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Sponges have a motile larval stage and become sessile at maturity. Conversely, many jellyfish develop as sessile polyps early in their life cycle. In the case of the cochineal , it is in the nymph stage (also called the crawler stage) that the cochineal disperses.
The release of eggs and sperm into the water is known as spawning. [4] In motile species, spawning females often travel to a suitable location to release their eggs. However, sessile species are less able to move to spawning locations and must release gametes locally. [4] Among vertebrates, external fertilization is most common in amphibians ...
The larvae of sessile forms which survive eventually settle and complete maturation on the substratum- then they may bud asexually to form a colony of zooids. The picture is more complicated for the philopatrically dispersed ascidians: sperm from a nearby colony (or from a zooid of the same colony) enter the atrial siphon and fertilization ...
[4] Motility is genetically determined, [5] but may be affected by environmental factors such as toxins. The nervous system and musculoskeletal system provide the majority of mammalian motility. [6] [7] [8] In addition to animal locomotion, most animals are motile, though some are vagile, described as having passive locomotion.
The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage.
The increase in kidney clearance during pregnancy causes more iodide to be excreted and causes relative iodine deficiency and as a result an increase in thyroid size. Estrogen-stimulated increase in thyroid-binding globulin (TBG) leads to an increase in total thyroxine (T4), but free thyroxine (T4) and triiodothyronine (T3) remain normal.
On Thursday (19 December), Stone shared a selection of photos that showed her looking shocked as she looked at a positive pregnancy test. She captioned the Instagram post: “The one where mummy ...
The male gamete cell, sperm, is usually motile whereas the female gamete cell, the ovum, is generally larger and sessile. The male and female gametes combine to produce the zygote cell. In multicellular organisms, the zygote subsequently divides in an organised manner into smaller more specialised cells, so that this new individual develops ...