Chernyshev A.V.*, Magarlamov T.Yu. 2025. Proboscis apparatus: What do we know (and not know) about nemerteans? // Invert. Zool. Vol.22. No.1: 30–43 [in English].
A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, ul. Palchevskogo 17, Vladivostok 690041 Russiaю
Alexey Chernyshev: nemertea1969@gmail.com ORCID https://orcid.org/0000-0002-2203-3001
Timur Magarlamov: biotimur@yandex.ru ORCID https://orcid.org/0000-0003-4175-5007
* Corresponding author
doi: 10.15298/invertzool.22.1.03
ABSTRACT: This paper provides an overview of recent data on the morphology and functions of the proboscis in nemerteans. It is still unclear whether rhynchocoel and proboscis are synapomorphies of the phylum Nemertea and whether rhynchocoel is homologous to coelom in other Spiralia. The proboscis initially had a structure similar to the body wall, which is typical of the class Palaeonemertea. However, subsequently, the proboscis evolved in two directions: (1) the development of bilateral symmetry in palaeonemerteans from the family Cephalotrichellidae and Pilidiophora (except some Valenciniidae species) and (2) the development of radial symmetry in Hoplonemertea. Pilidiophorans are characterized by a wide variety of proboscis structures, while hoplonemerteans have the most diverse rhynchocoel morphology. The emergence of the stylet apparatus in hoplonemerteans led to the loss of diagonal musculature and pseudocnidae in the proboscis, as well as to a decrease in the number of the family of peptide toxins.
KEY WORDS: proboscis, rhynchocoel, coelom, endothelium, pseudocnidae, armature, evolution.