A comparison of swimming structures and kinematics in three species of crustacean larvae

Crustacean larvae swim with paired rowing appendages that rotate around the body of the animal. The number of paired rowing appendages varies from one species of larvae to another. In addition, the size of the crustacean larvae is different between species and increases as they grow. The nature of the fluid forces changes as size increases, so the morphology and mechanics of swimming in these animals will change during increases in size. This article demonstrates the changing kinematics of locomotion between three species of crustacean larvae, which swim with one (Artemia franciscana), two (Carcinus maenas) or five (Homarus americanus) pairs of propulsive limbs. The relative change in the surface area and volume ratios of the locomotor structures are also demonstrated.     

Functional morphology and virtual models: physical constraints on the design of oscillating wings, fins, legs, and feet at intermediate reynolds numbers

Why do some animals swim by rowing appendages back and forthwhile others fly by flapping them up and down? One hypothesissuggests the answer lies in the sharply divergent physical environmentsencountered by small, slow animals, and large, fast animals.Flapping appendages allow large animals to move through a fluidenvironment quickly and efficiently. As size and speed decrease,however, viscous drag increasingly dominates the force balance,with negative consequences for both rowing and flapping appendages.Nevertheless, comparative data suggest that flapping does notoccur in animals at Reynolds numbers (Re) less than about 15.I used a computer simulation experiment to address the question,"Below what Re is rowing more effective than flapping?" Thesimulation, which employed a simple quasi-steady, blade-elementmodel of virtual oscillating appendages, has several importantresults. First, the mechanical efficiency of both rowing andflapping decrease dramatically with scale. Second, the performanceof rowing can increase substantially by taking advantage ofseveral dynamic shape modifications, including area and spanreduction during the recovery stroke. Finally, the relativeperformance of rowing and flapping is dependent on the advanceratio, which is a function of the travel speed relative to theoscillation frequency. The model predicts that rowing is moreefficient than flapping at Re < 20 for animals moving throughoutthe range of typically observed advance ratios.     

Non-consumptive effects of larval Salamandra on crustacean prey: can eggs detect predators?

Predators affect prey populations not only by prey consumption but also in nonconsumptive ways including modifying prey behavior. I tested the effects of fire salamander larvae (Salamandra infraimmaculata) on populations of co-occurring crustacean species in artificial outdoor pools. I also tested whether these effects were due entirely to prey consumption by Salamandra larvae or alternatively to some nonconsumptive effect. The soil (containing crustacean eggs) added to the artificial pools was collected from a dried-out temporary pool that is inhabited by Salamandra during the early part of the hydroperiod. I randomly assigned the pools to one of three treatments: control, free Salamandra, or caged Salamandra. Free salamander larvae could roam the entire pool and prey upon crustaceans. Caged salamander larvae were placed within a cage with having 250-μm mesh windows. They could not prey upon the crustaceans but could, for example, influence them by chemical cues. Densities of the three dominant crustacean species (Arctodiaptomus similis, Ceriodaphnia quadrangula and Cyzicus sp.) were drastically reduced in both salamander treatments compared to the control. Crustacean densities, however, were not significantly different between the two salamander treatments. One plausible explanation is that crustacean eggs can detect the presence of this predator via chemical cues and delay hatching. Received: 4 March 1996 / Accepted, 23 October 1996     

Creating conditions for changes in prey community structure by Chaoborus spp. in a lake in Sweden

In Lake G»rdsjön (Southwest Sweden), liming as an experimental improvement of living conditions for pelagic algae, resulted in a significant increase of algal biomass and a reduction of mean cell size. The algal development was beneficial for small sized filter feeding zooplankton, particularly rotifers, which showed a significant increase. The increase in abundance of small sized zooplankton created better food conditions for the smaller instars, and thus a much better overall survival of Chaoborus larvae. The resulting, 6–7 times larger population of Chaoborus larvae significantly changed the structure of the crustacean zooplankton community. Bosmina coregoni, the fastest swimmer of the crustacean species suffered most and was strongly reduced by the increased predation from Chaoborus. The share of cladocerans decreased, while copepods increased in importance.     

Distribution and Relative Size of the Swim Bladder in Percina, With Comparisons to Etheostoma, Crystallaria, and Ammocrypta (Teleostei: Percidae)

The distribution of the swim bladder was examined in 20 species representing all four genera (Percina, Etheostoma, Crystallaria, and Ammocrypta) of darters (Etheostomatini). Including data on species examined in other studies, swim bladders have been found in 15 of 17 species of Percina, but were absent in Crystallaria asprella, Ammocrypta pellucida, and the 18 species of Etheostoma examined. Relative swim bladder length in Percina was shown to be positively correlated with body size. Although not statistically significant, swim bladder size also correlates with habitat (riffle, run, or pool) and swimming behavior (midwater or benthic).     

Ontogeny of critical and prolonged swimming performance for the larvae of six Australian freshwater fish species

Critical (<30 min) and prolonged (>60 min) swimming speeds in laboratory chambers were determined for larvae of six species of Australian freshwater fishes: trout cod Maccullochella macquariensis, Murray cod Maccullochella peelii, golden perch Macquaria ambigua, silver perch Bidyanus bidyanus, carp gudgeon Hypseleotris spp. and Murray River rainbowfish Melanotaenia fluviatilis. Developmental stage (preflexion, flexion, postflexion and metalarva) better explained swimming ability than did length, size or age (days after hatch). Critical speed increased with larval development, and metalarvae were the fastest swimmers for all species. Maccullochella macquariensis larvae had the highest critical [maximum absolute 46·4 cm s^?1 and 44·6 relative body lengths (L_B) s^?1] and prolonged (maximum 15·4 cm s^?1, 15·6 L_B s^?1) swimming speeds and B. bidyanus larvae the lowest critical (minimum 0·1 cm s^?1, 0·3 L_B s^?1) and prolonged swimming speeds (minimum 1·1 cm s^?1, 1·0 L_B s^?1). Prolonged swimming trials determined that the larvae of some species could not swim for 60 min at any speed, whereas the larvae of the best swimming species, M. macquariensis, could swim for 60 min at 44% of the critical speed. The swimming performance of species with precocial life‐history strategies, with well‐developed larvae at hatch, was comparatively better and potentially had greater ability to influence their dispersal by actively swimming than species with altricial life‐history strategies, with poorly developed larvae at hatch.     

The post-embryonic development of Remipedia (Crustacea)—additional results and new insights

The post-embryonic development of a species of the enigmatic crustacean group Remipedia is described in detail for the first time under various aspects. Applying a molecular approach, we can clearly prove the species identity of the larvae as belonging to Pleomothra apletocheles. We document the cellular level of several larval stages and the differentiation of segments, limbs, and the general body morphology applying the techniques of confocal laser scanning microscopy and scanning electron microscopy. In addition, we document the swimming behavior and the peculiar movements of the naupliar appendages. A comparison of our results with published data on other Crustacea and their larval development tentatively supports ideas about phylogenetic affinities of the Remipedia to the Malacostraca. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Kinematics, dynamics, and energetics of rowing and flapping propulsion in fishes

The shape and motion of the pectoral fins vary considerablyamong fishes that swim in the labriform mode. Pectoral fin motionin fishes is highly variable, but one conspicuous axis of thisvariation is the rowing-flapping axis. At one extreme of thisaxis, paddle-shaped fins row back and forth in a plane thatis parallel to fish motion, while at the other extreme, wing-shapedfins flap up and down in a plane that is perpendicular to fishmotion. We have used two fish, the threespine stickleback (Gasterosteusaculeatus) and the bird wrasse (Gomphosus varius), that fallnear the extremes of the rowing-flapping axis to study the dynamic,energetic, and ecological and evolutionary consequences of thiskinematic variation. Our work confirms some traditionally heldassumptions about rowing and flapping dynamics and energeticsbut reject others. A computer simulation experiment of virtualrowing and flapping appendages makes several predictions aboutdifferences in maneuvering performance and swimming energeticsbetween rowing and flapping, which, in turn, make predictionsabout the behavior and ecological distribution of fishes thatvary along the rowing-flapping axis. Both laboratory and fieldstudies of labrid swimming ability and distribution supportthese predictions.     

Early Developmental Stages of the Green Tiger Prawn, Penaeus semisulcatus de Haan (Crustacea, Decapoda, Penaeidae)

Gravid females of Penaeus semisulcatus were spawned in the laboratory by natural means. The embryos were documented and the larvae were reared from hatching to postlarval stage at 28.2–30.0 °C and 33.5–34.5 g kg⁻¹ salinity for about 10 days (223 h 55 min). Six naupliar stages, three protozoea stages, three mysis stages and the first postlarval stage were described and illustrated. The larvae were fed only with microalgae Tetraselmis tetrathele and Chaetoceros gracilis from first protozoea until the second mysis, with about 90% survival rate; from the third mysis until the first postlarva they were fed with similar microalgae coupled with rotifer Brachionus plicatilis and Artemia nauplii. The embryonic and larval stages of P. semisulcatus are generally similar to those of other closely related species in the family Penaeidae, such as Melicertus canaliculatus, Fenneropenaeus merguiensis, and Marsupenaeus japonicus, except for the size and structure of diagnostic characters, setation of appendages and duration of metamorphoses. The change in the feeding habit during ontogeny was related to morphological transformation of the feeding apparatus of larvae and postlarvae. This paper is the first comprehensive and complete account of the early developmental stages of P. semisulcatus.     

Compound eyes and ocular pigments of crustacean larvae (Stomatopoda and decapoda,brachyura)

Larvae of decapod and stomatopod crustaceans possess paired compound eyes not unlike those of adult crustaceans. However, the visual demands of larval and adult life differ considerably. Furthermore, the eyes of adult stomatopods appear to be far more specialized than those of the larvae. We examined eyes of several stomatopod species just before and after larval metamorphosis. At this time, the entire larval retina is joined by a new, adult‐type retinal array which gradually replaces the remnants of the larval retina. The new retina of the postlarva is anatomically similar to that of the full‐grown adult, and has virtually identical assemblages of intrarhabdomal filters. We determined the photopigments of Gonodactylus aloha, the only species for which we were able to obtain both larval and adult specimens, using microspectrophotometry. The single middle‐wavelength larval rhodopsin (λ_max= 499 nm) disappears at metamorphosis; none of the 10 classes of adult rhodopsins has λ_max between 473 and 510 nm. This metamorphic change of visual pigment does not occur in a comparison species of decapod crustacean, the blue crab Callinectes sapidus. Here, rhodopsins both of the megalops larva and the adult had λ_max at 503–504 nm. The difference between these two species can be explained by the varying ecological requirements of their larvae and adults, and more study of visual pigments in retinas of larval and adult crustaceans is warranted.     

Sustainable control of mosquito larvae in the field by the combined actions of the biological insecticide Bti and natural competitors

Integrated management of mosquitoes is becoming increasingly important, particularly in relation to avoiding recolonization of ponds after larvicide treatment. We conducted for the first time field experiments that involved exposing natural populations of the mosquito species Culex pipiens to: a) application of the biological insecticide Bacillus thuringiensis israelensis (Bti), b) the introduction of natural competitors (a crustacean community composed mainly of Daphnia spp.), or c) a combined treatment that involved both introduction of a crustacean community and the application of Bti. The treatment that involved only the introduction of crustaceans had no significant effect on mosquito larval populations, while treatment with Bti alone caused only a significant reduction in the abundance of mosquito larvae in the short‐term (within 3–10 days after treatment). In contrast, the combined treatment rapidly reduced the abundance of mosquito larvae, which remained low throughout the entire observation period of 28 days. Growth of the introduced crustacean communities was favored by the immediate reduction in the abundance of mosquito larvae following Bti administration, thus preventing recolonization of ponds by mosquito larvae at the late period (days 14–28 after treatment). Both competition and the temporal order of establishment of different species are hence important mechanisms for efficient and sustainable mosquito control.     

Mechanics and Ecological Role of Swimming Behavior in the Caddisfly Larvae <Emphasis Type="Italic">Triaenodes tardus</Emphasis>

Caddisfly larvae are typically restricted to benthic microhabitats due to the presence of mobile tubular cases constructed out of mineral or organic material. Members of one family (Leptoceridae) use setae on extended metathoracic legs to swim. We describe the swimming behavior of a North American caddisfly, Triaenodes tardus, and experimentally evaluate two hypotheses proposed to explain this behavior. Triaenodes swam 1.47 cm/s, while carrying almost twice their mass in the case material. The larvae employ a stereotypic sequence of motions that likely reduce resistance during the upstroke and increases forward momentum during the downstroke. When placed on substrates of different sizes, larvae swam more on fine sediments but did not elevate off the sediment. After larvae were provided with living or artificial vegetation, the number of swimming bouts decreased compared to a pre-treatment observation period. These results indicate swimming likely does not function to facilitate movement off fine sediments, but rather, helps larvae locate and move between aquatic macrophytes which are the primary habitat of this, and other, swimming species.     

Phylogenetic implications of the Crustacean nauplius

The plesiomorphic mode of crustacean development is widely accepted to be via a larva called the nauplius. Extant taxa like the Cephalocarida, Branchiopoda, Ostracoda, Mystacocarida, Copepoda, Cirripedia, Ascothoracida, Facetotecta, Euphausiacea and Penaeidea hatch from an egg as a free-living nauplius. Other crustaceans show an embryonic phase of development suggestive of a naupliar organization. Several features of the nauplius larva have been proposed as diagnostic characters for the Crustacea: a median (nauplius) eye; at least three pairs of head appendages (antennules, antennae, mandibles); a posteriorly directed fold (the labrum) extending over the mouth and a cephalic (nauplius) shield. The relationship between trilobite protaspis with at least four appendages and the crustacean nauplius remains unclear, but reports of a copepod orthonauplius with four appendages are rejected. Swimming is suggested to represent the underived mode of locomotion for the crustacean nauplius, and that naupliar swimming directly results in naupliar feeding which also is underived.     

Summer depth selection in crustacean zooplankton in nutrient‐poor boreal lakes is affected by recent residential development

1. Strong vertical gradients in light, water temperature, oxygen, algal concentration and predator encounters during summer in stratified lakes may influence patterns of depth selection in crustacean zooplankton, especially Daphnia species. 2. To test how crustacean depth selection varies among lakes along a gradient of catchment disturbance by recent residential development and land use change, we calculated the weighted mean depth distribution of the biomass of crustaceans by day and night in eight nutrient‐poor boreal lakes. 3. Generally, the greatest biomass of crustaceans was located at the metalimnion or at the lower boundary of the euphotic zone during thermal stratification in July. The crustacean zooplankton avoided warm surface layers and tended to stay in colder deep waters by both day and night. They also remained at greater depths in lakes with a more extensive euphotic zone. 4. There was some evidence of upward nocturnal migrations of large Daphnia and copepods in some lakes, and one case of downward migration in a lake inhabited by chaoborid larvae. 5. Multivariate regression trees (MRT) were used to cluster crustaceans and Daphnia species in homogeneous groups based on lake natural and disturbance factors. For crustaceans, the depth of the euphotic zone, the sampling depth (epilimnion, metalimnion and hypolimnion), time (day or night) of sampling and the biomass of chlorophyll a were the main driving factors. For Daphnia species, the drainage area, the sampling depth, the cleared land surface area within the catchment and the concentration of total dissolved phosphorus were the main factors.     

Crustacean biodiversity as an important factor for mosquito larval control

Newly established ponds, which are highly dynamic systems with changing levels of biological interactions among species, are common larval mosquito habitats. We investigated the impact of crustacean abundance and taxa diversity on mosquito oviposition and larval development. The effects of the biological larvicide Bacillus thuringiensis israelensis (Bti) on mosquito larvae were monitored according to fluctuations in crustacean communities. Populations of the mosquito Culex pipiens colonized artificial ponds that contained crustacean communities at different time points of colonization by crustaceans: 1) ‘no colonization’ (no crustaceans), 2) ‘simultaneous colonization’ by crustaceans and mosquitoes, and 3) ‘head‐start colonization’ by crustaceans (preceding colonization by mosquitoes). All types of ponds were treated with three concentrations of Bti (10, 100, or 1,000 µg/liter). Colonization of all ponds by Cx. pipiens (in terms of oviposition, larval abundance, and larval development) decreased significantly with increasing diversity of crustacean taxa. The total abundance of crustaceans had a minor effect on colonization by Cx. pipiens. The presence of crustaceans increased the sensitivity of Cx. pipiens larvae to Bti treatment by a factor of 10 and delayed the time of recolonization. This effect of Bti was relevant in the short term. In the long term, the presence of Cx. pipiens was determined by crustacean biodiversity.     

Morphological development of the swim bladder in hatchery-reared striped trumpeter Latris lineata

This study examined swim bladder morphogenesis in three cohorts of striped trumpeter (Latris lineata), a euphysoclist species with physostomous larvae. The swim bladder was first discernible 1–2 days after hatching as an evagination on the dorsal surface of the incipient digestive tract. It comprised a cluster of mesenchymal cells surrounding an inner primordium of epithelial cells. At mouth opening in larvae of 5.3 mm standard length (SL), the swim bladder was noticeably enlarged. Histologically, the swim bladder lumen was dilated and liquid filled. The pneumatic duct was first seen during the dilation stage and the rete mirabile began forming among the connective tissue surrounding the swim bladder. Initial swim bladder inflation occurred on day 11 post‐hatching in Cohort 1, at 14°C, and day 9 post‐hatching, in Cohorts 2 and 3, at 16°C. Histologically, the lumens of inflated swim bladders were ellipsoid and the epithelium was squamous, except for cuboidal gas gland cells at the anterio‐ventral and anterio‐lateral regions of the swim bladder. During the initial inflation interval the pneumatic duct was dilated in larvae both with and without swim bladder inflation. The pneumatic duct began to regress in some larvae over 7.5 mm SL. The swim bladder of striped trumpeter was similar to larvae of other altricial perciform marine fish in respect to organ derivation, tissue differentiation, luminal dilation and initial gaseous inflation. However, variations, particularly the delay in initial swim bladder inflation until after the start of feeding, were observed that could be fundamental to problems encountered during larval rearing.     

A new,interstitial species of <Emphasis Type="Italic">Terrestricythere</Emphasis> (Crustacea: Ostracoda) and its microdistribution at Orito Beach,northeastern Sea of Japan

We describe Terrestricythere proboscidis sp. nov. from a littoral interstitial habitat at Orito Beach, Matsumae, southern Hokkaido, Japan, a site characterized by coarse sand with many pebbles. This is the fifth known species of the ostracod superfamily Terrestricytheroidea, the first interstitial species of the superfamily, and the first record of the superfamily from Japan. The new species is clearly distinguished from its four known congeners by its small carapace with a transversely flat ventral margin, and the seventh limb consisting of four podomeres; its hemipenis has a long, S-curved process. We also report here the habitat, microdistribution, and locomotory behavior of the new species. Quantitative sampling revealed that the species lives in an interstitial environment. T. proboscidis is euryhaline. Behavioral observations showed that T. proboscidis cannot swim, but uses its appendages to push itself among sediment grains. An analysis of variance showed temperature and grain size, as well as temperature-depth and temperature-grain size interactions, to be significant influences on variation in population density. Sediment moisture content is correlated with these variables and likely is a primary factor in this species’ microdistribution.     

Influences of host size and host species on theinfectivity and development of Heterorhabditismegidis (strain NLH-E87.3)

The infectivity, time to first emergence of infective juveniles (IJs), total number of IJs per insect and IJs body length of the entomopathogenic nematode Heterorhabditis megidis (strain NLH-E87.3) after development in larvae of two insect hosts, Galleria mellonella (greater wax moth) and Otiorhynchus sulcatus (vine weevil) was studied. At a dose of 30 IJs, larvae of G. mellonella show to be significantly more susceptible than O. sulcatus larvae. At a dose of one IJ, vine weevil larvae were more susceptible. The number of invading infective juveniles (IJs) increased with host size while the host mortality at a dose of one IJ decreased with the increase of host size. Time to first emergence was longer at a dose of one IJ per larva and increased with the increase of host size in both insect species. Reproduction of IJs differed between host species, host sizes and doses of nematodes. Generally, the IJs body size increased with an increasing host size. The longest infective juveniles were produced at the lowest IJ doses. Results are discussed in relation to the influence of different host species and their different sizes on the performance of H. megidis (strain NLH-E87.3) as a biological control agent.     

Larval development of the pedunculate barnacles Octolasmis angulata Aurivillius 1894 and Octolasmis cor Aurivillius 1892 (Cirripedia: Thoracica: Poecilasmatidae) from the gills of the mud crab,Scylla tranquebarica Fabricius, 1798

Detailed studies of larval development of Octolasmis angulata and Octolasmis cor are pivotal in understanding the larval morphological evolution as well as enhancing the functional ecology. Six planktotrophic naupliar stages and one non-feeding cyprid stage are documented in details for the first time for the two species of Octolasmis. Morphologically, the larvae of O. angulata and O. cor are similar in body size, setation patterns on the naupliar appendages, labrum, dorsal setae-pores, frontal horns, cyprid carapace, fronto-lateral gland pores, and lattice organs. Numbers of peculiarities were observed on the gnathobases of the antennae and mandible throughout the naupliar life-cycle. The setation pattern on the naupliar appendages are classified based on the segmentation on the naupliar appendages. The nauplius VI of both species undergoes a conspicuous change before metamorphosis into cyprid stage. The cyprid structures begin to form and modify beneath the naupliar body towards the end of stage VI. This study emphasises the importance of the pedunculate barnacle larval developmental studies not only to comprehend the larval morphological evolution but also to fill in the gaps in understanding the modification of the naupliar structures to adapt into the cyprid life-style.