Histological Divergence Underlying Globular Body Shapes in Ornamental Goldfish

Area of Science:

• Evolutionary biology
• Comparative morphology
• Domesticated animal science

Background:

• Vertebrate body shape is shaped by functional demands, environment, and development.
• Domesticated species, like goldfish (Carassius auratus), show remarkable artificial morphology.
• Ornamental goldfish have diversified into numerous strains with distinct body shapes via human selection.

Purpose of the Study:

• To compare body shapes of representative goldfish strains.
• To investigate the developmental and histological basis for body shape divergence.
• To understand the evolution of globular body shapes in goldfish.

Main Methods:

• Comparative analysis of body shapes in common goldfish, Ryukin, Oranda, Pearlscale, and Ranchu strains.
• Anatomical and histological examination of selected goldfish strains.
• Morphological and tissue-level analysis.

Main Results:

• Ryukin and Pearlscale goldfish strains showed significantly greater dorsal body circularity.
• Pearlscale goldfish exhibited a thicker lateral body wall, increased adipose tissue, and reduced muscle density.
• Ryukin goldfish differed histologically from Pearlscale, despite similar globular shapes.

Conclusions:

• Similar globular body shapes in different goldfish strains can evolve through distinct developmental routes.
• Morphological convergence is accompanied by histological divergence in goldfish domestication.
• Adipose accumulation and tissue organization offer insights into the evolution of globular body shapes.