Marine Invertebrate Populations Research Articles

Ecological effects of larval trematode infestation on littoral marine invertebrate populations

Evidence is presented that, contrary to common scientific “belief”, larva digeneans have profound effects on various components at various levels of the littoral marine ecosystem. Their ecological capacity includes: —Reduction of the breeding potential of host populations by “parasitic castration”; —Structural modification of host populations by generation of erratic growth patterns, size-class differential mortality and “negative growth”; —Induction of host-population mortality and control by increased susceptibility to environmental stress; —Induction of changes in community structure by removal of hosts from their normal trophic levels; —Interference with major energy-flow pathways by precocious removal of hosts from their normal food-web position; —Interference with host-biomass, production and turnover-rate estimations by by-passing of hostassimilated energy; —Interference with predator-prey systems by affecting either component(s) of such systems. The notorious neglect of these factors by marine ecologists and, even more, their total unawareness of the effects these factors produce, raise serious doubts about the validity of marine ecological data and concepts. For the parasitologist, on the other hand, the study of ecological aspects of marine parasite (digenean) biology may open new avenues of research. With a true synthesis of both scientific disciplines, we may eventually arrive at a point where “more complete knowledge of life cycles will permit more intelligent and more effective regulatory methods, the reduction of morbidity, the advancement of health, and the conservation of natural resources.” The latter statement has not been cited from a recent issue of a scientific journal; it has been written down as long as 46 (!) years ago by one of the most outstanding investigators of marine digenean life cycles—Horace W. Stunkard (1940, p 15), but has lost nothing of its actuality. It is hoped that Stunkard's far-sighted words might encourage parasitologists to devote some of their scientific power and skill to the study of marine ecoparasitological problems—for the sake of a better understanding of ecological processes and to the benefit of the endangered marine life.

Some limitations on the use of the lipofuscin ageing technique

Measurement of the amount of age pigments (lipofuscins) in tissue samples has recently been proposed as a method of discriminating between age classes within populations of marine invertebrates. During an attempt to use lipofuscin fluorescence as a technique in examining age structure in populations of the copepod Calanus hyperboreus and the euphausiid Meganyctiphanes norvegica collected in 1984, some technical problems were encountered. The fluorescence readings obtained from samples using this technique were found to be dependent on the previous treatment of the specimens. Formalin-preserved samples yielded the highest fluorescence readings, frozen specimens yielded the lowest and ethanol treatment of samples provided intermediate levels of fluorescence. Experiments on squid (Ilex illecebrosus) tissue indicated that fluorescence in formalin-preserved specimens increased with time spent in the preservative, that the formalin induced fluorescence elevation was not due to bleaching of masking pigments and that formalin appears to act on the lipofuscin itself to increase its fluorescence.

Transformation of organic matter in areas inhabited by natural and artificially cultured populations of marine invertebrates in the Bay of Pos'et (Sea of Japan)

Data are presented on seasonal changes in the quantity and quality of dissolved, particulate and sedimentary organic matter in natural and artificial marine ecosystems. The role of enzymatic processes in the metabolism of organic matter was studied. Comparison of the rates of proteolysis and aerobic oxidation of organic material in particulate matter and in the surface active layer of the sediments suggests that oxidation of organic matter to CO 2 and H 2O is a limiting stage of its transformation in marine ecosystems.

Transformation of organic matter in areas inhabited by natural and artificially cultured populations of marine invertebrates in the Bay of Pos'et (Sea of Japan): Agatova, A.I., N.M. Andreeva, A.V. Kucheryavenko and N.I. Torgunova, 1986. Aquaculture, 53(1):49–66

Transformation of organic matter in areas inhabited by natural and artificially cultured populations of marine invertebrates in the Bay of Pos'et (Sea of Japan): Agatova, A.I., N.M. Andreeva, A.V. Kucheryavenko and N.I. Torgunova, 1986. Aquaculture, 53(1):49–66

Viral diseases of marine invertebrates

Approximately 40 viruses are known from marine sponges; turbellarian and monogenetic flatworms; cephalopod, bivalve, and gastropod mollusks; nereid polychaetes; and isopod and decapod crustaceans. Most of the viruses can be tentatively assigned to the Herpesviridae, Baculoviridae, Iridoviridae, Adenoviridae, Papovaviridae, Reoviridae, “Birnaviridae”, Bunyaviridae, Rhabdoviridae, and Picornaviridae. Viruslike particles found in oysters might be representatives of the Togaviridae and Retroviridae. Enveloped single-stranded RNA viruses from crustaceans have developmental and morphological characteristics intermediate between families, and some show evidence of relationships to the Paramyxoviridae as well as the Bunyaviridae or Rhabdoviridae. Certain small viruses of shrimp cannot be assigned, even tentatively, to a particular family. Some viruses cause disease in wild and captive hosts, others are associated with disease states but may not be primary instigators, and many occur in apparently normal animals. The frequency of viral disease in natural populations of marine invertebrates is unknown. Several viruses that cause disease in captive animals, with or without experimental intervention, have also been found in diseased wild hosts, including herpeslike viruses of crabs and oysters, iridovirus of octopus, and reolike and bunyalike viruses of crabs. Iridolike viruses have been implicated in massive mortalities of cultured oysters. Baculoviruses, and IHHN virus, which is of uncertain affinities, cause economically damaging diseases in cultured penaeid shrimp. Double or multiple viral infection is common in crabs. For example, a reolike virus and associated rhabdolike virus act synergistically to cause paralytic and fatal disease inCallinectes sapidus. Information on host range, most susceptible stage, and viral latency is available only for viruses of shrimp. One baculovirus attacks five species of New World penaeid shrimp. IHHN virus infects three species ofPenaeus and causes catastrophic mortalities inP. stylirostris, but usually exhibits only inapparent infection inP. vannamei. Some shrimp viruses apparently are latent in larvae, causing disease only when shrimp have reached the postlarval or juvenile stages. Others are equally or more pathogenic in larvae. Studies of shrimp viruses and iridovirus-associated disease in cultured oysters point up the need for rapid and accurate diagnostic methods. Until appropriate cell cultures from marine invertebrates are devised, the viral identifications necessary for understanding of epizootiology, rapid containment of epizootics in cultured animals, and decisions regarding introductions of exotic species will be difficult or impossible.

Mercury in marine organisms of the Tay region.

THERE has been increasing concern recently about the quantities of heavy metals, such as mercury, which may accumulate in many organisms. In spite of studies in Japan1, Sweden2–4 and North America5,6, concentrations of mercury in populations of marine algae and invertebrates have received little attention, notably in the United Kingdom. Klein and Goldberg6 reported average mercury concentrations in epibenthic animals from near La Jolla, California, of 0.9 p.p.m. dry weight with a maximum of 21 p.p.m. in a cowry (Cypraea sp.) and values of 0.037 p.p.m. and 0.023 p.p.m. have been recorded in the algae Laminaria hyperborea and Fucus vesiculosus7. We present here data on mercury concentrations which were found in some organisms collected from the Tay region. These vary according to the sampling area examined and are highest in organisms receiving direct discharge from the Tay.

Resurgent Populations of Littoral Marine Invertebrates and Their Dependence on Ocean Currents and Tidal Currents

Resurgent Populations of Littoral Marine Invertebrates and Their Dependence on Ocean Currents and Tidal Currents