Reproduction and survival of Muscina stabulans under laboratory conditions (original) (raw)
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Growth models and longevity of freshwater pearl mussels ( Margaritifera margaritifera ) in Spain
Canadian Journal of Zoology, 2004
Growth rates of populations of the freshwater pearl mussel, Margaritifera margaritifera (L., 1758), in northwestern Spain were analysed based on measurements of annual annuli and using two nonlinear functions for length-atage data sets: von Bertalanffy's growth model and a hyperbolic function. These populations reach the smallest maximum shell length (90.5 mm) and have the shortest life-span (35 years) and the highest growth rate (k in von Bertalanffy's model >0.1·year -1 , on average) known for this species. The two models were similar in performance and were well fitted (around 99%) to shell-length-at-age data, although the hyperbolic function appears to be applicable only from 6 years of age. The growth rate (either k or k′ from the hyperbolic function) showed a large and significant variation across populations, both among and within drainages.
Effect of Stress on the Life Table-Demography of Moina Macrocopa
Hydrobiologia, 2004
We quantified the life history variables of M. macrocopa subjected to different treatments such as high temperature, epizoic infestation by the rotifer Brachionus rubens, periodic starvation and exposure to sublethal levels of cadmium using the life table demography method. These were compared against a treatment of Chlorella vulgaris offered at a concentration of 1 • 10 6 cells ml)1 and set at 25 AE 1°C, which served as the control. The effect of a diet of the colonial form of Scenedesmus quadricauda was compared against a diet of S. quadricauda as single cells, which acted as control. For each treatment the experimental design consisted of four cohorts of 20 neonates. Using standard life table demographic methods, we quantified average lifespan, gross and net reproductive rates, generation time and the rate of population increase. Except for the study on temperature effects, all experiments were conducted at 25°C. For the temperature experiments we exposed the test cladocerans to 35°C with the algal density and type being identical to the controls. To study the effect of starvation, we starved the test individuals for 8 h before offering Chlorella every day. Cadmium toxicity was evaluated using 0.04 mg l)1 , as nominal concentration of CdCl 2. Among the life history variables studied, the rate of population increase was the most sensitive, being influenced significantly by the stress factors studied. The responses of M. macrocopa subject to different conditions have been interpreted in terms of the life history strategies of M. macrocopa.
Aquatic Conservation: Marine and Freshwater Ecosystems, 2012
1. Freshwater unionoids are one of the most threatened animal groups worldwide and the freshwater pearl mussel Margaritifera margaritifera is currently listed as critically endangered in Europe. The EC Habitats Directive requires that EU Member States monitor the distribution and abundance of this species and report regularly on its conservation status. 2. The pearl mussel meta-population in Northern Ireland was surveyed to assess temporal population trends in Special Areas of Conservation (SACs) and mussel reproduction throughout its range. 3. Mussels occurred in six rivers and numbers within three SAC designated sites remained stable between 2004-2007 and 2011. The discovery of more than 8000 previously unknown individuals in the Owenreagh River contributed to an overall increase (+56.8%) in the total known population. All populations actively reproduced during 2010 with approximately half of all individuals gravid. Moreover, suitable salmonid hosts occurred at all sites with 10.7% of salmon and 22.8% of trout carrying encysted glochidia. Populations were composed entirely of aged individuals with little evidence of recent recruitment. 4. It is inferred that the break in the life cycle must occur during the juvenile stage when glochidia metamorphose and settle into the interstitial spaces within the substrate. Water quality parameters, most notably levels of suspended solids, exceeded the recommended maximum thresholds in all rivers. 5. It is posited that the deposition of silt may be the main cause of juvenile mortality contributing to a lack of recruitment. Consequently, all populations were judged to be in 'unfavourable' conservation status. Catchment-level management plans are urgently needed to reduce siltation with the aim of improving recruitment. These results have implications for the success of ex situ conservation programmes; specifically, the size at which captive-bred juveniles are released into the wild. Further research is required to assess the vulnerabilities of early life-stages of M. margaritifera to siltation.
Biological Conservation, 2021
Captive breeding is an effective conservation strategy, but it has risks, especially when a life history stage of an organism is bypassed. Freshwater mussels (Unionida) are critically imperiled, and their larvae are parasites on fishes. Traditional mussel captive breeding involves artificially infesting fishes with larvae (in vivo), but increasingly used in vitro methods allow larval metamorphosis in culture media, bypassing the parasitic stage. We provide the first comparisons of mussel performance between in vitro and in vivo methods in the wild and throughout the mussel life cycle using two mussel species. In six streams, survival and growth did not differ between in vitro-and in vivo-produced Lampsilis cardium. Metamorphosis of Sinanodonta woodiana differed sharply between two in vitro protocols (methods 1 and 2), but metamorphosis for method 2 was twice as high as in vivo. Survival and growth after eight days was lower for in vitro method 1 than method 2 and in vivo, showing that suboptimal in vitro protocols can have lingering effects on juvenile performance. However, survival and growth did not differ among methods by the end of the first and second growing seasons. Most importantly, in vitro-produced mussels survived, grew to maturity, and produced F 2 juveniles naturally on fishes, all at rates that did not differ from in vivo-produced mussels. We detected no strong side effects of bypassing the mussel host-fish stage, but this study illustrates the importance of assessing consequences of captive breeding methods for any organism in a variety of environmental and life history contexts.
Biological Conservation, 1995
The culture of juvenile Margaritifera margaritifera in cages is shown to be a useful method of raising the early post-parasitic stages in suitable rivers for scientific or conservation purposes. Survival rates of caged specimens are equal to those of free-living juveniles, and growth is equal or slower than under natural conditions. Factors affecting the viability of caged juveniles are: length of the shell, colonisation of cages by aquatic insects and amount of fine sediments accumulating in the cages.The influence of 12 water chemistry variables on the juveniles is analysed: growth and mortality largely depend upon water temperature; there is a negative relationship between growth and eutrophication.
Helgoland Marine Research, 2007
The horse-bearded mussel Modiolus barbatus (Linneus, 1758) is an important edible bivalve in the Adriatic Sea; its population is especially large in the Mali Ston Bay area, where the species is present at depths up to 8 m. In order to assess the sustainable exploitation rate for this species, as well as to estimate its potential capacity for a sustainable aquaculture production, we determined the species' reproductive cycle along with its nutrient storage strategy, employing histological and biochemical methods. The population shows significantly more females than males, and no hermaphrodites. The smallest adult individual, an active male, was 16.0 mm in length, suggesting that sexual maturation starts around this length. While the period between January and February is characterized by sexual repose, early and late stages of gametogenesis were found between March and May, and spawning peaked from June till August. The increase of oocyte diameter followed the same trend. A significant positive correlation was observed between gonad index and temperature, and a negative correlation between gonad index and salinity. Oscillations of stored nutrients were tightly coupled with the gametogenic cycle.
Journal of Shellfish Research, 2006
We review the variety of methods that have been used over the last 50 y in the Former Soviet Union, Eastern and Western Europe, and recently in North America to determine growth rate and longevity in zebra mussels (Dreissena polyrnorpha [Pallas]). These methods include: counting annual rings, analysis of size-frequency distributions, following growth under experimental conditions and monitoring marked mussels under natural conditions, without removing them from substrate. The last method provides the most reliable data, however this is the least common method used. Dreissena polyrnorpha growth rates depend on water temperature, season of the year, location in the water column, food availability, oxygen concentrations, water velocity and various other environmental factors. However, it is very difficult to separate the independent effects of each of these factors, especially in natural waterbodies. Several factors may overlap and have additive or synergistic effect that makes it difficult to determine the effects of a single factor. When comparing among studies that used the same methods, we found that zebra mussels grow faster in reservoirs than in lakes. The reported longevity of D. polyrnorpha varies from 2-19 y and it is not clear to what extent this variation is caused by biological variability and environmental conditions and what amount of the variation is caused by the methods used to assess age and longevity.
Aquaculture, 2008
The carnivorous gastropod Concholepas concholepas, known in Chile as "loco", is a species present only along the Chilean coast line and in central-southern Perú showing high economic and ecological importance. Its fishery, which in the past decades has ranged between 828 (2001) and 24,828 (1980) metric tons per year [SERNAP, 2005. Servicio Nacional de Pesca: Anuarios estadísticos. (http://www.sernap.cl/paginas/publicaciones/anuarios/index\_anuario.php)\], is based exclusively on the exploitation of wild stocks. So far, there has been limited interest in tackling the biological and technical feasibility of cultivation of C. concholepas. Hence, the knowledge about its early ontogenetic stages (i.e., larval, early postmetamorphic and small juvenile) cultivation is still deficient. In this study we investigated, under laboratory and field conditions, C. concholepas survivorship, growth rates, feeding rates and the onset of sexual reproduction. Competent loco's larvae were collected in the field and metamorphosed in the laboratory to assess growth rates and survivorship during the first six months of postmetamorphic life. Moreover, using small juvenile C. concholepas of ca. 20 mm of peristomal length, collected in the field, we monitored for the body size and live weight traits in laboratory and field rearing conditions. The feeding of the early postmetamorphics and small juveniles was exclusively based in mono diets of the mussel Semimytilus algosus. The rearing of small juveniles was conducted in two consecutive phases, using two specially designed rearing apparatus. The biochemical content of our laboratory cultivated specimens was compared with values obtained from specimens collected in natural habitats. Their rapid growth and good survivorship makes this species suitable for rearing of cocktail-size specimens (50-60 mm) in less than a year. According to the growing rates reported in this study the legal commercial size of C. concholepas: 100 mm of PL would be reached under field and laboratory conditions in 1.65 and 2.64 years respectively. Moreover, it was found that in our rearing conditions C. concholepas reach sexual maturity in less than a year of benthic life. In summary, considering the findings about C. concholepas high growth rates, and low mortalities, we suggest that our rearing methodologies may be scaled up and implemented for the commercial aquaculture of this unique and valuable muricid.
Mullus barbatus: Sexual maturity and spawning
The present study was designed to identify maturity of female red mullet, Mullus barbatus barbatus,using micro-scopic criteria, offering an accurate determination of the ovarian cycle and estimation of maturity size. Histological analysis of 499 females from 13 monthly samplings was applied (Thermaikos Gulf, N. Aegean Sea, Greece). Oocyte development was divided into five stages, with a mean oocyte size range from 56 to 363lm in diameter. Ovarian maturity was defined by the maturation stage of the most advanced oocytes and divided into four phases. By using the monthly changes in the percentage frequency of ovarian phases, the ovarian cycle ofM. barbatuswas divided into three periods: a long period of early oogenesis (November to February), a short period of vitellogenesis (February to April) and a spawning period from April through June with peak activity in May. Both gonadosomatic (up to 7.5%) and hepatosomatic indices (up to 2%) can be used together to predict the spawning period. Red mullet should be classified as a multi-ple spawning species. Females reached 50% maturity (Lm50) at 11.4 cm and 95% maturity (Lm95) at 15.5 cm TL. The Lm50 values for female red mullet populations across the Mediterranean Sea tended to show differences ranging from 11 to 14.4 cm FL or 11.4–14 cm TL. The current European Union fisheries management plan stipulates a minimum land-ing size (MLS) of 11 cm TL for Mullidae spp. fisheries in the Mediterranean. This MLS is at the lower part of the Lm50 range, thus allowing an extensive removal of immature juve-niles. A revision of this MLS value is recommended to help ensure that red mullet stocks remain within safe biological limits