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Differentiation and Growth of Myotomal Muscles in a Non‐Model Tropical Fish Pterophyllum scalare (Teleostei: Cichlidae)

Kacperczyk, A., Jędrzejowska, I., Daczewska, M.
Anatomia, histologia, embryologia 2011 v.40 no.6 pp. 411-418
Cichlidae, cell proliferation, cytoplasm, desmin, hypertrophy, morphometry, muscle development, muscle fibers, muscles, tropical fish
With 4 figures SUMMARY: Somite differentiation, muscle fibres formation and growth were analysed in a non‐model tropical fish Pterophyllum scalare. In this study, it was found that during somite differentiation, a primary myotome appears. The primary myotome is filled with multinucleated myotubes that constitute the major part of the somite. Subsequently, Pax‐3 (paired‐box protein)‐positive cells, located externally to the myotomes, appear. In post‐hatching stages, mononucleated proliferating cell nuclear antigen‐positive cells are observed in the inter‐myotomal spaces and within the myotomes. The mononucleated cells, situated in the myotomes, first express desmin in their cytoplasm and then Pax‐7 (paired‐box protein) in their nuclei. Expression of desmin indicates that they will enter myogenic pathway, whereas expression of Pax‐7 suggests their role of satellite cells. We assume that mononucleated intramyotomal cells are myogenic precursors involved in muscle growth. In advanced (post‐hatching) stages of myogenesis, myotomes contain both primary and new muscle fibres. Morphometric analyses show that in Pterophyllum scalare, growth of muscle fibres is mainly a result of hypertrophy.