G. Ramirezzarzosa et al., THE LARVAL DEVELOPMENT OF LATERAL MUSCULATURE IN GILTHEAD SEA BREAM SPARUS-AURATA AND SEA BASS DICENTRARCHUS-LABRAX, Cell and tissue research, 280(2), 1995, pp. 217-224
Fibre-type differentiation of the lateral musculature has been studied
in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval dev
elopment. Histochemical and ultrastructural techniques show two presum
ptive muscle layers and two germinative zones of presumptive myoblasts
. At hatching, myotomal muscle consists of a monolayer of thin undiffe
rentiated cells near the skin (first germinative zone) overlying anoth
er monolayer of small diameter fibres extending hypaxially and epaxial
ly away from the transverse septum. Below this, there is a much thicke
r, deep layer of fibres, generally large in diameter and polygonal in
shape. The presumptive myoblasts are located between these two layers
of fibres in the second germinative zone. Initially, the superficial a
nd deep muscle fibres show high and low myosin ATPase activity, respec
tively. Both layers grow by generating new fibres from the two mention
ed germinative zones. At the end of larval life, the superficial layer
changes its histochemical profile from high to low myosin ATPase acti
vity and, at the same time, intermediate or pink muscle fibres can be
observed by oxidative activity (the NADH-TR reaction). Morphometric an
alysis shows a significant increase in mean fibre diameter during succ
essive ages, as shown by the Student's t-test (hypertrophic growth). S
kewness and kurtosis values of fibre diameters point to the generation
of a new fibre population from the germinative zones (hyperplastic gr
owth).