Evolution of egg-laying strategies in Decapodiformes (Cephalopoda): how a nektonic clade became completely independent from the ocean floor

• Grant number: 23/09622-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2023
• End date: February 28, 2026
• Field of knowledge: Biological Sciences - Zoology - Morphology of Recent Groups
• Principal Investigator: José Eduardo Amoroso Rodriguez Marian
• Grantee: Aline Akemi Taba
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 22/02746-9 - Diving in the Mesozoic Marine Revolution from the perspective of benthic and nektonic mollusks, AP.PNGP.PI
• Associated scholarship(s): 24/18533-0 - Shedding light on fertilization dynamics in Decapodiformes (Cephalopoda): from tracing sperm pathway to unraveling egg encapsulation, BE.EP.MS

Abstract

An essential aspect of the evolution of coleoid cephalopods is the diversification of egg-laying strategies. In decapodiforms (e.g., squid and cuttlefish), for example, the egg masses are structurally complex and mostly benthic. However, in the suborder Oegopsida, which includes oceanic squid, eggs are either pelagic or brooded in the female's arms. Therefore, in an essentially nektonic clade, complete independence from the ocean floor has apparently evolved in only one lineage of Decapodiformes. This suggests intimate association between the evolution of the egg-laying behavior and the colonization of pelagic habitats, which indicates the potential of this trait for understanding Coleoidea diversification. However, it is still enigmatic how the complex decapodiform egg masses are formed, which also hinders the understanding of the fertilization process, given that both processes are simultaneous. In this context, the present proposal aims to investigate the evolution of egg-laying and egg case formation in Decapodiformes by combining integrative microscopy techniques, experimentation and comparative methods, to unravel both the fertilization process and the role of egg-laying behavior in the diversification of Decapodiformes. To understand egg case formation and the fertilization process, we will use model species to integrate behavioral observations and detailed morphological analysis of the egg case and the female reproductive system using light, electron and confocal microscopy. To infer the evolution of egg-laying behavior, we will compile information from literature and from preserved museum specimens to estimate ancestral character states based on a molecular phylogeny.