larvaldevelopment

Larval development is the phase that follows egg hatching and precedes adulthood. In many animals, larvae are morphologically and ecologically distinct from adults, often specialized for feeding, growth, and dispersal. The larval stage involves growth and differentiation programs regulated by genes and hormones, and in some lineages leads to metamorphosis that produces a markedly different adult form.

Patterns vary widely. Some species display direct development, where juveniles resemble small adults and molt to reach reproductive maturity; others undergo indirect development with metamorphosis. In insects, major modes include ametabolous development (no metamorphosis), hemimetabolous (incomplete metamorphosis; nymphs resemble adults but lack full wings), and holometabolous (complete metamorphosis with a larval and pupal stage). Many marine invertebrates have larval forms such as nauplius, trochophore, or bipinnaria that enable dispersal and feeding. Amphibians generally hatch as aquatic larvae (tadpoles) that undergo metamorphosis, and crustaceans and some worms display a variety of larval types, from free-swimming to parasitic forms.

Developmental control and ecology: Timing and progression of larval development are influenced by environmental cues such as temperature, food availability, and photoperiod. Hormones coordinate metamorphosis and tissue remodeling; ecdysone and juvenile hormone operate in arthropods, whereas thyroid hormones regulate amphibian metamorphosis. Studying larval development informs life-history evolution, developmental plasticity, and the ecological strategies animals use to occupy different niches.