Dichogamy

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In the reproductive biology of zoology and botany, the phenomenon of different maturity times of female and male sexual organs is called dichogamy , temporal separation of the sexes.

General definitions

A dichogamy usually occurs in hermaphroditic flowers (intrafloral dichogamy) and animals, but it also exists in diclinic plants (interfloral dichogamy), where male and female flowers are separate. In the case of hermaphrodites there are two different forms with different goals, proterogyny (pre-female, female maturity occurs earlier) and proterandry (pre-male, male maturity occurs earlier); if they ripen at the same time, this is called homo- or adichogamy . In diclinic plants, in which the female flowers ripen first, one speaks of metandry , the male flowers ripen first, of metagyny ; the simultaneous maturation is called synchronogamy here .

There are different sub-forms:

  • Heterodichogamy: The occurrence of metandric and metagynic individuals in a plant species or the fluctuation of a species between protogynic and proterandric dichogamy, whereby the flowers in the male state bloom at the same time as the flowers in the female state.
  • Homodichogamy: Describes the occurrence of homogamous and dichogamous individuals in a species.
  • Duodichogamy: a sequence of male, then female and again male flowers, as in the sweet chestnut ( Castanea sativa ).
  • Synchronous dichogamy (temporal diocyte ): The male and female reproductive organs on a plant appear or mature at different times during the day.
  • Codichogamy: the occurrence of both earlier male and female maturation in some individuals of a dichogamous population.
  • Ecodichogamy: Different ripening times of male and female individuals in dioecious plants.

Dichogamy in Zoology

Almost all flatworms are hermaphrodites ( hermaphrodites ). As a rule, the male gonads mature first (proterandry or pre-masculinity). The reverse case rarely occurs (proterogyny or pre-femininity). Dichogamy avoids self-fertilization and thus promotes mutual fertilization. The sperm are kept in the semen pouch until the eggs have matured. Afterwards fertilization takes place in the ootype (enlarged initial section of the uterus of many flukes).

Proterandry

Proterandry is understood as the special form of hermaphroditism, which also occasionally occurs in the animal kingdom, in which the individual initially develops male genitals in the course of his life and mates with other "female", i.e. older conspecifics. With increasing age, it gradually develops more and more female genitals and male genitals recede. This process ultimately leads to a full-fledged “female” who takes care of the development and bearing of eggs or young. Examples can be found in most species of snails , earthworms and some marine polyps and mussels, as well as the sea bream and the nasal moray .

Proterogyny

Hermitism in reverse order, i.e. from female to male, is called proterogyny. In some vertebrates, including some marine perch relatives (Percomorphaceae), this form of developmental sex reassignment occurs .

Dichogamy in botany

Proterogyny

From Proterogynie (also Protogynie or pre- or Erstweiblichkeit ) occurs when the female reproductive organs ( carpels ) before the male (the anthers ) mature. If self-fertility is given, a completely separate time of ripening of the genital organs completely prevents self- pollination ( strong proterogyny ), while a ripening time that is only partially offset in time favors cross-pollination, but allows the flower to self-pollinate if it has remained unpollinated ( weak proterogyny ).

Examples of proterogyny

Proterandry

In contrast to proterogyny is proterandry (also protandry, proteroandry, protoandry or fore or first masculinity ). Here the anthers ripen before the carpels, so the pollen is released before the pistil has matured. Self- pollination is also excluded, since proterandry is also often found in self-sterile flowers, it is also considered that this prevents the stigma from being blocked by its own pollen and thus the required pollination by other individuals is increased.

Examples of proterandry

Individual evidence

  1. ↑ a b Walter Durka: floral and reproductive biology ( Memento of 13 April 2018 Internet Archive ). Series of publications for vegetation science, issue 38, Federal Agency for Nature Conservation, Bonn 2002, pp. 133–175 (PDF; 532 kB).
  2. ↑ a b c Karl Linsbauer (Hrsg.): Short dictionary of botany. 2nd Edition. Engelmann, 1917, pp. 304, 306, 440 archive.org .
  3. ↑ Monica A. Geber, Todd E. Dawson, Lynda F. Delph: Gender and Sexual Dimorphism in Flowering Plants. Springer, 1999, ISBN 978-3-642-08424-9 , p. 6.
  4. ^ Edward M. Barrows: Animal Behavior Desk Reference. Third Edition, CRC Press, 2011, ISBN 978-1-4398-3651-4 , p. 218.
  5. ^ Sparus aurata (Linnaeus, 1758). FAO Cultured Aquatic Species Information Program, accessed September 24, 2014.
  6. ↑ Thomas Schöpke: Pre-femininity. Pharmacy Uni-Greifswald ( Memento from June 23, 2007 in the Internet Archive ).