Visceral mesoderm fails to elongate dorso-ventrally and remains belt shaped until the end of embryogenesis in mutant embryos. Somatic myogenesis appears unaffected in the mutant embryos.

hkb^gurt/hkb² embryos show the visceral mesoderm defects seen in hkb^gurt embryos.

Visceral mesoderm cell identifies (fusion competent myoblasts and founder cells) are specified correctly in hkb^gurt mutant embryos.

Epidermal morphology and hindgut development are normal in hkb^gurt mutant embryos, but severe defects are seen in the foregut. The anterior midgut primordium does not form. Malpighian tubules fail to develop properly, forming a sac-like structure that also seems to include the remnants of the posterior midgut rudiment.

Stage 13 hkb^gurt embryos show initial stretching of the visceral bands, as occurs in wild type, although the visceral bands of these embryos appear densely packed and contain many myotubes with a slightly angular orientation. Subsequent elongation of the visceral circular muscles does not occur in the mutant embryos and stage 15-16 hkb^gurt embryos have strong defects in the visceral muscle. The determination of the longitudinal visceral muscle primordium at the posterior end of the mesoderm occurs normally in the mutant embryos. During later stages, anterior migration of longitudinal muscle cells and longitudinal muscle fusion occurs in the mutant embryos, as occurs in wild type.

The extracellular matrix shows a scattered appearance along the visceral muscle strands in stage 13-14 mutant embryos.