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The freshwater pearl mussel Margaritifera margaritifera is considered to be the most rapidly declining species of freshwater bivalve, whereas its colonies in rivers of the White Sea Basin remain the most numerous in the world. The lipid profiles of mantle, muscle (foot), and digestive gland tissues of the freshwater pearl mussel from the Kem, Ukhta, and Vozhma Rivers in autumn (end of September, early October) were studied using high performance thin-layer chromatography. The highest total lipid [TL] content was found in the digestive gland. Cholesterol esters, non-esterified fatty acids, phospholipids, and cholesterol were the dominant lipids in all studied tissues. The reduced triacylglycerol content in the mussels was associated with its utilization during the spawning period. The colony of the freshwater pearl mussel inhabiting the Vozhma River was distinguished by higher TL content in the mantle and digestive gland. Data on the size-age characteristics of mollusks from the Kem, Ukhta, and Vozhma Rivers and the relationship between the structural and storage lipid content and size-age parameters are discussed. The results are important for different conservation strategies of endangered species, such as the freshwater pearl mussel, especially in ecological monitoring based on evaluation of the physiological and biochemical state of mollusks and rare natural colonies. [ABSTRACT FROM AUTHOR]

Mass mortality of Unionidae from the genera Middendorffinaia, Buldowskia, and Sinanodonta was observed in the plain rivers of the south of Primorsky Krai (south of the Russian Far East) in the abnormally hot and low-water summer–autumn season of 2021. Nodularia douglasiae (Griffith et Pidgeon, 1833) was the most resistant and thus least affected species, the species from the genera Sinanodonta and Middendorffinaia, the least resistant and the most affected. [ABSTRACT FROM AUTHOR]

The freshwater pearl mussel Margaritifera margaritifera is considered to be the most rapidly declining species of freshwater bivalve, whereas its colonies in rivers of the White Sea Basin remain the most numerous in the world. The lipid profiles of mantle, muscle (foot), and digestive gland tissues of the freshwater pearl mussel from the Kem, Ukhta, and Vozhma Rivers in autumn (end of September, early October) were studied using high performance thin-layer chromatography. The highest total lipid [TL] content was found in the digestive gland. Cholesterol esters, non-esterified fatty acids, phospholipids, and cholesterol were the dominant lipids in all studied tissues. The reduced triacylglycerol content in the mussels was associated with its utilization during the spawning period. The colony of the freshwater pearl mussel inhabiting the Vozhma River was distinguished by higher TL content in the mantle and digestive gland. Data on the size-age characteristics of mollusks from the Kem, Ukhta, and Vozhma Rivers and the relationship between the structural and storage lipid content and size-age parameters are discussed. The results are important for different conservation strategies of endangered species, such as the freshwater pearl mussel, especially in ecological monitoring based on evaluation of the physiological and biochemical state of mollusks and rare natural colonies.

Freshwater pearl mussels (family Margaritiferidae) are sensitive to human impact and environmental changes. Large declines in their abundance have prompted studies of distribution and estimations of population densities.Iturup Island, a part of Kuril Islands, Russia, is considered to be within the distribution area of freshwater pearl mussels, but this information is based on only two specimens collected several decades ago. Detailed survey of the island is challenging as most of its territory is nearly impassable.A preliminary analysis of island rivers was carried out prior to the surveys to discover potential freshwater pearl mussel habitats. Based on previous experience from European Russia, freshwater pearl mussel habitat was expected to occur in rivers flowing out of lowland lakes.Live individuals of Margaritifera laevis were found during surveys in one river together with the unionid Beringiana beringiana, which were also found in two other rivers where the predicted habitat occurred. Based on prediction and surveys, the occurrence of freshwater pearl mussels in other rivers of Iturup Island is unlikely.Pearl mussels were concentrated in a small section of the Zmeika River with a population of about 100,000 mussels. Present threats to the population include overharvest of host fish masou salmon (Oncorhynchus masou).Surveys using similar methods can help to reveal unknown freshwater mussel populations on other Kuril Islands and on the mainland. [ABSTRACT FROM AUTHOR]

The freshwater pearl mussel (Margaritifera margaritifera) is a highly host-specific parasite, with an obligate parasitic stage on salmonid fish. Atlantic salmon (Salmo salar) and brown trout (Salmo trutta f. trutta and Salmo trutta f. fario) are the only hosts in their European distribution. Some M. margaritifera populations exclusively infest either Atlantic salmon or brown trout, while others infest both hosts with one salmonid species typically being the principal host and the other a less suitable host. Glochidial abundance, prevalence and growth are often used as parameters to measure host suitability, with the most suitable host species displaying the highest parameters. However, it is not known if the degree of host specialisation will negatively influence host fitness (virulence) among different host species. In this study we examined the hypothesis that glochidial infestation would result in differential virulence in two salmonid host species and that lower virulence would be observed on the most suitable host. Atlantic salmon and brown trout were infested with glochidia from two M. margaritifera populations that use Atlantic salmon as their principal host, and the difference in host mortality among infested and control (sham infested) fish was examined. Higher mortality was observed in infested brown trout (the less suitable host) groups, compared to the other test groups. Genetic assignment was used to identify offspring from individual mother mussels. We found that glochidia from individual mothers can infest both the salmonid hosts; however, some mothers displayed a bias towards either salmon or trout. We believe that the differences in host-dependent virulence and the host bias displayed by individual mothers were a result of genotype × genotype interactions between the glochidia and their hosts, indicating that there is an underlying genetic component for this parasite-host interaction. [ABSTRACT FROM AUTHOR]

This study re-examines the type series of the Early Cretaceous freshwater bivalve Unio valdensis Mantell, 1844 , in relation to the assignment of the species to the genus Paraheudeana Starobogatov (1970) , and the subgenus Pseudunio by Mongin (1961). For the first time, we recognise the type specimens as incomplete lacking critical posterior portions of the shell. We observe that the lectotype, superficially oval in outline, has a shallow, but distinct postero-ventral sinus, seemingly out-grown, the broken ventral margin not preserving actual shell shape or the commissure. Significantly, many other specimens confirm the presence of the postero-ventral sinus and elongate-oval outline. It is unclear why Starobogatov removed Margaritifera (Pseudunio) valdensis but maybe the perceived oval outline was sufficient for separation. Combined with diagnostic characters such as mantle pits, we retain the freshwater mussel Unio valdensis in the genus Margaritifera and refute the validity of the genus Paraheudeana Starobogatov (1970). Araujo et al. (2016) reviewing the phylogeny of the Margaritiferidae, concluded only the genus Margaritifera was valid, discounting Pseudunio as a valid genus or subgenus, placing further doubt upon the use of the then subgenus, conversely more recent studies have supported the genus Pseudunio promoting it to a genus. [ABSTRACT FROM AUTHOR]

The freshwater pearl mussel (Margaritifera margaritifera) is an endangered bivalve with an obligate parasitic stage on salmonids. Host suitability studies have shown that glochidial growth and load vary significantly between host strains as well as among individuals of a suitable strain. Variation in host suitability has been linked to environmental conditions, host age and/or size, genetic composition of the host and parasite, or a combination of these factors. In our study, we wanted to investigate if brown trout (Salmo trutta) displayed an age-dependent response to glochidial infestation. We hypothesised that 1+ naive brown trout hosts tolerate glochidial infestation better than 0+ hosts. In order to test our hypothesis, we infested 0+ and 1+ hatchery reared brown trout with glochidia from closely related mothers and kept them under common garden conditions. This allowed us to observe a pure age dependent host response to infestation, as we eliminated the confounding effect of genotype-specific host interactions. We analysed the interaction between glochidial load and host condition, weight and length, and observed a significant age-dependent relationship. Glochidial load was negatively correlated to host condition in 0+ fish hosts and positively correlated in 1+ hosts. These contradictory findings can be explained by a change in host response strategy, from resistance in young to a higher tolerance in older fish. In addition, we also examined the relationship between glochidial load and haematocrit values in the 1+ hosts and observed that haematocrit values were significantly higher in heavily infested hosts. Our results have important conservation implications for the management of wild pearl mussel populations, as well as for captive breeding programmes. [ABSTRACT FROM AUTHOR]

The freshwater pearl mussel Margaritifera margaritifera (L., 1758) is considered to be a critically endangered species. It is important to obtain information on the distribution and status of the surviving populations of the species, but in Russia this work is still problematic due to the size of the country's territory, combined with the insufficient number of available specialists. "Searching rules" have been proposed to remotely identify potential pearl mussel habitats in rivers. The most important criteria are relating to the lakes found at the rivers' sources, as well as to the extent of the deforestation along river basins. About 200 watercourses of the Russian section of the Baltic Sea basin were evaluated using these "rules". As a result, two previously unknown, viable populations were discovered (comprising about 53,000 specimens), while the absence of pearl mussels was made evident among some rivers which were traditionally believed to be their habitats. The obtained data provides an update on the status of pearl mussels in Russian territories located south of the 61 st degree of latitude. There are 10 populations of this species; 4 of them are almost extinct, 6 are relatively numerous but declining. The total number of pearl mussels hardly exceeds 90,000 individuals. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Each germ cell cluster in acinus is entirely covered by Sertoli cells. • Each cluster is composed of germ cells of the same developmental stage. • Clusters of different stages are randomly arranged along the acinus periphery. • The central region of the acinus is occupied by spermatozoa. • The germ cell arrangement seen in this species may be characteristic of Unionoidea. Abstract Spermatogenesis in the freshwater pearl mussel Margaritifera laevis was investigated using light and electron microscopy. The testes of M. laevis are composed of numerous acini. We observed type A spermatogonia, large cells of irregular shape, solely near the acinus basal lamina. Type A spermatogonia proliferate and become type B spermatogonia, which are also irregular in shape and form clusters of germ cells of the same developmental stage. The numerous clusters differ with respect to developmental stage and are arranged randomly along the acinus periphery. The central region of the acinus was observed to contain only mature spermatozoa. This germ cell arrangement contrasts that of other bivalvians and may be characteristic of Margaritiferidae and Unionidae. We noted that each germ cell cluster is entirely covered throughout spermatogenesis by Sertoli cells that are loosely bound together. This report is the first to describe the involvement of Sertoli cells in Unionoidea spermatogenesis. Mature spermatozoa of M. laevis are of the primitive sperm type, having a cylindrical head with a discoidal acrosome and a midpiece with five spherical mitochondria. [ABSTRACT FROM AUTHOR]

Two Unionida (freshwater mussel) families are present in the Northern Hemisphere; the Margaritiferidae, representing the most threatened of unionid families, and the Unionidae, which include several genera of unresolved taxonomic placement. The recent reassignment of the poorly studied Lamprotula rochechouartii from the Unionidae to the Margaritiferidae motivated a new search for other potential species of margaritiferids from members of Gibbosula and Lamprotula . Based on molecular and morphological analyses conducted on newly collected specimens from Vietnam, we here assign Gibbosula crassa to the Margaritiferidae. Additionally, we reanalyzed all diagnostic characteristics of the Margaritiferidae and examined museum specimens of Lamprotula and Gibbosula . As a result, two additional species are also moved to the Margaritiferidae, i.e. Gibbosula confragosa and Gibbosula polysticta . We performed a robust five marker phylogeny with all available margaritiferid species and discuss the taxonomy within the family. The present phylogeny reveals the division of Margaritiferidae into four ancient clades with distinct morphological, biogeographical and ecological characteristics that justify the division of the Margaritiferidae into two subfamilies (Gibbosulinae and Margaritiferinae) and four genera ( Gibbosula , Cumberlandia , Margaritifera , and Pseudunio ). The systematics of the Margaritiferidae family is re-defined as well as their distribution, potential origin and main biogeographic patterns. [ABSTRACT FROM AUTHOR]

Abstract: European freshwater pearl mussels are among the most critically threatened bivalve molluscs. Margaritifera margaritifera and Margaritifera durrovensis are endangered, and both occur in Ireland and are currently listed separately in Annex II of the European Habitats Directive. This study had the objective of guiding the conservation of freshwater pearl mussels in Ireland based on a genetic characterization of the most important Irish populations of both species using microsatellite and mitochondrial DNA (mtDNA) analyses. Margaritifera durrovensis from the Nore was found to have the highest genetic divergence from all the populations studied; however, there was substantial relatedness between the genetic constitution of the Nore and of central–eastern M. margaritifera populations, placing the Nore pearl mussel within the M. margaritifera taxon (Habitats Directive species code 1029). Two main conservation units of pearl mussel were identified: a mostly salmon‐dependent western cluster and a trout‐dependent central–eastern cluster. The genetic diversity of western Irish freshwater pearl mussels, as expressed by allelic richness and observed heterozygosity, was greater by a factor of two than in central European and central–eastern Irish populations, suggesting a genetic diversity hot spot and low effects of genetic drift and selection. The trout‐dependent central and eastern populations had much lower genetic variability, but had the greatest differentiation and uniqueness. Conservation of freshwater pearl mussels in Ireland should recognize the existence of a minimum of two conservation units (western and central–eastern) that differ in their use of host fish and in geographic isolation. Low levels of genetic drift and inbreeding in western populations should be secured by sustaining optimal habitat conditions favourable for the recruitment of mussels and their migratory salmonid hosts. The small population sizes of central–eastern populations and problems with recruitment require urgent action, e.g. by captive breeding and augmentation, to prevent any further erosion of their genetic variability. [ABSTRACT FROM AUTHOR]

This work investigates whether a submarine volcanic eruption off El Hierro (Canary Islands) in October 2011 influenced the metal contents of two deep water cephalopod species: Abraliopsis morisii and Pyroteuthis margaritifera . This was assessed by comparing metal contents in specimens collected off the island of El Hierro and in the neighbouring islands of La Palma and Tenerife during an experimental deep water fishing trip. The concentration of 20 heavy metals was analyzed in 180 specimens of A. morisii and P . margaritifera collected around the three islands to test for inter-island differences for each species and metal. While both species showed geographical differences in metal concentrations, the main finding was that A. morisii could be a bioindicator species for metals such as Li, Sr and Ca. [ABSTRACT FROM AUTHOR]

The critically endangered Giant Freshwater Pearl Mussel Margaritifera auricularia was presumed extinct before its rediscovery in Spain in 1985 and France in 2000. Since then, numerous surveys have been set up to search for living populations in France and Spain. This article presents an up-to-date account of species distribution based on available data, i.e. the literature, museum collections and recent field surveys, and provides unpublished molecular data for France. There are still three populations of the Giant Freshwater Pearl Mussel in the Ebro River in Spain, and eight populations in France (two in the Loire watershed, one in the Charente watershed, two in the Garonne watershed and three in the Adour watershed). The biggest population lives in the Charente River with an estimated 100,000 individuals. Recruitment is very scarce in all populations but living specimens estimated to be less than 10 years old have been found in the Ebro in Spain and in the Vienne, Charente, Dronne and Adour rivers in France. The recent rediscovery of populations in France was mainly a result of intensive dedicated surveys including scuba diving. Subsequent advances in knowledge show how large rivers and downstream ecosystems remain a terra incognita for the hydrobiologist. [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the potential for augmentation of freshwater pearl mussel populations Margaritifera margaritifera through short-term captive breeding to early juvenile stage and thus avoiding the growing-on stage of juveniles in captivity, which can have a high mortality rate. Fish encysted with Margaritifera glochidia were transferred to a tank lined with a thin layer of river gravels. Juvenile mussels were left to drop-down into these gravels and were then transferred, with the gravels, into suitable habitat in their native river. Redox potential measurements and near bed flow velocities were measured in the tops and tails of riffles to determine the best potential areas to transfer the juveniles. Following a year in the wild, juvenile mussels were found to be living in the areas in which they had been placed. This technique is recommended for rivers with populations of Margaritifera that have lost habitat quality, but where preferential flows maintain some areas that are still capable of juvenile survival. [ABSTRACT FROM AUTHOR]

Here we analyse in detail, for the first time, the growth pattern of the endangered freshwater mussel Margaritifera auricularia in the Ebro basin, a life history trait essential for conservation purposes. We combined information on size and age from captive bred juveniles, together with growth annuli from living preadults studied in the field, and empty shells of preadult and adult individuals. We compared the fit of six types of (asymptotic and sigmoid) non-linear growth models and, in terms of residual errors and AIC values, the sigmoid ones were superior, being the Generalized von Bertalanffy and Richards models the best fitted ones. After an initial exponential growth phase in juveniles, growth rate starts to decelerate at an inflection point corresponding to an age of seven years. At an age of about 30 years, the growth rate markedly declines and attains an asymptote at c. 150 mm shell length. Global growth rate is relatively low but comparable to other members of the family, and the maximum age estimated from ring counts was 68 years. We demonstrate that the use of sigmoid models provides more accurate estimation of growth patterns in freshwater mussels, as previously observed for other bivalves. [ABSTRACT FROM AUTHOR]

SinceMargaritifera marocana(Pallary, 1918) andM. laosensis(Lea, 1863) were rediscovered,M. homsensis(Lea, 1865) remains the only pearl mussel species known solely based on old shell samples from natural history museums. This is also the last pearl mussel species, which is absent in a phylogeny of the family. Here, we aimed to provide an integrative revision of the taxonomic status ofM. homsensisfrom the Orontes Basin. Using a newly collected specimen from the River Karasu, Hatay Province, southern Turkey, five gene partitions were sequenced, the cytochrome c oxidase subunit I (COI), large ribosomal subunit rRNA (16S), large ribosomal subunit rDNA (28S) and its D3 expansion segment (D3), and small ribosomal subunit rDNA (18S). The multi-gene phylogeny indicates thatM. homsensisis a sister taxon ofM. auricularia, but both these species are closely related toM. marocanaby nuclear genes. The main conchological features, i.e., the shell shape, teeth morphology, and mantle attachment scars, as well as Fourier shell shape analysis have not shown principal differences betweenM. homsensisandM. auricularia. Based on these data, we concluded thatM. homsensisis a valid species that is most closely related toM. auricularia. Special conservation efforts for a population ofM. homsensisdiscovered in Turkey, including the formation of a nature reserve, might contribute to the conservation of the species. Finally, an extensive search for surviving populations in Orontes drainage (southern Turkey, Lebanon, and Syria) and the Nahr-el-Kabir River (Lebanon and Syria) remains necessary to develop a transboundary conservation strategy for this unique taxon. [ABSTRACT FROM AUTHOR]

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Parasitic species often have detrimental effects on host growth and survival. The larvae of the genus Margaritifera (Bivalvia), called glochidia, are specialist parasites of salmonid fishes. Previous studies have reported negligible influences of the parasite on their salmonid hosts at natural infection levels. However, those studies focused mainly on their instantaneous effects (i.e., during the parasitic period). Given the time lag between physiological and somatic responses to pathogen infections, the effect of glochidial infection may become clearer during the post-parasitic period. Here, we examined whether the effect of glochidial infections of Margaritifera laevis on its salmonid host Oncorhynchus masou masou would emerge during the post-parasitic period. We performed a controlled aquarium experiment and monitored fish growth at two time intervals (i.e., parasitic and post-parasitic periods) to test this hypothesis. Consistent with previous observations, the effects of glochidial infection were unclear in the middle of the experiment (day 50; parasitic period). However, even with a natural glochidial load (48 glochidia per fish), we found a significant reduction in growth rates of infected fish in the extended period of the experiment (day 70; post-parasitic period). Our results suggest that examining only instantaneous effects may provide misleading conclusions about mussel-host relationships. [ABSTRACT FROM AUTHOR]

Gill parasites on fish are likely to negatively influence their host by inhibiting respiration, oxygen transport capacity and overall fitness. The glochidia larvae of the endangered freshwater pearl mussel (FPM, Margaritifera margaritifera (Linnaeus, 1758)) are obligate parasites on the gills of juvenile salmonid fish. We investigated the effects of FPM glochidia encystment on the metabolism and haematology of brown trout ( Salmo trutta Linnaeus, 1758). Specifically, we measured whole-animal oxygen uptake rates at rest and following an exhaustive exercise protocol using intermittent flow-through respirometry, as well as haematocrit, in infested and uninfested trout. Glochidia encystment significantly affected whole-animal metabolic rate, as infested trout exhibited higher standard and maximum metabolic rates. Furthermore, glochidia-infested trout also had elevated levels of haematocrit. The combination of an increased metabolism and haematocrit in infested fish indicates that glochidia encystment has a physiological effect on the trout, perhaps as a compensatory response to the potential respiratory stress caused by the glochidia. When relating glochidia load to metabolism and haematocrit, fish with low numbers of encysted glochidia were the ones with particularly elevated metabolism and haematocrit. Standard metabolic rate decreased with substantial glochidia loads towards levels similar to those of uninfested fish. This suggests that initial effects visible at low levels of encystment may be countered by additional physiological effects at high loads, e.g. potential changes in energy utilization, and also that high numbers of glochidia may restrict oxygen uptake by the gills. [ABSTRACT FROM AUTHOR]

The black-lipped pearl oyster, Pinctada margaritifera, is the most important farmed mollusc species in French Polynesia. Donor oyster selection among wild P. margaritifera individuals, chosen according to their inner shell colour, makes it possible to obtain the broadest range of cultured pearl colours of any species. This study demonstrates the relative influence of using black [B] or red [R] outer shell phenotypes, combined with green [G] or yellow [Y] inner shell phenotypes, on pearl darkness level, colour categories and lustre. A large scale grafting experiment was designed and carried out over five grow-out locations, covering three archipelagos: Tuamotus, Society and Gambier. Results revealed that the [B + G] phenotypes may be used as donors to produce dark green pearl, which suit the demands of the Asian market; whereas, phenotypes incorporating [R] and/or [Y] phenotypes may be used to obtain multicolour pearls of medium/light darkness, which suit the demands of the European market. From an environmental point of view, the 1) [B] phenotype showed no significant variation for light and other pearl colour production, and 2) [Y] phenotype produced both the same rate of pearl darkness level and green colour pearls whatever the grow-out location. A classification tree model was built to predict, according to shell phenotype and culture location, the colour and darkness level of harvested pearls. Lustre was shown to be more influenced by the environment than by phenotype. These results should be taken into account in pearl farm production management and in selective breeding programmes. [ABSTRACT FROM AUTHOR]

1. The freshwater pearl mussel Margaritifera margaritifera is threatened throughout its Holarctic range, but the occurrence of this species is insufficiently mapped. For the conservation of M. margaritifera, it is important to identify populations more comprehensively. 2. Traditionally mussels have been searched for visually using techniques such as diving and aquascope, both of which are potentially time-consuming and demanding survey methods. 3. In this study, a new search method is presented. As glochidia of M. margaritifera are larval parasites on the gills of salmonid fish, electrofishing and non-destructive examination of salmonids with the naked eye may reveal the presence of glochidia and therefore the occurrence of M. margaritifera in watercourses. This method was tested in both the field and laboratory in northern Finland. 4. In summer, when M. margaritifera glochidia were large, the status of salmonids being infected or uninfected by M. margaritifera was correctly identified with the naked eye with 62, 80, 88 and 93% accuracy in four streams sampled, 96% accuracy in the laboratory, and 100% accuracy in all cases when at least 20 glochidia per fish were present. Intensity of infection was also assessed successfully; a specifically tailored, qualitative abundance score correlated significantly with the real number of glochidia. However, during autumn with small glochidia freshly attached to fish, glochidia infection could be observed only under microscopic examination. 5. When the method was used in 40 previously incompletely surveyed tributaries, three M. margaritifera populations were found. The infection in salmonids was observed always with the naked eye, being subsequently confirmed microscopically. The existence of adult mussels in two of these rivers was also confirmed. 6. The results indicate that electrofishing and a relatively quick naked-eye check of salmonids provides a new, non-destructive, and potentially cost-effective way to search for new, previously unrecorded M. margaritifera populations. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Freshwater mussels, historically a component of freshwater benthic invertebrate biomass, are one of the most imperilled animal groups on the planet. Margaritifera auricularia was once a common freshwater mussel inhabiting large rivers throughout Western Europe. It was believed to be extinct until 1996 when a few small populations were found in Spain and France., Currently M. auricularia is one of the most endangered species in the world. The current status of this mollusc in the Ebro River was surveyed, finding a few adult specimens at only two localities, and many old, empty shells throughout the river., Using a simple analysis of historical hydrological data, dramatic changes in water flow might have led to localized extirpation of this freshwater mussel., Other factors contributing to the slow extirpation of this long-lived invertebrate from other areas of the Ebro Basin include the continuous reduction of water levels during the reproductive season, overharvesting for nacre, construction of impoundments, extinction of fish hosts, and impaired water quality., Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Oswaldocruzia chambrieri Ben Slimane et Durette-Desset, 1993 is redescribed from specimens collected from the small intestine of the South American common toad, Rhinella margaritifera, from Caxiuanã National Forest in Pará, Brazil, using light and scanning microscopy and molecular analysis of Cytochrome Oxidase I (COI) - coding regions of DNA. The discovered nematodes are characterized by a type III caudal bursa with two papillae, rays 4 with a median groove, and spicules divided into a blade, a shoe and a fork. Cervical alae are absent, the cephalic vesicle is divided into two portions, and the synlophe has low ridges without chitinous supports. The present study establishes the Caxiuanã National Forest as a new location for O. chambrieri, which had previously been reported as a parasite of R. margaritifera in Ecuador, uses light microscopy and scanning electron microscopy (SEM) to identify new morphological characters of the species and represents the second molecular sequence deposited for the Oswaldocruzia genus. [ABSTRACT FROM AUTHOR]

Breeding strategies and parental effects play a major role in genetic selection programmes for quality trait improvement. The black-lip pearl oyster, Pinctada margaritifera, is a protandrous hermaphrodite species in which the number of mature females is low, and these only appear after 4 years of culture. This difference underlines the importance of studying the contributions of dams and sires in the production and selection of donor pearl oyster families to choose the most appropriate breeding strategies for cultured pearl quality trait improvement. Laboratory crosses were made using wild dams and sires to produce half-sib families from polyandry and polygyny mating designs. The resulting half-sib families were used as donor oysters in a large grafting experiment of 900 grafts with random recipient oysters, using nuclei of the same size and brand, the same operating technician and the same grow-out site. After 18 months of culture, 497 cultured pearls were harvested. Comparison between half-sib pairs revealed that for nacre thickness, weight and shape, a polygyny effect exists, whereas no significant effect was observed for the polyandry mating. By contrast, no evidence of dam- or sire-related benefits was found for the presence/absence of circles, darkness level and colour categories or grade and its components: lustre and surface defects. These results should have important implications for the selective breeding of donor pearl oysters for hatchery management. [ABSTRACT FROM AUTHOR]