Is it safe to eat oysters during months without the letter R? How can you tell if an oyster has gone bad? Can you recycle oyster shells? Oysters eat phytoplankton or small bits of algae suspended in the water. They are filter feeders, which means that they obtain their food by filtering water in and over their gills. Adult Virginica oysters can filter up to 50 gallons of water per day.
To demonstrate their fascinating ability, here is a time-lapse of oysters in filtering action. Oysters are voracious vegetarians, but fairly picky about what they nosh on.
The Isochrysis goes into the gut and the Chlorella and silt goes into the pseudofeces rendering it bright green! I have done this with radiotracers and the degree of efficiency is remarkable.
It is one reason why the American oyster is so adaptable and can survive in high silt loaded waters while many other organisms struggle and suffocate with fouled gills. Yes, yes they do. Oysters expel both real poop AND pseudofeces , which are particles of non-food things in their food. I mean, can someone just register oysterpoop. Probably not. There is limited scientific evidence that supports this claim, but what we lack in science-based data, we humans love to fill in with anecdotal truth!
Basically, if eating a dozen oysters get you in the mood, then just call it a win. How did oysters get such an amorous reputation? Oysters do contain a pretty high amount of zinc and other great nutrients vitamin B12, thiamin, riboflavin, niacin, vitamins C, D, and E, iron, magnesium, and selenium , which are important in reproductive development and overall health.
A study published in found two amino acids, D-aspartic acid D-Asp and N-methyl-D-aspartate NMDA , in shellfish, like oysters, that were shown—at least in animals—to increase testosterone production. So there is that. But foods and the act of eating can suggest sex to the mind, which in turn can help stimulate desire in the body.
Many of us probably unknowingly was introduced to the term aphrodisiac in grade school while studying Greek mythology. The word is derived from Aphrodite, the Greek goddess of sexual love and beauty. If you come across an oyster with green-tinted gills, like the ones as shown above, consider yourself lucky. The greenish color comes from Haslea ostrearia , a type of microalgae that the oysters are eating.
If the oyster is happy with the algae it will move it up to its mouth. Then the mouth will push the particles to the stomach. This organ is a brownish-greenish color because of all the algae it eats. However, in the winter, all the food disappears and the temperature levels fall.
Infection refers to the establishment of a foreign organism infectious agent or parasite in the tissues of another organism, called the host. Disease indicates damage to a body part, organ, or system such that the affected organism no longer functions normally.
Infection does not necessarily lead to disease. Many infectious agents cause localized tissue damage but relatively little overall harm to their hosts. Infectious agents capable of causing disease are termed pathogens. Some pathogens are so virulent that they cause disease and mortality in susceptible hosts regardless of the physiological state of the host.
Examples include Haplosporidium nelsoni and Perkinsus marinus the disease agents , which cause MSX and Dermo diseases, respectively, in the Eastern oyster, C. Other pathogens are described as opportunistic. Opportunistic pathogens, however, may proliferate and cause disease if the host is compromised in some manner so that it can no longer effectively defend itself or if the number of opportunistic pathogens in the environment is large enough to overwhelm host defenses. Examples are the various bacterial and fungal species that infect and cause mortalities of cultured molluscan larvae and juveniles Elston, Similarly, the herpes viruses associated with mortalities of larval and juvenile stages of a number of molluscan species in commercial hatcheries and nurseries are thought to be promoted by culture conditions, especially high temperature and high density Farley et al.
For disease to occur, a potential pathogen must find a susceptible host in a favorable environment. A parasite may infect one species without causing apparent harm but can cause catastrophic disease outbreaks when.
Pathogens may also be present in an environment that inhibits their proliferation. Under these conditions they remain undetectable, either by causing no observable effect such as death of the host or because they are too few to be found by standard diagnostic assays. Climate warming, for instance, is hypothesized to have favored outbreaks of Dermo disease from existing undetected foci of P.
While all commercial molluscan species examined so far are infected by some parasites, oysters have more reported lethal diseases than any other commercial species Bower et al. Transmission of some parasites, such as P. The mode of transmission, and indeed the complete life cycle of others, such as H. Those not attributable to predation, siltation, or freshwater influxes were simply ascribed to unknown causes Orton, ; Roughley, ; Sindermann and Rosenfield, , although one such case was later ascribed to a pathogen Farley et al.
Another early disease outbreak, which killed large numbers of C. The disease agent is still present but has yet to be identified. Not until the discovery of P. Shortly thereafter, pathogens were associated with catastrophic mortalities of two oyster species C. A virus identified in the gills of C. The loss of C. Typically found associated with mortalities of larvae and juveniles in commercial culture; has been found in adults and in wild larvae and juveniles, but without observed mortality.
Causative agent unknown, but transmissible; probably has bacterial cause, but may also involve other factors. Caused mortalities from New York to Maine during the s. Problem subsided in most regions in late s.
Associated with mortality of juveniles, but adults also suffer. Probably has various causes. May weaken oyster and diminish marketability. In Europe, causes epizootic mortalities in O. Causes epizootic mortalities in C.
In Europe, causes epizootic mortalities in; O. Not known to caused mortalities in O. Also found in C. First outbreak in ; oysters in affected areas appear to have developed resistance. Has been associated with mortality of marine bivalves, but not necessarily as the causative agent—more probably opportunist. Found more frequently in dense associations of bivalves e. The C. The resulting mortalities caused a precipitous decline in O.
Infections of marine molluscs by other agents, including parasitic worms, protozoans, Rickettsiales- and Chlamydiales-like organisms RLOs and CLOs , bacteria, and viruses are not uncommon Bower et al. Some are found when mortalities, often of cultured molluscs, are investigated. Culture conditions, in which the molluscs are grown at high density and often using poor animal husbandry practices, favor the proliferation and transmission of opportunistic pathogens, which can then cause or exacerbate disease and mortality in the cultured organisms Meyers, ; Elston, ; Bower, ; Bricelj et al.
Various bacterial species and the herpes virus are examples of pathogens most commonly associated with disease outbreaks in hatcheries and nurseries Hine et al. Others are encountered during routine surveys or health examinations required for the shipment of molluscs across governmental boundaries. Most occur at low prevalence and intensity and appear to cause no harm to the host. For instance, certain microorganisms, such as the intracellular bacterialike RLOs and CLOs, have been found in all bivalves examined so far, typically without evidence of being harmful.
They have often been associated with mortality Gulka and Chang, ; Le Gall et al. Although not exhaustive, Table 4. Adults are intertidal and subtidal dwellers, typically found in assem-.
The general morphological, physiological, and life history characteristics of oysters described earlier apply equally to C. This section provides more detailed characteristics of C. Reproduction of C. Gametogenesis begins in the spring and spawning occurs from late May to late September in the mid-Atlantic, with the season contracted or extended to the north and south, respectively Shumway, ; Thompson et al. Small oysters 10 to 20 mm sometimes develop gametes, almost always sperm.
Under favorable growth conditions in the mid-Atlantic, this may occur during the late summer after setting, although it is uncertain whether such individuals actually spawn or produce embryos because they do not ripen until after the normal spawning period. In the southeastern United States and the Gulf of Mexico, sexual maturity is typically reached about 3 months after setting, and the prolonged reproductive period in this region increases the probability that these juveniles do participate in the overall reproductive effort of the population.
Males are more sensitive to spawning stimuli, such as temperature and food, than females and tend to spawn first. The presence of sperm in the water stimulates females to release eggs, which are then fertilized externally. Gametes deteriorate within a few hours of spawning and can be rapidly diluted by water currents; thus, the proximity of oysters to one another increases the chances of synchronous spawning and successful fertilization.
In the first 24 hours, oyster larvae develop a large ciliated structure, the velum, which acts as both a swimming and food-gathering organ. Initially, the shell is secreted as a single event at about 24 to 48 hours; thereafter, growth occurs through accretion to both thicken and extend the shell.
The larval stage lasts for about 2 to 3 weeks, depending on food availability and temperature. Larvae appear to migrate vertically, particularly at later stages, tending to concentrate near the bottom during the outgoing tide and rising in the water column during the incoming tide, thus increasing their chance of being retained in the estuary Kennedy, ; Shumway, As is the case with all oyster species, C.
Oyster shells meet those criteria if they are not covered with silt or heavily fouled by other epifaunal organisms although the larvae settle on any type of hard substrate, such as pilings, rocks, and ship bottoms. The suitability of oyster shell for setting, the concentrating mechanisms of wind and.
Without continuous setting and growth of juveniles on the reef, it will usually become covered with silt. Despite the knowledge of where the larvae consistently settle, the parental stock for these sets is rarely, if ever, known.
The potential obviously exists for oysters to be carried long distances during their larval life, both within and between estuaries; the current state of knowledge is insufficient to predict where larvae originating from oysters in a particular area will be transported or to estimate the likelihood that larvae from one estuary will be carried, along the coast, to another estuary.
Oyster larvae are common in summer in water samples collected in East Coast estuaries Kennedy, ; however, investigators sampling nearshore waters off New Jersey for surf clam larvae report seeing only one or two Crassostrea sp. Grassle, Rutgers University, Port Norris, personal communication, For the Gulf of Mexico, Livingston et al. A widespread heavy set occurred in Chesapeake Bay in even though the oyster population was severely depleted.
Unfortunately, most of the oysters suffered disease-caused mortalities before they reached marketable size. From a few hundred microns in size at the time of setting, C. They are typically marketed in the United States when they reach about 75 mm about 3 inches.
Growth rates vary with temperature, food, turbidity, and salinity. In the mid-Atlantic, market-sized C. To the south, C. Growth rates of oysters held in floating aquaculture trays are typically much greater than those of oysters on the bottom.
The average life span is about 6 to 8 years; the maximum is probably about 25 years. Oysters provide food for numerous predatory species, including flatworms, crabs, oyster drills, starfish, and certain finfish.
Mortality rates diminish as the spat grow but remain high during the first several months after setting. Newell et al. Predation, especially by oyster drills and crabs, continues on older oysters MacKenzie, In addition to providing habitat for numerous other species, a principal ecological function provided by oysters is considered to be their ability to remove, or filter, particles from surrounding water Newell, A large C.
The rates that when used in a numerical growth model most closely fit field observations for C. Filtration rates are a function of several environmental factors, including temperature, salinity, and suspended particulate concentration Shumway, Rates increase with temperature, decrease with salinity below about 8 ppt, and also decrease with particle load Powell et al. The highest rates occur during the summer. In the mid-Atlantic and the northeastern United States, C.
Temperature and salinity, and their interaction, are undoubtedly the two most important environmental factors governing survival, growth, and reproduction of C. Many investigators have attempted to define the temperature and salinity tolerance limits and optimum ranges for C. Differences in methodology laboratory versus field observations , acclimation conditions Davis, ; Davis and Calabrese, , and geographically associated genetic traits Barber et al.
In addition, food and turbidity can confound the interpretation of field observations, especially in the case of salinity, as food availability is often limiting at low-salinity sites. Despite the variability, it is clear that C. For instance, adults can survive freezing during winters in the Northeast and summer temperatures averaging 36 o C in Florida and the Gulf of Mexico, with at least short-term temperatures close to 50 o C at intertidal sites.
They grow in locations with salinities averaging 5 to 40 ppt, although major oyster aggregations are typically found at 10 to 30 ppt. They can survive for weeks in winter in nearly fresh water. Spat appear to have the same tolerance limits and optimal ranges as adult oysters, but those of larvae are more restricted and, in the case of salinity, depend on the conditions in which their parents developed gametes. In the laboratory, normal larval development has been observed at temperatures of about 15 o to 30 o C and salinities of 15 to 33 ppt.
Over most of their range in the United States, C. Larval growth rates increase rapidly with increasing temperature; the fastest rates occur near 30 o C. Although the species has a wide geographic distribution, clear genetic differences have been identified among geographically separated populations of C.
Earlier studies indicated that oysters from higher latitudes spawned at lower temperatures than those from more southern locations Stauber, ; Loosanoff and Nomejko, , a difference later demonstrated to have a genetic basis Barber et al. Dittman et al. Disease resistance also has a regional genetic component.
The greater resistance of southern oysters to the pathogen P. The existence of geographically distinct genetic traits underscores the potential problems of moving individuals, even within the same species, between regions and environments in which they have evolved.
Suspension-feeding bivalves are common inhabitants of coastal and estuarine habitats throughout the world. Since these species are capable of capturing large amounts of particulate material from the water column. Suspension feeders also provide other types of ecosystem functions. For instance, their filtering activity may enhance water clarity, increasing light penetration and trapping contaminants entering coastal waters Cloern, ; Newell, Materials ingested by the bivalves are expelled as feces and pseudofeces, which other groups of organisms living in or on the seafloor may bury or remobilize.
Sedimentation of materials by filter feeders can change organic matter decomposition rates and anaerobic or aerobic decomposition processes. Reef-building bivalve species e. As a consequence, the reefs can enhance ecosystem productivity and biodiversity. The structures also stabilize sediments, reduce coastal erosion, and alter the hydrography of shallow-water marsh creeks and embayments Kirtley and Tanner, ; Dame, ; Meyer et al.
Some suspension feeding bivalves can attain densities of 4, to 10, individuals per square meter and, when particularly abundant, have the potential to directly influence resource availability to pelagic species in the ecosystem by causing state changes in abiotic and biotic materials e.
Over the past 7, years the dominant epifaunal suspension-feeding bivalve inhabiting the Chesapeake Bay ecosystem has been the Eastern oyster, C. But as the C. Loss of oysters is generally attributed to overfishing, habitat degradation, disease pressures, and the interaction among these factors, while destruction of reef habitat is the direct result of fishing practices used to harvest the oysters. Oyster reefs provide essential habitat for the maintenance of oyster populations through provision of substrate for larval settlement, refuge from predators and near-bottom hypoxia, and vertical relief above the.
Reef formation occurs through a chemically mediated cue Tamburri et al. While there is some controversy regarding the source of the settlement cue i. Reefs can vary in size and shape hundreds to thousands of square meters and in subtidal regions can be up to 4 m in height Ingersoll, ; Winslow, ; DeAlteris, Reefs with higher profiles above the seafloor appear to promote enhanced oyster productivity.
Low-profile reefs, frequently a result of harvesting practices e. High siltation levels on reefs also impair habitat quantity and quality for settling larvae and attached juveniles Bahr, Experimental studies in North Carolina have demonstrated the importance of the interaction of reef morphology i.
In addition to reef morphology, increased amounts of interstitial spaces within artificially constructed reef were found to enhance juvenile oyster survival Bartol and Mann, , presumably by providing the young life stages with a refuge from predators.
While these studies indicate there is a complex interaction between the physical nature of an oyster reef and the physical environment surrounding it, there are few studies examining the direct and indirect impacts of reef destruction over the past century.
Experimental studies, similar to those of Lenihan and Peterson and Coen and Luckenbach , provide a framework for unraveling some of these complexities. Despite the fact that oyster reefs have been a conspicuous element of the benthic landscape in the Chesapeake Bay for thousands of years, there is surprisingly little information on how reefs provide habitat for other species.
The most conspicuous feature is that reefs add habitat complexity relative to the surrounding sediments. Species that enhance structural complexity can be important determinants of population and community dynamics e.
However, it is not well understood whether oyster reefs simply act as physical attractants or actually enhance the overall productivity of species that co-occur on the reefs. A number of community-based surveys of finfish and macroinverte-brates inhabiting oyster reef habitat have been conducted along the south Atlantic and Gulf coasts. For example, Dame recorded 37 macrofaunal species on an intertidal oyster reef in South Carolina, and Wells found a total of species inhabiting several reefs in North Carolina.
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