Wollesen Tim, Wanninger Andreas, Klussmann-Kolb Annette
Institute for Ecology, Evolution and Diversity, J. W. Goethe University, Frankfurt a. M., Germany.
J Morphol. 2008 Jul;269(7):776-89. doi: 10.1002/jmor.10601.
To date only few comparative approaches tried to reconstruct the ontogeny of the musculature in invertebrates. This may be due to the difficulties involved in reconstructing three dimensionally arranged muscle systems by means of classical histological techniques combined with light or transmission electron microscopy. Within the scope of the present study we investigated the myogenesis of premetamorphic, metamorphic, and juvenile developmental stages of the anaspidean opisthobranch Aplysia californica using fluorescence F-actin-labeling in conjunction with modern confocal laser scanning microscopy. We categorized muscles with respect to their differentiation and degeneration and found three true larval muscles that differentiate during the embryonic and veliger phase and degenerate during or slightly after metamorphosis. These are the larval retractor, the accessory larval retractor, and the metapodial retractor muscle. While the pedal retractor muscle, some transversal mantle fibers and major portions of the cephalopedal musculature are continued and elaborated during juvenile and adult life, the buccal musculature and the anterior retractor muscle constitute juvenile/adult muscles which differentiate during or after metamorphosis. The metapodial retractor muscle has never been reported for any other gastropod taxon. Our findings indicate that the late veliger larva of A. californica shares some common traits with veligers of other gastropods, such as a larval retractor muscle. However, the postmetamorphic stages exhibit only few congruencies with other gastropod taxa investigated to date, which is probably due to common larval but different adult life styles within gastropods. Accordingly, this study provides further evidence for morphological plasticity in gastropod myogenesis and stresses the importance of ontogenetic approaches to understand adult conditions and life history patterns.
迄今为止，只有少数比较研究方法试图重建无脊椎动物肌肉组织的个体发育过程。这可能是由于借助传统组织学技术结合光学或透射电子显微镜来重建三维排列的肌肉系统存在困难。在本研究范围内，我们使用荧光F-肌动蛋白标记结合现代共聚焦激光扫描显微镜，研究了无壳后鳃亚纲海兔加利福尼亚海兔变态前、变态期和幼体发育阶段的肌发生。我们根据肌肉的分化和退化对其进行了分类，发现了三条真正的幼虫肌肉，它们在胚胎期和担轮幼虫期分化，并在变态期间或变态后不久退化。这些肌肉是幼虫牵缩肌、附属幼虫牵缩肌和后足牵缩肌。虽然足牵缩肌、一些横向外套膜纤维和头足部肌肉组织的主要部分在幼体和成体阶段得以延续和细化，但颊部肌肉组织和前牵缩肌构成了在变态期间或变态后分化的幼体/成体肌肉。后足牵缩肌在其他腹足纲分类群中从未被报道过。我们的研究结果表明，加利福尼亚海兔的晚期担轮幼虫与其他腹足纲动物的担轮幼虫有一些共同特征，比如幼虫牵缩肌。然而，变态后的阶段与迄今为止研究的其他腹足纲分类群只有很少的一致性，这可能是由于腹足纲动物幼虫生活方式相同但成体生活方式不同所致。因此，本研究为腹足纲动物肌发生中的形态可塑性提供了进一步的证据，并强调了个体发育研究方法对于理解成体状态和生活史模式的重要性。
