Our knowledge of haptophytes life cycles is limited to the few species that survive in laboratories, and even these species rarely give up their secrets easily. Like many algae, haptophytes can reproduce asexually or sexually, and can switch between haploid (half the normal DNA compliment) and diploid (complete DNA compliment) phases. Haptophytes are unusual, however, in that they can maintain reproducing populations in both haploid and diploid states and survive this way for many years in laboratories. They obviously switch from one phase to another in the natural environment but we know little of why and how this happens, although it may allow them to resist viral attack or respond to detrimental environmental changes. In some coccolithophores this switch is also accompanied by production of a completely different coccosphere, most commonly haploid motile phases producing holococcoliths and motile and non-motile diploid phases producing heterococcoliths. They do not always conform to this pattern, however, and additional phases may occur, such as benthic stages in near-shore species, and non-coccolith structures or naked stages may also occur.
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