Growth increments in the shell of the living brachiopod Terebratalia transversa
Growth increments in the shell of the living brachiopod Terebratalia transversa
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现存腕足动物 Terebratalia transversa 外壳的生长增量
DOI：
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发表时间：
1988
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通讯作者：
R. D. Tkachuck
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文献类型：
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作者：
W. W. Hughes;G. D. Rosenberg;R. D. Tkachuck
扫描电子显微照片显示，1982-1984年夏季在美国华盛顿阿纳科特斯（Anacortes）收集到的现存的Terebratalia transversa腕足类动物的初级壳层生长增加。增量扩展到二级shell层，但只是作为定义不明确的延续。生长增量周期性地变窄和变宽，产生类似于潮汐诱导的双壳类软体动物每两周生长一次的模式。由成对的宽带和窄带组成的“不对称”增量或“双线”提供了额外的证据，表明生长模式是由潮汐（24小时50分钟）和太阳（24小时）对生长的日常环境影响的干扰产生的，双壳类动物就是这种情况。生长增量在潮汐生境的标本中相对明确，而在潮下标本中则定义不清。在实验室水族箱中生长并经受模拟潮汐和淹没的标本具有明确定义的增量，而在水族箱中连续浸泡的标本具有不明确定义的增量，与自然栖息地中不同深度产生的生长增量的独特性相似。transversa的生长增量的产生可能与阀门的运动和地幔腔pH的变化有关。当阀门关闭时，pH下降，当阀门打开时，pH上升。套膜组织和液体的高效液相色谱（HPLC）未能检测到任何可能导致pH变化的单一有机酸，证实了与双壳类软体动物相比，T. transversa的中间代谢非常低。计算表明，中间代谢的循环可能导致生长增量生产和壳溶解的循环。
Scanning electron micrographs revealed growth increments in the primary shell layer of the extant terebratulid brachiopod Terebratalia transversa collected from Anacortes, Washington, USA, during the summers of 1982–1984. The increments extend into the secondary shell layer, but only as poorly-defined continuations. Growth increments narrow and widen cyclically, producing patterns similar to tidally-induced, fortnightly growth patterns in bivalve molluscs. “Asymmetric” increments or “doublets” that consist of paired wide and narrow bands present additional evidence that the growth pattern is produced by the interference of tidal (24 h 50 min) and solar (24 h) daily environmental influences on growth, as is the case in bivalves. Growth increments are relatively well-defined in specimens from tidal habitats and are poorly-defined in subtidal specimens. Specimens grown in laboratory aquaria and subjected to simulated tidal emersions and submersions had well-defined increments, whereas those that were continuously submerged in aquaria had poorly-defined increments, paralleling the distinctness in growth increments produced at various depths in the natural habitat. Production of growth increments in T. transversa may be related to valve movement and changes in mantle-cavity pH. When the valves are closed, pH drops and, when they are open, pH rises. Highperformance liquid chromatography (HPLC) of mantle tissue and fluid failed to detect any single organic acid that could have been responsible for the pH changes, confirming that intermediate metabolism in T. transversa is very low compared to that of bivalve molluscs. Calculations indicate that cycles in intermediate metabolism may nevertheless be responsible for cycles in growth-increment production and shell dissolution.