scholarly journals Temporally balanced selection during development of larval Pacific oysters ( Crassostrea gigas ) inherently preserves genetic diversity within offspring

2021 ◽  
Vol 288 (1958) ◽  
pp. 20203223
Author(s):  
Evan Durland ◽  
Pierre De Wit ◽  
Chris Langdon
Keyword(s):  
Genetic Diversity ◽  
Crassostrea Gigas ◽  
Life Histories ◽  
Developmental Stages ◽  
Balancing Selection ◽  
Genetic Load ◽  
Selection Pressures ◽  
Pacific Oysters ◽  
The Pacific ◽  
Large Populations

Balancing selection is one of the mechanisms which has been proposed to explain the maintenance of genetic diversity in species across generations. For species with large populations and complex life histories, however, heterogeneous selection pressures may create a scenario in which the net effects of selection are balanced across developmental stages. With replicated cultures and a pooled sequencing approach, we show that genotype-dependent mortality in larvae of the Pacific oyster ( Crassostrea gigas ) is largely temporally dynamic and inconsistently in favour of a single genotype or allelic variant at each locus. Overall, the patterns of genetic change we observe to be taking place are more complex than what would be expected under classical examples of additive or dominant genetic interactions. They are also not easily explained by our current understanding of the effects of genetic load. Collectively, temporally heterogeneous selection pressures across different larval developmental stages may act to maintain genetic diversity, while also inherently sheltering genetic load within oyster populations.

Overt and Concealed Genetic Loads Revealed by QTL Mapping of Genotype-dependent Viability in the Pacific Oyster Crassostrea gigas

Genetics ◽  
2021 ◽  
Author(s):  
Xiaoshen Yin ◽  
Dennis Hedgecock
Keyword(s):  
Genetic Diversity ◽  
Crassostrea Gigas ◽  
Pacific Oyster ◽  
Genetic Load ◽  
High Density ◽  
High Genetic Diversity ◽  
High Fecundity ◽  
Recessive Mutations ◽  
Genotype Frequencies ◽  
The Pacific

Abstract Understanding the genetic bases of inbreeding depression, heterosis, and genetic load is integral to understanding how genetic diversity is maintained in natural populations. The Pacific oyster Crassostrea gigas, like many long-lived plants, has high fecundity and high early mortality (type-III survivorship), manifesting a large, overt, genetic load; the oyster harbors an even greater concealed genetic load revealed by inbreeding. Here, we map viability QTL (vQTL) in six interrelated F2 oyster families, using high-density linkage maps of single nucleotide polymorphisms generated by genotyping-by-sequencing (GBS) methods. Altogether, we detect 70 vQTL and provisionally infer 89 causal mutations, 11 to 20 per family. Genetic mortality caused by independent (unlinked) vQTL ranges from 94.2% to 97.8% across families, consistent with previous reports. High-density maps provide better resolution of genetic mechanisms, however. Models of one causal mutation present in both identical-by-descent (IBD) homozygotes and heterozygotes fit genotype frequencies at 37 vQTL; consistent with the mutation-selection balance theory of genetic load, 20 are highly deleterious, completely recessive mutations and 17 are less deleterious, partially dominant mutations. Another 22 vQTL require pairs of recessive or partially dominant causal mutations, half showing selection against recessive mutations linked in repulsion, producing pseudo-overdominance. Only eight vQTL appear to support the overdominance theory of genetic load, with deficiencies of both IBD homozygotes, but at least four of these are likely caused by pseudo-overdominance. Evidence for epistasis is absent. A high mutation rate, random genetic drift, and pseudo-overdominance may explain both the oyster’s extremely high genetic diversity and a high genetic load maintained primarily by mutation-selection balance.

scholarly journals Distribution, Condition and Gonad Maturity of the Invasive Pacific Oysters (Crassostrea Gigas, Thunberg 1793) in Cimanuk Delta, Indramayu, West Java, Indonesia

Omni-Akuatika ◽  
2017 ◽  
Vol 13 (2) ◽  
Author(s):  
Selia Hermawati ◽  
Sulistiono Sulistiono ◽  
Agustinus M Samosir
Keyword(s):  
Distribution Pattern ◽  
Crassostrea Gigas ◽  
Brackish Water ◽  
Pacific Oyster ◽  
Condition Factor ◽  
Maturity Stage ◽  
West Java ◽  
Gonad Maturity ◽  
Pacific Oysters ◽  
The Pacific

Pacific oyster (Crassostrea gigas) is an invasive species which is able to adapt a wide range of environmental conditions. The study was conducted from August to October 2014. Objective of this study was to asses the distribution pattern, condition and gonad maturity length (Lm 50%) of the Pacific oysters in mangrove ecosystem of Cimanuk Delta, Indramayu, West Java, Indonesia.  This study was conducted in two adjacent areas:  Pabean Ilir and Pagirikan subdeltas. The oysters were collected from the estuary, brackish water ponds and the coastal flat, and  observed for their abundance, total length (mm) and weight (g). Morphological and histological methods were used to estimate the gonad maturity stage. Analysis were carried out to estimate distribution pattern and condition factor. According to the study, the Pacific oyster distribution pattern was clumped. The condition factor of the oyster was higher in the brackish water pond and estuary than in the coastal flat.  The Pacific oyster was found in gonad maturity stage (GMS) I – IV. The oyster was hermaprodit protandry and had length maturity (Lm 50%) of 47,46-48,43 mm (male) and 75,27-75,50  mm (female). 

Spatial Distribution of Pacific Oyster (Crassostrea gigas) Population Related Environment Factor in Coastal Water of Pabean Ilir, Indramayu

2020 ◽  
Vol 4 (1) ◽  
pp. 38-47
Author(s):  
Risma Qurani ◽  
Fredinan Yulianda ◽  
Agustinus Mangaratua Samosir
Keyword(s):  
Spatial Distribution ◽  
Coastal Water ◽  
Crassostrea Gigas ◽  
Pacific Oyster ◽  
Oyster Population ◽  
Pacific Oysters ◽  
The Pacific ◽  
Arc Gis ◽  
Environment Factor ◽  
Spatial Condition

Pacific oysters (Crassostrea gigas, Thunberg, 1793) is a benthic organisme that tend to live and settle in the bottom. One of the pacific oyster habitat is Coastal Water of Pabean Ilir, Indramayu. The purpose of this study was to map spatial condition of the population related habitat of the oyster (Crassostrea gigas). The mapping were done with laptop, using Arc GIS. There were 15 points of sampling. The oyster population in Pabean Ilir can be categorized into three categories: low, medium, and high density. Based on the similarity of environmental characteristics the habitat were divided into four groups. Condition Coastal Water of Pabean Ilir such as temperature, salinity, pH, BOD, TSS, TDS, COD, and composition of substrate indicated Coastal Water of Pabean Ilir have compatibility optimum sufficient habitat to support the growth of pacific oyster

Limitations of the A-IM Method for Fecal Coliform Enumeration in the Pacific Oyster (Crassostrea gigas)

1987 ◽  
Vol 70 (3) ◽  
pp. 535-537
Author(s):  
Charles A Kaysner ◽  
Stephen D Weagant
Keyword(s):  
Escherichia Coli ◽  
Positive Reaction ◽  
Crassostrea Gigas ◽  
Water Samples ◽  
Fecal Coliform ◽  
Pacific Oyster ◽  
Food Products ◽  
Fecal Coliforms ◽  
Pacific Oysters ◽  
The Pacific

Abstract Use of the A-IM method, which was originally devised for testing water samples, has recently been extended for enumeration of fecal coliforms and Escherichia coli in shellfish and other food products. Results of our study indicate that while this method is reliable for analysis of growing waters, the use of the A-IM method for testing Pacific oysters may be less reliable because bacteria not belonging to the coliform group but which are sometimes present in these animals also give a positive reaction.

Genetic diversity and pedigree assignment in tetraploid Pacific oysters (Crassostrea gigas)

Aquaculture ◽  
2014 ◽  
Vol 433 ◽  
pp. 318-324 ◽  
Author(s):  
Penny A. Miller ◽  
Nicholas G. Elliott ◽  
René E. Vaillancourt ◽  
Peter D. Kube ◽  
Anthony Koutoulis
Keyword(s):  
Genetic Diversity ◽  
Crassostrea Gigas ◽  
Pacific Oysters

Genetic Diversity of Cultured, Naturalized, and Native Pacific Oysters,Crassostrea Gigas, Determined from Multiplexed Microsatellite Markers

2012 ◽  
Vol 31 (3) ◽  
pp. 611-617 ◽  
Author(s):  
Penny A. Miller ◽  
Nicholas G. Elliott ◽  
Anthony Koutoulis ◽  
Peter D. Kube ◽  
René E. Vaillancourt
Keyword(s):  
Genetic Diversity ◽  
Microsatellite Markers ◽  
Crassostrea Gigas ◽  
Pacific Oysters

High Genetic Load in the Pacific Oyster Crassostrea gigas

Genetics ◽  
2001 ◽  
Vol 159 (1) ◽  
pp. 255-265 ◽  
Author(s):  
Sophie Launey ◽  
Dennis Hedgecock
Keyword(s):  
Inbreeding Depression ◽  
Genetic Load ◽  
Inbred Lines ◽  
Hybrid Vigor ◽  
Bivalve Molluscs ◽  
Recessive Mutations ◽  
Pacific Oysters ◽  
The Pacific ◽  
Microsatellite Dna Markers ◽  
Segregation Ratios

Abstract The causes of inbreeding depression and the converse phenomenon of heterosis or hybrid vigor remain poorly understood despite their scientific and agricultural importance. In bivalve molluscs, related phenomena, marker-associated heterosis and distortion of marker segregation ratios, have been widely reported over the past 25 years. A large load of deleterious recessive mutations could explain both phenomena, according to the dominance hypothesis of heterosis. Using inbred lines derived from a natural population of Pacific oysters and classical crossbreeding experiments, we compare the segregation ratios of microsatellite DNA markers at 6 hr and 2–3 months postfertilization in F2 or F3 hybrid families. We find evidence for strong and widespread selection against identical-by-descent marker homozygotes. The marker segregation data, when fit to models of selection against linked deleterious recessive mutations and extrapolated to the whole genome, suggest that the wild founders of inbred lines carried a minimum of 8–14 highly deleterious recessive mutations. This evidence for a high genetic load strongly supports the dominance theory of heterosis and inbreeding depression and establishes the oyster as an animal model for understanding the genetic and physiological causes of these economically important phenomena.

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