater osmolalities. Oxygen consumption rate was significantly higher in summer than in other seasons. Haemolymph osmolality and the concentration of the inorganic ions sodium and potassium were not influenced by temperature or season. Determination of haemolymph osmolalities and concentrations of inorganic ions revealed that G. oceanicus is a strong hyper-osmotic and hyper-ionic regulator in dilute seawater. The concentration of potassium in the haemolymph is less influenced by seawater osmolality than haemolymph osmolality and the haemolymph concentration of sodium.     

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.     

Effects of temporary starvation on the survival,and on subsequent feeding and growth,of oyster (Crassostrea gigas) larvae

Larvae of oysters, Crassostrea gigas, were maintained without food for 1 to 8 d after fertilization, and fed daily thereafter. There was little difference in survival and growth between controls and larvae kept without food for 2 or 3 d. Survival and growth rates were depressed in larvae starved for 4 or 5 d. For larvae starved for 6 to 8 d, survival was negligible or nil; even those larvae which survived the starvation period died later in the presence of food, apparently because of impaired digestion. Therefore, food availability in the first few days after spawning appears to be of paramount importance to the successful recruitment of Pacific oysters.     

Effects of ammonia, nitrite and nitrate on hemoglobin content and oxygen consumption of freshwater fish, Cyprinus carpio (Linnaeus)

Lethal effects of nitrogenous compounds ammonia, nitrite and nitrate on freshwater fish Cyprinus carpio were studied and the static LC50 values obtained for these 3 toxicants for 24 hr were 0.80 ppb, 171.36 ppm; 1075.10 ppm and continuous flowthrough LC50 values for 24 hr were 0.72 ppb, 154.31 ppm; 967.63 ppm respectively. The fish were exposed to lethal concentrations to study the changes in hematological parameters and the rate of oxygen consumption. During the period of exposure general decline in the content of hemoglobin was observed. Methemoglobin content increased in case of nitrite exposure consequently the hemoglobin levels decreased drastically. It is also observed that rate of oxygen consumption decreased progressively with the increase of toxicant concentration and duration of the exposure.     

Effects of feeding history on mobilisation and deposition of body constituents and on growth in juvenile Ambassis vachelli (Pisces: Chandidae)

Young Ambassis vachelli (Richardson) 40 to 50 d old, were used in a laboratory experiment to test the effects of starvation and subsequent re-feeding on body constituents and growth. Fish in three laboratory treatments (fed continuously; fed for 9 d and then starved for 15 d; starved for 9 d and fed for 15 d), were compared to fish from a local field population. Different body stores were mobilised at different times and rates during starvation. Carbohydrates were mobilised from the onset of starvation and were depleted after 3 d. Lipid and protein were mobilised at an increasing rate from the onset of starvation. The mortality in starved fish was relatively high (up to 70%) until re-feeding. Upon feeding, all body stores were restored rapidly in fish that were starved, with carbohydrate levels displaying an overshoot (carbohydrate level exceeding normal levels) in comparison to the levels in continuously fed fish. After 15 d of feeding, the starved fish had levels of constituents similar to those in continuously fed fish. Fish that were fed and subsequently starved were able to maintain themselves for at least 15 d prior to death, indicating a better degree of starvation resistance than fish without a history of feeding. This implies that feeding history in the early life of a fish is important in growth and survival but that young fish may have growth regimes flexible enough to survive relatively long periods of starvation.     

Combined effects of temperature and salinity on the survival and growth of the larvae of Pandalus jordani (Decapoda: Pandalidae)

Survival and growth over an environmental range of temperature and salinities were examined in order to help assess the importance of these environmental factors in affecting the distribution, abundance and survival of larvae and provide greater understanding of factors affecting fluctuations in adult Pandalus jordani Rathbun population sizes. Larvae were shown to have a wide tolerance to salinity, especially in the early stages, but a relatively narrow tolerance to temperature. The optimal temperatures for survival, 8° to 11°C, were also optimal for growth as reflected by maximal growth increments and body size. It is therefore felt that fluctuations in temperature as seen within and between successive larval seasons would have profound effects on larval survival, growth rates and size at metamorphosis to the benthic juvenile phase.     

Otolith record of age, growth, and ontogeny in larval and pelagic juvenile Stephanolepishispidus (Pisces: Monacanthidae)

Juveniles of the planehead filefish Stephano-lepishispidus (Pisces: Monacanthidae) (Linnaeus, 1766) are a major component of the Sargassum spp. community, yet little is known of their ecology. In this study, the otolith record of age, growth, and ontogeny in S. hispidus was examined. Juveniles caught off Beaufort Inlet, North Carolina (USA) on 30 June 1996 were marked with alizarin complexone and reared in a flow-through, outdoor tank for up to 19 days. Examination of marked otoliths at several time intervals showed that increment formation was not significantly different than one increment per day, and thus, increment number was used to estimate age. Depth-distribution, morphology, and meristics of larvae and juveniles collected (1990–1992) between Cape Romain, South Carolina, and Cape Hatteras, North Carolina, were examined to identify the timing of the larval to juvenile transition. All indicators suggested the transition occurred between 17 and 20 days. Mean otolith increment widths exhibited a marked change at about 20 days, coinciding with the timing of the larval to juvenile transition and a change in the depth distribution from bottom to surface waters. Increment width of individual juveniles, however, did not exhibit the same pattern; only 40% conformed to the pattern identified for all fish. Thus, the record of the larval to juvenile transition is clear at the population level, but unresolved at the individual level. Received: 1 November 1999 / Accepted: 18 December 2000     

Compartmental distribution of free amino acids and protein in developing yolk-sac larvae of Atlantic halibut (Hippoglossus hippoglossus)

Free amino acids (FAA) and protein have been measured in whole laboratory-readed halibut larvae and on dissected individuals separated into yolk and body compartments. At hatching both FAA and protein are mainly located in the yolk compartment. During the first 12 d of the yolk-sac stage more than 70% of the FAA pool disappeared from the yolk without any significant changes in the yolk protein pool. This suggests different uptake mechanisms for FAA and protein from the yolk, and a sequential utilisation of the endogeneous reservoirs of free and protein amino acids in Atlantic halibut larvae. The data suggest that in the early yolk-sac stage FAA enter the embryo from the yolk and are utilised both for energy and protein synthesis. Later on when the free pool cannot fulfil the nutritional requirements, additional amino acids are recruited from yolk protein. Of the total amino acids (free + protein amino acids) present at hatching ca. 60% will be used as precursors for body protein synthesis while the remaining 40% are used as fuel in the larval energy metabolism.     

Temperature-time relationships for survival of embryos and larvae of Mulinia lateralis (Mollusca: Bivalvia)

The influence of temperature over 8 time intervals on survival of cleavage stages, trochophore larvae, and straighthinge veliger larvae of Mulinia lateralis (Say) was investigated using a thermal gradient apparatus. There was a direct relationship of mortality with increased period of exposure. As the clams aged, temperature tolerance increased, with cleavage stages being most sensitive to higher temperatures and straight-hinge larvae least sensitive. Multiple-regression equations were developed to allow prediction of percentage mortalities under different conditions of temperature and time exposure. Entrainment of M. lateralis embryos and larvae in the cooling-water systems of steam-electric power plants should be as short as possible to keep mortality toa minimum.Contribution No. 550 of the Natural Resources Institute, University of Maryland, and Contribution No. 531 of the Virginia Institute of Marine Science.     

Effects of high temperature on larval development and metamorphosis of Arachnoides placenta (Echinodermata: Echinoidea)

Adults of the sea urchin Arachnoides placenta (L.) were induced to spawn, and eggs were fertilized at 28°C in September 1989. After 5 min, eggs were transferred to 28, 31, 34, or 37°C and reared to metamorphosis. Embryos were observed at 20-min intervals during the first 2 h; larvae were observed daily. The cleavage was higher at higher temperatures. Embryos reared at 28°C were still at the 4th cleavage (16-cell stage) after 100 min, while those at 34°C had reached the 5th cleavage (32-cell stage). All embryos reared at 37°C died on the second day. Incidence of abnormality was 20 to 30% at 28 and 31°C, 48% at 34°C, and 77% at 37°C. The 8-arm stage was reached after 4 d at 28°C, 3 d at 31°C and 2 d at 34°C. Larvae displayed decreasing body length and arm length with increasing temperature. Larvae at 31°C have relatively long arms, as a result of a decrease in body length, not because of increased arm length. Incidence of metamorphosis was 43.9±1.7% (mean/plusmn;SD) at 28°C, 24.5±1.9% at 31°C, and 5.3% at 34°C. The size of metamorphosed juveniles was significantly larger at 28°C than at 31 and 34°C. Temperatures of 31°C negatively affect larvae and juveniles of the sand dollar.