The Tentacular Strike Behavior in Squid: Functional Interdependency of Morphology and Predatory Behaviors During Ontogeny

Abstract

This study examines the relationship between morphology and predatory behaviors to evaluate the ontogeny of the specialized tentacular strike (TS) in Doryteuthis opalescens squid reared under laboratory conditions [hatching to 80 day-old; 2-16 mm mantle length (ML)]. Ontogenetic morphological changes in the arm-crown and the role played by the arms and tentacles during predatory behavior was correlated with prey types captured and revealed interconnected morphological and behavior traits that enabled paralarvae to perform the TS. Hatchlings have a poorly developed arm-crown and tentacles that resemble and function as arms, in which tentacular clubs (suckerfull non-contractile portion) and stalks (suckerless contractile portion) have not yet formed. Only a basic attack (BA) behavior was observed, involving arms and tentacles, which were not ejected during prey capture. A more elaborated behavior, the arm-net (AN) was first employed by 30 day-old (>4.7 mm ML) paralarvae, in which the tentacles were eject down, but not toward the prey. The TS was first observed in 40-50 dayold (6.7-7.8 mm ML) squid, which stay stationary by sustainable swimming prior to ejecting the tentacles toward the prey. Thus, the ability to perform sustainable swimming and acquisition of swimming coordination (schooling behavior) are prerequisites for the expression of the TS. The arms played the same roles after prey was captured: hold, subdue and manipulate the prey, while the actions performed by the tentacles truly defined each behavior. Prey size captured increased with increasing squid size. Morphometric data showed that hatchlings have little ability of elongating their tentacles, but this ability increases significantly with size. Squid older than 40 days could elongate their tentacles up to 61% of their ML, whereas early paralarvae 13% on average. Paralarvae were frequently observed elongating and contracting their tentacles, while not attempting to capture prey, which could perhaps serve to adjust muscle activity and development, while specializations for the strike-stalks, clubs, muscle fibers, armcrown and swimming coordination-are still being developed. The expression of the TS is constrained by development in early paralarvae as it involves interdependency of morphology and behavior and as such, represents a major developmental milestone in the early life history of squid.

Impact of squid predation on juvenile fish survival

“…Regionally, Ohshimo et al 49 estimated the mean PPMR in the pelagic system of the ECS and the western Sea of Japan as 3–5 × 10 3 based on nitrogen stable isotope analysis of zooplankton, 18 fish species, and only one squid species. Squids employ their tentacles first to capture prey fish and hold it with their arms, after which they administer a lethal bite behind the head 28 , 45 , 50 . This feeding behaviour probably allows squids to consume larger prey relative to their size compared with fish that swallow prey smaller than their mouth/oesophagus diameter; thus, it is likely that the PPMR of squid and fish is generally lower than that between fishes, as has been indicated by previous studies 15 , 26 .…”

Connecting polarized light and water turbidity with feeding rates in Octopus americanus paralarvae

“…FRs measure predatory success that depends on several biotic and abiotic factors. Among the biotic ones, size, morphology, mobility, pigmentation, escape capacity, behavior, and palatability of the prey, as well as prey capture, and swimming ability of the predator are determinants (Chesney, 2005;Vidal & Salvador, 2019;Vidal, Zeidberg, & Buskey, 2018). Regarding the environmental factors, temperature, turbulence, water density, turbidity, and light are essential (Chesney, 2005;Vidal & Boletzky, 2014).…”

“…Thus, this study aims to evaluate whether polarized light and water turbidity enhance O. americanus paralarvae FRs when fed on natural preys (i.e., copepods). Given that both cephalopod vision (Cartron, Dickel, Shashar, & Darmaillacq, 2013) and predation ability are improved with experience (Chen, VanDykhuizen, Hodge, & Gilly, 1996;Vidal & Salvador, 2019), we tested newly-hatched, 8-dayold, and 15-day-old paralarvae. Besides, we quantified paralarvae FRs on natural prey and estimated their energy consumption based on their prey types.…”

A practical staging atlas to study embryonic development of Octopus vulgaris under controlled laboratory conditions

“…The last stages of development (maturation) are more difficult to compare between cephalopods, since species that produce large eggs generally hatch out as juveniles that are miniature adults, while small egg-embryos hatch out as small planktonic paralarvae. The latter still have to go through major morphological changes to attain the juvenile form, such as the development of the arm-crown complex, swimming control, the chromatophore system and horizontal pupillary response [9][10][11]. Furthermore, taxon specific features that arise in cuttlefish (e.g.…”