Omura A.1, Masaki N.2, Ohta I.3 2024. The shape of sucker ring teeth in the hectocotylized part of kisslip cuttlefish (Sepia lycidas) // Invertebrate Zoology. Vol.21. No.1: 58–66 [in English].
1 Design Course, Nihon University College of Art, 2-42-1, Asahigaoka, Nerima-ku, Tokyo, Japan.
2 Hamamatsu BioPhotonics Innovation Chair, Hamamatsu University School of Medicine, 1-20-1, Handayama, Higashi-ku, Hamamatsu, Shizuoka, Japan.
3 Ultrastructual Analysis, Advanced Research Facilities and Services, Hamamatsu University School of Medicine, 1-20-1, Handayama, Higashi-ku, Hamamatsu, Shizuoka, Japan.
* Corresponding author: cuttlefish.ayano.o@gmail.com
Ayano Omura: ORCID 0000-0002-2986-5265
Noritaka Masaki: ORCID 0000-0002-4624-4727
doi: 10.15298/invertzool.21.1.02
ABSTRACT: Decapodiform cephalopods have ‘sucker ring teeth’ in the suckers of their arms and tentacles. The sucker ring teeth are hard structures, and their shape is related to their function; for example, the sucker ring teeth on the arm are long and sharp, aiding in prey capture. Among decapodiform cephalopods, cuttlefish have small suckers on their hectocotylus, in addition to their arms and tentacles. The hectocotylus, a modified (hectocotylized) arm present in male cephalopods, is specifically morphologically adapted for grasping and transferring a batch of spermatophores to females during mating. Therefore, understanding the shape of the hectocotylus is crucial for comprehending the mating behavior and reproductive strategy of cephalopods. However, the morphology of the sucker ring teeth on the hectocotylus in cuttlefish remains unknown. Here, we report the morphological features of the sucker ring teeth on the hectocotylized part of Sepia lycidas. We examined and quantified the teeth of the sucker ring using field emission scanning electron microscopy (FE-SEM) and compared the shape of the sucker teeth on the hectocotylus with those on the regular arm. The teeth on the hectocotylized part were shorter and more obtuse compared to those on the arm, and there were little differences in teeth shape by position on the ring circumference. In contrast, the teeth on the arm were longer and sharper, and their length and sharpness varied between the oral and aboral sides. Possible causes for the morphological features of hectocotylized suckers in mating behavior are discussed; we suggest that the shorter and more obtuse sucker teeth around the circumference of hectocotylized part would be optimized to avoid damaging the spermatophores and to efficiently transfer them to the female. This result contributes to understanding the basic morphology of the hectocotylus and mating strategy of cuttlefish.
KEY WORDS: cuttlefish, Decapodiforms, hectocotylus, Mollusca, sucker, sucker ring teeth.