For species attached to foreign bodies or to the substrata, for those to whom nature grants food abundantly and effortlessly, the role of the male is limited to fertilization; when it is necessary to search, chase, or fight to provide food needed for offspring, the male often helps with their maintenance; this help becomes absolutely indispensable in a species where children remain incapable of taking care of their own needs for a long period after the mother stops nursing them: the male's work then takes on an extreme importance; the lives he brought forth could not maintain themselves without him.