Resting eggs and amictic eggs

Resting eggs

When a so-called "mictic stimulus" ("Mixis stimulus" in German) occurs in the environment, which could be for example: changes in the chemical composition of the surrounding water or the temperature, the females may produce haploid eggs. If these eggs are not fertilized they develop into haploid males (blue) which are usually much smaller (there are exceptions, for instance Asplanchna) and look different from the females. They are called dwarf males. (sexual dimorphism). The males can now fertilize the mictic eggs of mictic females. These fertilized eggs (brown) are called "resting eggs". The resting eggs have a mechanichal and also chemical very durable shell which is species-specific and enables the eggs to survive bad environmental conditions like ice in ponds or dryseasons

Here are some of them:

Anuraeopsis fissa
Ascomorpha ecaudis
Brachionus urceolaris
Collotheca coronetta
Conochilus natans
Hexarthra mira
Asplanchna girodi
Asplanchna priodonta
Cephalodella tenuior
Encentrum lutra
Encentrum permolle
Filinia longiseta
Gastropus stylifer
Keratella quadrata
Keratella serrulata
Lecane bulla
Lepadella ovalis
Euchlanis triquetra
Polyarthra sp.
Ptygura pilula
Rhinoglena frontalis

Amictic eggs

monogonont rotifers may reproduce either by parthenogenesis or sexually. Therefore they have different types of eggs. The eggs that are produced while reproducing parthenogenetically are diploid and are either carried by the female (eg. Anuraeopsis, Brachionus), deposited near the sheath (eg. Collotheca; Ptygura) or they develop inside the mother untile the daughter is born (eg. Asplanchna; Rhinoglena). These eggs are called amictic eggs, becaues they develop without mixis (fertilization partenogenetic reproduction enables the population to increase rapidly because there is no need for finding a sexual partner, which is always an advantage if the distance between specimen is large, eg in lakes or ponds.)

Here are some of them:

Anuraeopsis fissa
Ascomorpha ecaudis
Cephalodella auriculata
Collotheca coronetta
Collotheca pelagica
Filinia longiseta
Lecane clara
Lepadella ovalis
Pompholyx sulcata
Polyarthra sp
Proalides tentaculatus

Synchaeta pectinata
freshwater life
marine life