TY - JOUR

T1 - Evolution of Orthonectida body plan

AU - Slyusarev, George S.

AU - Skalon, Elizaveta K.

AU - Starunov, Victor V.

PY - 2023/10/27

Y1 - 2023/10/27

N2 - Orthonectida is an enigmatic group of animals with still uncertain phylogenetic position. Orthonectids parasitize various marine invertebrates. Their life cycle comprises a parasitic plasmodium and free-living males and females. Sexual individuals develop inside the plasmodium; after egress from the host they copulate in the external environment, and the larva, which has developed inside the female infects a new host. In a series of studied orthonectid species simplification of free-living sexual individuals can be clearly traced. The number of longitudinal and transverse muscle fibers is gradually reduced. In the nervous system, simplification is even more pronounced. The number of neurons constituting the ganglion is dramatically reduced from 200 in Rhopalura ophiocomae to 4–6 in Intoshia variabili. The peripheral nervous system undergoes gradual simplification as well. The morphological simplification is accompanied with genome reduction. However, not only genes are lost from the genome, it also undergoes compactization ensured by extreme reduction of intergenic distances, short intron sizes, and elimination of repetitive elements. The main trend in orthonectid evolution is simplification and miniaturization of free-living sexual individuals coupled with reduction and compactization of the genome.

AB - Orthonectida is an enigmatic group of animals with still uncertain phylogenetic position. Orthonectids parasitize various marine invertebrates. Their life cycle comprises a parasitic plasmodium and free-living males and females. Sexual individuals develop inside the plasmodium; after egress from the host they copulate in the external environment, and the larva, which has developed inside the female infects a new host. In a series of studied orthonectid species simplification of free-living sexual individuals can be clearly traced. The number of longitudinal and transverse muscle fibers is gradually reduced. In the nervous system, simplification is even more pronounced. The number of neurons constituting the ganglion is dramatically reduced from 200 in Rhopalura ophiocomae to 4–6 in Intoshia variabili. The peripheral nervous system undergoes gradual simplification as well. The morphological simplification is accompanied with genome reduction. However, not only genes are lost from the genome, it also undergoes compactization ensured by extreme reduction of intergenic distances, short intron sizes, and elimination of repetitive elements. The main trend in orthonectid evolution is simplification and miniaturization of free-living sexual individuals coupled with reduction and compactization of the genome.

KW - Orthonectida

KW - body plan

KW - confocal microscopy

KW - evolution

KW - genomics

KW - immunohistochemistry

KW - morphology

KW - parasitism

UR - https://www.mendeley.com/catalogue/2cba807d-0675-3c72-843e-71279452a665/

U2 - 10.1111/ede.12462

DO - 10.1111/ede.12462

M3 - Article

JO - Evolution and Development

JF - Evolution and Development

SN - 1520-541X

ER -