Sucker formation in a bigfin reef squid: Comparison between arms and tentacles

Area of Science:

• Marine Biology
• Developmental Biology
• Evolutionary Morphology

Background:

• Cephalopods, including squids and cuttlefishes (Decapodiformes), are agile marine predators with specialized arms and tentacles.
• Suckers on these appendages are crucial for prey capture, exhibiting unique morphologies, particularly on tentacles.
• The developmental processes underlying sucker formation, especially the differences between arms and tentacles, remain largely unexplored.

Purpose of the Study:

• To investigate and compare the developmental processes of sucker formation on the second arms and tentacles of the bigfin reef squid, Sepioteuthis lessoniana.
• To elucidate the developmental mechanisms responsible for the unique morphologies of tentacular suckers.
• To understand the temporal and spatial differences in sucker development between arms and tentacles.

Main Methods:

• Embryonic development of Sepioteuthis lessoniana was observed.
• Morphological analysis of sucker development was conducted.
• Histological examination of sucker formation was performed on both second arms and tentacles.

Main Results:

• Sucker formation on second arms initiated distally, with invagination forming isolated sucker buds proximally.
• Tentacular sucker development began earlier and resulted in a significantly higher number of suckers compared to arms.
• Four sucker rows in the tentacular club appear to be formed by the compression of two sets of two rows.

Conclusions:

• Sucker formation processes exhibit distinct temporal and spatial patterns between arms and tentacles in Sepioteuthis lessoniana.
• The observed patterns in S. lessoniana show both conserved and unique features compared to other Decapodiformes species.
• These findings suggest diversification in sucker formation patterns across different Decapodiformes lineages during evolution.