Reproduction

 
A. gemmata is sexually mature after one or two years and spawning is performed by up lifting the girdle to form a spout, but there is no evidence of sexual pairing.^(2,3) Males are thought to spawn first and the presence of the sperm stimulates the female to spawn. ^(2,3)

Chitons exhibit marked period periodicities in their gonad development and spawning seasons. ⁽³⁾ The specific timing and duration of spawning in A. gemmata differ depending on geographical location and environmental conditions (such as day length, sea temperature etc).^(2,3) For example a study conducted on One Tree Island suggested that A. gemmata spawns over 6-7 months from mid-spring to early autumn, while the same species in the Gulf of Suez spawns over 3 months from late summer to autumn during the hottest part of the year. ⁽²⁾

Chiton eggs can be held together in a gelatinous string or can sometimes accumulate in a loose pile behind the female.^(2,3) The eggs are spherical (approximately 200-220 micro meters in diamater) and are very rich in yolk. The eggs are also provided with 2 membranes; an inner membrane around the egg and an outer membrane which is usually ornamented with diverse projections such as spines or cones.^(3,) The colour of the eggs vary with the degree of maturity of the eggs however they are mostly black and covered with spines. ^(3,10)

The developmental process in chitons is holoblastic, nearly equal, spiral and determinate.⁽³⁾⁽³⁾ The duration of the free-swimming, trochophore larvae stage can be between 0.5-4 days (Figure 1).⁽³⁾ Settlement occurs with appropriate cues, where the larvae can further develop into an adult (Figure 1). Metamorphosis starts with dorso-ventral flattening of the body and this usually occurs on the fifth day (Figure 1).⁽³⁾