Behavioural significance of pressure responses in megalopa larvae of Callinectes sapidus and Macropipus sp.

In field experiments, rnegalopae of the intertidal crab Pachygrapsus crassipes Randall. released in the water column at 1 to 5 m depths and observed by a SCUBA diver, swam to the surface. Laboratory experiments on the orientation of megalopae demonstrated a positive phototaxis at 3 light intensities (1240, 690, 70 lux), negative geotaxis, high baro-and photokinesis, and a strong tendency to cling to objects in the water. Spontaneous swimming of megalopae yielded an average speed of 9.5 cm S-'. These observations are consistent with the hypothesis that P. crassipesmegalopae inhabit the neuston and are transported shoreward by tidally forced internal waves.

Section: Discussionmentioning

confidence: 94%

Behavioral basis of internal-wave-induced shoreward transport of megalopae of the crab Pachygrapsus crassipes

Shanks¹

1985

“…The method used here for megalopae was the same as that reported by Sulkin and Van Heukelem (1982) for determining barokinesis in Callinectes sapidus megalopae and is based on the same principle as that employed by Naylor and Isaac (1973). The method utilizes the combined effects of kinesis and taxis and exploits the fact that when locomotory activity increases, megalopae will move upwards due to photo-and/or geotactic orientation responses.…”

Section: Responses To Hydrostatic Pressure In the Megalopamentioning

confidence: 99%

“…Change in response to pressure does occur, often resulting in lower sensitivity and less precise control for depth regulation in later zoeal stages (Sulkin, 1973;Bentley and Sulkin, 1977;Wheeler and Epifanio, 1978;Sulkin et al, 1980). On the other hand, megalopae of the swimming crabs Macropipus sp, and Callinectes sapidus show high sensitivity to pressure, in the case of C. sapidusreversing an ontogenetic trend (Naylor and Isaac, 1973;Sulkin and Van Heukelem, 1982). However, because pressure sensitivity is so closely related to depth regulation in the water column and because the transitional megalopa stage is characterized by both larval and adult traits, it is tempting to attribute the low response threshold to pressure in megalopae of these two species to the swimming habit of the adult.…”

Section: Introductionmentioning

confidence: 99%

Behavioral basis of depth regulation in hatching and post-larval stages of the mud crab Eurypanopeus depressus

Sulkin¹,

Heukelem²,

Kelly³

1983

Stage I larvae of the benthic mud crab Eurypanopeus depressus Hay and Shore are negatively geotactic and show high barokinesis at a low response threshold, traits which should promote upward migration. A vertical temperature gradient of 10 "C has no inhibitory effect on upward migration of first stage zoeae under laboratory conditions. Vertical stratification in estuarine spawning grounds should not influence movement to the surface of the hatching stage of estuarine brachyurans. Megalopae show a low response threshold to pressure increase, similar to earlier reports for rnegalopae of swimming crabs, indicating such sensitivity to pressure is probably widespread among brachyuran species. High degree of pressure sensitivity in brachyuran megalopae creates high precision in depth regulation, a trait important in successful recruitment to appropriate adult habitats.

“…This behavior could be endogenous or stimulated by cues in the environment. Megalopae are sensitive to pressure change and respond to increasing pressure by raising their level of activity which, in concert with negative geotaxis, results in upward movement (Naylor & Isaac 1973, Sulkin & Van Heukelem 1982. Increasing salinity may also stimulate activity in larval crustaceans (Sulkin 1984).…”

Section: Field Distributions: Response To Tidesmentioning

confidence: 99%

Vertical migration of blue crab Callinectes sapidus megalopae: implications for transport in estuaries

Olmi¹

1994

Following larval development in coastal waters, postlarvae (megalopae) of the blue crab Callinectes sapidus Rathbun enter inlets and, against the net seaward flow of estuarine waters, move upstream to juvenile habitats. Abundance and vertical distribution of blue crab megalopae in the York River, Virginia, USA, a subestuary of Chesapeake Bay, was quantified to examine the hypothesis that megalopae are not transported simply as passive particles, but display behaviors that augment their immigration. Megalopal abundance and depth distribution and environmental variables were measured at shallow (3 to 4 m) sites in 1988 and 1989 and at a deep (10 m) site in 1990. Megalopae were more abundant in the water column during flood than ebb, indicating a net upstream flux of megalopae. Densities were always low during ebb. Highest densities occurred during night flood tides, when megalopae were aggregated near the surface. During day flood tides, megalopae were generally less abundant and distributed deeper in the water column. Occasionally, however, they were abundant during day flood, concentrated near the bottom in deep water. At shallow sites, megalopae were never abundant during day, apparently not ascending into well-lit waters. Abundance and depth distribution of megalopae were not affected by current speed, wind speed, water temperature or salinity. A conceptual model of vertical migration of estuarine blue crab megalopae is presented. Megalopae which behave according to this model should lower their susceptibility to predation in the water column by selectively utilizing flood currents to rapidly reach juvenlle nursery grounds while avoiding well-lit waters.