When a is in 0.5 - 1 the animals form dioecious structure, if the p is low ( p→0) the animals will change the sex ratio of filial generation and if the p is high ( p→1) the animals sex will be revered according to environment variation.
The Hydra that lives in inorganic ion-rich water can normally live and reproduce only in the water of natural habitat. The pH of living water is between 6.3 and 7.6. The dioecious Hydra robusta (Iт 1947) and H. dagingensis (Fan 2000) are dominant species among the entire Hydra, which distribute over Heilongjiang province.
生活水域 p H 6.3～ 7.6之间 . 黑龙江省分布的水螅 ,雌雄异体的强壮水螅和大庆水螅为优势种 .
When a is high (α→ 1) the dioecious animal evolutes the higher animals with the high p, otherwise if the p is low ( p→0) the animals must get longevity to wait low reproductive probability and care their generation carefully or not the animals become extinction.
When the specialization degree a is very low (α→0) the animals sex is hermaphrodites, at this time if the probability p of completing market transaction is low ( p→0) the reproductive form of hermaphrodite is autogamy and the p is very high (p→1) the reproductive form is heterogamy.
This species was found to be a simultaneous hermaphroditic brooder, hence gonochorism is not the rule in the order Haplosclerida.
Gonad morphology and gonochorism versus hermaphroditism appear to be constrained phylogenetically at the family or genus level.
Selection for outcrossing between long-lived individuals is proposed as the reason for gonochorism and for synchronous spawning of hermaphroditic broadcasters, and also for the large amount of sperm produced by hermaphroditic brooders.
Gonochorism, paired seminal vesicles and two pairs of male gonoducts opening in chaetigers 9 and 10 with a distal glandular part most likely belong to the ground pattern of Parergodrilidae.
Protogynous hermaphroditism and gonochorism in four Caribbean reef gobies