Jon G. Stanley

Polyploidy induced in the American oyster, Crassostrea virginica, with cytochalasin B

Abstract Polyploidy was induced in the American oyster by treating the zygote with cytochalasin B. In treatments begun at 50 min after fertilization and lasting 20 min, 13 of 22 oysters treated with 0.1 mg/l cytochalasin and 3 of 4 treated with 1.0 mg/l were polyploid. In treatments with 0.5 mg/l, cytochalasin given from 0 to 15 min after fertilization resulted in 10 polyploids out of 20 and, from 15 to 30 min, 34 polyploids out of 46 examined. Juvenile oysters had about the same percentage of polyploid individuals as embryos. Only triploids were seen at 8 months, whereas triploids and tetraploids were observed in embryos. Oysters developed from treated zygotes set normally and subsequent survival was indistinguishable from those of controls. At 8 months the control and treated oysters both averaged 13 mm in shell height. Survival at 24 h was about 33% that of controls for the 0.1 mg/l treatment and 15% for the 1.0 mg/l treatment. Survival was greater for oysters treated for 15 min beginning immediately after fertilization than if treatment began later at 15 or 40 min.

Growth of American oysters increased by polyploidy induced by blocking meiosis I but not meiosis II

Abstract Triploidy in American oysters ( Crassostrea virginica ) was induced by blocking polar body formation with cytochalasin B. Triploid oysters created by treatment during meiosis I grew faster during the first 3 years of life than did diploid siblings. Triploid oysters created during meiosis II grew at the same rate as their controls. Because heterozygosity was higher in oysters created during meiosis I than in other groups, the increased growth must be due to heterozygosity rather than to triploidy per se.

Reproductive Requirements and Likelihood for Naturalization of Escaped Grass Carp in the United States

Abstract Information on reproductive requirements of grass carp (Ctenopharyngodon idella Val.) was obtained from published accounts, from a visit to rivers in the USSR where introduced grass carp have reproduced, and from discussions with Soviet fishery workers. Turbulent areas at the confluence of rivers or below dams are the focal points for reproduction. Successful spawning occurs only in large rivers or canals where water velocity exceeds 0.8 m/s and volume is roughly 400 m3/s. The eggs are carried 50 to 180 km, depending on water temperature and current speed. The larvae hatch 1 day after spawning and make their way to vegetated lagoons, impoundments, or lakes closely connected to the river. They begin feeding on rotifers at 2 to 4 days and change to larger zooplankton in about a week. Temperatures required for stimulation of sexual maturation, egg incubation, and survival of young range from 19 to 30 C, with an optimum of about 23 C. Because requirements for each factor must be found in juxtapositio...

ABNORMAL GAMETOGENESIS AND SEX RATIO IN TRIPLOID SOFT-SHELL CLAMS (MYA ARENARIA)

Triploid soft-shell clams (Mya arenaria) were produced by inhibiting polar body extrusion with cytochalasin B immediately after fertilization. Diploid and triploid clams grown in suspended tray culture were examined histologically during the reproductive season of their second year. Most diploids had matured by the end of May and displayed normal gametogenic development in every individual. Triploids did not mature and most had undeveloped gonads. The few triploid females which developed some oocytes by the end of May had abnormal maturation. Triploids were 77% female as judged by the presence of oocytes; another 16% were female-like and may have been intersexes; the sex of 6% could not be identified because there was no sexual differentiation. Sex determination in this species, based on the sex ratio in triploids, best fits the model of an X:autosome balance mechanism as exemplified in some insect species.

Reproductive Sterility in Polyploid Brook Trout, Salvelinus fontinalis

Abstract Erythrocyte nuclear volumes were measured in brook trout (Salvelinus fontinalis) from Phillips Hatchery in Maine to document naturally occurring polyploid sterility. In eight brook trout in which gonads were lacking or undeveloped, the nuclei were large, suggesting polyploidy. The average size of the erythrocyte nuclei in other sterile fish fell within the normal range but all of the eight fish appeared to have some erythrocytes that were polyploid. All polyploids appeared to be mosaics, containing diploid, triploid, tetraploid, or pentaploid cells. The cause of the polyploidy was not determined but may have been caused by the inadvertent exposure of the eggs to low temperatures after fertilization.

Polyploid Mosaics Induced by Cytochalasin B in Landlocked Atlantic Salmon Salmo salar

Abstract Polyploid mosaicism was induced in landlocked Atlantic salmon by treatment of fertilized eggs with 10 mg/liter solution of cytochalasin B. On the basis of nuclear size in 3,025 erythrocytes and chromosome counts we judged the treated fish to be polyploid mosaics of diploid, triploid, and tetraploid cells. The dominant polyploid cell type in test fish was triploid rather than tetraploid, in contrast to previous reports of Atlantic salmon exposed to cytochalasin B. Control groups had mainly diploid cells but a few triploid cells were measured in most individuals.

Ploidy of Hybrid Grass Carp X Bighead Carp Determined by Flow Cytometry

Abstract Flow cytometry was used to identify polyploid fish by means of measuring deoxyribonucleic-acid fluorescence in erythrocytes. One polyploid grass carp Ctenopharyngodon idella and one polyploid bighead carp Hypophthalmichthys (=Aristichthys) nobilis were identified among 38 fish of each species. Ten hybrids identified as diploids on the basis of morphology were confirmed to be diploid. All hybrids identified as polyploid morphologically were indeed polyploid, but two of these were tetraploid rather than triploid. Received May 14, 1982 Accepted February 15, 1983

Reproduction of the Grass Carp (Ctenopharyngodon Idella) Outside Its Native Range

Abstract Grass carp (Ctenopharyngodon idella) spawned after they were introduced into the Volga, Ili, Terek, Amu-Darya, and Kuban Rivers, and the Kara-Kum Canal of the Soviet Union; the Tone River of Japan; the Ah Kung Tien Reservoir of Taiwan; the Pampangi River of the Philippines; and the Rio Balsas and the Bodegas Lake system of Mexico. Natural reproduction in the United States seems likely as soon as the large numbers of grass carp released into the Mississippi River system in 1973–1975 reach sexual maturity, probably in 1978 or 1979.

Theory and Practice of Forage-Fish Management in New England

Abstract Several fish species serve as forage for freshwater predatory fish in New England, but only the alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax have been managed extensively. Management consists of transplantation and regulation of sport, bait, and commercial fisheries. Rainbow smelt are transplanted by transfer of eggs naturally deposited on burlap bags, or by transfer of mature adults in aerated containers; alewives are established or maintained by transfer of ripe adults. Both species have anadromous populations; larval rainbow smelt migrate almost immediately to sea, but alewives remain in freshwater ponds for the first summer, where they provide food for predator fish. Landlocked populations of rainbow smelt are more valuable than those of alewives, because rainbow smelt distribution within the water column more closely matches that of most coldwater predators. Landlocked Atlantic salmon Salmo salar depend almost totally on rainbow smelt for good growth. When alewives and rainb...

Loss of Freshwater Shellfish After Water Drawdown in Lake Sebasticook, Maine

ABSTRACT Water drawdown to improve water quality of Lake Sebasticook, Maine, exposed virtually all mussel habitat and stranded freshwater mussels. Populations of adult (6- to 18-year-old) eastern elliptio (Elliptio complanata) and eastern lamp mussel (Lampsilis radiata), which had a combined density of 1.4 ± 0.4 m−2 in water 2 to 4 m deep, largely disappeared after drawdown. They survived only near the lakes inlet, and here the population declined from 1.9 m−2 to 0.14 m−2 in the following year. The movement rate of 1 to 16 mm min−1 of the elliptio would have allowed escape to open water as the water receded; however the movement was random.