Dyspanopeus Sayi Research Articles

Biotic potential and environmental resistance in the American oyster ( Crassostrea virginica) in Long Island Sound

The American oyster ( Crassostrea virginica) in Long Island Sound was studied throughout its life span on commercial beds by conducting SCUBA surveys and supporting laboratory tests from 1966–1972. The oyster had a biotic potential of a magnitude large enough to cover the entire bottom of the Sound within a few years, given optimum environmental conditions. The limiting factors were mainly: low temperatures, a lack of clean shell substratum on which oyster larvae could set, and about 20 causes of mortality in sedentary oysters, the most substantial of which were: (1) predation by starfish ( Asterias forbesi), oyster drills ( Eupleura caudata and Urosalpinx cinerea) and crabs ( Cancer irroratus and Neopanope sayi); (2) competition by slipper-shells ( Crepidula fornicata and Crepidula plana) and other animals on shells; (3) suffocation by silt and (4) shell fracture during transplanting by oyster growers. Oyster mortalities occurred mostly from spring to fall and were negligible during winter. The mortalities were area-specific within beds, bed-specific and much higher in spat than in 1, 2 and 3-year-old oysters. The survival of oysters from setting of spat throughout their life span on cultured beds was estimated to be 2–5%. Few oysters could survive in the Sound without bed culture. During 1966 and continuing afterwards, the growers applied improved cultural methods and new technologies to remove a number of limiting factors from the beds, and this resulted in an oyster “abundance and production takeoff”.

Larval Development Under Laboratory Conditions of the Xanthid Mud Crab Eurytium limosum (Say, 1818) (Brachyura: Xanthidae) from Georgia

Larvae of the xanthid mud crab Eurytium limosum were reared in the laboratory from hatching to first crab stage. Four zoeal stages and one megalops staged were obtained and are described. Complete larval development required about 15 days under culture conditions of 26.0° to 28.0°C and 25 ppt sea water. A long antenna and short antennal exopods consign E. limosum to the Group I xanthid zoeae of Rice (1980). The first stage zoea closely resembles that of Panopeus herbstii and is distinguished by having the dorsal spine strongly recurved at the extremity. Stages 2 to 4 are distinguished from Rhithropanopeus harrisii and Neopanope sayi larvae by having two lateral spines on the telson.

Agonistic and Sexual Behavior of the Xanthid Crab, Neopanope sayi

The social behavior ofNeopanope sayi is more complicated than that usually reported for totally aquatic brachyurans. Ritualized visual displays, especially the Lateral Merus, are important in agonistic encounters. Fights are rare. During sexual interactions stereotyped periodic movements immediately after the male grabs the female may be responsible for species, sexual, and mate discrimination. Behavior prior to the Grab resembles advanced agonistic encounters, which may explain why males almost always copulate with females smaller than themselves. Females mate while in the hard stages of the molt cycle and sometimes when ovigerous.

The role of pelagic larvae in recruitment to populations of adult decapod crustaceans in the York River estuary and adjacent lower Chesapeake Bay, Virginia

The distribution patterns exhibited by some larval decapod crustaceans within the York River system and adjacent lower Chesapeake Bay, Virginia, suggest means by which young stages can be recruited to the adult benthic and bentho-pelagic populations. Species considered are four caridean shrimp ( Crangon septemspinosa, Hippolyte pleuracantha, Ogyrides limicola and Palaemonetes spp.) and 12 brachyuran crabs ( Callinectes sapidus, Cancer irroratus, Hexapanopeus angustifrons, Neopanope sayi, Ovalipes ocellatus, Pinnixa chaetopterana, Pinnixa sayana, Pinnotheres maculatus, Pinnotheres ostreum, Rhithropanopeus harrisii, Sesarma reticulatum and Uca spp.). Larvae of the species which are heavily dependent on estuarine habitats were more abundant in the lower layer of the water column where net transport is upstream than near the surface and thus tended to be retained within the estuary. For these species, retention of larvae in the estuary may be the primary mechanism of recruitment to estuarine adult populations. No distributional adaptations for retention within the bay were apparent among larvae of Cancer irroratus, Crangon septemspinosa and O. ocellatus, species not restricted to estuarine habitats, nor for Callinectes sapidus, a migratory estuarine species which also occurs on the inner continental shelf. While chance retention of larvae may affect recruitment, especially of C. septemspinosa, the major mechanism by which the bay populations of these species are restocked is probably the immigration of juveniles or adults from inner shelf waters. Thus, there appear to be two basic mechanisms of recruitment of young to estuarine decapod crustacean populations: (1) recruitment by retention of larvae and (2) recruitment by immigration of juveniles and adults. Various combinations of the two mechanisms are expressed among the different populations of an estuary, and the tendency of a species to exhibit one more than the other is influenced primarily by the degree of its dependence upon the estuary.