Incipient Reproductive Isolation between Geographic Populations of Ophryotrocha labronica (Polychaeta, Dorvilleidae)

Åkesson, B. (Department of Zoology, University of Gothenburg, Göteborg, Sweden.) Incipient reproductive isolation between geographic populations of Ophryotrocha labronica (Polychaeta, Dorvilleidae). Zocl. Scripta 1 (5): 207–210, 1972.–The mechanism of sex determination and the incipient reproductive isolation between geographic populations of Ophryotrocha labronica are studied in intra- and interpopulation crosses. Two populations from the Naples area and one from Leghorn are employed in the crosses. The considerable genetic difference between the Leghorn population and any of the Naples populations is reflected in some crossing combinations by changes in sex ratios, by occurrence of individuals with a reduced viability in the progeny, by a decreased mating propensity, and by discrimination of mates from alien populations. It is stated that the changes in sex ratios, the decreased mating propensity, the dwarfed individuals in the progeny, and the preferential mating all reflect the incompatibility of gene complexes. The differences between reciprocal crosses are not fully explained. The occurrence of extranuclear DNA, as well as the existence of a maternal heredity in intrapopulation crosses, indicate that cytoplasmic inheritance may be one of the factors behind these reciprocal differences.     

IL-6 immunoreactivity changes during aging in the polychaete Ophryotrocha labronica (Polychaeta: Dorvilleidae)

IL-6 is a pleiotropic pro-inflammatory cytokine thought to play a role in age physiology, even if its possible modulation by aging mechanisms has not been fully defined. In this paper, the morpho-functional modifications and IL-6 immunoreactivity during aging in a simple invertebrate model, Ophryotrocha labronica, are reported. The comparison between newly-hatched, juveniles, young adult and 3-month-old females showed significant differences in the nervous and genital systems. There is evidence of nerve cell loss and a decline in oocyte growth and maturation at the gonad level. Immunohistochemistry reveals a different distribution of IL-6-like molecules, and a decreased number of reactive nerve cells in the central nervous system of aged O. labronica associated to the induced morphological modifications.     

Distribution of cells containing FMRFamide-related molecules in the embryonic development of Ophryotrocha labronica (Polychaeta: Dorvilleidae)

Abstract. The timing and spatial distribution of cells containing FMRFamide-related molecules in the embryogenesis of the polychaete Ophryotrocha labronica were studied immunocytochemically. FMRFamide-like molecules emerge early during embryonic development. They are found at the one-cell stage, are asymmetrically distributed in the first phases of cleavage, associated with gastrular movements, and label the central nervous system morphogenesis. Moreover, during embryogenesis, the pattern of gut cells with the FMRFamide-like phenotype that is present in adults is already established. The early occurrence of FMRFamide-like molecules in O. labronica suggests that these molecules are involved as pre-nervous growth signals in the regulation of basic neuronal cell behaviors.     

Evolution and development of polarized germ cell cysts: new insights from a polychaete worm, Ophryotrocha labronica

Polarized oogenic cysts are clonal syncytia of germ cells in which some of the sister cells (cystocytes) differentiate not as oocytes, but instead as nurse cells: polyploid cells that support oocyte development. The intricate machinery required to establish and maintain divergent cell fates within a syncytium, and the importance of associated oocyte patterning for subsequent embryonic development, have made polarized cysts valuable subjects of study in developmental and cell biology. Nurse cell/oocyte specification is best understood in insects, particularly Drosophila melanogaster. However, polarized cysts have evolved independently in several other animal phyla. We describe the differentiation of female cystocytes in an annelid worm, the polychaete Ophryotrocha labronica. These worms are remarkable for their elegantly simple cysts, which comprise a single oocyte and nurse cell, making them an appealing complement to insects as subjects of study. To elucidate the process of cystocyte differentiation in O. labronica, we have constructed digital 3D models from electron micrographs of serially sectioned ovarian tissue. These models show that 2-cell cysts arise by fragmentation of larger “parental” cysts, rather than as independent units. The parental cysts vary in size and organization, are produced by asynchronous, indeterminate mitotic divisions of progenitor cystoblasts, and lack fusome-like organizing organelles. All of these characteristics represent key cytological differences from “typical” cyst development in insects like D. melanogaster. In light of such differences and the plasticity of female cyst structure among other animals, we suggest that it is time to reassess common views on the conservation of oogenic cysts and the importance of cysts in animal oogenesis generally.     

Sponge-associated marine bacteria as indicators of heavy metal pollution

Sponges invariably filter a large volume of seawater and potentially accumulate heavy metals and other contaminants from the environment. Sponges, being sessile marine invertebrates and modular in body organization, can live many years in the same location and therefore have the capability to accumulate anthropogenic pollutants such as metals over a long period. Almost all marine sponges harbor large number of microorganisms within their tissues where they reside in the extra- and intra-cellular spaces. Bacteria in seawater have already been established as biological indicators of contamination. The present study was intended to find out the heavy metal resistance pattern of sponge-associated bacteria so as to develop suitable biological indicators. The bacteria associated with a marine sponge Fasciospongia cavernosa were evaluated as potential indicator organisms. The associated bacteria including Streptomyces sp. (MSI01), Salinobacter sp. (MSI06), Roseobacter sp. (MSI09), Pseudomonas sp. (MSI016), Vibrio sp. (MSI23), Micromonospora sp. (MSI28), Saccharomonospora sp. (MSI36) and Alteromonas sp. (MSI42) showed resistance against tested heavy metals. Based on the present findings, Cd and Hg emerged as the highly resistant heavy metal pollutants in the Gulf of Mannar biosphere reserve. Plasmids in varied numbers and molecular weights were found in all the isolates. Particularly the isolates MSI01 and MSI36 harbored as many as three plasmids each. The results envisaged that the plasmids might have carried the resistance factor. No correlation was observed in number of plasmids and level of resistance. The literature evidenced that the sponge-associated bacteria were seldom exploited for pollution monitoring though they have been extensively used for bioprospecting. In this background, the present findings come up with a new insight into the development of indicator models.     

The use of theVibrio harveyi luminescence mutagenicity assay as a rapid test for preliminary assessment of mutagenic pollution of marine sediments

Mutagenic pollution of the natural environment is currently one of the most serious environmental problems. It includes the pollution of marine sediments. Therefore, rapid detection of the presence of mutagens is an important issue. Recently, we have developed a novel microbiological assay for rapid assessment of mutagenicity of samples from the natural environment. This assay is based on bioluminescence of a mutant Vibrio harveyi strain, and was shown to be useful in testing samples of marine water and plant tissues. Here we demonstrate the usefulness of this assay in preliminary assessment of mutagenic pollution of marine sediments. Mutagenicity of environmental samples taken from the Baltic Sea, is documented and compared here with a commercially available standard sediment sample (IAEA 383), which contains known amounts of mutagenic compounds. The whole procedure, from obtaining a sample in the laboratory to getting final results, is very short (less than 4 h).     

Fish disease as a monitor for marine pollution: the case of the North Sea

Summary The use of fish diseases to monitor marine pollution is reviewed and evaluated, with particular reference to the North Sea and associated waters. Criteria for epidemiological surveys are outlined, an international overview of research is given, and recent studies in the North Sea area are described and evaluated.The basic approach is to identify spatial and temporal patterns of disease prevalence, which can be related to pollution. A major obstacle is to distinguish effects of pollution from those of other variables, especially as most diseases appear to have a multifactorial aetiology. Field studies can be evaluated against a number of criteria: these include the accuracy and precision of prevalence estimates, the extent to which possible causal factors other than pollution are taken into account, and whether or not exposure of the study population to pollution is measured directly.A distinction can be made between intensive, thorough studies, which frequently use a histopathological approach, and the more extensive surveys of large numbers of fish for grossly observable lesions. Broadly speaking, North American research has emphasized the former approach, and research in the North Sea the latter. Nevertheless, although the most comprehensive evidence for a causal relationship between disease and pollution has been gathered in North America, there are also good examples from the North Sea area, particularly in local areas with distinct sources of pollution. The data from wider-ranging surveys are more ambiguous: while some provide circumstantial evidence for a role of pollution, the apparent complexity of disease aetiology and the limitations of the epidemiological approach may prevent any clear demonstration of pollution as a cause over wide geographical areas. Extensive surveys are nevertheless useful for detecting long-term trends in disease prevalence and hot-spots of anomalously high prevalence, and for examining the relationship between disease and a complex of environmental variables.For the future, greater emphasis should be placed on the recording of liver lesions, on the measurement of exposure to pollution, and on experimental work.     

Adaptation capacity of the larvae of marine invertebrates under variation of environmental parameters as a sensitive test of sea water pollution

The possibility of using the adaptive capacity of the larvae of marine invertebrates under the variation of environmental parameters was studied as a sensitive test of sea water pollution. The object of the research was the larvae of Cryptonatica janthostoma (Naticidae), the environmental factor was the freshening of sea water, and the toxic factor used was copper ions. Adding copper to sea water at a concentration of 0.005 mg/l did not reveal any pronounced effect on the development, behavior and growth of larvae in conditions of normal salinity (32‰), however their adaptive potential decreased with a decrease of salinity to 24‰. The results of the present work and experiments carried out previously enabled us to conclude that before assessing any concentration of pollutant as one not affecting marine organisms, it is necessary to investigate not only their development, growth and survival, but also their adaptive capacity relative to the variation of natural environmental parameters, such as even temperature and salinity.     

Comparison of the Ames test and a newly developed assay for detection of mutagenic pollution of marine environments

Mismatch repair (MMR) genes, such as Msh2, are classified as "mutator" genes, responsible for the microsatellite instability identified in many tumors. In the current study, the mutation frequency and mutational spectrum in thymic lymphoma arising in Msh2 deficient mice are investigated. Thymic lymphoma developed in Msh2-/- background displayed an eight to nine-fold increase in mutation frequency compared to the normal thymi in Msh2 deficient animals. Sequencing demonstrated significantly different mutational spectra between normal thymus tissue and thymic lymphomas in Msh2-/- mice (P=0.02). The tumor mutational spectrum is characterized by an increase in base substitutions occurring at A:T sites, and multiple mutations, as well as a minor increase in -1 frameshifts. We analyzed mutations in different parts of the tumors, and different regional hotspots could be identified. Several hotspot mutations that are a rare event in normal tissues were identified in the tumor tissues. We conclude that thymic lymphomas arising in Msh2 deficient genetic background are hypermutable and the altered mutational spectrum might be an indication of infidelity of DNA replication during tumorigenesis.     

A comparative study of animal erythrocyte agglutinins from marine algae

1. Fifteen marine algal species were analyzed for agglutinins to rabbit, sheep and human A, B and O blood group erythrocytes. 2. Protein extracts from all marine algae agglutinated rabbit erythrocytes, whereas twelve and five extracts agglutinated sheep and human erythrocytes, respectively. 3. The highest agglutination titers were consistently observed with rabbit erythrocytes. 4. Dictyota dichotoma strongly agglutinated human B blood group erythrocytes relative to A and O group erythrocytes. 5. Agglutination titer of rabbit erythrocytes by six algal extracts was not inhibited by mono- or polysaccharides, yet was reduced by glycoproteins.     

The rat as an animal model for the study of senile idiopathic osteoporosis

Bone robustness of the major limb bones of 2-year-old and 3-year-old male Sprague-Dawley rats was determined and compared to that of 3-month-old male Sprague-Dawley rats. The results were compared to the published data on two different breeds of laboratory rats to ascertain if the laboratory rat is an appropriate animal model for the study of senile idiopathic osteoporosis in humans. The results show that the limb bone that becomes the most osteoporotic is the male Sprague-Dawley tibia. If one were selecting for the most appropriate breed of rat, it would be the Buffalo rat.     

Molecular phylogeny of the model annelid Ophryotrocha.

Annelids of the genus Ophryotrocha are small opportunistic worms commonly found in polluted and nutrient-rich habitats such as harbors. Within this small group of about 40 described taxa a large variety of reproductive strategies are found, ranging from gonochoristic broadcast spawners to sequential hermaphroditic brooders. Many of the species have a short generation time and are easily maintained as laboratory cultures. Thus they have become a popular system for exploring a variety of biological questions including developmental genetics, ethology, and sexual selection. Despite considerable behavioral, reproductive, and karyological studies, a phylogenetic framework is lacking because most taxa are morphologically similar. In this study we use 16S mitochondrial gene sequence data to infer the phylogeny of Ophryotrocha strains commonly used in the laboratory. The resulting mtDNA topologies are generally well resolved and support a genetic split between hermaphroditic and gonochoristic species. Although the ancestral state could not be unambiguously identified, a change in reproductive strategy (i.e., hermaphroditism and gonochorism) occurred once within Ophryotrocha. Additionally, we show that sequential hermaphroditism evolved from a simultaneous hermaphroditic ancestor, and that characters previously used in phylogenetic reconstruction (i.e., jaw morphology and shape of egg mass) are homoplasic within the group.     

Genetically modified Vibrio harveyi strains as potential bioindicators of mutagenic pollution of marine environments

For biodetection of mutagenic pollution of marine environments, an organism naturally occurring in these habitats should be used. We found that marine bacterium Vibrio harveyi may be an appropriate bioindicator of mutagenic pollution. For positive selection of mutants, we developed a simple method for isolation of V. harveyi mutants resistant to neomycin. We constructed genetically modified V. harveyi strains that produce significantly more neomycin-resistant mutants upon treatment with low concentrations of mutagens than the wild-type counterpart. The sensitivity of the mutagenicity test with the V. harveyi strains is at least comparable to (if not higher than) that of the commonly used Ames test, which uses Salmonella enterica serovar Typhimurium strains. Therefore, we consider that the V. harveyi strains described in this report could be used as potential bioindicators of mutagenic pollution of marine environments.     

An integrated database for managing animal study proposals and animal inventory for the small animal facility

The authors describe how they created a user-friendly, multifunctional database for use by a variety of vivarium staff.