scholarly journals A tail’s tale: Biomechanical roles of dorsal thoracic spine of barnacle nauplii

2021 ◽  
Author(s):  
E N Branam ◽  
J Y Wong ◽  
B K K Chan ◽  
K Y K Chan
Keyword(s):  
Thoracic Spine ◽  
Life Histories ◽  
Marine Invertebrates ◽  
Larval Performance ◽  
Phase Lag ◽  
Image Velocimetry ◽  
Beat Pattern ◽  
Area Of Influence ◽  
Planktonic Larval Stage ◽  
Stroke Cycle

Abstract Many marine invertebrates have complex life histories that begin with a planktonic larval stage. Similar to other plankton, these larval invertebrates often possess protruding body extensions, but their function beyond predator deterrence is not well-documented. For example, the planktonic nauplii of crustaceans have spines. Using the epibiotic pedunculate barnacle Octolasmis spp., we investigated how the dorsal thoracic spine affects swimming and fluid disturbance by comparing nauplii with their spines partially removed against those with intact spines. Our motion analysis showed that amputated Octolasmis spp. swam slower, in jerkier trajectories, and were less efficient per stroke cycle than those with intact spines. Amputees showed alterations in limb beat pattern: larger beat amplitude, increased phase lag, and reduced contralateral symmetry. These changes might partially help increase propulsive force generation and streamline the flow, but were insufficient to restore full function. Particle image velocimetry further showed that amputees had a larger relative area of influence, implying elevated risk by rheotactic predator. Body extensions and their interactions with limb motion play important biomechanical roles in shaping larval performance, which likely influences the evolution of form.

Phoronida

2017 ◽  
Author(s):  
Judith Fuchs
Keyword(s):  
Life Cycle ◽  
Small Group ◽  
Larval Stage ◽  
Intertidal Zone ◽  
Marine Invertebrates ◽  
Tree Of Life ◽  
General Morphology ◽  
Family Level ◽  
Planktonic Larval Stage

This chapter describes the taxonomy of Phoronida, a small group of exclusively marine invertebrates found in most of the world's oceans from the intertidal zone to about 400 metres depth. Phoronids are meroplanktonic with a planktonic larval stage usually less than 2 mm in length and a benthic adult whose length ranges from a few cm up to 50 cm. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

Maximizing the efficiency of a flexible propulsor using experimental optimization

2015 ◽  
Vol 767 ◽  
pp. 430-448 ◽  
Author(s):  
Daniel B. Quinn ◽  
George V. Lauder ◽  
Alexander J. Smits
Keyword(s):  
Leading Edge ◽  
The Body ◽  
Phase Lag ◽  
Force Measurements ◽  
Experimental Optimization ◽  
Image Velocimetry ◽  
Flexible Panel ◽  
Gradient Based ◽  
Power Scale ◽  
Effective Angle

AbstractExperimental gradient-based optimization is used to maximize the propulsive efficiency of a heaving and pitching flexible panel. Optimum and near-optimum conditions are studied via direct force measurements and particle image velocimetry (PIV). The net thrust and power scale predictably with the frequency and amplitude of the leading edge, but the efficiency shows a complex multimodal response. Optimum pitch and heave motions are found to produce nearly twice the efficiencies of optimum heave-only motions. Efficiency is globally optimized when (i) the Strouhal number is within an optimal range that varies weakly with amplitude and boundary conditions; (ii) the panel is actuated at a resonant frequency of the fluid–panel system; (iii) heave amplitude is tuned such that trailing-edge amplitude is maximized while the flow along the body remains attached; and (iv) the maximum pitch angle and phase lag are chosen so that the effective angle of attack is minimized. The multi-dimensionality and multi-modality of the efficiency response demonstrate that experimental optimization is well-suited for the design of flexible underwater propulsors.

Larvae and Direct Development

2018 ◽  
pp. 151-178
Author(s):  
Richard R. Strathmann
Keyword(s):  
Larval Stage ◽  
Life Histories ◽  
Marine Invertebrates ◽  
Larval Feeding ◽  
Evolutionary Transitions ◽  
Evolutionary Origins ◽  
Marine Crustaceans ◽  
Oxygen Capacity ◽  
Marine Larvae ◽  
Maternal Protection

Modes of development of marine crustaceans and other marine invertebrates include presence or absence of a larval stage, of larval feeding, and of maternal protection of offspring. These different developmental modes impose different compromises (trade-offs) between the number of offspring and their size or the extent of maternal protection. Crustaceans differ from many marine animals in not shedding eggs prior to fertilization, which eliminates the complication of selection on size of eggs as a target for sperm. Features shared with marine invertebrates of several phyla include rare and ancient origins of feeding larvae, irreversible losses of a feeding larval stage, a constraint on brooding imposed by embryos’ need for oxygen, and possible benefits from slower development of protected embryos. Crustaceans differ, however, in having a diverse exoskeletal tool kit that has provided unusual capabilities. Nauplii and zoeae are diverse in form, behavior, and habitat, despite each being nominally one type of larva. Nauplii, as feeding larvae, have adapted to both the benthos and plankton. Settling stages (cyprids and decapodids) with enhanced speed have evolved twice. Some very large adults can supply their large broods with oxygen. Capacity for defense of offspring and home has led a few times to eusociality. The need to molt to grow and change form imposes episodic risk and growth and, in some cases, links evolution of egg size and size at metamorphosis. Crustaceans’ diverse life histories enable comparisons with broad implications for marine invertebrates: opportunity for dispersal is similar for larvae and adults of some crustaceans, demonstrating that marine larvae need not be adaptations for dispersal; development from very small eggs is enabled by less equipment needed for first larval feeding and also by postlarval stages being parasites; eggs shed into the water suffer greater mortality than planktonic larvae or brooded eggs, yet some planktonic crustaceans depend on benthic resting eggs for persistence of populations; larvae escape predation in diverse ways, and bigger larvae are not consistently safer; predation near the seafloor makes settlement a risky stage. Parallels with other taxa are numerous, but the crustacean exoskeletal tool kit has conferred unusual evolutionary opportunities and constraints. Even among marine crustaceans, however, evolutionary options for life histories differ among clades because of rare evolutionary origins of traits of larvae and mothers and biased evolutionary transitions in those traits.

scholarly journals Hydrodynamics of metachronal paddling: effects of varying Reynolds number and phase lag

2019 ◽  
Vol 6 (10) ◽  
pp. 191387 ◽  
Author(s):  
Mitchell P. Ford ◽  
Hong Kuan Lai ◽  
Milad Samaee ◽  
Arvind Santhanakrishnan
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Total Momentum ◽  
Phase Lag ◽  
Vertical Orientation ◽  
Image Velocimetry ◽  
Order Of Magnitude ◽  
Phase Lags ◽  
Downward Propagation ◽  
Negatively Buoyant

Negatively buoyant freely swimming crustaceans such as krill must generate downward momentum in order to maintain their position in the water column. These animals use a drag-based propulsion strategy, where pairs of closely spaced swimming limbs are oscillated rhythmically from the tail to head. Each pair is oscillated with a phase delay relative to the neighbouring pair, resulting in a metachronal wave travelling in the direction of animal motion. It remains unclear how oscillations of limbs in the horizontal plane can generate vertical momentum. Using particle image velocimetry measurements on a robotic model, we observed that metachronal paddling with non-zero phase lag created geometries of adjacent paddles that promote the formation of counter-rotating vortices. The interaction of these vortices resulted in generating large-scale angled downward jets. Increasing phase lag resulted in more vertical orientation of the jet, and phase lags in the range used by Antarctic krill produced the most total momentum. Synchronous paddling produced lower total momentum when compared with metachronal paddling. Lowering Reynolds number by an order of magnitude below the range of adult krill (250–1000) showed diminished downward propagation of the jet and lower vertical momentum. Our findings show that metachronal paddling is capable of producing flows that can generate both lift (vertical) and thrust (horizontal) forces needed for fast forward swimming and hovering.

Section 1 Summary—Evolutionary Origins and Transitions in Developmental Mode

2018 ◽  
Keyword(s):  
Life Histories ◽  
Marine Invertebrates ◽  
Morphological Characteristics ◽  
Biotic Interactions ◽  
Reproductive Mode ◽  
Marine Species ◽  
Comparative Approach ◽  
Closely Related Species ◽  
Larval Stages ◽  
Evolutionary Origins

Abiotic variables and biotic interactions can act on variation in life history traits, ultimately leading to divergence in reproductive mode. Marine invertebrates have a remarkable diversity in such strategies, sometimes even between closely related species. It is this natural diversity that lends itself to employing a powerful comparative approach, both for particular morphological characteristics as well as molecular signatures from developmental genes. For example, complex life histories, where a larval stage is interposed between the embryo and juvenile, likely represent the product of numerous selection pressures, historical and current, that have shaped the diversity of larval stages in extant marine species. In fact, the very question about “what is a larva?” has to be addressed, as it is so intimately connected to bentho-planktonic life cycle and metamorphosis. Furthermore, novel larval types have evolved in particular lineages and larvae have been secondarily lost in others. This in itself creates an interesting and exciting playground to test evolutionary developmental hypotheses....

Vortical feeding currents in nauplii of the calanoid copepod Eucalanus pileatus

2020 ◽  
Vol 638 ◽  
pp. 51-63 ◽  
Author(s):  
H Jiang ◽  
GA Paffenhöfer
Keyword(s):  
High Speed ◽  
Calanoid Copepod ◽  
Imaging System ◽  
Ventral Surface ◽  
Food Concentration ◽  
Core Flow ◽  
Micro Particle Image Velocimetry ◽  
Swimming Motion ◽  
Image Velocimetry ◽  
Beat Pattern

The goal of this study was to quantify feeding-current generation processes in mid to late nauplii and early copepodites of the calanoid copepod Eucalanus pileatus. Using a high-speed microscale imaging system (HSMIS) to conduct both microvideography and micro-particle image velocimetry (µPIV), free-swimming nauplii of E. pileatus were shown to use a novel ‘double draw-and-cut’ continuous appendage beat pattern, which is nonreciprocal, to generate a vortical feeding current at a Reynolds number of ~0.8. The feeding current consists of a core flow towards the ventral surface and 2 laterally flanking viscous vortices reinforcing the core flow. This feeding current is spatially limited with an r-3 decay, potentially reducing predation by rheotactic predators. The feeding current displaces water at ~1.0 × 106 naupliar body volumes per day towards the mouthpart zone. This would result in a clearance rate providing sufficient food at a relatively high environmental food concentration. HSMIS videos revealed that E. pileatus nauplii combine their feeding current and swimming motion to displace algae towards their mouth for capture, and can react to an incoming alga at a 300-500 µm distance away from the nearest naupliar setae, indicating remote detection presumably via chemoreception. The r-3-decay naupliar feeding current is suggested to enhance chemoreception by more effectively elongating the algal phycosphere towards the nauplius. Compared with nauplii, E. pileatus early copepodites, being larger in size and negatively buoyant, beat appendages in a more complex, intermittent pattern to generate an r-1-decay feeding current for displacing more water, indicating a trade-off among feeding, predator avoidance, and alga perception.

scholarly journals Time-varying span efficiency through the wingbeat of desert locusts

2011 ◽  
Vol 9 (71) ◽  
pp. 1177-1186 ◽  
Author(s):  
Per Henningsson ◽  
Richard J. Bomphrey
Keyword(s):  
High Speed ◽  
Schistocerca Gregaria ◽  
Time Varying ◽  
Flight Performance ◽  
Near Wake ◽  
Image Velocimetry ◽  
Lifting Capacity ◽  
Measured Flow ◽  
Wing Stroke ◽  
Stroke Cycle

The flight performance of animals depends greatly on the efficacy with which they generate aerodynamic forces. Accordingly, maximum range, load-lifting capacity and peak accelerations during manoeuvres are all constrained by the efficiency of momentum transfer to the wake. Here, we use high-speed particle image velocimetry (1 kHz) to record flow velocities in the near wake of desert locusts ( Schistocerca gregaria , Forskål). We use the measured flow fields to calculate time-varying span efficiency throughout the wing stroke cycle. The locusts are found to operate at a maximum span efficiency of 79 per cent, typically at a plateau of about 60 per cent for the majority of the downstroke, but at lower values during the upstroke. Moreover, the calculated span efficiencies are highest when the largest lift forces are being generated (90% of the total lift is generated during the plateau of span efficiency) suggesting that the combination of wing kinematics and morphology in locust flight perform most efficiently when doing the most work.

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