Larval release behaviors in the blue crab Callinectes sapidus: role of chemical cues (original) (raw)
Related papers
Journal of Experimental Marine Biology and Ecology, 2010
Blue crabs Callinectes sapidus, like most decapods, synchronously hatch eggs and release larvae over a very short time period. Synchrony is achieved though vigorous abdominal pumping in response to pheromones from hatching eggs. We hypothesized that these or related pheromones stimulate vertical swimming associated with larval release and ebb-tide swimming during the last few days before egg hatching. We used abdominal pumping and swimming assays to investigate the roles of pheromones. We tested responses of crabs to egg extract containing pheromones, trypsin (an enzyme that generates peptide pheromones), and bradykinin (a peptide pheromone mimic). We delivered test substances directly into the egg mass via capillary tubing. In response to egg extract, ovigerous crabs increased abdominal pumping and vertical swimming, showing native pheromones evoke both behaviors. Delivery of trypsin and bradykinin caused increased pumping but not vertical swimming. These results suggest that pheromones generated from eggs stimulate vertical swimming during ebb-tide transport, but that peptides that induce abdominal pumping are not sufficient to cause swimming. We hypothesize that swimming is stimulated by a blend of molecules that includes these peptide pheromones.
Journal of experimental zoology. Part A, Comparative experimental biology, 2006
Hatching of embryos in the estuarine crab Sesarma haematocheir is highly synchronized with nocturnal high tide and completes within 1 hr among all embryos incubated by the female. This highly synchronized hatching is induced by a "Hatching-Program Inducing Factor (HPIF)" released from the female. To further define the cues involved in synchronized hatching, experiments were designed to characterize this factor and to determine possible sites of release and temporal release patterns using strategies involving isolation of egg masses, perfusion, and ablation experiments on fully developed embryos that had not yet entered the hatching program. Embryo transplantations indicate that not only HPIF may be released from the branchial chamber, but that it is extraordinarily unstable, and loses activity within 15 min, which frustrates further attempts at characterization. Nevertheless, with regard to temporal release patterns, it was established that HPIF activity was detected durin...
Control of larval release in the Caribbean spiny lobster, Panulirus argus: role of chemical cues
Marine Biology, 2007
The current model for larval release in subtidal crustaceans suggests that hatching time is controlled by the embryos, which release a pheromone that stimulates the parent female to undergo behaviors that synchronize larval release. Alternatively, hatching could be controlled by the females. Ovigerous spiny lobsters Panulirus argus (Latreille) exhibit stereotypic behaviors during larval release, including rapid abdominal extensions and pleopod-pumping activity. Ovigerous P. argus were collected from coral reefs in the Florida Keys, USA during the summers of 2005 and 2006. Pleopod-pumping activity was quantiWed to determine if a female's pumping activity correlates with the developmental state of the embryos. The role of pheromones released by developing and hatching embryos in controlling pumping behaviors was tested by measuring the pumping response of ovigerous lobsters to (1) hatch water, (2) homogenized embryo water, (3) embryo-conditioned water (unhatched late-stage embryos soaked for 20 h), and (4) water containing homogenized post-hatch embryo cases. Bioassays were conducted under constant conditions (dim-red light) in the laboratory at random times during the day to control for any possible rhythm in pumping activity. Spontaneous pleopod-pumping activity increased signiWcantly with increasing embryo development. Upon exposure to hatch water, ovigerous lobsters with late-stage embryos displayed increased pleopod pumping with increased treatment concentration. Water individually conditioned with homogenized late-stage embryos, intact late-stage embryos, and homogenized post-hatch embryo cases all induced larval release behaviors in females with late-stage embryos. Ovigerous females with early-stage embryos did not respond to water conditioned with homogenized early-or late-stage embryos. These results suggest that active substances are released by embryos at the time of hatching and induce the stereotypical pumping behaviors of the female that synchronizes larval release. The results support the model that larval release in subtidal crustaceans is controlled by pheromones released from hatching embryos.
Chemical Mediation of Larval Release Behaviors in the Crab Neopanope sayi
The Biological Bulletin, 1991
Control of egg hatching was investigated in ovigerous females of the crab Neopanope sayi. Larval release is a brief event, generally lasting less than 15 min, during which females perform stereotypic behaviors involving vigorous abdomen pumping. Substances released by hatching eggs (pumping factors) of N. sayi, Rhithropanopeus harrisii, and Uca pugilator, but not Sesarma cinereum, evoked these stereotypic behaviors (pumping response) in ovigerous N. sayi. Spontaneous pumping and responsiveness to pumping factors varied with the age of the embryos. These results indicate that the eggs release pheromones around the time of hatching, which supports the general model for egg-hatching control described for R. harrisii (Forward and Lohmann, 1983). The chemistry of N. sayi pumping factors was investigated, and the pumping response was used as a bioassay in this study. Pumping factors adsorbed to Amberlite XAD-7 resin and could be eluted from it with methanol. Size fractionation by cascade pressure dialysis showed that the active molecules were < 1000 daltons. Acid hydrolysis followed by reverse-phase HPLC amino acid analysis showed that the biologically active fraction contained peptides. Cysteine, glycine, methionine, and isoleucine were the four most common amino acids in these peptides. The responsiveness of N. sayi to hatch water from R. harrisii, the general similarity of adsorptive characteristics of hatch waters from the two species toward XAD-7 resin, and the amino acid compositional analysis suggest that the pumping factors from both species are similar. This supports the hypothesis that N. sayi pumping factors are also small peptides, as was suggested for those of R. harrisii (Rittschof et al., 1985, 1989).
Pheromones inhibit the hatching of diapausing Anostraca (Crustacea: Branchiopoda
Hatching of resting eggs of Streptocephalus torvicornis (Waga, 1942) and Branchipus schaefferi Fischer, 1834, two sympatric fairy shrimps, was tested using medium in which these two species and Chirocephalus diaphanus (Prévost, 1803) had been raised. The medium of adults inhibited the hatching of conspecific nauplii, even when diluted by 50% using distilled water. Streptocephalus torvicornis resting eggs hatch in the medium of C. diaphanus but not in the medium of B. schaefferi. Resting eggs of B. schaefferi hatched in low numbers in S. torvicornis medium, and in high numbers in that of C. diaphanus.
Ecophysiological studies on developing eggs and ovigerous females of intertidal crabs
2011
Morphological, ecological and physiological adaptations of ovigerous crabs and their developing eggs to conditions on shore were compared in two species of New Zealand intertidal crabs. Newly-laid eggs of both Heterozius rotundifrons and Cyclograpsus lavauxi are ellipsoidal, with initial mean volume of 204 and 10 nL respectively, increasing to 360 and 19 nL respectively before hatching. The incubation periods of eggs of H. rotundifrons and C. lavauxi were 194±3 and 56±1 days respectively at constant 15°C. Morphological criteria and timing of the 5 major developmental stages are reported: (1) Newly laid egg stage (2) Blastula stage (3) Gastrula stage (4) Eyespot and pigmentation stage and (5) Heart-beating stage. Two major membranes surround developing eggs at both early and late stages of H. rotundifrons. The thickness of the outer and inner membranes are approximately 3.4-4.8 and 0.6-0.9 µm respectively and are separated by a perivitelline space. The timing of larval release was ex...
Integrative and Comparative Biology, 2011
Synopsis Most semiterrestrial, intertidal and shallow subtidal brachyuran crabs that live in tropical and warm temperate estuaries, bays and protected coasts worldwide release their planktonic larvae near the times of nocturnal high tides on the larger amplitude tides in the biweekly or monthly cycles of tidal amplitude. Crab larvae usually emigrate quickly to the sea where they develop to return as postlarvae to settle in habitats suitable for their survival. Predators of larvae are more abundant where larvae are released than where they develop, suggesting that this migration from estuaries to the sea reduces predation on larvae. Crabs with larvae that are relatively well-protected by spines and cryptic colors do not emigrate and often lack strong reproductive cycles, lending support to this explanation. Adults control the timing of the release of larvae with respect to the biweekly and monthly cycles of tidal amplitude by controlling when they court and mate and females control when development begins by controlling when they ovulate and allow their eggs to be fertilized by stored sperm. By changing the time they breed, fiddler crabs (Uca terpsichores) compensate for the effects of spatial and temporal variation in incubation temperature on development rates so that embryos are ready to hatch at the appropriate time. Control of the diel and tidal timing of hatching and of release of larvae varies with where adults live. Females of the more terrestrial species often move from protected incubation sites, sometimes far from water, and they largely control the precise time, both, of hatching and of release of larvae. Females of intertidal species also may influence when embryos begin to hatch. Upon hatching, a chemical cue is released that stimulates the female to pump her abdomen, causing rapid hatching and release of all larvae in her clutch. Embryos, rather than females, largely control hatching in subtidal species, perhaps because females incubate their eggs where they release their larvae. Topics for further study include the mechanism whereby adults regulate the timing of breeding, the mechanisms by which females control development rates of embryos, the nature of communication between females and embryos that leads to precise and synchronous hatching by the number (often thousands) of embryos in a clutch, and the causes of selection for such precision. The timing of hatching and of release of larvae by cold-temperate, Arctic, and Antarctic species and by fully terrestrial and freshwater tropical species has received little attention.
Cues and context: Larval responses to physical and chemical cues
Biofouling, 1998
Most marine organisms have a highly specialized larval settlement stage. A major function of the settlement stage is response to environmental input that results in deposition of the larvae in a location which confers probability of survival and successful reproduction. The settlement stage is a prime target for management strategies because it is a key and vulnerable step in the colonization process. Published and unpublished work will be synthesized to provide an overview of responses of a variety of settlement stage larvae to chemical and physical cues. It is maintained that due to tiny larval brains and poor memories, it is environmental cues rather than larval choice that determines where larvae settle. Larval examples include ascidians, brachyurans, bryozoans, cirripedes, hydroids and polychaetes. Chemical cues include inorganic and organic compounds, including stimulatory peptides and odors. Physical cues include surface energy, vibration and light. The aims of this review are to find common ground with others in the field and to add to the theoretical context the consideration of environmental input for larval settlement.
Host cues induce egg hatching and pre-parasitic foraging behaviour
2013
The responses of eggs in diapause and the infective stage of the nematode, Strelkovimermis spiculatus, to larvae of its host, Culex pipiens pipiens, were investigated in the laboratory. The results indicated that the presence of the host induced the egg hatching. The hatching rate increased when larger numbers of host larvae were present. Second instar mosquito larvae induced significantly higher hatching rates than any other stages. These findings explain how S. spiculatus synchronizes its life cycle with its host life cycle and population dynamics to increase its fitness when the natural habitat is constantly covered by water. Direct exposure of the nematode eggs to host larvae resulted in consumption of as many as 20 eggs per host. The eggs consumed caused 0-70% host mortality depending on the number consumed, which indicated an infection path other than cuticle penetration although it may represent a rare situation in nature. The result of host cue assays showed that the combination of chemical cues and physical vibration induced the highest egg hatching, which may increase the chance of host availability after hatching. However, once hatched, the nematodes ignored vibrations and used only chemical cues for host location. These findings suggest that eggs hatch synchronously with the most susceptible mosquito stage and with peak mosquito larval density.
Egg activation in the black tiger shrimp Penaeus monodon
Aquaculture, 2004
This report describes morphological changes in the eggs in the black tiger shrimp Penaeus monodon upon contact with seawater, the process known as egg activation. Eggs from wild P. monodon broodstock were collected at 15-s intervals post-spawning during the first 15 min, and at 15-min intervals thereafter for 2 h. The samples were fixed and processed for light, scanning and transmission electron microscopy. As soon as the egg was released into seawater, the cortical rods began to emerge from the crypts on the periphery of the egg, and elevated the thin investment coat that covered the surface of the egg. Sperm in the first phase of the acrosome reaction were observed on both the egg and the surface of the investment coat. The rods protruded from the surface and were completely expelled out within 45 s. I0mmediately after complete extrusion, the cortical rods began to break up and formed the jelly layer around the egg. By this time, the interaction between the sperm at the second phase of the acrosome reaction and egg began. The hatching envelope had started formation at 1-min post-spawning, and was completed within 13 -15-min post-spawning. The first and second polar bodies extruded from the egg at 3 -5-and 10 -15-min post-spawning, respectively. It was apparent that after the hatching envelop had formed, additional sperm could not enter the egg. This study (B. Withyachumnarnkul).