TY - JOUR

T1 - Postembryonic development of pycnogonids: A deeper look inside

AU - Alexeeva, Nina

AU - Tamberg, Yuta

AU - Shunatova, Natalia

PY - 2018/5

Y1 - 2018/5

N2 - Sea spiders form a small, enigmatic group of recent chelicerates, with an unusual bodyplan, oligosegmentedlarvae and a postembryonic development that is punctuated by many moults. To date, only a fewpapers examined the anatomical and ultrastructural modifications of the larvae and various instars. Herewe traced both internal and external events of the whole postembryonic development in Nymphon brevirostreHODGE 1863 using histology, SEM, TEM and confocal microscopy. During postembryonic development,larvae of this species undergo massive reorganization: spinning apparatus and chelar glandsdisappear; larval legs redifferentiate; three new segments and the abdomen are formed with their correspondinginternal organs and appendages; circulatory and reproductive systems develop anew and thedigestive and the nervous systems change dramatically. The body cavity remains schizocoelic throughoutdevelopment, and no traces of even transitory coeloms were found in any instar. In Nymphon brevirostre,just like in Artemia salina LINNAEUS 1758 the heart arises through differentiation of the already existingschizocoel, and thus the circulatory systems of arthropods and annelids are not homologous. We foundthat classical chelicerate tagmata, prosoma and opisthosoma, are inapplicable to adult pycnogonids, withthe most striking difference being the fate and structure of the seventh appendage-bearing segment.

AB - Sea spiders form a small, enigmatic group of recent chelicerates, with an unusual bodyplan, oligosegmentedlarvae and a postembryonic development that is punctuated by many moults. To date, only a fewpapers examined the anatomical and ultrastructural modifications of the larvae and various instars. Herewe traced both internal and external events of the whole postembryonic development in Nymphon brevirostreHODGE 1863 using histology, SEM, TEM and confocal microscopy. During postembryonic development,larvae of this species undergo massive reorganization: spinning apparatus and chelar glandsdisappear; larval legs redifferentiate; three new segments and the abdomen are formed with their correspondinginternal organs and appendages; circulatory and reproductive systems develop anew and thedigestive and the nervous systems change dramatically. The body cavity remains schizocoelic throughoutdevelopment, and no traces of even transitory coeloms were found in any instar. In Nymphon brevirostre,just like in Artemia salina LINNAEUS 1758 the heart arises through differentiation of the already existingschizocoel, and thus the circulatory systems of arthropods and annelids are not homologous. We foundthat classical chelicerate tagmata, prosoma and opisthosoma, are inapplicable to adult pycnogonids, withthe most striking difference being the fate and structure of the seventh appendage-bearing segment.

KW - Chelicerata

KW - Sea spiders

KW - Tagmosis

KW - Organogenesis

KW - Appendages

KW - Appendages

KW - Chelicerata

KW - Organogenesis

KW - Sea spiders

KW - Tagmosis

KW - PHYLOGENY

KW - GREAT-APPENDAGE ARTHROPOD

KW - ADULT NEUROGENESIS

KW - EPIPERIPATUS-BIOLLEYI ONYCHOPHORA

KW - SEA SPIDERS PYCNOGONIDA

KW - EVOLUTION

KW - ULTRASTRUCTURE

KW - BODY CAVITY

KW - MORPHOLOGY

KW - VASCULAR SYSTEM

UR - http://www.scopus.com/inward/record.url?scp=85044337186&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/postembryonic-development-pycnogonids-deeper-look-inside

U2 - 10.1016/j.asd.2018.03.002

DO - 10.1016/j.asd.2018.03.002

M3 - Article

VL - 47

SP - 299

EP - 317

JO - Arthropod Structure and Development

JF - Arthropod Structure and Development

SN - 1467-8039

IS - 3

ER -