Petrova M.A.*, Bogomolova E.V. 2025. Cephalic limbs in postembryonic development of sea spiders (Pycnogonida): a review // Invert. Zool. Vol.22. No.1: 107–136 [in English].
Department of Invertebrate Zoology, Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow 119234 Russia.
Maria Petrova petrovama@my.msu.ru ORCID https://orcid.org/0009-0007-1272-2659
Ekaterina Bogomolova k-bogomol@yandex.ru ORCID https://orcid.org/0000-0002-7525-3032
* Corresponding author
doi: 10.15298/invertzool.22.1.08
ABSTRACT: Sea spiders (Pycnogonida) are an ancient group of marine arthropods, which has retained an oligomeric larva and hemianamorphic development. Postembryonic development varies across different pycnogonid taxa, producing terminological ambiguities, such as what instars can be reffered as “larva”, what periods one should distinguish during postembryonic development of pycnogonids, and whether the unified scheme of such periodization can be elaborated. In this work, we review postembryonic development of sea spiders with focus on the metamorphosis of the anterior three pairs of limbs (cephalic limbs), which we believe to be the most clear indicator of life mode changes. Morphology of larval appendages and their metamorphosis are reviewed by families and types of development. Taxonomic as well as life mode related trends in the morphology and metamorphosis of the cephalic limbs are traced. Application of different criteria of the term “larva” is tested on pycnogonids with different types of development. Based on the cephalic limbs metamorphosis and criteria of “larva” delimitation of “larval”, “postlarval” and “juvenile” periods in sea spiders development is suggested.
KEY WORDS: Pycnogonida, sea spiders, postembryonic development, metamorphosis, larva, larval limbs, provisional structures, larval adaptations.