Laboratory rearing of the clupeid fish Harengula pensacolae from fertilized eggs

Pelagic eggs of the scaled sardine Harengula pensacolae (Goode and Bean), have been hatched and reared in the laboratory for the first time. Larvae were reared in two 75 l aquaria under constant illumination, at an average temperature of 26.2°C. Zooplankton collected in a 35 mesh net was fed to the newly hatched larvae, and the diet was supplemented later with Artemia salina nauplii and a pelleted food. Larvae hatched at 4 mm TL (total length), and metamorphosed about 25 days later at 25 to 30 mm TL. Survivors averaged 76 mm TL 100 days after hatching. Of the 500 incubated eggs, 2.8% survived until 20 days, after which no significant natural mortality occurred. Sources of natural mortality included starvation, a copepod parasite (Caligus sp.), and injuries from contact with the sides of the tank. Larvae began feeding at 4.5 mm TL on copepod nauplii averaging 62 in body width. Scaled sardines were photopositive throughout the larval stage.Contribution No. 149, Bureau of Commercial Fisheries Tropical Atlantic Biological Laboratory, Miami, Florida 33149, USA.     

Larval development of the red crab Pleuroncodes monodon (Decapoda Anomura: Galatheidae) under laboratory conditions

Larvae of Pleuroncodes monodon (Milne-Edwards, 1837), a red crab of commercial importance in South America, were reared in the laboratory at 2 different temperatures (15° and 20°C), from hatching up to the last larval stage. The 5 typical stages, with their corresponding functional appendages, are described and figured. The main characteristics useful in differentiating larvae of P. monodon from those of the other Chilean species of Galatheidae and its northern congener P. planipes are discussed. Data on duration of each larval stage, length of moulting intervals and mortality at the 2 test temperatures are also given.This study was financially supported by the Chilean Ministry of Agriculture and by the National Commission for Scientific and Technological Research (CONICYT).     

Neue ergebnisse über die aufzucht von Carcinus maenas im laboratorium

The shore crab Carcinus maenas was reared in the laboratory from egg deposition to sexual maturity. Special enclosures were developed for cultivation of the larvae. Food and temperature proved to be the most important exogenous factors for rearing success. Fresh Artemia salina nauplii were the only food suitable for all larval stages. The following rearing temperatures proved most successful during larval development: (1) embryonic development, 10°C; (2) zoea stages, 15°C; (3) megalopa stage, 17.5°C. The larvae hatch preferably in darkness when reared under short-day conditions.     

An unusual abbreviated larval life in the estuarine burrowing prawn Callianassa kraussi (Crustacea: Decapoda: Thalassinidea)

The larval stages of Callianassa kraussi Stebb. were previously unknown. Larvae were bred out in the laboratory and found to be incapable of swimming. There are two larval stages, lasting 3 to 5 days in sea water of 34 to 35 S at 20 °C. Observations under simulated field conditions in the laboratory, and in the field—where burrow casts were made using a polyester resin, indicated that the larvae metamorphose to the first post-larval stage in the parent burrow, and then burrow directly into the wall of the parent burrow.     

Larval development of the spider crab Pisoides edwardsi (Decapoda,Brachyura) under laboratory conditions

Larvae of Pisoides edwardsi (Bell, 1835) have been reared in the laboratory at 2 different temperatures (13.8° and 18.5°C), from hatching to megalops stage. The two zoeal stages and the megalops, as well as the setation of the functional appendages are described and illustrated. The main characteristics useful to differentiate the larvae of P. edwardsi from those of Libidoclaea granaria, the other Chilean species belonging to the same sub-family, are discussed. Data on duration of zoeal development, length of moulting intervals, and mortality at the 2 test temperatures, are also given.This study was financially supported, in part, by the Chilean Ministry of Agriculture.     

Electrophoretic survey of genetic variation in Pecten maximus,Chlamys opercularis,C. varia and C. distorta from the Irish Sea

Food selection by young larvae of the gulf menhaden (Brevoortia patronus) was studied in the laboratory at Beaufort, North Carolina (USA) in 1982 and 1983; this species is especially interesting, since the larvae began feeding on phytoplankton as well as microzooplankton. When dinoflagellates (Prorocentrum micans), tintinnids (Favella sp.), and N1 nauplii of a copepod (Acartia tonsa) were presented to laboratory-reared, larval menhaden (3.9 to 4.2 mm notochord length), the fish larvae ate dinoflagellates and tintinnids, but not copepod nauplii. Larvae showed significant (P<0.001) selection for the tintinnids. Given the same mixture of food items, larger larvae (6.4 mm notochord length) ate copepod nauplii as well as the other food organisms. These feeding responses are consistent with larval feeding in the northern Gulf of Mexico, where gulf menhaden larvae between 3 and 5 mm in notochord length frequently ate large numbers of dinoflagellates (mostly P. micans and P. compressum) and tintinnids (mostly Favella sp.), but did not eat copepod nauplii. As larvae grew, copepod nauplii and other food organisms became important, while dinoflagellates and tintinnids became relatively less important in the diet. Since the tintinnids and nauplii used in the laboratory feeding experiments were similar in size as well as carbon and nitrogen contents, the feeding selectivity and dietary ontogeny that we observed were likely due to a combination of prey capturability and larval fish maturation and learning.Contribution No. 5575 of the Woods Hole Oceanographic Institution     

Feeding of laboratory-reared larvae of the sea bream Archosargus rhomboidalis (Sparidae)

Feeding by larvae of the sea bream Archosargus rhomboidalis (Linnaeus) was investigated from late September, 1972 to early May, 1973 using laboratory-reared larvae. Fertilized eggs were collected from plankton tows in Biscayne Bay, and the larvae were reared on zooplankton also collected in plankton nets. Techniques were developed to estimate feeding rate, food selection, gross growth efficiency, and daily ration. Daily estimates of these were obtained through 16 days after hatching at rearing temperatures of 23°, 26°, and 29°C. Feeding rate increased exponentially as the larvae grew, and increased as temperature was raised. At 23°C larvae began feeding on Day 3, at 26° and 29°C larvae began feeding on Day 2. Feeding rates at initiation of feeding and on Day 16 were, respectively: 23°C, 7.16 food organisms per larva per hour (flh) and 53.78 flh; 26°C, 7.90 flh and 168.80 flh; 29°C, 17.62 flh and 142.07 flh. Sea bream larvae selected food organisms by size. At initiation of feeding they selected organisms less than 100 m in width. As larvae grew they selected larger organisms and rejected smaller ones. The major food (more than85% of the organisms ingested) was copepod nauplii, copepodites, and copepod adults. Minor food items were barnacle nauplii, tintinnids, invertebrate eggs, and polychaete larvae. Mean values for gross growth efficiency of sea bream larvae ranged from 30.6% at 23°C to 23.9% at 29°C. Mean values for daily ration, expressed as a percentage of larval weight, ranged from 84% at 23°C to 151% at 29°C and tended to decline as the larvae grew.This paper is a contribution from the Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA     

Laboratory study of survival and duration of individual zoeal stages as a function of temperature in the brachyuran crab Cancer magister

Larvae were hatched from ovigerous Dungeness crabs, Cancer magister, collected from Puget Sound Basin, Washington, USA, in April, 1986, and the effects of temperature on rates of survival and development were studied for each of the five zoeal stages both in small batch-culture and in individual culture. Culture method had little effect on the results at 10°, 15°, and 20°C. Increased mortality was measured at all stages at 20°C, with 100% mortality occurring during the terminal fifth stage. Fifth stage larvae may also show higher mortality at 15°C than at 10°C. Stage duration varied inversely with temperature at all stages, although differences between 10° and 15°C were greater than between 15° and 20°C. The results indicate that survival and stage duration are independent of the values for the previous and subsequent stages, that variability among larvae in instar duration increases with temperature, and that the terminal fifth zoeal stage is the most sensitive to temperature stress. Duration of a late zoeal instar is not related to its earlier development rate nor can early development rates be used to predict whether individual zoeae will successfully develop to the megalopa. Measurements of megalopa dry weights indicate no differences due either to previous culture temperatures or to total time to the megalopa. Predictive models of larval transport that require estimates of larval duration should account for both changes in temperature response that can affect individual stage duration, and variability among individuals in stage duration that can influence the degree of larval dispersion.     

Larval development of Ocypode quadrata (Brachyura: Crustacea) under laboratory conditions

The larvae of Ocypode quadrata (Fabricius) have been reared in the laboratory, from hatching to megalopa stage, at 35 S, 25°C. The five zoeal stages and the megalopa are described, including functional appendages of each stage. On the basis of morphological characteristics, the first zoeal and megalopa stages of O. quadrata can be distinguished from similar stages of closely related Ocypodinae. At 25°C, the megalopa appeared in a minimum of 34 days following hatching.     

Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea)

Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates. In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy).     

Effects of nutrition and temperature on metabolic enzyme activities in larval and juvenile red drum,Sciaenops ocellatus,and lane snapper,Lutjanus synagris

The metabolic enzyme activities were determined in larvae of red drum, Sciaenops ocellatus, and lane snapper, Lutjanus synagris, to determine the effect of temperature and nutrition on metabolic enzyme activities and to evaluate if metabolic enzyme activities are useful in assessing the feeding condition of larval fish. During experiments conducted during the spring of 1990, lactate dehydrogenase (LDH) activities in both red drum and lane snapper were approximately an order of magnitude lower than values typical for adult fish; LDH and citrate synthase (CS) activities increased during early developmental stages, but nutritional effects were apparent. Clear differences (up to 4-fold) between well-fed and starving fish were evident in both LDH and CS activity in red drum. Differences between well-fed and poorly fed larvae were evident until 9 d after hatching. Lane snapper larvae reared at a 25°C had significantly lower LDH activities than larvae reared at 28°C.     

Embryogenesis and larval biology of the ahermatypic scleractinian<Emphasis Type="Italic"> Oculina varicosa</Emphasis>

The ivory tree coral Oculina varicosa (Leseur, 1820) is an ahermatypic branching scleractinian that colonizes limestone ledges at depths of 6–100 m along the Atlantic coast of Florida. This paper describes the development of embryos and larvae from shallow-water O. varicosa, collected at 6–8 m depth in July 1999 off Fort Pierce, Florida (27°32.542 N; 79°58.732 W). The effect of temperature on embryogenesis, larval survival, and larval swimming speed were examined in the laboratory. Ontogenetic changes in geotaxis and phototaxis were also investigated. Embryos developed via spiral cleavage from small (100 µm), negatively buoyant eggs. Ciliated larvae developed after 6–9 h at 25°C. Embryogenesis ceased at 10°C, was inhibited at 17°C, and progressed normally at 25°C and 30°C. Larval survival, however, was high across the full range of experimental temperatures (11–31°C), although mortality increased in the warmest treatments (26°C and 31°C). Larval swimming speed was highest at 25°C, and lower at the temperature extremes (5°C and 35°C). An ontogenetic change in geotaxis was observed; newly ciliated larvae swam to the water surface and remained there for approximately 18 h, after which they swam briefly throughout the water column, then became demersal. Early larvae showed no response to light stimulation, but at 14 and 23 days larvae appeared to exhibit negatively phototactic behavior. Although low temperatures inhibited the development of O. varicosa embryos, the larvae survived temperature extremes for extended periods of time. Ontogenetic changes in larval behavior may ensure that competent larvae are close to the benthos to facilitate settlement. Previous experiments on survival, swimming speeds, and observations on behavior of O. varicosa larvae from deep-water adults indicate that there is no difference between larvae of the deep and shallow populations.Communicated by J.P. Grassle, New Brunswick     

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.     

Effects of temperature on oxygen consumption,growth, and development of embryos and yolk-sac larvae of Siganus randalli (Pisces: Siganidae)

Eggs from laboratory spawnings of the coralreef fish Siganus randalli Woodland were incubated at two temperatures (27 and 30 °C). Eggs and larvae were sampled until larval starvation, while changes in oxygen consumption, growth, yolk utilization, and development were monitored. Oxygen consumption, which peaked at hatching, was higher for embryos incubated at 30 °C than at 27 °C. Rates of oxygen consumption (nl h^-1 individual^-1) at hatching were similar to those for other temperate and tropical species. Rates of oxygen consumption by yolk-sac larvae were highly variable, and these data suggest that larval oxygen consumption prior to yolk-sac absorption may not be significantly influenced by temperature. Rates of yolk depletion were higher for larvae at the higher temperature. After an initial rapid increase in length, length of larvae at 30 °C decreased with age. Egg size, egg weight, and maximum notochord length of larvae differed significantly between spawns. Age-specific oxygen consumption rates by the embryos varied between spawns, but regressions describing oxygen consumption as a function of age did not differ significantly. The initiation and completion of eye pigmentation were used as developmental markers to calculate the amount of yolk remaining for larvae at the different temperatures. Larvae maintained at 30 °C completed eye pigmentation approximately 3 h sooner than those maintained at 27 °C, but had less endogenous reserves. This finding indicates a trade-off between rapid development and efficient utilization of the endogenous reserves. The completion of eye pigmentation in larvae incubated at the higher temperature occurred at midnight and, depending on the amount of time that the larvae have to initiate feeding prior to the point-of-no-return, the timing of completion of eye pigmentation could influence larval survival.     

Rearing<Emphasis Type="Italic"> Pandalus borealis</Emphasis> (Krøyer) larvae in the laboratory

Northern shrimp Pandalus borealis (Krøyer) larvae hatch in the northern Gulf of St. Lawrence from early May to the end of June, and larval development occurs over a range of relatively cold water temperatures. Because of the long duration of the pelagic phase and the difficulty of sampling all successive larval stages at sea, we used laboratory experiments to assess the effects of water temperature on larval development and growth. In spring 2000, P. borealis larvae were reared from hatching to the first juvenile stages (i.e., stage VI and VII) at three temperatures (3, 5, and 8°C) representing conditions similar to those in spring in the northern Gulf of St. Lawrence. Larval development and growth were dependent on temperature, with longer duration and smaller size (cephalothorax length, CL, and dry mass, DM) at 3°C relative to the 5 and 8°C treatments. There were no significant differences in the morphological characters of the different stages among treatments, indicating that regular moults occurred at each temperature. The results suggest a negative impact of cold temperatures (lower intra-moult growth rates and smaller size) and, possibly, higher cumulative mortality due to longer development time that could affect the success of cohorts at sea. However, CL and DM for stage III and later larvae were smaller than those of larvae identified at the same developmental stage in field locations. It is possible that the diet offered to larvae in this experiment (Artemia nauplii, either newly hatched nauplii or live adults, depending on the developmental stage) was not optimal for growth, even though it is known to support successful P. borealis larval development. In the field, there is the possibility that phytoplankton contributes to the larval diet during the first stages and stimulates development of the digestive glands. Furthermore, the nutritional quality of the natural plankton diet (e.g., high protein content, fatty acid composition) might be superior and favourable to higher growth rates even at lower temperatures.Communicated by R.J. Thompson, St. Johns     

Yolk resorption,onset of feeding and survival potential of larvae of three tropical marine fish species reared in the hatchery

This paper provides basic early life-history information on milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) which may explain in part the observed differences in their survival performance in the hatchery. Egg size, larval size, amount of yolk and oil reserves and mouth size are all greater in milkfish than in seabass, and greater in the latter than in rabbitfish. During the first 24 h after hatching, rabbitfish larvae grow much faster than milkfish and seabass larvae at similar ambient temperatures (range 26°–30°C, mean about 28°C). The eyes become fully pigmented and the mouths open earlier in seabass and rabbitfish (32–36 h from hatching) than in milkfish (54 h). Seabass larvae learn to feed the earliest. Yolk is completely resorbed at 120 h from hatching in milkfish, and yolk plus oil at 120 h in seabass and 72 h in rabbitfish at 26° to 30°C. Milkfish and seabass larvae have more time than rabbitfish to initiate external feeding before the endogenous reserves are completely resorbed. Delayed feeding experiments showed that 50% of unfed milkfish larvae die at 78 h and all die at 150 h from hatching. Milkfish larvae fed within 54 to 78 h after hatching had improved survival times: 50% mortality occurred at 96 to 120 h, and 10 to 13% survived beyond 150 h. Unfed seabass larvae all died at 144 h, while 6 to 13% of those fed within 32 to 56 h after hatching survived beyond 144 h and well into the subsequent weeks. Unfed rabbitfish larvae all died at 88 h, while 7 to 12% of those fed within 32 to 56 h after hatching survived beyond 88 h. A delay in initial feeding of more than 24 h after eye pigmentation and opening of the mouth may be fatal for all three species.Contribution No. 167 from the SEAFDEC Aquaculture Department     

Early growth and mortality of the Caribbean king crab Mithrax spinosissimus reared in the laboratory

The berried females of the Caribbean king crab Mithrax spinosissimus (Lamarck) used in this study were collected from canals on Big Pine Key, Sugarloaf Key and Lower Matecumbe Key (south Florida, USA) on 9 August, 8 October and 15 November 1986. Viable spawns hatched as first zoeae and molted to second zoeae within ca. 10 to 12 h. Most of the larvae reached the megalopa stage 1 d later, and molted to first crab 4 to 8 d after hatching (water temperature: 27.2° to 28.8°C). Low water temperature and/or early lack of food had a negative effect not only on stage duration, but also on the size of the early crab stages. Successful molt to first crabs occurred, however, in the absence of food. The growth rate (carapace length) between molts in early crab stages varied between ca. 20 and 30%. When provided with good water exchange, stocking density could be very high (>22 500 individuals m^-2), with no increase in mortality. The highest mortality rate was recorded when the larvae molted to first crab, and the highest rates of survival were always recorded when feeding was not initiated until after 5 to 8 d after hatching. No cannibalism was observed among larvae, and cannibalism was low in early crab stages. The study indicates that to achieve viable hatches and high larval survival in rearing M. spinosissimus, a continuous and adequate supply of high-quality seawater is a prerequisite both in larviculture and in maintaining brooding females.Contribution No. 93, Department of Oceanography and Ocean Engineering, Florida Institute of Technology     

A dispersal model for larvae of the deep sea red crab Geryon quinquedens based upon behavioral regulation of vertical migration in the hatching stage

Behavioral responses to gravity, hydrostatic pressure, and thermoclines are described for Stage I zoeae of the deep sea red crab Geryon quinquedens Smith. Survival and rate of development as a function of temperature is presented for all larval stages. Although temperatures between 10° and 25°C have no direct effect upon survival, development time is five times longer at 10°C than at 25°C. Stage I larvae show strong negative response to gravity. Swimming rate increases with an increase in pressure up to 20 atm above ambient at 11°C, but not at 15°C. Swimming rates at 15°C are higher than those measured at 11°C at each pressure tested. Stage I larvae readily penetrate sharp thermoclines. Potential dispersal ranges of G. quinquedens larvae in the Mid-Atlantic Bight are suggested based on larval behavior, development time, and coastal hydrography. A testable recruitment model is proposed for G. quinquedens.Contribution no. 1365 of the Center for Environmental and Estuarine Studies     

Effects of temperature on morphological landmarks critical to growth and survival in larval Atlantic cod (Gadus morhua)

The morphology and function of structures important to energy acquisition were studied from spawning to the stage of transformation of larva to pelagic juvenile in Atlantic cod, Gadus morhua L., from December 1991 to July 1992. Fertilized eggs produced by adult fish from two genetically discrete populations (Newfoundland and Scotian Shelf) were raised under similar conditions in the laboratory at temperatures of 5 and 10°C. Subsamples of larvae were removed from cultures daily for 10 d, and then less frequently, and fixed for light microscopy and scanning electron microscopy. Nine functional morphological landmarks important to feeding, respiration and locomotion were chosen from observation of 280 ind. These landmarks defined 12 major developmental stages, from hatching to the pelagic juvenile stage. One of the feeding landmarks, intestinal stage, varied as a function of age and size and the variance in development was higher at 10°C than at 5°C; Newfoundland larvae developed more complex intestines than did Scotian Shelf larvae. In addition, Newfoundland larvae had significantly higher growth rates than those of Scotian Shelf larvae. Despite the higher growth rates and greater structural complexity of the intestine in Newfoundland larvae, the rate of yolk utilization was not significantly different between Newfoundland and Scotian Shelf larvae. Staging of respiratory landmarks showed that the gill arches were probably used preferentially in feeding while respiration was cutaneous. The gills, operculum and gill rakers developed late in larval life and accompanied the transition from cutaneous to branchial respiration. In the yolk-sac period, development of feeding and respiratory structures may be largely genetically controlled. During exogenous feeding, extrinsic factors also become important, as shown by the size and age-independent variation in intestinal development of larval cod raised at different temperatures.     

Development of the echinothurid sea urchin Asthenosoma ijimai

Development of an echinothurid sea urchin is described for the first time; eggs of Asthenosoma ijimai (Yoshiwara) have been fertilized in the laboratory, and development has been followed light-microscopically up to the early juvenile stage. The eggs, which are orange and float, are 1.2 mm in diameter, by far the largest echinoid eggs on record. The embryos, larvae and early juveniles are lecithotrophic, and no exogenous food is needed for development. The embryonic stages include a remarkable biscuit-shaped late blastula, which has never been described for any echinoid before. The larva, with its para-arms unsupported by skeletal ossicles, is unlike the echinoid prism or pluteus and more resembles the early bipinnaria or early auricularia of asteroids and holothurians, respectively. All stages through late larvae float just beneath the surface until settlement occurs during the third and fourth weeks at 20°C. Metamorphosis from late larva to juvenile is gradual and no part of the larval body appears to be cast off.This paper is dedicated to Professor Juro Ishida on the occasion of his seventieth birthday.