Free-swimming Phase Research Articles

Monitoring weekly progress of front crawl swimmers using IMU-based performance evaluation goal metrics.

Technical evaluation of swimming performance is an essential factor in preparing elite swimmers for their competitions. Inertial measurement units (IMUs) have attracted much attention recently because they can provide coaches with a detailed analysis of swimmers’ performance during training. A coach can obtain a quantitative and objective evaluation from IMU. The purpose of this study was to validate the use of a new phase-based performance assessment with a single IMU worn on the sacrum during training sessions. Sixteen competitive swimmers performed five one-way front crawl trials at their maximum speed wearing an IMU on the sacrum. The coach recorded the lap time for each trial, as it remains the gold standard for swimmer’s performance in competition. The measurement was carried out once a week for 10 consecutive weeks to monitor the improvement in the swimmers’ performance. Meaningful progress was defined as a time decrease of at least 0.5 s over a 25 m lap. Using validated algorithms, we estimated five goal metrics from the IMU signals representing the swimmer’s performance in the swimming phases (wall push-off, glide, stroke preparation, free-swimming) and in the entire lap. The results showed that the goal metrics for free-swimming phase and the entire lap predicted the swimmer’s progress well (e.g., accuracy, precision, sensitivity, and specificity of 0.91, 0.89, 0.94, and 0.95 for the lap goal metric, respectively). As the goal metrics for initial phases (wall push-off, glide, stroke preparation) achieved high precision and specificity (≥0.79) in progress detection, the coach can use them for swimmers with satisfactory free-swimming phase performance and make further improvements in initial phases. Changes in the values of the goal metrics have been shown to be correlated with changes in lap time when there is meaningful progress. The results of this study show that goal metrics provided by the phase-based performance evaluation with a single IMU can help monitoring swimming progress. Average velocity of the lap can replace traditional lap time measurement, while phase-based goal metrics provide more information about the swimmer’s performance in each phase. This evaluation can help the coach quantitatively monitor the swimmer’s performance and train them more efficiently.

Post-embryonic development of the Early Ordovician (ca. 480 Ma) trilobite Apatokephalus latilimbatus Peng, 1990 and the evolution of metamorphosis.

In many marine invertebrates metamorphosis entails a shift from a free-swimming larva to a benthic juvenile or adult. However, how the metamorphosis-entailing "indirect development" in arthropods arose from direct-developing ancestor is poorly understood. Trilobites left a rich fossil record, and some trilobite lineages had a metamorphosis-undergoing early developmental stage, termed the "asaphoid protaspis"-stage, providing a good opportunity to elucidate the rise of indirect development. Among others, the Ordovician representatives of Remopleuridioidea are known to possess a highly bulbous "asaphoid protaspis," while the Furongian (Late Cambrian) remopleuridioidean genus Haniwa did not possess it. Here we show the post-embryonic development of the remopleuridioidean trilobite, Apatokephalus latilimbatus, from the Tremadocian (485.4 Ma-477.7 Ma) Dongjeom Formation, Korea. The post-embryonic development of A. latilimbatus contains a free-swimming "commutavi protaspis" (a term replacing "asaphoid protaspis"). Interestingly, the earlier protaspid stage shows more similar morphology and size to the meraspis than the commutavi protaspid stage does. This indicates that the commutavi protaspid stage was intercalated into the ancestral direct development as a specialized stage for a better dispersal, and thus the "commutavi protaspis" of A. latilimbatus represents the initial phase of the evolution of indirect development. The duration of the free-swimming phase became longer in more derived remoplueridioidean trilobites, implying that the intercalated free-swimming strategy became emphasized during subsequent evolution. The morphological gap between the commutavi protaspis and the subsequent earliest meraspis provides a convincing case for the "selective independence" of developmental stages, explaining the various morphologies of commutavi protaspides in many trilobite lineages.

Cell division of Giardia intestinalis: Assembly and disassembly of the adhesive disc, and the cytokinesis

Trophozoites of Giardia are equipped with a special organelle of attachment, essential for parasite survival and pathogenicity, the ventral disc. Although its basic structure is well established, its reorganization and assembly during cell replication is poorly understood. We addressed some of these problems with aid of conventional, confocal and electron microscopy. We found that dividing Giardia alternates attached and free swimming phases in accordance with functional competence of the parent or newly assembled discs. The division started in attached cells by detachment of the disc microtubules from basal bodies. Shortening and eventual loss of the giardin microribbons, and unfolding of the microtubular layer resulting in collapse of the disc chamber and parasite detachment underlined gradual disassembly of the parent disc skeleton. Two daughter discs assembled on the dorsal side of the attached cell, with their ventral sides exposed on the parent cell surface and their microtubular skeletons growing in counter-clockwise direction. A depression between the assembling discs marked the cleavage plane. The splitting continued during the free-swimming phase with ventral-ventral axial symmetry in a plane of the daughter discs. Finally, the daughter cells with fully developed discs but still connected tail to tail by a cytoplasmic bridge, attached to a substrate and terminated the division by a process resembling adhesion-dependent cytokinesis. The mode of assembly of the daughter discs and plane of the division is compatible with maintenance of the left-right asymmetry of the Giardia cytoskeleton in progeny, which cannot be satisfactorily explained by alternative models proposed so far.

Energetics of larval swimming and metamorphosis in four species of Bugula (Bryozoa).

The amount of energy available to larvae during swimming, location of a suitable recruitment site, and metamorphosis influences the length of time they can spend in the plankton. Energetic parameters such as swimming speed, oxygen consumption during swimming and metamorphosis, and elemental carbon and nitrogen content were measured for larvae of four species of bryozoans, Bugula neritina, B. simplex, B. stolonifera, and B. turrita. The larvae of these species are aplanktotrophic with a short free-swimming phase ranging from less than one hour to a maximum of about 36 hours. There is about a fivefold difference in larval volume among the four species, which scales linearly with elemental carbon content and, presumably, with the amount of endogenous reserves available for swimming and metamorphosis. Mean larval swimming speeds (in centimeters per second) were similar among species. Specific metabolic rate and larval size were inversely related. For larvae of a given species, respiration rates remained similar for swimming and metamorphosis; however, because metamorphosis lasts about twice as long as a maximal larval swimming phase, it was more energetically demanding. Larger larvae expended more energy to complete metamorphosis than did smaller larvae, but in terms of the percentage of larval energy reserves consumed, swimming and metamorphosis were more "expensive" for smaller larvae. A comparison of the energy expended during larval swimming calculated on the basis of oxygen consumption and on the basis of elemental carbon decrease suggests that larvae of Bugula spp. may not use significant amounts of dissolved organic material (DOM) to supplement their endogenous energy reserves.

Distinct roles of an alternative sigma factor during both free-swimming and colonizing phases of the Vibrio cholerae pathogenic cycle.

Vibrio cholerae, the bacterium that causes cholera, has a pathogenic cycle consisting of a free-swimming phase outside its host, and a sessile virulent phase when colonizing the human small intestine. We have cloned the V. cholerae homologue of the rpoN gene (encoding sigma54) and determined its role in the cholera pathogenic cycle by constructing an rpoN null mutant. The V. cholerae rpoN mutant is non-motile; examination of this mutant by electron microscopy revealed that it lacks a flagellum. In addition to flagellar synthesis, sigma54 is involved in glutamine synthetase expression. Moreover, the rpoN mutant is defective for colonization in an infant mouse model of cholera. We present evidence that the colonization defect is distinct from the non-motile and Gln phenotypes of the rpoN mutant, implicating multiple and distinct roles of sigma54 during the V. cholerae pathogenic cycle. RNA polymerase containing sigma54 (sigma54-holoenzyme) has an absolute requirement for an activator protein to initiate transcription. We have identified three regulatory genes, flrABC (flagellar regulatory proteins ABC) that are additionally required for flagellar synthesis. The flrA and flrC gene products are sigma54-activators and form a flagellar transcription cascade. flrA and flrC mutants are also defective for colonization; this phenotype is probably independent of non-motility. An flrC constitutive mutation (M114-->I) was isolated that is independent of its cognate kinase FlrB. Expression of the constitutive FlrCM114-->I from the cholera toxin promoter resulted in a change in cell morphology, implicating involvement of FlrC in cell division. Thus, sigma54 holoenzyme, FlrA and FlrC transcribe genes for flagellar synthesis and possibly cell division during the free-swimming phase of the V. cholerae life cycle, and some as yet unidentified gene(s) that aid colonization within the host.

Effects of physical factors on larval behavior, settlement and recruitment of four tropical demosponges

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 138:169-180 (1996) - doi:10.3354/meps138169 Effects of physical factors on larval behavior, settlement and recruitment of four tropical demosponges Maldonado M, Young CM This study investigated the effects of light, water flow and water temperature on larvae and early juveniles of 4 shallow-water Caribbean demosponges, Tedania ignis, Haliclona tubifera, Sigmadocia caerulea and Halichondria magniconulosa. Larval release was not a synchronous event, either at the individual or population level in any of these species. Parenchymella larvae were photonegative during their whole life, but their swimming speed to escape from a light source varied with species and was related to the ratio of larval body length:flagellar tuft length. The presence of a water flow faster than the larval swimming speed had no effect on the settlement success of these 4 species in experimental flumes. Larvae of all 4 species preferred shaded sites at settlement in flumes. However, microhabitat irradiance in the field was correlated with abundances of adults only in 1 species, S. caerulea. The presence of water flow was positively associated with juvenile survivorship in the field only in the case of T. ignis. Water flow was also positively associated with the adult abundance of T. ignis, but negatively associated with the abundance of H. tubifera. Recruitment varied substantially among species, being extremely low in H. tubifera and H. magniconulosa. Larval activity and settlement of 2 species were strongly affected by abnormally low temperatures: swimming speed decreased, the free-swimming phase was dramatically shortened and recruitment was virtually inhibited. Low temperatures, therefore, potentially prevent larval dispersal and recruitment into cold waters and might restrict the geographic distribution of these species to tropical areas and warm shallow waters. Parenchymella larva . Photoresponse . Sponge settlement . Sponge recruitment Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 138. Publication date: July 25, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

A Cyphonautes Larva (Bryozoa: Gymnolaemata) from the Bellingshausen Sea, Antarctica

Bryozoans are an important component of the sessile, suspension-feeding fauna on the Antarctic continental shelf, (Knox & Cameron, 1970; Dell, 1972; Winston, 1983; Winston & Heimberg, 1988). Antarctic bryozoan faunas are systematically diverse, and display a broad range of colony morphotypes; they include fast-growing, short-lived species and long-lived perennials (Winston & Heimberg, 1988). Very little is presently known about the reproductive biology of Antarctic bryozoans, although it seems that a preponderance of species brood lecithotrophic larvae with a short, free-swimming phase. Planktotrophic larvae with a free-swimming phase of several weeks occur in a variety of gymnolaemate families, principally distributed in temperate coastal waters, and most often associated with specialized microhabitats or substrates. This type of larva, referred to as a cyphonautes (Zimmer & Woollacott, 1977), has not previously been reported from polar seas, and its occurrence in the Bellingshausen Sea, Antarctica, is thus of considerable interest.

Pelagic larval development in the brooding Antarctic brachiopod Liothyrella uva

Larvae of the Antarctic brachiopod Liothyrella uva (Broderip, 1833) were released by brooding females between 10 and 15 January 1992. They were collected and cultured for the ensuing 45 d. At release they were at the gastrula stage, and were recognisable as the usual brachiopod three-lobed larva from around 18 d after release. At ≃22 d post-release, larvae began to congregate under shell fragments placed in culture vessels as potential settlement substrata. However, the larvae showed no signs of settlement which, combined with the absence of many of the attributes of mature larvae seen in previous studies, was taken as evidence that these larvae had not reached fully competent stages. Previous work had shown that L. uva spawns in October, indicating that the developmental period lasts for a minimum of between 115 and 160 d. The release and subsequent development of larvae also shows that what was previously thought to be a brooding species combines a long brooding period with a free-swimming phase. If this is true of other brachiopod species, then there may need to be a recategorization of some species from brooding to combined brooding and free-swimming developmental types. Even though the development period in L. uva was likely to have been underestimated because a fully competent stage was not reached, a comparison with development rates for temperate species indicated a slowing of between 8 and 70 times. This dramatic slowing of development rate in brachiopods now joins similar data previously reported for echinoderms and nemerteans, suggesting that this is a very widespred, perhaps universal, attribute of Antarctic marine invertebrates.

Studies on the respiratory pigments of three species of serpulid polychaetes at different stages in the life cycle

Abstract Histochemical, histological and spectroscopic methods have been used to study the origins, distribution, spectral properties and functions ofthe blood pigments in various developmental stages of three closely related species of serpulid polychaetes. Histochemical reactions for the pigments, chlorocruorins in Spirorbis corallinae and S. spirorbis and haemoglobin in Janua pagensueheri, appear first in the unfertilised eggs as these mature in the ovary and body cavity. They occur initially around the animal pole but during cleavage and development of the free-swimming non-feeding larval stages are found increasingly in the endoderm. They become especially concentrated in the anterior walls ofthe differentiating stomach and granules giving these thermostable reactions are subsequently present at this site throughout life. The granules appear to be precursors ofthe soluble circulating blood pigments and it is concluded that the anterior stomach is a major haemopoietic organ. During the brief free-swimming phase the larvae develop prominent calcium-secreting glands in the peristomium, rich in acid and alkaline phosphatases, which at metamorphosis become the adult tube-forming glands. In the larval, settlement and early tube-building stages the glands contain large amounts of chlorocruorin or haemoglobin, identified spectroscopically as well as histochemically, but these disappear as the adult vascular system develops with its own pigmentladen plasma. Presence of the respiratory pigments throughout embryogenesis is probably linked to the brooding of the embryos in the adult tube (S. corallinae and S. spirorbis) or operculum (J. pagensuekeri) and their temporary occurrence in the tube-forming glands before development of the blood system equally has obvious functional significance. The pigments have well defined absorption bands in the visible spectrum whose peaks are in the range recorded for other serpulids; they react reversibly with oxygen and have a strong affinity for carbon monoxide. Treatment with CO causes clear shifts in absorption peaks but is not apparently harmful, treated worms continuing to feed, grow and reproduce. The shifts persist unchanged for at least 14 days but then progressively disappear; normal values, and reactivity with oxygen, are fully restored within a further 7 days.

Metamorphosis of the marine bryozoan Membranipora membranacea: An ultrastructural study of rapid morphogenetic movements.

The colonial marine bryozoan Membranipora membranacea produces a planktotrophic cyphonautes larva that is encased by a triangular bivalved shell. Following a relatively long free-swimming phase, the cyphonautes larva settles and undergoes a dramatic metamorphosis to become the sessile progenitor of the colony, referred to as the ancestrula. This paper examines the initial morphogenetic movements of metamorphosis that transform the cyphonautes larva into an incipient ancestrula. At the onset of metamorphosis, contractions of the striated median muscles situated along the anterior and posterior margins of the larva cause a retraction of the larval apical organ and a centripetal movement of the anterior and posterior ends of the larva. Concurrently, the ciliated corona at the base of the larva is pulled within the shell by contractions of the striated lateral muscles. As the larva assumes a more spherical shape, the posterior margins of the shell are spread apart, and the internal sac is everted. Eversion of the sac is apparently achieved by contractions of the lateral muscles that cause a buckling of the shell in the apical-basal direction. The neck region of the everted sac secretes adhesive granules that attach the larva to the substratum. Subsequently, contractions of the nonstriated sac muscles fold the valves of the shell over each other and draw the larva toward the substratum. The initial events of metamorphosis that culminate in the attachment and flattening of the larva are completed in 10-15 seconds. In the subsequent few minutes, the lateral edges of the everted sac fuse with the neighboring margins of the aboral epithelium underlying the shell and thus form the fully sealed body wall of the incipient ancestrula.

The systematics and ecology of a new genus of isopod (sphaeromatidae) from the west coast sandy beaches of India

A new genus and a new species of a psammobiotic, sphaeromatid isopod, Tholozodium ocellatum, is described from the west coast of India (Goa). It is found on fine sediment beaches (Mdo = 2·72-2·47) located in the vicinity of estuaries which receive large inputs of organic matter. The species is mainly distributed at the upper reaches of the beach and occurs in densities ranging from a few individuals to over 4700 m−2. The existing evidence indicates that this herbivorous/omnivorous species has a fossorial existence without the occurrence of a free-swimming phase and with little interaction with the rest of the fauna. Moreover T. ocellatum in common with some other platybranch genera does not fit into any of the sub-divisions of this group as proposed by Hansen (1905) . This suggests that with more information becoming available an extensive revision of this group of sphaeromatids is needed.

Mechanics of Escape Responses in Crayfish (Orconectes Virilis)

ABSTRACT Measurements of acceleration performance of crayfish (mean mass 0·018 kg) were made during lateral giant mediated tail flips (LG tail flips) and truncated tail flips at 15°C. The LG tail flip power stroke was composed of a lift-off phase, when crayfish accelerated vertically from the substrate, and a free swimming phase. The total duration of the power stroke was 44 ms, followed by a recovery stroke lasting 173 ms. Truncated tail flips were used in acceleration and swimming by crayfish free of the substrate. Power strokes had a mean duration of 36 ms, and recovery strokes 92 ms. Net velocities, acceleration rates, and distances travelled by the centre of mass were similar for both types of tail flips. Thrust was generated almost entirely by the uropods and telson. Velocities and angles of orientation to the horizontal of abdominal segments were similar for both types of tail flip. Angles of attack were large, varying from 30° to 90°. Pressure (drag) forces were considered negligible compared to inertial forces associated with the acceleration of added water mass. Thrust forces, energy and power were determined for exemplary tail flips. Thrust was 0·92 and 0·42 N for LG tail flip lift-off and swimming phases respectively, and 0·29 N for the swimming truncated tail flip. Rates of working were 0·39, 0·19, and 0·18 W respectively. The efficiency of converting muscle power to backward motion was estimated to be 0·5 for power strokes and o-68 for complete swimming cycles. Comparisons with fish performance suggested fish would be less efficient (0·1–0·2). The low efficiency is attributed to energy lost in lateral recoil movements.

Observations on thecate swarmers of Pyrocystis species in laboratory culture: Pyrocystis fusiformis Wyville Thomson ex Murray and Pyrocystis pseudonoctiluca Wyville Thomson ex Murray (Dinococcales)

Abstract Thecate swarmers of Pyrocystis fusiformis and P. pseudonoctiluca have been observed in laboratory cultures. At the time when inspections were made, during daylight hours, thecal development appeared to have been essentially complete. Release from the enclosing wall of the parent cell occurred in the early evening. The free-swimming phase was of short duration and was succeeded by ecdysis and rapid development of the extruded protoplast into the bladder-like vegetative form. A complete tabulation is presented here for P. fusiformis. Details of the thecal structure of this organism serve to clarify discrepancies in the literature concerning the armoured stages of both species. While the presence of thecate states remains a rare and, at present, unpredictable occurrence in the cultures of P. fusiformis and P. pseudonoctiluca maintained in this laboratory, their role in asexual reproduction appears to be similar to that of the more commonly observed athecate aplanospores.

Observations on some epibionts of gulf-weed, Sargassum natans (L.) Meyen

The succession of epibionts on gulf-weed, Sargassum natans (L.) Meyen, is described. Only the hydroid Clytia noliformis (McCrady) colonizes the newest algal growth, spreading rapidly from below towards the frond tips by means of stolons. The remaining species — the bryozoon Membranipora tuberculata (Bosc), the spirorbid Janua formosa (Bush) and the blue-green alga Calothrix crustacea Schousb. & Thurs. — establish themselves through a free-swimming phase but, instead of attaching near the meristem as is usual on other algae, the larvae and hormogonia (dispersal phase of Calothrix) settle well away from the growing tip of the Sargassum. Such behaviour is consistent with the view that tannins present in the young thallus inhibit the establishment of the surface microflora which is a pre-requisite for the settlement of larger epibionts. Janua shows a strong preference for the bladders of the Sargassum, and Calothrix for the leaflets; but Membranipora appears to settle equally well on bladders, leaflets, and stem. Observations on young colonies of Membranipora reveal that the metamorphosing larvae were orientated with respect to the axis of the Sargassum leaflets. Water flow, which has previously been considered as likely to provide a directional stimulus for such orientation, cannot be the operative factor in this case.