Physiology and functional biology of Rhizostomeae jellyfish.

Rhizostomeae species attract our attention because of their distinctive body shape, their large size and because of blooms of some species in coastal areas around the world. The impacts of these blooms on human activities, and the interest in consumable species and those of biotechnological value have led to a significant expansion of research into the physiology and functional biology of Rhizostomeae jellyfish over the last years. This review brings together information generated over these last decades on rhizostome body composition, locomotion, toxins, nutrition, respiration, growth, among other functional parameters.

Hydromechanical properties of metachronal swimming in polychaetes.

Free-swimming polychaetes are common in marine habitats and exhibit a unique form of swimming whereby a metachronal wave occurs simultaneously with a bending body wave. This body wave is unusual among swimming animals because it travels in the same direction as the animal's swimming direction. However, we currently lack a mechanistic understanding of this unusual form of locomotion.

Spinning and corkscrewing of oceanic macroplankton revealed through in situ imaging.

Helical motion is prevalent in nature and has been shown to confer stability and efficiency in microorganisms. However, the mechanics of helical locomotion in larger organisms (>1 centimeter) remain unknown. In the open ocean, we observed the chain forming salp, , swimming in helices.

Nectophore coordination and kinematics by physonect siphonophores.

Siphonophores are ubiquitous and often highly abundant members of pelagic ecosystems throughout the open ocean. They are unique among animal taxa in that many species use multiple jets for propulsion. Little is known about the kinematics of the individual jets produced by nectophores (the swimming bells of siphonophores) or whether the jets are coordinated during normal swimming behavior.

Ontogenetic transitions, biomechanical trade-offs and macroevolution of scyphozoan medusae swimming patterns.

Ephyrae, the early stages of scyphozoan jellyfish, possess a conserved morphology among species. However, ontogenetic transitions lead to morphologically different shapes among scyphozoan lineages, with important consequences for swimming biomechanics, bioenergetics and ecology. We used high-speed imaging to analyse biomechanical and kinematic variables of swimming in 17 species of Scyphozoa (1 Coronatae, 8 "Semaeostomeae" and 8 Rhizostomeae) at different developmental stages.

A fundamental propulsive mechanism employed by swimmers and flyers throughout the animal kingdom.

Even casual observations of a crow in flight or a shark swimming demonstrate that animal propulsive structures bend in patterned sequences during movement. Detailed engineering studies using controlled models in combination with analysis of flows left in the wakes of moving animals or objects have largely confirmed that flexibility can confer speed and efficiency advantages. These studies have generally focused on the material properties of propulsive structures (propulsors).

Quantifying the feeding behavior and trophic impact of a widespread oceanic ctenophore.

Oceanic ctenophores are widespread predators on pelagic zooplankton. While data on coastal ctenophores often show strong top-down predatory impacts in their ecosystems, differing morphologies, prey capture mechanisms and behaviors of oceanic species preclude the use of coastal data to draw conclusion on oceanic species. We used high-resolution imaging methods both in situ and in the laboratory to quantify interactions of Ocyropsis spp.

Cooperative hydrodynamics accompany multicellular-like colonial organization in the unicellular ciliate .

Evolution of multicellularity from early unicellular ancestors is arguably one of the most important transitions since the origin of life. Multicellularity is often associated with higher nutrient uptake, better defense against predation, cell specialization and better division of labor. While many single-celled organisms exhibit both solitary and colonial existence, the organizing principles governing the transition and the benefits endowed are less clear.

Distributed propulsion enables fast and efficient swimming modes in physonect siphonophores.

Many fishes employ distinct swimming modes for routine swimming and predator escape. These steady and escape swimming modes are characterized by dramatically differing body kinematics that lead to context-adaptive differences in swimming performance. Physonect siphonophores, such as , are colonial cnidarians that produce multiple jets for propulsion using swimming subunits called nectophores.

"Indirect development" increases reproductive plasticity and contributes to the success of scyphozoan jellyfish in the oceans.

Ecologists and evolutionary biologists have been looking for the key(s) to the success of scyphomedusae through their long evolutionary history in multiple habitats. Their ability to generate young medusae (ephyrae) via two distinct reproductive strategies, strobilation or direct development from planula into ephyra without a polyp stage, has been a potential explanation. In addition to these reproductive modes, here we provide evidence of a third ephyral production which has been rarely observed and often confused with direct development from planula into ephyra.

Teamwork in the viscous oceanic microscale.

Nutrient acquisition is crucial for oceanic microbes, and competitive solutions to solve this challenge have evolved among a range of unicellular protists. However, solitary solutions are not the only approach found in natural populations. A diverse array of oceanic protists form temporary or even long-lasting attachments to other protists and marine aggregates.

Cool your jets: biological jet propulsion in marine invertebrates.

Pulsatile jet propulsion is a common swimming mode used by a diverse array of aquatic taxa from chordates to cnidarians. This mode of locomotion has interested both biologists and engineers for over a century. A central issue to understanding the important features of jet-propelling animals is to determine how the animal interacts with the surrounding fluid.

Developing Biohybrid Robotic Jellyfish () for Free-swimming Tests in the Laboratory and in the Field.

Biohybrid robotics is a growing field that incorporates both live tissues and engineered materials to build robots that address current limitations in robots, including high power consumption and low damage tolerance. One approach is to use microelectronics to enhance whole organisms, which has previously been achieved to control the locomotion of insects. However, the robotic control of jellyfish swimming offers additional advantages, with the potential to become a new ocean monitoring tool in conjunction with existing technologies.

Neuromechanical wave resonance in jellyfish swimming.

For organisms to have robust locomotion, their neuromuscular organization must adapt to constantly changing environments. In jellyfish, swimming robustness emerges when marginal pacemakers fire action potentials throughout the bell's motor nerve net, which signals the musculature to contract. The speed of the muscle activation wave is dictated by the passage times of the action potentials.

The most efficient metazoan swimmer creates a 'virtual wall' to enhance performance.

It has been well documented that animals (and machines) swimming or flying near a solid boundary get a boost in performance. This ground effect is often modelled as an interaction between a mirrored pair of vortices represented by a true vortex and an opposite sign 'virtual vortex' on the other side of the wall. However, most animals do not swim near solid surfaces and thus near body vortex-vortex interactions in open-water swimmers have been poorly investigated.

Field Testing of Biohybrid Robotic Jellyfish to Demonstrate Enhanced Swimming Speeds.

Biohybrid robotic designs incorporating live animals and self-contained microelectronic systems can leverage the animals' own metabolism to reduce power constraints and act as natural chassis and actuators with damage tolerance. Previous work established that biohybrid robotic jellyfish can exhibit enhanced speeds up to 2.8 times their baseline behavior in laboratory environments.

The role of suction thrust in the metachronal paddles of swimming invertebrates.

An abundance of swimming animals have converged upon a common swimming strategy using multiple propulsors coordinated as metachronal waves. The shared kinematics suggest that even morphologically and systematically diverse animals use similar fluid dynamic relationships to generate swimming thrust. We quantified the kinematics and hydrodynamics of a diverse group of small swimming animals who use multiple propulsors, e.

The Hydrodynamics of Jellyfish Swimming.

Jellyfish have provided insight into important components of animal propulsion, such as suction thrust, passive energy recapture, vortex wall effects, and the rotational mechanics of turning. These traits are critically important to jellyfish because they must propel themselves despite severe limitations on force production imposed by rudimentary cnidarian muscular structures. Consequently, jellyfish swimming can occur only by careful orchestration of fluid interactions.

Thrust generation during steady swimming and acceleration from rest in anguilliform swimmers.

Escape swimming is a crucial behavior by which undulatory swimmers evade potential threats. The hydrodynamics of escape swimming have not been well studied, particularly for anguilliform swimmers, such as the sea lamprey For this study, we compared the kinematics and hydrodynamics of larval sea lampreys with those of lampreys accelerating from rest during escape swimming. We used experimentally derived velocity fields to calculate pressure fields and distributions of thrust and drag along the body.

Maneuvering Performance in the Colonial Siphonophore, .

The colonial cnidarian, , is highly proficient at moving in three-dimensional space through forward swimming, reverse swimming and turning. We used high speed videography, particle tracking, and particle image velocimetry (PIV) with frame rates up to 6400 s to study the kinematics and fluid mechanics of during turning and reversing. achieved turns with high maneuverability (mean length-specific turning radius, R/L = 0.

Hydrodynamics of Vortex Generation during Bell Contraction by the Hydromedusa (Romanes, 1876).

Swimming bell kinematics and hydrodynamic wake structures were documented during multiple pulsation cycles of a (Romanes, 1876) medusa swimming in a predominantly linear path. Bell contractions produced pairs of vortex rings with opposite rotational sense. Analyses of the momentum flux in these wake structures demonstrated that vortex dynamics related directly to variations in the medusa swimming speed.

A ctenophore (comb jelly) employs vortex rebound dynamics and outperforms other gelatinous swimmers.

Gelatinous zooplankton exhibit a wide range of propulsive swimming modes. One of the most energetically efficient is the rowing behaviour exhibited by many species of schyphomedusae, which employ vortex interactions to achieve this result. Ctenophores (comb jellies) typically use a slow swimming, cilia-based mode of propulsion.

Propulsive design principles in a multi-jet siphonophore.

Coordination of multiple propulsors can provide performance benefits in swimming organisms. Siphonophores are marine colonial organisms that orchestrate the motion of multiple swimming zooids for effective swimming. However, the kinematics at the level of individual swimming zooids (nectophores) have not been examined in detail.

Widespread utilization of passive energy recapture in swimming medusae.

Recently, it has been shown that some medusae are capable of swimming very efficiently, i.e. with a low cost of transport, and that this is in part due to passive energy recapture (PER) which occurs during bell relaxation.

How the bending kinematics of swimming lampreys build negative pressure fields for suction thrust.

Swimming animals commonly bend their bodies to generate thrust. For undulating animals such as eels and lampreys, their bodies bend in the form of waves that travel from head to tail. These kinematics accelerate the flow of adjacent fluids, which alters the pressure field in a manner that generates thrust.