Sapidus Larvae Research Articles

Growth, fatty acid and amino acid composition of Nannochloropsis sp. (D.J. Hibberd, 1981) used in the feeding trials of crab Callinectes sapidus larvae

Growth, fatty acid and amino acid composition of Nannochloropsis sp. (D.J. Hibberd, 1981) used in the feeding trials of crab Callinectes sapidus larvae

Larval development of the blue crab Callinectes sapidus: effect of enriched rotifers as live food

Understanding nutrition and its effect on growth is essential for developing diets in commercially important species. This study aimed to evaluate the larval development of Callinectes sapidus fed with rotifers (Brachionus plicatilis) enriched with Chlorella pyrenoidosa (Ch) as a main protein source and a lipid emulsion (Spr) rich in highly unsaturated fatty acids. The enriched compositions had seven ratios Ch/Spr (w/w): 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60. The enriched rotifers with each ratio were called diets. Lipids increased progressively between 100/0 and 40/60 (7.48 to 11.30 g 100 g-1), as well as energy (21.88 to 23.16 kJ g-1), but the protein level did not show a clear trend (63.93 and 67.50 g 100 g-1). The production response of blue crab larvae showed significant differences within diets (P < 0.05). The highest survival (29 to 34%) was obtained in the 50/50 and 40/60 treatments. In the 40/60, 50/50, and 60/40 diets, the larval cycle was shorter (P < 0.05), and the megalopa stage was reached between 49 and 52 days of culture. Metamorphosis to megalopa occurred between the fifth and eighth molts; its corresponding weight varied from 0.72 to 1.33 mg, the length varied from 2,632 to 2,926 µm, and Le Cren´s condition factor varied from 0.83 to 1.16. The most important factor in the production response was the diet lipid content, which was significantly correlated with the survival, weight, length, and condition factor of C. sapidus larvae. Findings of the present study can be applied in future efforts towards mass culture of blue crab larvae in the Caribbean and can also potentially be used to study other crustacean species with similar characteristics.

Brief Episodes of Nocturnal Hypoxia and Acidification Reduce Survival of Economically Important Blue Crab (Callinectes sapidus) Larvae

Many shallow coastal systems experience diel fluctuations in dissolved oxygen (DO) and pH that can intensify throughout the summer season and expose estuarine organisms to repeated episodes of coastal hypoxia and acidification. In temperate regions, larval release of the economically important blue crab Callinectes sapidus occurs in the summer, and while the earliest stage (zoea I) larvae are susceptible to persistent low DO and low pH conditions, their sensitivity to diel fluctuations is unknown. Here, a series of short-term (≤96 h) experiments were conducted to investigate the survival of C. sapidus zoea I larvae exposed to a range of diel cycling hypoxic and acidified conditions and durations. Two experiments comparing a diel cycling DO/pH treatment (fluctuating from ∼30% air saturation to ∼103% averaging ∼66%/and from pH ∼7.26 to ∼7.80 averaging ∼7.53) to a static low DO/pH treatment (∼43%/∼7.35), a static moderate DO/pH treatment (∼68%/∼7.59), and a static control treatment (∼106%/∼7.94) indicated that survival in the diel cycling treatment was significantly lower than the moderate treatment (p < 0.05) by 75 and 48% over 96 and 48 h, respectively, despite comparable mean experimental DO/pH values. Three other experiments aimed at identifying the effective minimum duration of low DO/low pH to significantly depress larval survival under diel cycling conditions revealed that 8 h of low DO/low pH (∼28%/∼7.43) over a 24-h diel cycle consistently decreased survival (p < 0.05) relative to control conditions by at least 55% regardless of experimental duration (72-, 48-, and 24-h experiments). An increase in DO beyond saturation to supersaturation (160%) and pH beyond normocapnic to highly basified (8.34) conditions during the day phase of the diel cycle did not improve survival of larvae exposed to nocturnal hypoxia and acidification. Collectively, these experiments demonstrate that diel cycling does not provide newly hatched C. sapidus larvae a temporal refuge capable of ameliorating low DO/pH stress, but rather is more lethal than chronic exposure to comparable average DO/pH conditions. Given that larvae exposed to a single nocturnal episode of moderate hypoxia and acidification experience significantly reduced survival, such occurrences may depress larval recruitment.

Cloning of aquaporin-1 of the blue crab, Callinectes sapidus: its expression during the larval development in hyposalinity.

BackgroundOntogenetic variation in salinity adaptation has been noted for the blue crab, Callinectes sapidus, which uses the export strategy for larval development: females migrate from the estuaries to the coast to spawn, larvae develop in the ocean, and postlarvae (megalopae) colonize estuarine areas. We hypothesized that C. sapidus larvae may be stenohaline and have limited osmoregulatory capacity which compromises their ability to survive in lower salinity waters. We tested this hypothesis using hatchery-raised larvae that were traceable to specific life stages. In addition, we aimed to understand the possible involvement of AQP-1 in salinity adaptation during larval development and during exposure to hyposalinity.ResultsA full-length cDNA sequence of aquaporin (GenBank JQ970426) was isolated from the hypodermis of the blue crab, C. sapidus, using PCR with degenerate primers and 5′ and 3′ RACE. The open reading frame of CasAQP-1 consists of 238 amino acids containing six helical structures and two NPA motifs for the water pore. The expression pattern of CasAQP-1 was ubiquitous in cDNAs from all tissues examined, although higher in the hepatopancreas, thoracic ganglia, abdominal muscle, and hypodermis and lower in the antennal gland, heart, hemocytes, ovary, eyestalk, brain, hindgut, Y-organs, and gill. Callinectes larvae differed in their capacity to molt in hyposalinity, as those at earlier stages from Zoea (Z) 1 to Z4 had lower molting rates than those from Z5 onwards, as compared to controls kept in 30 ppt water. No difference was found in the survival of larvae held at 15 and 30 ppt. CasAQP-1 expression differed with ontogeny during larval development, with significantly higher expression at Z1-2, compared to other larval stages. The exposure to 15 ppt affected larval-stage dependent CasAQP-1 expression which was significantly higher in Z2- 6 stages than the other larval stages.ConclusionsWe report the ontogenetic variation in CasAQP-1 expression during the larval development of C. sapidus and the induction of its expression at early larval stages in the exposure of hyposalinity. However, it remains to be determined if the increase in CasAQP-1 expression at later larval stages may have a role in adaptation to hyposalinity.

Morphological Characteristics of Early Life History Stages of the Blue Crab, Callinectes sapidus Rathbun, from the Northern Gulf of Mexico with a Comparison of Studies from the Atlantic Seaboard

Zoeae, megalopae, and early crab stages of Callinectes sapidus Rathbun, 1896 were described from the northern Gulf of Mexico (nGOM). Observations during this study were based on larvae reared in the laboratory through the early crab stages and on megalopae and early crab stages collected in the wild. Gulf of Mexico data are compared with similar information for the southeast Atlantic coast of the United States. Size and setation of C. sapidus larvae reared from nGOM stocks were different than those in published descriptions of larvae reared from Atlantic populations. Seasonal differences in size were noted in both reared and wild caught specimens. Zoeal stages I, II and III of larvae cultured in the spring were larger than corresponding larvae hatched in the summer/fall. Data sets on zoeal stages IV and V were incomplete; however, seasonal differences in measurements on all structures tended to be smaller in the summer/fall reared larvae. No seasonal differences were observed for the sixth and seventh zoeal stages, megalopal stage and first crabs. Spring reared larvae had higher survival rates when reared at optimal temperature (25°C) and required fewer zoeal stages (6) to reach the megalopal stage. Megalopae and first crabs collected from the plankton exhibited distinct seasonal variations and were larger in the spring than in fall.

Circatidal swimming behavior of brachyuran crab zoea larvae: implications for ebb-tide transport

Larvae of the blue crab Callinectes sapidus and fiddler crab Uca pugilator are exported from estuaries and develop on the continental shelf. Previous studies have shown that the zoea-1 larvae of some crab species use selective tidal-stream transport (STST) to migrate from estuaries to coastal areas. The STST behavior of newly hatched larvae is characterized by upward vertical migration during ebb tide followed by a descent toward the bottom during flood. The objectives of the study were (1) to determine if newly hatched zoeae of U. pugilator and C. sapidus possess endogenous tidal rhythms in vertical migration that could underlie STST, (2) to determine if the rhythms persist in the absence of estuarine chemical cues, and (3) to characterize the photoresponses of zoeae to assess the impact of light on swimming behavior and vertical distribution. Ovigerous crabs with late-stage embryos were collected from June to August 2002 and maintained under constant laboratory conditions. Following hatching, swimming activity of zoeae was monitored in darkness for 72 h. U. pugilator zoeae displayed a circatidal rhythm in swimming with peaks in activity occurring near the expected times of ebb currents in the field. Conversely, C. sapidus zoeae exhibited no clear rhythmic migration patterns. When placed in a light field that simulated the underwater angular light distribution, C. sapidus larvae displayed a weak positive phototaxis at the highest light levels tested, while U. pugilator zoeae were unresponsive. Swimming behaviors and photoresponses of both species were not significantly influenced by the presence of chemical cues associated with offshore or estuarine water. These results are consistent with predictions based on species-specific differences in spawning and the proximity of hatching areas to the mouths of estuaries. U. pugilator larvae are released within estuaries near the adult habitat. Thus, ebb-phased STST behavior by zoeae is adaptive since it enhances export. Selective pressures for a tidal migration in C. sapidus larvae are likely weaker than for U. pugilator since ovigerous females migrate seaward prior to spawning and hatching occurs near inlets and in coastal waters.

The synergism between hydrocarbon pollutants and UV radiation: a potential link between coastal pollution and larval mortality

Coastal, benthic invertebrates with complex life history strategies are exposed to stage- and habitat-specific selective forces. In the coastal environment, benthic adults are exposed to polycyclic aromatic hydrocarbon pollutants (PAHs) due to their proximity to human activities (shipping, urbanization, and industrialization). Benthic invertebrates produce lipid-rich eggs or larvae that absorb PAHs from polluted estuaries and coastal waters. The larvae of many coastal invertebrates move offshore following release from benthic adults. During development in offshore waters, larvae of some species are exposed to relatively high levels of ultraviolet (UV) radiation. Marine organisms vary in their tolerance to PAHs and UV radiation. The purpose of this study was to examine the effects of the sequential exposure of the larvae of marine crabs to PAHs and UV radiation. Using laboratory experiments, the larvae of four crab species were exposed to PAHs and UV radiation. There was a significant synergistic effect of exposure to PAH (fluoranthene or pyrene) and UV radiation on larvae of the spider crab ( Libinia dubia), the stone crab ( Menippe adina) and the mud crab ( Panopeus herbstii). Larvae of blue crabs ( Callinectes sapidus) were exposed to PAHs and UV radiation in both laboratory and solar UV experiments. Significantly higher mortality occurred for C. sapidus larvae using either type of UV-artificial or solar. Larvae of coastal invertebrates with complex life history strategies are susceptible to the combined effects of PAHs and UV radiation. In this study, the exposure of crab larvae to PAHs and UV radiation resulted in mortality to crab larvae using laboratory and solar UV experiments. There were no effects on larval crab mortality due to PAH or UV radiation independently but mortality was as high as 100% when both factors were present.

Effects of the anionic surfactant, sodium dodecyl sulfate, on newly-hatched blue crabs, Callinectes sapidus, and other routinely tested estuarine crustaceans

This study describes the use of newly hatched larvae of Callinectes sapidus (blue crab) in a 48-h acute toxicity test and compares their sensitivity to two other estuarine crustaceans (Mysidopsis bahia and Palaemonetes pugio) commonly used for evaluation of effects of potentially toxic materials. C. sapidus larvae were twice as sensitive to sodium dodecyl sulfate as ≤ 24-h post-release M. bahia, and five times more sensitive than ≤ 24-h-old P. pugio larvae. We found the blue crab toxicity test to be simple, rapid and accurate and it provides low variability and high reproducibility. Since the data indicate high sensitivity of this commercially important species to a reference toxicant and the potential impact on its survival during a critically sensitive developmental stage, we propose future research further evaluating C. sapidus as a potential toxicity test species.

Responses of estuarine crab megalopae to pressure, salinity and light: Implications for flood-tide transport

The megalopal larval stage of many estuarine brachyuran crabs appears to return to adult habitats by undergoing rhythmic vertical migrations which result in saltatory up-estuary transport on flood tides. Larval ascent into the water column during rising tides may be cued by changing hydrologic variables. To test this hypothesis, we investigated the responses of field-caught megalopae of the blue crab Callinectes sapidus and the fiddler crab Uca spp. to constant rates of pressure and salinity change under laboratory conditions. For both genera, pressure changes resulted in increased movement (barokinesis) and upward migration in the test chamber, with C. sapidus megalopae having a lower response threshold (2.8×10-2 mbar s-1) than Uca spp. larvae (5×10-2 mbar s-1). Similarly, larvae ascended in response to increasing salinity, with C. sapidus larvae being more sensitive. Larvae were negatively phototactic and failed to respond to pressure increases at light levels above 1.0×1015 and 1.0×1013 photons m-2 s-1 for C. sapidus and Uca spp. megalopae, respectively. Such responses are thought to explain the low abundances of larvae in the water column during daytime flood tides. Nevertheless, threshold sensitivities to increasing pressure for both genera were above levels experienced during floodtide conditions in the field. Similarly, it is unlikely that increasing salinity is sufficient to induce ascent in Uca spp. postlarvae. However, rates of salinity increase during midflood tide typically reach levels necessary to induce an ascent in C. sapidus megalopae. These results are consistent with the hypothesis that fiddler crab megalopae utilize an endogenous activity rhythm for flood-tide transport, while blue crab megalopae rely upon external cues, especially salinity changes, to time their sojourns in the water column.

Transport of blue crab larvae by surface currents off Delaware Bay, USA

Weekly abundance of larval blue crabs CaUinectes sapidus was determined during late summer (1983 and 1984) at 15 stahons on the inner continental shelf within 50 km of Delaware Bay, USA. Simultaneous measurements of subtidal, surface flow were made at 5 current meter stations within the study area. During both years, larval abundance was greatest during early August when concentrations in excess of 100 zoeae m-3 were commonly observed. By the thud week in September, early zoeal stages had &sappeared from the water column, and zoeal abundances at all stations were less than 10 zoeae Results of the current meter measurements provide firm evidence of sustained northward flow of surface water on the inner shelf off Delaware Bay during late summer when C. sapidus larvae are common in the plankton. This northward flow occurs on time scales relevant to the rate of larval development of C. sapidus and may be important in retaining zoeae near the parent estuary.

Dispersal strategies of two species of swimming crab on the continental shelf adjacent to Delaware Bay

Brachyuran crab larvae were collected on 5 cruises from late July through early September (1981 and 1982) at 3 stations located along a transect extending 30 km SE from Cape Henlopen at the mouth of Delaware Bay, USA Samples were taken from the neuston, from l m beneath the surface, from mld-depth, and from l m above the bottom. All stations were dominated by 3 taxa: Callinectes sapidus, Ovalipes ocellatus, and Uca spp Two of these dominant taxa belong to the same famlly (Portunidae) and have spawning populatlons in the estuary or in the sublittoral zone of the adlacent inner shelf. C, sapidus maintained a distribution near the surface at each of the 3 stations. In contrast 0. ocellatus showed a deeper distribution at stations farther offshore. At the station farthest from the bay mouth (30 km), 0. ocellatus showed a distinct concentration at the thermocline during daylight. At that station, C. sapidus larvae maintained a surface distribution regardless of time of day, while 0. ocellatus showed a pronounced shift up the water column after sunset and a shift down the water column after sunrise. At the offshore station, very few larvae of either species were found below the thermocline regardless of time of day.

Measuring the effects of thermoclines on the vertical migration of larvae of Callinectes sapidus (Brachyura: Portunidae) in the laboratory

An experimental system is described that is capable of maintaining precise and stable thermoclines of specified magnitude for laboratory study of behavior of planktonic organisms. Behavioral responses to encounters with thermoclines of various magnitudes were measured in stage I larvae of the portunid crab Callinectes sapidus Rathbun. Larvae adapted to an initial temperature of 15°C were able to swim up through a temperature gradient of 10°C, but showed increasing inhibition of upward migration when Δt=12.5°C. Larvae adapted to 17.5°C were unable to penetrate Δt=10°C. Thermoclines of 5° or 10°C slowed passive sinking rates. Results suggest that larvae avoid an upper temperature of 27.5°C by a cessation of swimming, accompanied by passive sinking. Thermal gradients of the magnitude present in the natural habitat are unlikely to alter larval vertical migration that is regulated by other exogenous stimuli. Naturally occurring thermoclines should seldom influence dispersal characteristics of C. sapidus larvae.

Effects of soluble fractions of drilling fluids on development of crabs, Rhithropanopeus harrisii and Callinectes sapidus

The mud aqueous fraction (MAF) and suspended particulate phase (SPP) of low-density lignosulfonate type mud with uerrochrome added were nontoxic to larvae during the complete larval development of Rhithropanopeus harrisii. Five percent (5000 ppm, 0.5 % v/v mud in water) MAF and SPP were not toxic to Callinectes sapidus. Survival of C. sapidus larvae decreased as concentrations of MAF and SPP increased from 5 % (5000 ppm, 0.5 v/v mud in water) to 50% (50000 ppm, 5 % v/v mud in water). No larvae reached the 1st crab stage in 100% (100000 ppm, 10% v/v mud in water) MAF and SPP. Statistical analysis of the data on survival, mortality, and behavior are presented.

Effects of methoxychlor on larval development of mud-crab and blue crab

Laboratory experiments were conducted to determine the effects of methoxychlor on the larval development of the mud-crab, Rhithropanopeus harrisii, and the commercial blue crab, Callinectes sapidus, from the time of hatching until the 1st crab stage was reached. The effect of a range of concentrations of methoxychlor on survival of larvae of C. sapidus and R. harrisii was determined, as well as the concentrations which were sublethal and lethal. Since concentrations as low as 1.3, 1.6 and 1.9 ppb (μg l−1) methoxychlor were acutely toxic to C. sapidus larvae, and it took a concentration as high as 7.0 ppb to be acutely toxic to R. harrisii larvae, it was concluded that C. sapidus larvae were much more sensitive to methoxychlor than R. harrisii larvae. Zoeal and total development to the 1st crab stage of R. harrisii and C. sapidus were prolonged in relation to increased concentrations of methoxychlor. The developmental stages in which larvae were particularly sensitive varied in the two species. Methoxychlor residues of R. harrisii and C. sapidus larvae reared in concentrations of methoxychlor were determined.