Urazaeva A.O.1*, Kosobokova K.N.2, Temereva E.N.1 2024. Internal structure of the reproductive system of the deep-sea chaetognath Eukrohnia hamata based on histological data and 3D reconstructions // Invert. Zool. Vol.21. No.3. P.261–278 (published online on August 24th, 2024).
1 Invertebrate Zoology Department, Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow, 119234 Russia.
2 Shirshov Institute of Oceanology, RAS, Nakhimovskiy Prospekt 36, Moscow 117997 Russia.
Anastasiya Urazaeva: urazaevanas@gmail.com ORCID 0000-0002-5523-9823
Ksenia Kosobokova: xkosobokova@ocean.ru ORCID 0000-0002-3039-4480
Elena Temereva: temereva@mail.ru ORCID 0000-0001-7791-0_+553
* Corresponding author
doi: 10.15298/invertzool.21.3.02
ABSTRACT: The internal structure of the reproductive system and the reproductive biology of chaetognaths remain poorly understood, especially for deep-sea species. This study investigates the anatomical and histological features of gonad maturation patterns in the deep-sea chaetognath Eukrohnia hamata (Möbius, 1875) from the Arctic Ocean, based on histological examination of the late stages of development (from the third to sixth, according to Kosobokova, Isachenko, 2017). A detailed description of the female and male reproductive systems is presented. We found such unusual features as ventral and dorsal lobes of the tail coelom and ciliated funnels around the female genital openings, which emerge during the third stage of development and fully develop by the sixth stage. We assume that the paired lobes of the tail coelom allow E. hamata to accumulate a larger number of sperm, and the ciliated funnels increase the chance of capturing male gametes during copulation. For the first time, paired blood vessels associated with the posterior blood sinus have been described in the longitudinal mesentery of the tail part of the body. These blood vessels presumably provide a better supply of nutrients for developing male gametes. A 3D reconstruction is provided to improve visualization of the genital structures in the area of the posterior sept and adjacent trunk and tail parts of the body.
KEY WORDS: Chaetognatha, Eukrohniidae, lobes of the tail coelom, posterior sept, ciliated funnels, tail blood vessels.