Environmental Relationships of Shell Form and Structure of Unionacean Bivalves

Tevesz, Michael J. S.; Carter, Joseph Gaylord

doi:10.1007/978-1-4899-4995-0_9

Cited by 55 publications

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“…Considered to vary little among unionids, the thickness of the periostracum is 15 to 50 µm in most of the species of this group, classified by TEVESZ & CARTER (1980) as 'intermediate thickness'. Varying around 20.1 µm, the periostracum of A. trapesialis perfectly fits this classification.…”

Section: Discussionmentioning

confidence: 99%

“…These inclusions of organic matter were first described by BØGGILD (1930) so that, due to the intercalation of the organic matrix, the nacreous part is dissolved more slowly by acids. TEVESZ & CARTER (1980) and KAT (1985) described this event and suggested that mollusks with an excessively thin periostracum are inefficient in terms of protection against the dissolution of the calcareous structures of the shell. On the basis of these statements, we may suggest that the presence of these organic sublayers may act by strengthening and protecting the nacreous structure since the periostracum of A. elongatus is much thinner (7.0 µm) than that of A. trapesialis (20 µm).…”

Section: Discussionmentioning

confidence: 99%

“…On the basis of these statements, we may suggest that the presence of these organic sublayers may act by strengthening and protecting the nacreous structure since the periostracum of A. elongatus is much thinner (7.0 µm) than that of A. trapesialis (20 µm). TEVESZ & CARTER (1980) also stated that the intermediate layers of conchiolin are frequent in Unionidae species, especially those living in environments subjected to acidification, or may be a response of the organisms to exposure to contaminants that penetrate between the shell and the mantle. This question was the starting point for IMLAY (1982) when he suggested the use of freshwater bivalve shells to monitor not only the presence of heavy metals, but also the levels of turbidity, low oxygen concentrations, temperature and pollutants in a general manner.…”

Section: Discussionmentioning

confidence: 99%

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Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil

Callil

Mansur

2005

Rev. Bras. Zool.

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ABSTRACT. Based on optical and SEM microscopic observations, the projections of the outer surface of the periostracum and inner micro-structures of the shell are described and redefined. The outer surface of the periostracum is practically smooth in both species. Considering a mesoscopic view of the periostracum, A. trapesialis (Lamarck, 1819) presents regular corrugations in the form of radial sequences of arches on the disk region, isolated rays or horizontal sequences of rays on the anterior lower region. A. elongatus presents corrugations formed by series of oblique arches on the disc and oblique rays on the carina. Under SEM, micro ridges were more evident in A. elongatus, but a wide diversity of shapes and patterns of micro fringes were observed in A. trapesialis, especially in young individuals. Considering the profile of the shell layers, the periostracum is relatively thin and apparently simple in A. trapesialis and thinner in A. elongatus. The prismatic layer is thick in both species, consisting of a single series of elongated prisms and wedge-shaped prisms close to the outer surface. The nacreous layer consists of very fine lamellae without pattern or with a slight staircase-like; in A. elongatus this layer is divided by a laminar inclusion of conchiolin. The fringes are abundant and diversified in A. trapesialis, a species less resistant to desiccation due to the presence of a wide intervalvar gap. The existence of a greater density of micro fringes and spikes in juveniles may be related to the orientation of the animal in order to search for an ideal site for development or for escape from regions subject to seasonal droughts, like Pantanal. KEY WORDS. Mycetopodidae, periostracum projections, shell layers.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil

Callil

Mansur

2005

Rev. Bras. Zool.

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“…Laterally extensive conchiolin sublayers, the secretion of which does not represent a response to an external stimulus, such as corrosion or parasitic infestation of the shell or mantle (teVesZ & Carter, 1980). Present in many unionoids, e.g., in the margaritiferid Margaritifera falcata (Gould, 1850) (Fig.…”

Section: Fig 237 Pectinid Similipecten Nanusmentioning

confidence: 99%

Treatise Online no. 48: Part N, Revised, Volume 1, Chapter 31: Illustrated Glossary of the Bivalvia

Carter¹,

Harries²,

Malchus³

et al. 2012

TREON

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“…Haas 1969;Clarke 1973;Tevesz & Carter 1980;Hingh & Bailey 1988;Yin & Fürsich 1991;Scholz 2003), it is reasonable and reliable to classify the non-marine Jurassic bivalves by studying populations and using the fossil species concept above, combined with environmental analysis.…”

Section: Methodsmentioning

confidence: 99%

Middle Jurassic unionids (non-marine Bivalvia) from the Shiwandashan Basin, southern China, with special emphasis onCuneopsisSimpson

Pan

Sha

2009

GFF

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Articulated non-marine unionid bivalves from red beds of the Middle Jurassic lower member of the Nadang Formation of Banyou, Shiwandashan Basin, Guangxi province, southern China, comprise five morphotypes of Cuneopsis johannisboehmi (Frech). They have been recognised on the basis of a population study by their: (1) transversely elliptical shape, with subparallel and substraight dorsal and ventral margins, (2) elongated cuneiform shape, with a shallow concavity near the posteroventral margin, (3) elongated cuneiform shape, with a sharp posterior end, but without a clear posteroventral concavity, (4) sub-triangular shape, with a sharply pointed posterior and a relatively rounded anterior margin and gently convex ventral margin and (5) suboval shape, with a convex ventral margin. The analysis demonstrates that these unionids are morphologically variable and leads to revision of at least 15 species of unionids, which are merged into Cuneopsis johannisboehmi. In the Shiwandashan Basin, the unionids are preserved in two types of shell assemblage (2D and 3D). Morphological features such as relatively thick shells, medium to large inflation, a large H/L ratio (more than 0.5) and anteriorly placed umbones all indicate a habitat of large rivers for this unionid.

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Environmental Relationships of Shell Form and Structure of Unionacean Bivalves

Cited by 55 publications

References 0 publications

Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil

Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, Brazil

Treatise Online no. 48: Part N, Revised, Volume 1, Chapter 31: Illustrated Glossary of the Bivalvia

Middle Jurassic unionids (non-marine Bivalvia) from the Shiwandashan Basin, southern China, with special emphasis onCuneopsisSimpson

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