Myogenesis in the trunk and leg during development of the tadpole of Xenopus laevis (Daudin 1802)

Abstract

Xenopus embryos pass through five behavioural stages between the end of neurulation (stage 20) and the accomplishment of free swimming (stage 33). These are (I) non-motile (stage 20–22) when the myotome muscle begins to differentiate; (II) pre-motile (stage 22–24) when the first striated fibrils are visible and contractions are possible; (III) early flexure (stage 24–27) when reflex responses are given and peripheral nerves are present; (IV) early swimming (stage 28–33); and (V) free swimming (stage 32–46) when co-ordinated swimming is possible but the myotome muscles are still uninucleate. At the onset of metamorphosis (stage 48–50) the myotome muscle becomes multinucleate, possibly by fusion with satellite cells at the ends of the fibres, and has the appearance of adult skeletal muscle. The hind limb of Xenopus passes through similar behavioural stages but at a later stage in development: (i) non-motile (stage 48–52) when little differentiation of the limb-bud has occurred but nerves are present; (ii) pre-motile (stage 53–54) when the limb trembles and muscles are just beginning to acquire striated fibrils; (iii) motile (stage 55–58) when the limb can make stepping movements and the muscles are striated and multinucleate; and (iv) fully functional (stage 60–63) when the limbs are fully differentiated. Unlike the myotome muscle the limb muscle becomes multinucleate before striated myofibrils are assembled. By stage 60 myotome and limb muscle are similar in appearance except that the myotome muscle has larger fibres with fewer nuclei than the limb muscle. In Xenopus, myotome and limb muscle become multinucleate at more or less the same time in the development of the tadpole. In the myotome this is long after contractility and nervous control have appeared, in the limb it precedes the formation of striated fibrils and the ability to contract. It is suggested that the difference in development of the myotome and limb muscles with respect to the stage at which they become multinucleate may be due to some substance produced just before or during metamorphosis.

Ontogeny of the meniscus in the anuran Xenopus laevis

“…Always considering that they are not fixed structures, and continuously in development. In general terms, the earlier stages belong to the motile stage of Muntz (1975), whereas in the later stages, the specimens have fully functional hindlimbs. Thus, apparently, changes related to the transition of motile to fully functional limbs imply more adjustments in shape than the previous non‐motile, pre‐motile, motile transitions (Manzano et al, 2013).…”

Screening of Chemical Libraries UsingXenopusEmbryos and Tadpoles for Phenotypic Drug Discovery

“…Automated morphological screens are also complicated by the fact that Xenopus embryos change orientation once they start moving. Movements develop from simple local twitching of a few swimming muscles starting at stage 37/38 to free forwardmoving, upright swimming by stage 45 (Muntz 1975). Customized imaging systems can track phenotypes in moving embryos and tadpoles; however, we only recommended them in the following cases: (a) when chemical library screening becomes a core activity of the laboratory; (b) when the goal is to screen chemical libraries larger than 10,000 compounds; or (c) when performing complex behavioral screens (see the subsection Behavioral Readouts below).…”

Blastopore gating mechanism to regulate extracellular fluid excretion

“…Interestingly, early Xenopus laevis embryos, which have no functional muscle, 20 , 21 excrete fluid through the blastopore that lies at the opening of the archenteron during the late neurula stage. 22 , 23 This process is termed “collapse of the archenteron.” However, the mechanism that controls blastopore opening at a tissue level is unclear.…”