Genetics and shell morphology in a hybrid zone between the hard clams Mercenaria mercenaria and M. campechiensis

Dillon, Robert T.; Manzi, John J.

doi:10.1007/bf00391961

Cited by 43 publications

(33 citation statements)

References 9 publications

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“…Those authors reported no contribution from M. mercenaria. A similar historical perspective was provided by Dillon & Manzi (1989a) using results from morphological and allozyme analyses of clams collected near Cedar Key, Florida, and their data agreed with ours from work in that same region (Arnold et al 2004). Finally, Baker et al (2008) conducted a rangewide mitochondrial DNA analysis of M. mercenaria and concluded that the occurrence of that species in the GOM is the result of recent introductions.…”

Section: Discussionsupporting

confidence: 73%

“…Menzel's focus was on the feasibility of developing hard clam aquaculture in the northern GOM and the relative efficacy of the 2 species of hard clam Mercenaria mercenaria and M. campechiensis and their various hybrid forms for that purpose. However, only M. campechiensis is native to GOM coastal waters (Menzel 1968, Dillon & Manzi 1989a, Harte 2001, Baker et al 2008. Although Menzel (1968Menzel ( , 1969 suggested that a subspecies (M. m. texana) did occur in northern GOM waters, genetic analyses refuted that and instead classified texana as a subspecies of M. campechiensis (Dillon & Manzi 1989b).…”

Section: Introductionmentioning

confidence: 99%

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Mercenaria mercenaria introductions into Florida, USA, waters: duration, not size of introduction, influences genetic outcomes

Arnold¹,

Geiger²,

Stephenson³

2009

Aquat. Biol.

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Wild stocks of hard clams from the genus Mercenaria historically supported commercial fisheries, but, as these stocks have been depleted, market demand has been filled by clams produced in aquaculture operations. Along the east coast of the USA, M. mercenaria is indigenous and used for aquaculture. Indigenous Gulf of Mexico (GOM) clam populations consist of M. campechiensis, a species less suited to aquaculture because of its short shelf life. Aquaculture operations have introduced M. mercenaria into GOM waters, resulting in altered Mercenaria species composition to the detriment of M. campechiensis. Where M. mercenaria have been introduced, the population now includes both M. mercenaria and M. campechiensis, and hybrids are common. This is particularly evident where commercial aquaculture is ongoing and introductions are, therefore, continuous. Where shortterm introductions have occurred for research purposes, M. mercenaria is restricted to oyster reefs. At those sites, and at sites where no documented introductions of M. mercenaria have occurred, hybrids are rare and M. campechiensis dominate the more common sand/seagrass habitats. As the 2 species continue to interbreed, pure M. campechiensis will become rarer and hybrids more common, potentially resulting in reduced fitness of M. campechiensis from GOM waters. The trend towards hybrids may be ameliorated by an increased intensity of gonadal neoplasia in the hybrid clams. These results indicate that M. mercenaria introductions into the GOM, even on the relatively small scale of scientific research efforts, have a substantial and long-lasting influence on the genotype composition of hard clam populations in GOM waters.

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Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Mercenaria mercenaria introductions into Florida, USA, waters: duration, not size of introduction, influences genetic outcomes

Arnold¹,

Geiger²,

Stephenson³

2009

Aquat. Biol.

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“…Although we intended on using M. mercenaria in our experiments, Arnold et al (2009) documented that M. mercenaria hybridizes with M. campechiensis in the Southern Cross Sea Farms hatchery, with roughly 25% of the hard clams having the hybrid genotype and the remainder being pure M. mercenaria. Differences exist in growth rates among genotypes and vary with environmental factors (Dillon & Manzi 1989, Arnold et al 1996, with hybrids typically growing faster. The comparison of hatchery source of hard clams was not originally intended to be part of the experimental design, but limitations on organism availability required that we utilize 2 sources for experimental organisms.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, differences in shell growth follow complex responses to environmental factors when genotype and hybridization of Mercenaria spp. are taken into account (Dillon & Manzi 1989, Arnold et al 1996. Understanding pH-shell growth dynamics at this early post-larval stage is vital, as the post-larval settlers will be exposed to relatively lower pH within sediments than at the pelagic larval stage, and growth through this post-larval stage is crucial for recruitment to adult populations.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp.

Waldbusser

Bergschneider²,

Green³

2010

Mar. Ecol. Prog. Ser.

106

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Increasing atmospheric carbon dioxide threatens to decrease pH in the world's oceans. Coastal and estuarine calcifying organisms of significant ecological and economical importance are at risk; however, several biogeochemical processes drive pH in these habitats. In particular, coastal and estuarine sediments are frequently undersaturated with respect to calcium carbonate due to high rates of organic matter remineralization, even when overlying waters are saturated. As a result, the post-larval stages of infaunal marine bivalves must be able to deposit new shell material in conditions that are corrosive to shell. We measured calcification rates on the hard clam, Mercenaria spp., in 5 post-larval size classes (0.39, 0.56, 0.78, 0.98, and 2.90 mm shell height) using the alkalinity anomaly method. Acidity of experimental water was controlled by bubbling with air-CO 2 blends to obtain pH values of 8.02, 7.64, and 7.41, corresponding to pCO 2 values of 424, 1120, and 1950 µatm. These pH values are typical of those found in many near-shore terrigenous marine sediments. Our results show that calcification rate decreased with lower pH in all 5 size classes measured. We also found a significant effect of size on calcification rate, with the smaller post-larval sizes unable to overcome dissolution pressure. Increased calcification rate with size allowed the larger sizes to overcome dissolution pressure and deposit new shell material under corrosive conditions. Size dependency of pH effects on calcification is likely due to organogenesis and developmental shifts in shell mineralogy occurring through the post-larval stage. Furthermore, we found significantly different calcification rates between the 2 sources of hard clams we used for these experiments, most likely due to genotypic differences. Our findings confirm the susceptibility of the early life stages of this important bivalve to decreasing pH and reveal mechanisms behind the increased mortality in post-larval juvenile hard clams related to dissolution pressure, that has been found in previous studies.KEY WORDS: Calcification · Acidification · Size-dependent · Hard clam · Post-larval Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 417: [171][172][173][174][175][176][177][178][179][180][181][182] 2010 dation of reduced metabolites in sediments during bioirrigation and particle reworking processes (Green et al. 2004b). As a result, estuarine or coastal pH is far more variable than that of the open ocean and subject to multiple processes making it difficult to parameterize, measure, and predict (Blackford & Gilbert 2007, Soetaert et al. 2007, Borges & Gypens 2010. However, gradual shifting-baseline type decreases in carbonate saturation state of coastal sediment pore waters due to rising atmospheric CO 2 has been noted (Andersson et al. 2006). Determining the potential ecological and economic consequences of acidification on living resources in coastal areas requires additional empirical data of shell producti...

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“…Successful hybridization results in fertile FI hybrids and backcrosses (hybrid crossed with a pure-type) (Harrison 1993;Gardner 1996;Arnold 1992). Interspecific hybridization has been found to exist in many marine invertebrates such as sea urchins (Lessios and Pearse 1996), oysters (Allen and Gaffney 1993), crabs (Bert and Arnold 1995), clams (Dillon and Manzi 1989), and mussels (Coustau et al 1991;Gardner 1995;Saavedra et al 1996). Hybrid zones occur when genetically distinct groups of organisms meet and mate, resulting in at least a portion of viable offspring of mixed ancestry (Harrison, 1993).…”

Section: Introductionmentioning

confidence: 99%

Survival, growth and the possible environmental impacts of introduced blue mussels (Mytilus spp.) in Georgia Strait, British Columbia: Implications for mussel aquaculture.

Yanick¹

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Genetics and shell morphology in a hybrid zone between the hard clams Mercenaria mercenaria and M. campechiensis

Cited by 43 publications

References 9 publications

Mercenaria mercenaria introductions into Florida, USA, waters: duration, not size of introduction, influences genetic outcomes

Mercenaria mercenaria introductions into Florida, USA, waters: duration, not size of introduction, influences genetic outcomes

Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp.

Survival, growth and the possible environmental impacts of introduced blue mussels (Mytilus spp.) in Georgia Strait, British Columbia: Implications for mussel aquaculture.

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