Tentacules, tentacles directly associated with odontodes, develop on the pectoral fin spine of the males of some species. Males also have evertible cheek odontodes which are less developed or absent in females. . Ancistrus species have the capability of obtaining oxygen through their modified stomach. Courtship includes expanding the dorsal and caudal fins and attempts by the male to escort the female to the nest. While the female inspects the nest, the male keeps close contact.
The female plays no role in parental care; the male takes care of its young. Males will clean the eggs and the cavity with its fins and mouth. Males inspect eggs to remove diseased or infertile eggs, and aerates the clutch by fanning them with its pectoral and pelvic fins. The eggs hatch in 4–10 days over a period of 2–6 hours; the male guards the eggs for 7–10 days after hatching.
If an intruding male manages to evict another male from the nest, it may cannibalize the other male's young. A male bristlenose may guard several clutches of eggs simultaneously. Females prefer males that are already protecting eggs and may prefer males that are protecting larvae; it has been suggested that the tentacles may act as a fry mimic to attract females, which would allow males without eggs in their nest to compete with males guarding eggs.
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