Zimina V.R. 2024. Statocysts of cephalopods can function with asymmetric statoliths: on the discovery of an anomality in statolith ontogenetic development in squid Berryteuthis septemdentatus (Gonatidae: Coleoidea) // Invertebrate Zoology. Vol.21. No.1: 67–80 [in English].
Invertebrate Zoology Department, Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow 119234 Russia. E-mail: zimina@vniro.ru
ORCID 0009-0006-4902-5921
doi: 10.15298/invertzool.21.1.03
ABSTRACT: The article presents a description of the first discovered squid Berryteuthis septemdentatus with an asymmetric pair of statoliths. One statolith from a pair had three initial crystallization points, two of which gave rise to the development of two separate paralarval statoliths during squid ontogenesis. These paralarval statoliths were located in one statocyst chamber at the time of hatching, and merged into single statolith only on the fourth day after paralarva hatching. The statolith that appeared after merging, retained an abnormal modified form until the adulthood. The second statolith of the pair had normal shape for this species. The finding suggests the presence of unknown mechanisms that may compensate asymmetry in the statolith-statocyst system functioning and allow a squid with defects in vestibular apparatus to survive and reach adulthood. Apparently, on early stages of paralarvae ontogenetic development the statocysts do not play a vital role, which may be related to rather inactive, planktonic lifestyle of paralarvae. Data on morphometry of statoliths is presented for the commander squid Berryteuthis magister from the Bering Sea and Pacific Ocean and the previously considered of its subspecies B. septemdentatus, inhabiting the Sea of Japan. Morphometry of adult and paralarval statoliths of these two species is compared. The paralarval statoliths are larger in B. septemdentatus than in B. magister. This is due to the fact that paralarvae of B. septemdentatus hatch from the larger eggs than paralarvae of B. magister.
KEY WORDS: Berryteuthis septemdentatus, Berryteuthis magister, asymmetric statoliths, paralarval statolith, nuclei, morphometry.