Sexual Dimorphism of Shell Shape and Growth of Villosa Villosa (Wright) and Elliptio Icterina (Conrad) (Bivalvia: Unionidae)

Kotrla, Marián; James, Frances C.

doi:10.1093/mollus/53.1.13

Cited by 14 publications

(10 citation statements)

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“…Our data analysis uses the principles and methods developed by Mosimann (1970Mosimann ( , 1975a, Mosimann and James (1979), and Darroch and Mosimann (1985). For other applications of these methods to problems of allometry in marine invertebrates, see Kotrla and James (1987) and Spivey (1988). Size and shape variables are defined a priori, and the models use the assumption of lognormally distributed variables (Rohlf 1990).…”

Section: Analysis Of Datamentioning

confidence: 99%

Developmental Plasticity in the Shell of the Queen Conch Strombus Gigas

Martin-Mora

James

Stoner³

1995

Ecology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. To evaluate the developmental plasticity of shell morphology in the queen conch Strombus gigas, we conducted transplant experiments at five sites in the Exuma Cays, Bahamas. Juvenile conchs from a sixth site were placed in cages at three sites, in an open cage at a fourth site, and in a naturally confined area at a fifth site. All animals spent 8 mo in the field. At the end of the experiments, the morphology of their shells was quantified by means of univariate and multivariate analyses of size and shape as advocated by Mosimann and James (1979). Comparisons were made within and among experimental groups at the first three sites, between groups at the fourth and fifth sites, and between experimental groups and naturally occurring animals at all six sites.Although the experiments extended over only 20% of the juvenile growth period, analyses showed that experimental animals at three of the sites differed significantly in the shapes of their shells. The shapes of these shells were also significantly different from those of the long-spined, bulky shells of naturally occurring animals of similar age at the source site. The greatest change in shape and growth rate occurred at the fifth site, where the rapidly growing uncaged experimental animals developed relatively slender, short-spined shells with large apertures and short spires. These changes were clearly in the direction of the size and shape of unmanipulated animals in the foster population. The results of these experiments, when combined with those of others, suggest that, although variation in the morphology of marine gastropods can have a genetic basis and can be influenced by natural selection, direct environmental induction can be the dominant process underlying patterns of local among-population differentiation. We recommend (1) that the morphometric methods used here to investigate the complex consequences of variation in the size and shape of organisms be applied in other taxa and (2) that the extent to which among-population patterns of geographic variation are directly induced by the environment be given more attention.

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Section: Analysis Of Datamentioning

confidence: 99%

Developmental Plasticity in the Shell of the Queen Conch Strombus Gigas

Martin-Mora

James

Stoner³

1995

Ecology

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“…Median values of lifespan and K for all these groups range from 25 to 50 and 0.10 to 0.17, respectively (Haag and Rypel 2011). Westralunio carteri is similar to these groups in having no sexual dimorphism and little difference in growth between sexes, although the small sex-specific differences in growth seen in the Brunswick River could indicate the presence of subtle, quantitative differences in growth trajectories between males and females (e.g., Kotrla and James 1987). Another important similarity to these long-lived groups is the prob- Table 2.…”

Section: Discussionmentioning

confidence: 94%

Age and growth in the Australian freshwater mussel, Westralunio carteri, with an evaluation of the fluorochrome calcein for validating the assumption of annulus formation

et al. 2014

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Growth and longevity of freshwater mussels (Unionida) are important for defining life-history strategies and assessing vulnerability to human impacts. We used mark-recapture and analysis of shell rings to investigate age and growth of the hyriid, Westralunio carteri, at 5 sites in southwestern Australia. We tested the utility of the in situ marker calcein for validating the assumption of annulus formation in adults. Calcein was incorporated into the shells of all recovered individuals, but it provided an interpretable reference mark in only 4 of 16 individuals. These 4 individuals produced 1 shell ring subsequent to the mark, supporting the assumption of annulus production during the austral winter. Maximum age ranged among populations from 36 to 52 y and maximum size ranged from 72.9 to 82.8 mm. Mean age and length did not differ between sexes, and growth trajectories differed between sexes at only 1 site. Estimates of growth measured by the von Bertalanffy growth constant, K, ranged from 0.021 to 0.336 among sites. Estimates from mark-recapture experiments were 20 to 52% lower than values from shell annuli at all sites except 1 where K from shell annuli was ∼½ that estimated from mark-recapture. Both methods showed a positive relationship between K and mean water temperature among sites, suggesting a role of riparian shading in regulating stream temperature, and hence, indirectly influencing mussel growth. Mussel growth and mean N or P concentrations were not related among sites, but total N at the site with highest mussel growth was >2× higher than at any other site. Westralunio carteri is a long-lived, slow-growing bivalve. Maximum age, K, and probable age at maturity (4-6 y) are similar to other slow-growing freshwater bivalve groups. This suite of life-history traits is considered an adaptation for stable aquatic habitats. Therefore, W. carteri can be expected to adapt poorly to human impacts, such as riparian clearing and water extraction, which increase the temporal variability of environmental conditions in streams.

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“…That said, in our proposed schema identification of sex using shell morphology is the easiest method for assigning sex, in terms of effort, and is non-lethal, but is also inaccurate as we have shown with this study ( Fig 3a ). This approach is frequently used [ 18 , 19 , 53 – 55 ] but should be abandoned until it can be demonstrated that error rates are less than what was shown in this study or if it is used only to provide preliminary estimates of sex that are then surveyed using more robust methods. Shell analysis with the aid of morphometric and shape recognition approaches could provide more reliable estimates of sex based on external morphology and has been used with other aquatic taxa [ 56 – 58 ] ( Fig 3b ).…”

Section: Discussionmentioning

confidence: 99%

Misidentification of sex for Lampsilis teres, Yellow Sandshell, and its implications for mussel conservation and wildlife management

Hess¹,

Inoue²,

Tsakiris³

et al. 2018

PLoS ONE

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Correct identification of sex is an important component of wildlife management because changes in sex ratios can affect population viability. Identification of sex often relies on external morphology, which can be biased by intermediate or nondistinctive morphotypes and observer experience. For unionid mussels, research has demonstrated that species misidentification is common but less attention has been given to the reliability of sex identification. To evaluate whether this is an issue, we surveyed 117 researchers on their ability to correctly identify sex of Lampsilis teres (Yellow Sandshell), a wide ranging, sexually dimorphic species. Personal background information of each observer was analyzed to identify factors that may contribute to misidentification of sex. We found that median misidentification rates were ~20% across males and females and that observers falsely identified the number of female specimens more often (~23%) than males (~10%). Misidentification rates were partially explained by geographic region of prior mussel experience and where observers learned how to identify mussels, but there remained substantial variation among observers after controlling for these factors. We also used three morphometric methods (traditional, geometric, and Fourier) to investigate whether sex could be more correctly identified statistically and found that misidentification rates for the geometric and Fourier methods (which characterize shape) were less than 5% (on average 7% and 2% for females and males, respectively). Our results show that misidentification of sex is likely common for mussels if based solely on external morphology, which raises general questions, regardless of taxonomic group, about its reliability for conservation efforts.

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Sexual Dimorphism of Shell Shape and Growth of Villosa Villosa (Wright) and Elliptio Icterina (Conrad) (Bivalvia: Unionidae)

Cited by 14 publications

References 0 publications

Developmental Plasticity in the Shell of the Queen Conch Strombus Gigas

Developmental Plasticity in the Shell of the Queen Conch Strombus Gigas

Age and growth in the Australian freshwater mussel, Westralunio carteri, with an evaluation of the fluorochrome calcein for validating the assumption of annulus formation

Misidentification of sex for Lampsilis teres, Yellow Sandshell, and its implications for mussel conservation and wildlife management

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