Rotifer Diet Research Articles

Biological Performance of Red Porgy (Pagrus pagrus) Larvae under Intensive Rearing Conditions with the use of an Automated Feeding System

Pagrus pagrus is one of the promising species for the industry in the Mediterranean but its rearing is still far from satisfactory. In the present work, the conditions and results of larval rearing with the use of an automatic feeding system are presented. Eight populations were reared for 20 days with the ‘pseudo green water’ methodology in two successive trials. Larvae were fed enriched rotifers during the entire rearing period, a mixed diet of rotifers and Artemia (Instar I when larvae reached 5 mm in length, replaced by Instar II after larvae reached 5.5 mm) and a formulated diet (after day 16 post hatching). A computerized system for feeding management was used. A total of 388,000 eggs were incubated and after 20 days, 237,973 larvae (TL = 6.96 ± 0.17 mm) were produced with a survival rate of 61.4 ± 6.3%. Individuals grew in terms of wet weight with an exponential rate of 0.167 ± 0.008 daily (R2= 0.983) with no variations between replicates. Mean individual daily consumption at first feeding (day 4-post hatching), was 0.20 ± 0.06 mg of food (0.03 ± 0.01 dry weight), that is, 180–300 rotifers, while on day 20, consumption increased by 10 (2.081 ± 0.106 mg and 0.276 ± 0.014 in wet and dry weight, respectively). When compared with sea bream, consumption was higher by approximately 3–4-fold. The mean food conversion ratio of the experimental period was 4. In comparison with sea bream larviculture, food consumption of red porgy is higher, and a different feeding strategy is required to satisfy the requirements of the larvae.

Effect of temperature on resting egg formation of the tropical SS-type rotifer Brachionus rotundiformis Tschugunoff

ABSTRACT: Tropical minute rotifer strains (SS-type) induce mixis at 30–35°C but sexual reproduction and resting egg formation do not proceed well due to rapid environmental change. The present study examined the effect of temperature regulation on rotifer Brachionus rotundiformis (Langkawi strain, SS-type) resting egg formation in small (500 mL in culture volume)- and large-scale (500 L in culture volume) experiments. Rotifers were cultured at 30°C in 15–17 p.p.t. seawater with an initial density of 1 individual (ind.)/mL. After 4 days, when cultures were in exponential growth stage with active mixis induction, the culture temperature of the experimental rotifers was changed to 25°C. Control rotifers were cultured at 30°C throughout the experiment. Fresh or frozen Nannochloropsis oculata and condensed freshwater Chlorella vulgaris were used as the rotifer diets in the small- and large-scale experiments, respectively. Significantly higher resting egg production was observed with the experimental rotifers (30→ 25°C) versus the control rotifers. In the large-scale trial, experimental rotifers produced 2.6 × 106 resting eggs during a 9-day experiment, which was 1.6-fold more than the control rotifers. Moreover, the efficiency of resting egg formation was found to increase by a factor of 1.8. The present study indicates that decreasing culture temperature from 30 to 25°C after active mixis increased resting egg formation in B. rotundiformis (SS-type).

Causes of Growth Depensation in Red Drum, Sciaenops Ocellatus, Larvae

Individual growth rates, and thus sizes at a given age, vary within cohorts of fishes reared in the laboratory, field enclosures, and the wild, but the causes of this variability are poorly understood. We examined effects of three variables (food availability, a diet shift, and fish density) on growth depensation in red drum, Sciaenops ocellatus, larvae in laboratory experiments. Absolute variance in length of larvae was greater with higher food availability, and relative variance (CV) for a cohort at 14 d posthatching was positively correlated with its CV at 7 d posthatching, over which time CV doubled. Supplementation of a rotifer diet with Artemia nauplii (diet shift) increased growth rate and length variance, but not CV. Individually-reared and group-reared larvae had similar growth rates, but group-reared larvae exhibited higher CVs than individually-reared larvae. The observation that food availability and diet shifts affected absolute size variance, while fish density affected relative size variance of red drum larvae, indicates that both absolute and relative size variance are important to understand how environmental factors affect growth depensation.

Cultured copepods as food for West Australian dhufish ( Glaucosoma hebraicum) and pink snapper ( Pagrus auratus) larvae

Copepods have often improved larviculture of marine fish species that are not easily reared using rotifers. One such species is Glaucosoma hebraicum. G. hebraicum larvae were reared on a combined diet consisting of equal numbers of cultured copepod nauplii and rotifers and a diet of rotifers only. Growth was significantly greater in larvae fed with the combined diet. Survival was 37% in the copepod/rotifer-fed larvae compared to 5% in the rotifer-fed larvae. Two separate methods of presenting copepod nauplii to Pagrus auratus larvae were also examined. Firstly, copepods nauplii were provided as the sole diet during the first feeding phase followed by rotifers. Secondly, rotifers were supplemented with copepod nauplii for an extended period. P. auratus larvae grew faster than rotifer fed controls in both trials. Larvae fed with the supplemented diet for an extended period grew fastest. There was no significant difference in survival and swim bladder inflation in P. auratus larvae, although those treatments with copepods in their diet were consistently higher. Improved larval growth and survival in both fish species were attributed to preferential selection of copepod nauplii and their high nutritional content.

Investigations of Selected Parameters for Growth of Larval and Juvenile Black Sea Bass Centropristis striata L.

Abstract.— The black sea bass Centropristis striata L. endemic to the U. S. Atlantic and Gulf of Mexico coasts is a highly sought species that commands a high price in the marketplace. Investigations were undertaken to determine the basic requirements for culture of sea bass larvae and juveniles. Adult black sea bass were captured from the wild and were found to be robust and to adapt well to captivity. Larvae were obtained by strip spawning of these adults and survived and grew at higher rates in seawater supplemented with algae (greenwater) and maintained at 22 C, than in seawater with or without supplemental algae at 18 C. Larvae were provided a diet of rotifers through 12 d post hatch (DPH) and weaned over a 3‐d period to enriched Anemia replenished daily to a density of 10 individuals/mL. By 18 DPH, larvae began ingesting a formulated diet for marine finfish and were completely weaned from live feed by 25 DPH, which coincided with the onset of metamorphosis. Juveniles tolerated a range of salinity from 10–32 ppt with the highest growth rate observed at 20 ppt. Culture of larvae and juveniles on a commercial scale was successful using conditions similar to those employed in the laboratory. The findings presented here suggest the potential for commercial culture of this species in the USA.

Feeding behaviour of greenback flounder larvae, Rhombosolea tapirina (Günther) with differing exposure histories to live prey

This study examined the feeding performance of cultured larvae of the greenback flounder Rhombosolea tapirina, using the live feed organisms, Brachionus plicatilis and Artemia sp., to determine the primary sensory modality involved in feeding, and the effect of previous exposure to prey on subsequent prey selection. The proportion of larvae that fed on rotifers in the light (400–700 nm daylight fluorescent tubes — light intensity of 5–6 μmol s −1 m −2), increased significantly from 66% to 96% from day 12 to day 27 post-hatching, respectively. In comparison, the proportion of larvae that fed on rotifers in total darkness, never exceeded 5% during the same period. This indicates that greenback flounder larvae are primarily dependent upon vision to feed. Prior feeding experience of greenback flounder larvae with either rotifers only (R-treatment) or a mixed diet of Artemia and rotifers (A&R-treatment) significantly affected subsequent prey selection when larvae were offered a mixed diet of Artemia and rotifers. It did not, however, affect the temporal onset of selection of the novel prey species ( Artemia) by R-treatment larvae. Therefore, the differences in prey selection by larvae, with or without prior exposure to Artemia prey, were not due to the inability of larvae to handle and ingest a novel prey species, but they reflect positive selection for familiar prey. The latter indicates a learned component in the feeding behaviour of fish larvae. This has implications for the timing of the introduction of new live prey species during intensive culture of marine fish larvae.

The significance of feeding history on the value of heterotrophic microzooplankton as prey for larval crabs

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 186:219-225 (1999) - doi:10.3354/meps186219 The significance of feeding history on the value of heterotrophic microzooplankton as prey for larval crabs Stephen D. Sulkin*, Gene L. McKeen Shannon Point Marine Center, 1900 Shannon Point Road, Anacortes, Washington 98221, USA *E-mail: sulkin@cc.wwu.edu ABSTRACT: Larvae of 4 species of crabs of the genus Cancer (C. gracilis, C. magister, C. oregonensis and C. productus) were raised in the laboratory from hatching to the post-larval megalopa stage on diets of nauplii of the brine shrimp Artemia sp. and on 2 diets of the rotifer Brachionus plicatilis. One of the rotifer diets had been cultured on the chlorophyte Dunaliella tertiolecta, the other on the chrysophyte Isochrisis galbana. In 3 of the 4 crab species, Dunaliella-fed rotifers did not support development to the megalopa, whereas Isochrisis-fed rotifers did. In the fourth species, C. productus, survival to the megalopa was only 1% on Dunaliella-fed rotifers, whereas Isochrisis-fed rotifers supported development equal to that of the Artemia-fed control. Differences between the 2 rotifer diets were evident in all species by Stage 3, although the first significant occurrence of increased mortality on the Dunaliella-fed rotifer diet varied among species. In all 4 species, development rate was faster as early as the first molt on the Isochrisis-fed rotifer diet as compared to the Dunaliella-fed rotifer diet, a difference maintained throughout development. Only in C. gracilis did survival to the megalopa on the Isochrisis-fed rotifer fall substantially below that seen for Artemia-fed larvae. Stage mortality on the Isochrisis-fed rotifer diet typically equaled that of the Artemia sp. control. Differences in development rates between the Isochrisis-fed rotifer diet and the Artemia sp. diet varied among species, as did megalopa weight. We attribute differences between the 2 rotifer diets to the high content of long-chain ω-3 polyunsaturated fatty acids in I. galbana and their absence in D. tertiolecta. The value of heterotrophic microzooplankton as prey for crab larvae, either in culture or in nature, will depend upon the prey's own feeding history. KEY WORDS: Crab larvae · Diet · Heterotrophs · Microzooplankton Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 186. Publication date: September 17, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

The enrichment and retention of ascorbic acid in rotifers fed microalgal diets

The enrichment and retention of ascorbic acid (AA) was investigated in rotifers Brachionus plicatilis fed on microalgae (Nannochloropsis oculata and Isochrysis sp. (T.ISO)) and baker's yeast Saccharomyces cerevisiae. The concentrations of AA of the rotifer diets used in the study differed significantly: 4200 μg g−1 of dry weight in Isochrysis sp. (T.ISO), 2600 μg g−1 in N. oculata and only 77 μg g−1 in S. cerevisiae. Rotifers contained 620 μg AA g−1 prior to the experimental feeding. When subsequently fed for 3 h on microalgae at a ration of 0.13 mg dry microalgae per 106 rotifers rapidly and efficiently increased their content of AA: Isochrysis sp.-fed rotifers contained 1600 μg AA g−1 and N. oculata-fed rotifers contained 1100 μg AA g−1. Concentrations were boosted by a further feeding of a second ration of algae at three times the initial feeding ration; 21 h later, Isochrysis sp.-fed rotifers contained 2500 μg AA g−1 and N. oculata-fed rotifers contained 1700 μg AA g−1. This represented a 180% and 310% increase in the pre-feeding vitamin concentrations in Isochrysis sp. and N. oculata-fed rotifers, respectively. There were no significant changes in AA concentration in rotifers fed a similar ration of yeast throughout the feeding period (520-620 μg AA g−1). Rotifers retained AA during a subsequent 24 h non-feeding period, with no significant changes in the concentrations in any of the rotifer groups. The production of rotifers rich in AA may be particularly valuable for the culture of fish larvae that have a high requirement for the vitamin.

Juvenile production of Amphiprion bicinctus (Pomacentridae, Teleostei) and rehabilitation of impoverished habitats

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 151:295-297 (1997) - doi:10.3354/meps151295 Juvenile production of Amphiprion bicinctus (Pomacentridae, Teleostei) and rehabilitation of impoverished habitats Maroz A, Fishelson L This study on the Red Sea fish Amphiprion bicinctus was aimed at developing a method of producing large numbers of juveniles for reintroduction into their symbiotic sea anemones in natural habitats. By establishing reproductive pairs in captivity and providing them with a diet of rotifers and various stages of nauplius and adult Artemia salina, reproduction was achieved at frequencies of 2 to 3 times per month per pair, resulting in large numbers of larvae. Juveniles attaining 16 to 28 mm TL were introduced into sea anenomes on the coral reefs at Eilat, Israel, at depths of 10 to 25 m. Despite heavy losses, numerous juveniles successfully acclimated and survived in their new habitat, many in anenomes previously occupied by adult fish. Three years of follow-up revealed that 8 pairs of such reintroduced fish had grown into maturity and become reproductive. It would appear that this method of production in captivity followed by resettlement in impoverished natural habitats may be effective for community rehabilitation. Amphiprion · Propagation · Reintroduction in nature Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 151. Publication date: May 22, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Testing protein-walled microcapsules for the rearing of first-feeding gilthead sea bream (Sparus aurata L.) Larvae

Two basic types of protein-walled microcapsules were developed with the aid of using different preparation techniques. One type (Type A) was spherical and hard-walled, whereas the other (Type G) was irregularly shaped and soft-walled. The present work examined the larval growth and development of Sparus aurata reared either with these microcapsules as the sole food source or with a mixed diet of microcapsules and rotifers from the start of feeding. Larvae fed on Type A microcapsules evacuated them practically intact. These larvae showed strong degeneration of the gut epithelium, liver and pancreas and died within two to three days after the onset of feeding. In contrast, larvae fed from first feeding with Type G microcapsules alone ingested and broke down the particles from the onset of feeding. No larval growth was observed, but some larvae were still alive at the end of the experiment (Day 13). Larvae reared with a mixed diet, including Type G microcapsules and a small amount of rotifers (0.5 rotifer mL-1), showed in general normal development of gut epithelium. These larvae had good growth but survival was reduced to one-half of that obtained under routine rearing of larvae fed on rotifers alone. Type G microcapsules appear to represent an adequate departure point for the development of an inert diet able to support larval growth in marine fish.

Ontogenetic diet shifts and diet overlap among three closely related neotropical armoured catfishes

Analysis of stomach contents of larvae, juveniles and adults of three closely related armoured catfishes in coastal plain swamps of Suriname, South America, revealed major ontogenetic diet shifts. Larvae of Hoplosternum littorale, H. thoracatum and Callichthys callichthys showed a restricted diet of rotifers and microcrustacea. Diets of juveniles and adults were more diverse, but large volumes of microcrustacea, aquatic insect larvae and detritus were always present. In all three species diet overlap was especially low between larvae and adults. The proportion of detritus in the stomach was positively related to fish size, which probably reflected the inability of larger size classes to separate effectively benthic invertebrate prey from bottom substrata, and not a specialization towards detritivory. Adults showed only minor seasonality in diet composition, and no effect of season on diet breadth. Interspecific diet overlap among larvae, juveniles and adults did not differ significantly from 1 (complete overlap). Lack of food partitioning was probably related to a similar morphology of the three catfishes. Intraspecific between‐size class diet overlap was considerably lower than interspecific within‐size class overlap. It is suggested that large interspecific diet overlap occurred because food was not limiting the populations of these catfish. However, the nest habitats of the three species differed.

A method for the early assessment of the quality of turbot larvae

The bacterial environment should be taken into account for assessing the quality of fish larvae, besides biochemical and developmental criteria. Detrimental effects of associated flora have been observed on the survival rates of larvae (e.g. Nicolas et al., 1989), and experimental infections were performed on fish larvae by introducing the pathogen either directly into the rearing medium or into live food organisms (e.g. Kusuda et ai, 1986). A challenge test was used for assessing the effect of a food additive on the ability of turbot (Scophthalmus maximus) larvae to resist infection, but that required rearing the larvae separately (Gatesoupe, 1993). Bergh et al. (1992) have proposed an infection test with transfer of eggs into polystyrene dishes, but it was not convenient for larvae with exogenous food source. The present paper was an attempt to develop a new test with transfer of larvae after feeding. Then this test was inserted into a simple survey of the quality of turbot larvae, with a view to drawing up relations between rearing success, associated bacteria and resistance against pathogens. For this purpose, seven batches of larvae were successively reared in 150 1 cylindrical tanks with conical bottoms from day 1 after hatching until day 10. Three tanks were used for batches 1, 3, 5 and 6, while five tanks were used for batches 4 and 7. The larvae of batch 2 were reared in one tank. The rearing temperature was gradually increased from 14 °C to 18 °C by day 5. The salinity was 35%. For feeding the larvae, rotifers (Brachionus plicatilis) were cultured in seawater according to the method already described (Gatesoupe, 1990). The rotifer diet was made up of baker's years, menhaden (Breuoortia tyrannus) oi l (Sigma F8020), soybean lecithin, DL-a-tocopherol (USB), and vitamin premix (Spyridakis et ai, 1988), at the daily rates of 60.8, 7.7, 0.7, 0.015, and 0.7 mg r1, respectively, on a dry matter basis. The larvae were fed with the rotifers from day 3 to day 9, at the daily rates of 20, 50, 75, 100, 150, 200, and 250 rotifers per initial larva, corresponding to the seven consecutive days of feeding. Each day, the rotifers were transferred from their culture medium into clean seawater tanks (200 rotifers m l 1 ) , where they were enriched with spray-dried fish autolysate, menhaden oi l , soybean lecithin, and DL-a-tocopherol, at the rates of 15, 7.7, 0.7, and 0.015 mg T 1 , respectively, on a dry matter basis. The rotifers were continuously distributed to turbot with a peristaltic pump, the flow rate of which was adjusted so that the whole volume was carried through in 24 h. At day 10, the survivors were counted and 30 fish were sampled in each tank,

Growth, development and behaviour of artificially reared larval Pagrus auratus (Bloch & Schneider, 1801) (Sparidae)

Pagrus auratus eggs were obtained from wild broodstock with naturally and artificially ovulated fish. Larvae were cultured for periods of up to 1 month on a diet of marine rotifers, Brachionus plicatilis. Small yolk-sac larvae hatched without functional eyes, mouth or digestive tract and for 3 days spent long periods at rest. Growth was initially rapid but slowed by 3 days as yolk reserves were nearing depletion. By Days 4-5, the mouth had opened, eyes were pigmented, yolk was depleted, and a rudimentary gut had formed. Larvae were now able to maintain a horizontal swimming mode and were actively searching for and attacking prey. First-feeding was observed in some larvae. Growth was retarded during the transition from endogenous to exogenous nutrition and then increased, probably as feeding proficiency improved with experience. Larvae starved from hatching did not survive for longer than 8 days.

Nutritional significance of long-chain polyunsaturated fatty acids to the zoeal development of the brachyuran crab, Eurypanopeus depressus (Smith)

Larvae of the mud crab Eurypanopeus depressus (Smith) showed higher survival and faster development rate from hatching to the megalopa stage when fed a diet of brine shrimp nauplii than when fed rotifers. When the rotifer diet was supplemented with the lipid-free fraction of brine shrimp in encapsulated form, larval growth was not enhanced. However, when only the lipid fraction of brine shrimp was added in encapsulated form to the rotifer diet, larvae showed enhanced survival and development rate to the megalopa as compared to rotifer-fed controls. When the rotifer diet was supplemented with microcapsules containing specific polyunsaturated fatty acid, enhanced larval survival and development rate resulted. The greatest effect was achieved on docosahexaenoic acid (22 : 6ω3). The results indicate that long-chain polyunsaturated fatty acids, especially 20 : 5ω3 and 22 : 6ω3, are significant in promoting successful development to the megalopa.

SPAWNING, OOCYTE DEVELOPMENT AND LARVAE REARING OF THE FLORIDA POMPANO (Trachinotus carolinus)

AbstractTwenty‐five spawning attempts on the most reproductively developed fish were conducted on conditioned and unconditioned Florida pompano (Trachinotus carolinus). Human chorionic gonadotropin (HCG) was used to stimulate ovarian development. Dosage levels of .55 IU/g and .275 IU/g were usually administered 24 to 48 hours apart. Strip spawning and semi‐natural spawning were used, Spawning occurred 7 to 208 hours after initial injection depending on initial oocyte size. Optimum oocyte size (580–718 μ) produced spawning in 30–40 hours. A close correlation exists between rate of fertilization and oocyte growth during the first 16–25 hours. Fertilized eggs may shrink as much as 16% within one hour after fertilization.Two successive batches of pompano were reared to juvenile stage in 23 days. Larvae were fed a mixed diet of natural plankton (66 μ mesh net), protozoans, rotifers (Brachionus plicatilus) and copepod nauplii (Oithona sp.). Water was initially conditioned with 40 liters of dense algae (Dunaliella sp. and Tetraselmis sp.). Water quality was controlled by partial exchanges from a 40,000‐liter biologically filtered system. Eighteen‐hour lighting was used. Larvae developed edema at 8–10 days and, combined with low aeration, reduced survival to only 300 juveniles.

Nutritional requirements during larval development of the portunid crab, Callinectes sapidus Rathbun

Three kinds of diet were used to identify the critical periods of nutritional vulnerability during larval development of the portunid crab, Callinectes sapidus Rathbun. A diet consisting solely of the rotifer Brachionus plicatilis Müller is not sufficient for complete developmetn. Development to metamorphosis can occur if rotifers are replaced by Day 15 with Artemia salina L. nauplii, but a diet of A. salina between Days 15 and 21 is also not sufficient for complete development. Delay in giving a brine shrimp diet beyond Day 15 causes a reduction in survival to the megalopa with an apparent threshold between Days 22 and 29, delay in molting in late instars, and increased frequency of supernumeracy larvae, many of which molt subsequently to the megalopa. Development to the megalopa on the rotifer diet is possible if crab larvae are initially fed a favorable control diet for as little as 14 days after hatching. Extension of time on the control increases survival to the megalopa slightly, has little effect on molt frequency, but reduces the number of zoeal instars. These data are interpreted in the context of identification of the unknown dietary requirement and for its implication to evolution of reproduction in the Brachyura.

A Selected Bibliography on the Mass Propagation of Rotifers with Emphasis on the Biology and Culture of Brachionus plicatilis

The rotifer Brachionus plicatilis has shown great promise as food for artificially reared fish and crustacean larvae. A list of references on mass propagation of rotifers is presented alphabetically by author. Citations cover and are indexed as culture, diet, ecology, physiology, population dynamics, reproduction, systematics, geographical distribution, food, and biology of rotifers with emphasis on Brachionus plicalilis. INTRODUCTION tion, and nutrient value. and it has shown great promise as initial and supplementary food for larval fishesand crusThere has been a growing demand in recent vears for taceans. The following list of references, arranged in alphabetical order by author, is incomplete, but provides an easy reference to the pertinent literature. Citations cover and are indexed as culture, diet, ecology, physiology, population dynamics, reproduction, systematics, geographical distribution, food, and biology of rotifers with emphasis on the genus Brachionus. The term “diet” refers to food utilized by rotifers, whereas “food” denotes usage of rotifers by other organisms for food. food-organisms for artificially propagated fish and crustacean larvaeThe brine shrimp, Artemia salina, is a widely used organism to feed larval forms. However, increasing costs of brine shrimp cysts have forced the aquaculturist to seek alternate sources of living food-organisms. Some rotifers appear to fill this need in addition to providing other benefits. The rotifer Brachionus plicatilis is especially notable because of its short life cycle, simple dietary requirements, capability of high density cultiva-

Induced winter spawning and culture of larvae of the blue crab, Callinectes sapidus rathbun

Female blue crabs were induced to produce eggs out of their normal spawning season. One group of crabs, held in the laboratory at 19° C, was fed every 7 days; another group, held at 15° C, was offered food at the same interval. Photoperiod simulated ambient winter conditions in both groups. Of ten crabs held at 19° C, two produced egg masses and one died when spawning was about to commence. Among those crabs not producing egg masses during the experiment, ovarian development at 19° C proceeded further than among those held at 15° C. Survivorship of larvae from induced eggs raised on a rotifer diet was comparable with that for naturally spawned larvae through the first 28 days of development. Zoeae survived well to metamorphosis when fed a diet of rotifers during the first two stages, followed by Artemia salina nauplii. However, only six zoeal stages were present instead of the usual seven. Possible explanations for this observation include genetically controlled variation, variation due to origin of eggs (induced), or effect of diet. Survivorship and growth were not adversely affected when synthetic sea water was used as the culture medium.

Comparison of rotifers and other diets for rearing early larvae of the blue crab, Callinectes sapidus Rathbun

The following four diet treatments were applied to the first two zoeal stages of the blue crab, Callinectes sapidus Rathbun: unfed control, freshly-hatched nauplii of the brine shrimp Artemia salina L., gastrulae of the sea urchin Lytèchinus variegatus Lamarck and the rotifer Brachionus plicatilis Muller. Survival and molt frequency were measured through the second molt. Unfed crab larvae died by day 7 without molting to the second stage. Mortality was delayed slightly in larvae fed A. salina nauplii but molting to the second zoeal stage was not achieved. Development to the third zoeal stage was achieved using both sea urchin larvae and rotifers as diets. Survival was higher on the rotifer diet than on either the sea urchin diet used in this study or on other published diets. Molting to the second zoea was significantly faster on the rotifer diet than on the sea urchin diet and was more synchronous. The rotifer provides a good diet for rearing the first two zoeal stages of C. sapidus in the laboratory, after which they may be reared on A. salina nauplii with good results.