Newly-hatched Larvae Research Articles

Effect of Light Intensity on Initial Survival of Fat Snook (Centropomus parallelus, Pisces: Centropomidae) Larvae

Different light intensities were tested during the larval rearing of fat snook (Centropomus parallelus) to evaluate its influence on survival and functional swim bladder rate. Newly-hatched larvae were obtained by stripping of hormonally induced broodstock, and were stocked in 32-liter tanks at densities from 30 to 50 L-1. Four experiments were carried out testing six light intensities: 50, 100, 200, 500, 1500, and 2500 lx, and total darkness as a control. Mean survival ranged from 0.06 to 16.0% and were significantly influenced by light intensity. Complete darkness resulted in 100% mortality after one week, larvae appeared to have starved since they had empty stomachs. The species has the characteristics of a visual-feeder. Survival was the highest at 200 lx, while at 500 lx was higher than at 50, 100, and 2500 lx. Frequency of functional swim bladder ranged from 36.8 to 100%, but it was not significantly correlated with light intensity. Based on this study, a medium light intensity, 200 to 1500 lx, is recommended for rearing fat snook larvae. Extreme values must be avoided, mainly in the first two weeks after hatching.

Characteristics of egg and larval production in captive bluespotted gobies

Spawning of the Hawaiian coral-reef goby Asterropteryx semipunctata was diurnal, occurring at various times throughout the day. Mean length of eggs deposited in nests was 0·76 mm (range 0·67–0·84); mean egg width was 0·47 mm (range 0·41–0·52). Clutch size varied from 296 to 1552 eggs (mean=886±309), and was independent of standard length, total body weight, and body condition. Mean relative clutch size was 1·59 eggs mg-1 total body weight (range 0·84–2·43). Clutches hatched 4–5 nights after being deposited in a nest. Mean notochord length of newly-hatched larvae was 1·88 mm (range 1·60–2·04). The minimum period of time that elapsed between egg deposition and subsequent growth of a new batch of oocytes to spawning size was 5–6 days, providing a reasonable estimate of minimum spawning interval. Compared with other gobiids, tropical species tend to have shorter incubation periods, smaller eggs and smaller larvae at hatching.

Early ontogeny of coal grunter from hormone-induced spawnings and laboratory-reared embryos and larvae

Spawning of coal grunter Hephaestus carbo was successfully induced using doses of human chorionic gonadotrophin (hCG) between 500 and 3000 IU kg (body weight)−1. Water hardened eggs are telolecithal, amber in colour, spherical, transparent, demersal and slightly adhesive with a single large oil droplet and perivitelline space 47% of total egg volume. Cleavage begins 10–15 min after fertilization. Epiboly begins 6h after fertilization and continues for 4 h. Invagination of the neural tube is apparent 11·5 h after fertilization, followed by progressive organogenesis up to hatching 60–80 h after fertilization. An invagination in the yolk, consistent in shape, position and time of appearance among embryos spawned from numerous brood stock pairs, was visible in all fertilized eggs between neurulation (11-5 h) and early organogenesis (20 h). The functional significance of this yolk invagination is unknown. Newly-hatched larvae (4·2 mm LT) are elongate and possess well developed eyes, a functional mouth, and a large yolk sac. Yolk is fully resorbed and first feeding occurs at 6 days posthatching. The sequence of fin formation is caudal, second dorsal and anal, first dorsal, pectoral and pelvic. The prefiexion larval stage lasts for c.8 days and flexion of the notochord is complete within a further 8–9 days. Squamation commences at 30 days posthatching and transition to the juvenile life stage is complete by 35–40 days posthatching.

Early ontogeny of coal grunter from hormone‐induced spawnings and laboratory‐reared embryos and larvae

Spawning of coal grunter Hephaestus carbo was successfully induced using doses of human chorionic gonadotrophin (hCG) between 500 and 3000 IU kg (body weight)−1. Water hardened eggs are telolecithal, amber in colour, spherical, transparent, demersal and slightly adhesive with a single large oil droplet and perivitelline space 47% of total egg volume. Cleavage begins 10–15 min after fertilization. Epiboly begins 6h after fertilization and continues for 4 h. Invagination of the neural tube is apparent 11·5 h after fertilization, followed by progressive organogenesis up to hatching 60–80 h after fertilization. An invagination in the yolk, consistent in shape, position and time of appearance among embryos spawned from numerous brood stock pairs, was visible in all fertilized eggs between neurulation (11‐5 h) and early organogenesis (20 h). The functional significance of this yolk invagination is unknown. Newly‐hatched larvae (4·2 mm LT) are elongate and possess well developed eyes, a functional mouth, and a large yolk sac. Yolk is fully resorbed and first feeding occurs at 6 days posthatching. The sequence of fin formation is caudal, second dorsal and anal, first dorsal, pectoral and pelvic. The prefiexion larval stage lasts for c.8 days and flexion of the notochord is complete within a further 8–9 days. Squamation commences at 30 days posthatching and transition to the juvenile life stage is complete by 35–40 days posthatching.

Embryonic and larval development of the tub gurnard Trigla lucerna (Pisces: Triglidae)

The embryonic and early larval development of the laboratory-reared tub gurnard, Trigla lucerna are described. The eggs ranged in diameter from 1·33 to 1·40 mm, with a mean of 1·36±0·236 mm, were pelagic and spherical with a homogeneous and unsegmented yolk. There was single oil globule in the eggs. Globule ranged in diameter from 0·25 to 0·29 mm (mean 0·28±0·012 mm). Embryonic development lasted 115 h 2 min at mean temperature 13·5 °C. Newly-hatched larvae were 3·09±0·014 mm in total length. Absorption of the yolk sac was complete after the sixth day, when larvae reached 4·85±0·015 mm in total length. The only character for identifying eggs among species could be diameter, since the values obtained are lower than those obtained for Eutrigla gurnardus and Aspitrigla cuculus, but larger than those for Trigloporus lastoviza. The length of newly hatched yolk-sac larvae of tub gurnard is significantly lower (t-test, P<0·05) than those of most of the other gurnard species. Characters likely to help in identification of species will probably prove to be the length, shape and pigmentation of the pectoral fin, and the degrees of development of spiny armature on the head.

Egg and early larval development of laboratory reared goldblotch grouper, <i>Epinephelus costae</i> (Steindachner, 1878) (Pisces, Serranidae)

The embryonic and early larval development of the laboratory-reared goldblotch grouper, Epinephelus costae (Steindachner, 1878), are described and illustrated. The eggs, with a mean diameter of 926±19 µm and a range from 890-950 µm, were spherical and transparent with transparent chorion. Embryonic development lasted 24 hours at 25.5°C. Newly-hatched larvae were 1.762±0.047 mm in length. Absorption of the yolk sac was complete after the third day, when larvae reached 2.95±0.231 mm in total length. The mouth opened 60 hours after hatching, and was in function after 80 hours, with an opening diameter ranging from 280-320 µm. Larvae had two fields of intensive pigmentation, one above the intestine, and the other between the anus and the end of the notochord.

Development of eggs, larvae and juveniles of laboratory-reared blue whiting, Sillago parvisquamis (Percoidei: Sillaginidae)

The embryonic, larval and juvenile development of blue whiting,Sillago parvisquamis Gill, are described from a series of laboratory-reared specimens. Mean egg diameter and mean total length (TL) of newly-hatched larvae were 0.71 mm and 1.58 mm, respectively. The eggs were non-adhesive, buoyant and spherical with an oil globule (mean diameter 0.18 mm). Hatching occurred about 20 hours after fertilization at a temperature of 24.0–25.0°C, newly-hatched larvae having 38–40 myomeres. The yolk and oil globule were completely absorbed 3 days after hatching at 2.8–3.2 (mean 3.0) mm TL. Notochord flexion was completed by 7.2–8.2 (7.7) mm TL, and pectoral and caudal fin rays fully developed by approximately 10 mm and 8.5 mm TL, respectively. Completion of fin development occurred in the following sequence: caudal, pectoral, anal and second dorsal, first dorsal and pelvic, the last-mentioned by approximately 11 mm TL. The larvae ofS. parvisquamis andS. japonica, which closely resemble each other in general morphology and pigmentation, could be distinguished as follows. Newly-hatchedS. parvisquamis larvae had more myomeres thanS. japonica (38–40 vs. 32–34) and more melanophores on the dorsal surface of the body (19–28 vs. about 40).Sillago japonica had a vertical band of melanophores on the caudal peduncle, which was lacking in postflexionS. parvisquamis larvae. In addition, juveniles ofS. parvisquamis (larger than 23 mm TL) had melanophores on the body extending anteriorly to below the lateral line to form a midlateral band, whereas no obvious band occurred on similarly-sizedS. japonica juveniles.

Shift of Chloride Cell Distribution during Early Life Stages in Seawater-Adapted Killifish, Fundulus heteroclitus

The shift of chloride cell distribution was investigated during early life stages of seawater-adapted killifish (Fundulus heteroclitus). Chloride cells were detected by immunocytochemistry with an an-tiserum specific for Na(+), K(+)-ATPase in whole-mount preparations and paraffin sections. Chloride cells first appeared in the yolk-sac membrane in the early embryonic stage, followed by their appearance in the body skin in the late embryonic stage. Immunoreactive chloride cells in the yolk-sac membrane and body skin often formed multicellular complexes, as evidenced by the presence of more than one nucleus. The principal site for chloride cell distribution shifted from the yolk-sac membrane and body skin during embryonic stages to the gill and opercular membrane in larval and later developmental stages. Our observations suggest that killifish embryos and newly-hatched larvae could maintain their ion balance through chloride cells present in the yolk-sac membrane and body skin until branchial and opercular chloride cells become functional.

Larval developmental stages of laboratory-reared silver pomfret, Pampus argenteus

Eggs of the silver pomfret,Pampus argenteus, were collected and artificially fertilized by stripping fully-ripe male and female broodstock caught by gillnets in Kuwait waters during June 1997. Larvae hatched from fertilized eggs were reared until 90 days after hatching (DAH) in water temperatures of 27–30°C. Newly-hatched larvae grew from an average of 2.4 mm in body length (BL) to 3.7, 4.4, 7.2 and 8.4 mm at 8, 12, 24 and 30 DAH, respectively. Myomere and vertebral numbers ranged from 34 to 36. Transformation from the larval to juvenile form was completed at 22.2 mm BL (40 DAH). Dorsal and anal fin spines first appeared when juveniles reached 38.8 mm BL (50 DAH). Body depth increased with increase in body length; a rapid increase in body depth occurred in larvae 7.1–8.0 mm, reaching 57% of BL, and further increased to 69% of BL in juveniles 38.8 to 47.9 mm. Pigmentation during development is described and illustrated.

Measures of egg quality in induced spawns of the Asian sea bass, Lates calcarifer Bloch.

The egg morphometry and lipid and protein components were determined in induced spawns (n=14) of the sea bass, Lates calcarifer, to identify measures of egg quality. Based on fertilization and hatching rates, the spawns were classified either in Group I, (zero fertilization) or Group II (where fertilization and hatching occurred). The egg morphometry did not differ between the two groups (p > 0.05). The total lipid was higher in Group II than in Group I, although the difference was not significant (p > 0.05). The EPA and linoleic acid were significantly higher in Group II (p 0.05). Proline, glycine, p-ethanolamine, and aspartic acid were significantly higher in Group II (p < 0.05), while tyrosine and glutamic acid were significantly higher in Group I (p < 0.05). Phosphoserine and fertilization rate were positively correlated (p < 0.03; r=0.60), as well as aspartic acid and hatching rate (p < 0.05; r=0.54). Arginine was negatively correlated with fertilization rate (p < 0.03; r=−0.61) and the percentage of normal zygotes (p < 0.03; r=−0.63). Serine was inversely correlated with yolk volume of the newly-hatched larvae (p < 0.03; r=−0.77). The moisture content of the eggs, which was significantly higher in Group II than in Group I (p < 0.03), was directly correlated with the FAAs:protein ratio (p < 0.03; r=0.76). The present results reveal egg components that may be used as quality measures in induced spawns of sea bass, a euryhaline teleost that spawn pelagic eggs containing an oil globule.

Growth and morphological development of larval and juvenileepinephelus bruneus (perciformes: Serranidae)

The growth and morphological development of larval and juvenileEpinephelus bruneus were examined in a hatchery-reared series. Average body length (BL) of newly-hatched larvae was 1.99 mm, the larvae growing to an average of 3.96 mm by day 10, 6.97 mm by day 20, 12.8 mm by day 30, 22.1 mm by day 40 and 24.7 mm by day 45 after hatching. Newly-hatched larvae had many mucous cells in the entire body epidermis. By about 4 mm BL, the larvae had developed pigment patterns peculiar to epinepheline fishes, including melanophores on the dorsal part of the gut, on the tips of the second dorsal and pelvic fin spines, and in a cluster on the ventral surface of the tail. Spinelets on the second dorsal and pelvic fin spines, the preopercular angle spine and the supraocular spine, had started to develop by about 6 mm BL. The notochord tip was in the process of flexion in larvae of 6–8 mm BL, by which time major spines, pigments and jaw teeth had started to appear. Fin ray counts had attained the adult complement at 10 mm BL. After larvae reached 17 mm BL, elements of juvenile coloration in the form of more or less densely-pigmented patches started to appear on the body. Squamation started at 20 mm BL. Major head spines had disappeared or became relatively smaller and lost their serrations by 20–25 mm BL.

Economic assessment of commercial hatchery production of milkfish (Chanos chanos Forsskal) fry

The economic viabilities of two types of commercial hatchery milkfish (Chanos chanos Forsskal) fry operations were assessed and compared. Based on the actual cost of input, the physical facilities, and the potential production yields, four commercial hatcheries previously used for shrimp (Penaeus monodon Fabricius) fry production were classified as either large- or small-scale operations. Cost–return analysis revealed high profits for both types of operation. The return on investment (54–61%) and the payback period (≈ 1.5 years) were comparable between the two types, although a large-scale operation (476%) had double the working capital return of a small-scale hatchery (221%). Benefit–cost analysis over a 5-year period also revealed positive and above-baseline discounted economic indicators [net current value = 0.2–2.2 million Philippine Pesos (1 US Dollar = 25 Philippine Pesos); internal rate of return = 88–107%]. The net benefit–cost ratio of a large-scale operation (2.0) was higher than that of a small-scale hatchery (1.4), suggesting a slight edge in the investment viability of a large-scale hatchery. Compared with a large-scale operation, a small-scale hatchery was more sensitive to changes in the acquisition price of eggs or newly-hatched larvae and in the price of selling hatchery fry. Both types of operation are viable nonetheless when the acquisition cost is P6000 per million eggs or larvae and hatchery fry are sold at P0.50 each. Together, profit and investment in milkfish hatchery fry production appear viable, making milkfish an alternative commodity for production in many abandoned shrimp hatcheries. The limited availability of spawned eggs and larvae for rearing and the quality of hatchery fry are issues requiring urgent attention.

Susceptibility of estuarine crab larvae to ultraviolet radiation

Estuarine crab larvae are often hatched into shallow salt marshes and may remain near the water’s surface while dispersing from shorelines. Residence in surface waters or entrapment in shallow backwaters of marshes may expose larvae to damaging ultraviolet radiation-B (UVBR, 280–320 nm). To determine the effects of UVBR exposure on larval survival, larvae of three species of salt marsh crabs, Uca pugnax (Smith, 1870), Sesarma reticulatum (Say, 1817), and Dyspanopeus sayi (Smith, 1869), were reared for 4 days in UVBR-transparent and UVBR-opaque containers that were suspended 10 and 25 cm below the sea surface in a shallow salt marsh located on Long Island, New York, USA. UVBR, UV-A radiation (UVAR, 320–400 nm) and photosynthetically active radiation (PAR, 400–700 nm) were measured from the surface to the bottom of the water column during the course of five replicate trials. UVBR, UVAR and PAR were all rapidly attenuated in the turbid salt marsh. Nevertheless, UVBR decreased larval survival of all three species. Survival of Sesarma reticulatum larvae decreased as UVBR exposure increased during the course of the experiment. Survival of Uca pugnax larvae initially declined but stabilized thereafter. Survival of Dyspanopeus sayi larvae did not decline during the first day of the experiment but it decreased each day thereafter. Therefore, UVBR may quickly kill newly hatched larvae that become trapped in the marsh or remain within 1 m of the water’s surface. However, larvae in Flax Pond were released during nocturnal ebb tides, and 97.7% of newly-hatched larvae were flushed from the marsh before daybreak. Thereafter, larvae may avoid the top 1 m of the water column during the daytime ( U. pugnax and D. sayi) or may reside at depth throughout the day ( S. reticulatum). The two surface oriented species also may be protected from UVBR by photorepair mechanisms or mycosporine-like amino acids (MAAs). Though larvae remaining high in the water column may be exposed to sublethal doses of UVBR, larvae of these three species may not be killed directly by short-term exposure to UVBR while dispersing from temperate shorelines.

Histological Characteristics and Development of the Retina in the Japanese Sardine &lt;i&gt;Sardinops melanostictus&lt;/i&gt;

Histological characteristics and the distribution pattern of the visual cells, single cones, twin cones, and rods in the retina of the eye of wild adult Japanese sardine Sardinops melanostictus were investigated. The developmental process of the visual cells was also examined in the reared and wild larvae. In the specialized part (area temporalis) of the adult retina, slender twin cones were regularly distributed in a square mosaic pattern with central single cones. In the unspecialized part, twin cones with stout ellipsoids were regularly distributed and many rods were recognizable. A newly-hatched larva had developing lens and undifferentiated retinal cells. The retinal differentiation proceeded rapidly, with the pigment epithelial cells and visual cells already formed in a 31.5 hour-old larva. In a 79.5 hour-old larva at the first-feeding stage, the visual cell layer consisted of only single cones. A so-called pure-cone retina was still recognized in a larva of 18.6mm standard length (SL). In a 20.9mm SL larva, rod-like cells with thin ellipsoids and outer segments appeared and twin cones also observed. In larvae greater than about 20mm SL, the rods and twin cones rapidly increased in number. The retina of a 35.6mm SL juvenile basically did not differ from the adult one.

Cathepsin L in eggs and larvae of perch Perca fluviatilis: variations with developmental stage and spawning period

This study describes changes in cathepsin L activity during early development in Eurasian perch (Perca fluviatilis) and determines to which extend a precocious proteolysis of the yolk reserves by activated cathepsin L could be involved in the seasonal decline of egg and larval quality. During embryogenesis and early larval stages, samples were collected for determination of fertilization and hatching rates, assays of cathepsin L activity, and evaluation of larval resistance to stress (osmotic shock and fasting). Cathepsin L activity increased significantly during the embryonic development, reaching a maximum of 177.1±12.3 nmol min−1mg fresh weight−1 on day 1 post-hatching and significantly decreasing on day 3. Activity increased significantly during the spawning season and individual variations between egg strands became very high during the second half of the spawning period. An inverse relationship was established between the cathepsin L activity in 7-day old eggs and the decrease of hatching rate. A negative exponential regression was calculated between the cathepsin L activity of eggs and the resistance of corresponding newly-hatched larvae to osmotic shock. Resistance to fasting was significantly reduced in larvae from eggs with cathepsin L activity higher or lower than 20 nmol min−1 mg−1 (lethal time50=4.7±0.7 and 3.5±0.4 days, respectively). The involvement of cathepsin L in the degradation of yolk reserves and its potential consequences on the quality of perch eggs and larvae are discussed in relation to results reported in salmonid fishes.

Egg and early larval development of laboratory reared dusky grouper, &lt;i&gt;Epinephelus marginatus&lt;/i&gt; (Lowe, 1834) (Picies, Serranidae)

The embryonic and early larval development of the laboratory-reared dusky grouper, Epinephelus marginatus (Lowe, 1834) are described and illustrated. The eggs, with a mean diameter of 846.68 ± 41 µm and a range from 736-940 µm, were spherical and transparent with transparent chorion. Embryonic development lasted 30 hours at 23°C. Newly-hatched larvae were 1.52 ± 0.066 mm in length. Absorption of the yolk sac was complete after the fourth day, when larvae reached 2.63 ± 0.123 mm in total length. The mouth opened 72 hours after hatching, and was in function after 96 hours, with an opening diameter ranging from 250-300 µm. Larvae had two fields of intensive pigmentation, one above the intestine, and the other between the anus and the end of the notochord.

Effect of administering sustained-release thyroxine microparticles on reproductive performance and egg quality in tilapia (Oreochromis mossambicus) broodstock

Summary Biodegradable sustained-release microparticles containing thyroxine (T4) were developed to study the influence of hormone manipulation on broodstock reproductive performance and the quality of their eggs. Female tilapia (Oreochrotnis mossumbicus) were injected with either microparticles containing T4 (2.5 μg g-1 body weight) or an equivalent amount of blank microparticles. The administration of sustained-release T4 microparticles generated a large increase in serum T4 levels soon after injection [day 2); this was followed by a gradual decline in serum T4, but the level remained significantly higher than in the controls during the 2-day study period. Significantly higher T4 levels in eggs and newly hatched larvae were also observed in the groups from females injected with sustained-release T4 microparticles compared with those injected with blank microparticles. However, no significant differences were observed in the spawning intervals, egg number per spawn, egg diameter, or percentage fertilizability and hatchability. Morphometric examination of the newly-hatched larvae revealed that in the group of females injected with T4 microparticles, the mean total length and the standard length were significantly increased, whereas no clear effect was observed in other parameters such as yolk area and eye diameter. These data indicate that manipulation of the T4 hormone level in broodstock through sustained release did not affect the reproductive performance significantly, but resulted in an improvement in the quality of their eggs as shown by the significantly larger larvae at hatch.

The Larval Development of Palaemonid Shrimps from the Amazon region reared In the laboratory. VII. Abbreviated development of Pseudopalaemon amazonensis Ramos-Porto, 1979 (Crustacea: Decapoda: Caridea)

Larval development of the freshwater shrimp Pseudopalaemon amazonensis Ramos-Porto was studied in the laboratory based on the offspring of ovigerous females collected in a small “terra-firme” forest stream near Manaus, Brazil. Ovigerous females with a mean total length of 36.5 ± 1.9 mm carried 13-19 eliptical, yolk-rich eggs measuring 2.55 ± 0.16 x 1.64 ± 0.11 mm. The larval period consisted of 3 benthie stages and the larvae accomplished metamorphosis after 7-8 days without feeding. The newly-hatched larva had sessile eyes and all appendages, except for the uropods; chelipeds were present as uniramous buds, but walking legs were fully developed and functional. Descriptions and illustrations of the 3 larval and first juvenile stages are presented.

Lipid composition and utilization in developing eggs of two tropical marine caridean shrimps (Decapoda: Caridea: Alpheidae, Palaemonidae)

Changes in biomass and lipid biochemistry during egg development were studied in the tropical shrimps, Alpheus saxidomus and Palaemonetes schmitti, from Pacific Costa Rica. Freshly-laid eggs of P. schmitti were substantially smaller than those of A. saxidomus; dry mass decreased during embryogenesis in the former species but remained almost constant in the latter one. Water content of eggs close to hatching were similar among both species (roughly 75%). Newly-produced eggs of the two species contained ≈20% fatty acids per egg dry mass; a comparison with data concerning decapods inhabiting tropical and temperate waters revealed that eggs produced by shrimps inhabiting tropical waters tend to have a higher lipid egg content per dry mass than those from temperate regions. Major lipid classes in the eggs of both species were phospholipids and triacylglycerols which increased and decreased during the incubation period, respectively. The predominant fatty acids of P. schmitti eggs were 16:0, 20:5(n-3) and 22:6(n-3) whereas eggs of A. saxidomus showed high amounts of 16:0, 20:5(n-3) and 16:1(n-7), and remarkably low values of 22:6(n-3) fatty acid. Lipid utilization was more pronounced in P. schmitti; in A. saxidomus, eggs close to hatching still contained 70% of the initially deposited fatty acid content which may indicate an enhanced independence of the newly-hatched larvae on external energy resources. The observed differences may partially be related to different habitat preferences, however, the role of adaptation and phylogeny as determinants of egg lipid biochemistry in caridean shrimps remains to be clarified.

Protists and detrital particles as prey for the first larval stage of the brachyuran crab, Hemigrapsus oregonensis

Newly-hatched larvae of the brachyuran crab, Hemigrapsus oregonensis, were raised in the laboratory on an autotrophic dinoflagellate ( Prorocentrum micans), a heterotrophic dinoflagellate ( Noctiluca milaris), a green alga ( Dunaliella tertiolecta), an unfed control, and a fed control of Artemia sp. nauplii. Larvae also were fed preparations of seagrass detritus that had been cultured both to promote microbial colonization and to discourage it. Detrital diets were used both alone and in combination with sub-optimal applications of Artemia sp. nauplii. Larvae raised on P. micans showed survival to zoeal stage II equal to those raised on the Artemia sp. nauplii control, although development was delayed. Larvae raised on N. milaris showed substantial (34.7%) survival to zoeal stage II; however survival was lower and development slower than for Artemia sp. nauplii-fed larvae. Survival on D. tertiolecta was less than 3%. Larvae fed microbially-enriched detritus showed a delay in mortality as compared to unfed controls. No larvae fed solely on detritus survived to zoeal stage II. When larvae were fed a sub-optimal diet of Artemia nauplii, supplemented by detrital particles, survival to zoeal stage II increased, although not to the level shown by Artemia-fed larvae in optimal application. Development was not accelerated over the sub-optimal diet in either treatment. The potential for larval crabs to utilize a wide variety of potential prey immediately upon hatching is significant given their susceptibility to early starvation. Such omnivory also suggests a trophic link between carbon sources of the microbial loop and crab larvae.