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At least 19 recordsLinked to original sources
USGS1996

Comparative biology of zebra mussels in Europe and North America: an overview

SYNOPSIS. Since the discovery of the zebra mussel, Dreissena polymorpha , in the Great Lakes in 1988 comparisons have been made with mussel populations in Europe and the former Soviet Union. These comparisons include: Population dynamics, growth and mortality rates, ecological tolerances and requirements, dispersal rates and patterns, and ecological impacts. North American studies, mostly on the zebra mussel and a few on a second introduced species, the quagga mussel, Dreissena bugensis , have revealed some similarities and some differences. To date it appears that North American populations of zebra mussels are similar to European populations in their basic biological characteristics, population growth and mortality rates, and dispersal mechanisms and rates. Relative to European populations differences have been demonstrated for: (1) individual growth rates; (2) life spans; (3) calcium and pH tolerances and requirements; (4) potential distribution limits; and (5) population densities of veligers and adults. In addition, studies on the occurrence of the two dreissenid species in the Great Lakes are showing differences in their modes of life, depth distributions, and growth rates. As both species spread throughout North America, comparisons between species and waterbodies will enhance our ability to more effectively control these troublesome species.

American Zoologist↗
USGS1996

Zebra mussel infestation of unionid bivalves (Unionidae) in North America

In 1989, zebra mussels received national attention in North America when they reached densities exceeding 750,000/m2 in a water withdrawal facility along the shore of western Lake Erie of the Laurentian Great Lakes. Although water withdrawal problems caused by zebra mussels have been of immediate concern, ecological impacts attributed to mussels are likely to be the more important long-term issue for surface waters in North America. To date, the epizoic colonization (i.e., infestation) of unionid bivalve mollusks by zebra mussels has caused the most direct and severe ecological impact. Infestation of and resulting impacts caused by zebra mussels on unionids in the Great Lakes began in 1988. By 1990, mortality of unionids was occurring at some locations; by 1991, extant populations of unionids in western Lake Erie were nearly extirpated; by 1992, unionid populations in the southern half of Lake St. Clair were extirpated; by 1993, unionids in widely separated geographic areas of the Great Lakes and the Mississippi River showed high mortality due to mussel infestation. All infested unionid species in the Great Lakes (23) have become infested and exhibited mortality within two to four years after heavy infestation began. Data indicate that mean zebra mussel densities >5,000–6,000/m 2 and infestation intensities >100-200/unionid in the presence of heavy zebra mussel recruitment results in near total mortality of unionids. At present, all unionid species in rivers, streams, and akes that sympatrically occur with zebra mussels have been infested and, in many locations, negatively impacted by zebra mussels. We do not know the potential consequences of infestation on the 297 unionid species found in North America, but believe zebra mussels pose an immediate threat to the abundance and diversity of unionids.

American Zoologist↗
USGS1996

Variations in the reproductive cycle of Dreissena polymorpha in Europe, Russia, and North America

The reproductive cycle of the zebra mussel { Dreissena polymorpha ) is highly variable throughout its range in Europe, Russia , and North America. The environmental factors influencing this variation are poorly understood, but successful reproduction is occurring in areas where it was initially believed that adult zebra mussels could not survive (i.e., southern United States). The differences in mussel reproduction occurring from site-to-site make it difficult to predict timing of specific events, such as the start of larval production, that are important in initiating containment or control procedures. For example, the amount of time required for a fertilized egg to develop into a juvenile mussel can be as short as 8 days, or as long as 240 days. Release of gametes by adults can be a highly synchronized event, focused over a 1–2 week period, or it can be completely non-synchronized, occurring throughout the year. Zebra mussels in some localities start spawning at water temperatures of 12–13°C, but do not start until water temperatures reaches 22°C at other sites. While some of this variability in reproductive behavior stems from mussel adaptation to local conditions, part is due to difficulties in sampling these events. It is difficult to determine reproductive success of a specific population because of the problems in separating locally produced larvae from larvae drifting in from other areas. Further research is needed not only on the relationship between reproduction and environment at the community level, but also on the variability in response of individual mussels.

American Zoologist↗
USGS1999

Coral adaptation and acclimatization: A most ingenious paradox

Reef corals and the communities they form evidently possess effective mechanisms of adaptation and acclimation that have ensured their survival and recurrence over geologic time. Current reef degradation suggests that these mechanisms are being taxed beyond their limits; understanding of the problem is hampered by serious inadequacies in our understanding of physiological stress responses, the range and implications of reproductive strategies, and the mechanisms of calcification and algal symbiosis. Reef community and population responses to environmental change appear substantially different on different time scales, and a combination of short-term perspectives and definitional confusion complicates interpretation and prediction of reef responses. Calcium carbonate saturation state is now recognized as a potentially important control of reef calcification, which means that rising atmospheric CO 2 represents a direct threat to reef ecosystems on a global scale.

American Zoologist↗
USGS1969

The fossil record of shell boring by snails

The predatory boring habit common to many recent snails probably arose first in the Polinicinae (Naticacea) during Upper Cretaceous (Cenomanian) times (100 million years B.P.) . In the fossil record the frequency of bored shells increases greatly in rocks of latest Cretaceous age and becomes more widespread during early Tertiary times coincident with the major diversification of the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show the same characteristics of preference of penetration in one pelecypod valve rather than the other or in position of the boring site on the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 million years old) that have previously been attributed to gastropod predation are herein attributed to other but unknown boring organisms. In part these borings are not accepted as evidence of Paleozoic gastropod predation because it necessitates: (1) Postulation of the separate development of a boring habit with its concomitant development of an accessory boring organ in a group whose descendants are all herbivores, and (2) The development of such a habit hundreds of millions of years before the appearance of any relatives of present day borers.

American Zoologist↗
USGS1985

Growth and blood chemistry of ducklings reared on acidified wetlands

Acid deposition is one factor that may be responsible for the decline of some waterfowl populations. Growth and physiological condition were monitored in captive-reared black ducks (Anas rubripes) exposed for 10-day trials (day 11-20 of life) on control (pH 6.8) and acidified (pH 5.0) man-made emergent wetlands. Impaired growth (body weight, culmen and tarsus length) and increased mortality (50%) were apparent in broods (hen + 4 ducklings) reared on acidified wetIands. Ducklings exbibiting poor growth had reduced hematocrit, plasma protein and cholesterol levels. This subset of birds had elevated plasma uric acid concentration and creatine kinase activity (perhaps due to enhanced protein and nucleotide catabolism). and elevated pIasma K+ levels. Based upon overt appearance, growth and blood chemistry, ducklings exposed to acidified wetlands were concluded to be in poorer condittion than those exposed on circumneutral pH wetlands.

American Zoologist↗
USGS1983

Fifty-ninth Christmas Bird Count. 176. Ocean City, Md

Some organophosphorus insecticides have been reported to interfere with reproduction and even cause the decline of small mammal populations. The effects of such anticholinesterases on plasma LH concentrations were examined in male mice (Peromyscus leucopus noveboracensis) intubated with water (OW) or acephate (50 and 100 mg/kg) and sacrificed after 4 h. Brain acetylcholinesterase (AChE) activity was inhibited by 45 and 56%, and basal LH levels were reduced by 29 and 25% in mice receiving the 2 doses of acephate. Responsiveness to LHRH did not appear to be affected 4 h after intubation with 100 mg/kg acephate, as 5 ug/kg LHRH ip evoked a comparable rise in plasma LH after 30 min (2.4 and 3.6 fold) in OW-control and treated mice. Subchronic dietary exposure to 0, 25, 100, and 400 ppm acephate for 5 days resulted in a dose-dependent decline in brain AChE activity (23, 42, and 57%), but did not affect LH concentration or the weights of testes and seminal vesicles. These findings suggest that acute exposure to organophosphorus insecticides may impair reproductive function by altering LH secretion.

American Zoologist↗