Larval Organ

Larval Organ

 

an organ characteristic of the embryo or larva of a multicellular animal that disappears during the animal’s further development. Larval organs ensure the most important functions of an organism before it is formed and before the organs of the adult individual begin functioning. Examples are the abdominal limbs and gills of insect larvae; the gills, the horny mouthparts, and the tail of tadpoles; the vitelline vessels in the embryos of fish, reptiles, and birds; and the allantoic blood vessels in the embryos of reptiles, birds, and mammals.

An understanding of the structure and development of larval organs is helpful in determining the evolution of various groups of animals. Such knowledge is also used in the description of the ancestors of modern species; similar organs were characteristic of adult animals in a number of cases. Some larval organs of extant organisms, however, are embryonic adaptations to certain conditions of existence. Such adaptations, for example, the embryo sacs of Amniota, cannot be used to determine the structure of adult ancestors.

References in periodicals archive ?
in the normal sequence of events affects the ability of the larvae to progress to the next step whether that be the loss of a larval organ or the acquisition of a post-larval one" (Turner 1976a).
The layer of flagellated cells is a larval organ for swimming, therefore those cells disappear soon after settlement.
Bacteria isolated from the different developmental stages and larval organs of the obligate parasitic fly, Wohlfahrtia magnifica (Diptera: Sarcophagidae).
Changes in superoxide dismutase activity in various larval organs of greater wax moth Galleria mellonella L., (Lepidoptera: Pyralidae) Induced by Infection with Bacillus thuringiensis Ssp.
The structural difference lies usually in the presence of special larval organs, such as locomotory or feeding structures, that are lost in the transition from the larva to the juvenile.
The other possibility for the decrease in the postthaw survival rates of older larvae could be caused by the additional differentiation of larval organs after the D-larval stage.
In addition to demonstrating the extent of the larval nervous system, the present study also provides further insights into the structures of larval organs by elucidating their varied neural components.
Larval organs and tissues present at hatching in both planktotrophic and lecithotrophic larvae are oriented toward sustaining the larva through a planktonic period that may include both feeding and growth to metamorphic competence.
Additional neurons often appear in association with newly formed or enlarged larval organs. For example, the ciliated band continues to grow in length until the fourth and final pair of arms, the pre-oral arms, are formed.