TY - JOUR

T1 - Revisiting kinorhynch segmentation

T2 - variation of segmental patterns in the nervous system of three aberrant species

AU - Herranz, Maria

AU - Park, Taeseo

AU - Di Domenico, Maikon

AU - Leander, Brian S.

AU - Sørensen, Martin V.

AU - Worsaae, Katrine

N1 - Publisher Copyright: © 2021, The Author(s).

PY - 2021

Y1 - 2021

N2 - Background: Kinorhynch segmentation differs from the patterns found in Chordata, Arthropoda and Annelida which have coeloms and circulatory systems. Due to these differences and their obsolete status as ‘Aschelminthes’, the microscopic kinorhynchs are often not acknowledged as segmented bilaterians. Yet, morphological studies have shown a conserved segmental arrangement of ectodermal and mesodermal organ systems with spatial correspondence along the anterior-posterior axis. However, a few aberrant kinorhynch lineages present a worm-like body plan with thin cuticle and less distinct segmentation, and thus their study may aid to shed new light on the evolution of segmental patterns within Kinorhyncha. Results: Here we found the nervous system in the aberrant Cateria styx and Franciscideres kalenesos to be clearly segmental, and similar to those of non-aberrant kinorhynchs; hereby not mirroring their otherwise aberrant and posteriorly shifted myoanatomy. In Zelinkaderes yong, however, the segmental arrangement of the nervous system is also shifted posteriorly and misaligned with respect to the cuticular segmentation. Conclusions: The morphological disparity together with the distant phylogenetic positions of F. kalenesos, C. styx and Z. yong support a convergent origin of aberrant appearances and segmental mismatches within Kinorhyncha.

AB - Background: Kinorhynch segmentation differs from the patterns found in Chordata, Arthropoda and Annelida which have coeloms and circulatory systems. Due to these differences and their obsolete status as ‘Aschelminthes’, the microscopic kinorhynchs are often not acknowledged as segmented bilaterians. Yet, morphological studies have shown a conserved segmental arrangement of ectodermal and mesodermal organ systems with spatial correspondence along the anterior-posterior axis. However, a few aberrant kinorhynch lineages present a worm-like body plan with thin cuticle and less distinct segmentation, and thus their study may aid to shed new light on the evolution of segmental patterns within Kinorhyncha. Results: Here we found the nervous system in the aberrant Cateria styx and Franciscideres kalenesos to be clearly segmental, and similar to those of non-aberrant kinorhynchs; hereby not mirroring their otherwise aberrant and posteriorly shifted myoanatomy. In Zelinkaderes yong, however, the segmental arrangement of the nervous system is also shifted posteriorly and misaligned with respect to the cuticular segmentation. Conclusions: The morphological disparity together with the distant phylogenetic positions of F. kalenesos, C. styx and Z. yong support a convergent origin of aberrant appearances and segmental mismatches within Kinorhyncha.

KW - Acetylated tubulin

KW - Confocal laser scanning microscopy

KW - FMRFamide

KW - Kinorhyncha

KW - Meiofauna

KW - Mismatch

KW - Nervous system

KW - Serotonin

U2 - 10.1186/s12983-021-00438-5

DO - 10.1186/s12983-021-00438-5

M3 - Journal article

C2 - 34674731

AN - SCOPUS:85117734601

VL - 18

JO - Frontiers in Zoology

JF - Frontiers in Zoology

SN - 1742-9994

M1 - 54

ER -