Early Swimming Research Articles

An opinion paper: emphasis on white muscle development and growth to improve farmed fish flesh quality

Due to rapid depletion of wild stocks, the necessity to cultivate fish is eminent. Current fish farming practices seek to improve flesh quality. The notion that white muscles are the main target of the fishing industry is emphasized. A novel approach is suggested based on the development of white muscles in wild fish from eggs to adults. A compilation of facts about white muscle structure, function and ontogeny is followed by an account of the changes in swimming behaviour and performance related to the use of white muscle during growth from larva to adult. Ecological data narrate early swimming performance with white muscle development and growth, unveiling some of the important natural selection factors eliminating weak swimmers and poor growers from the breeding stock. A comparison between fish culture practise and natural conditions reveals fundamental differences. New approaches following wild breeding processes promise several important advantages regarding the quality of white muscle.

Early swimming activity of hatchling flatback sea turtles Natator depressus: a test of the ‘predation risk’ hypothesis

Marine turtle hatchlings emerge from nests on oceanic beaches, crawl to the surf zone and migrate offshore. Predators in shallow water can take many hatchlings, but once the turtles reach deeper water, both encounters with predators and mortality rates probably decline. Behavioral stud- ies have demonstrated that hatchlings show changes in swimming activity as they migrate offshore. During the first 24 h of migration, most species swim continuously (the 'frenzy'), thereby minimizing their time in shallow waters; however, swimming activity later declines in duration and vigor, espe- cially at night (the 'postfrenzy'). One interpretation of these differences is that hatchling migratory behavior evolved in response to the threat of predators (the 'predation risk' hypothesis). To further test this hypothesis, we quantified the daily swimming activity shown by the flatback Natator depres- sus, the only marine turtle that lacks an oceanic phase in its development. Instead, the hatchlings remain in relatively shallow Australian (continental shelf) waters where they may frequently encounter predators. We speculated that because of these encounters, flatback hatchlings might have evolved activity patterns that show little, if any, decline during migration. Over 4 d of laboratory observations, flatback activity at night declined by <13%. Over the same time period, nocturnal activity declined by 60 to 95% (depending on species) in other marine turtles with an oceanic phase in their life history. Our data therefore support the hypothesis that predation played an important role in shaping the evolution of hatchling migratory behavior, although they do not provide direct evi- dence of a cause and effect relationship.

Early Swimming Clubs: A Question of Class

The early swimming clubs during the Victorian period met the varying needs of a range of different groups within society at the time. The groups associated with the different types of clubs include firstly the upper and middle classes. They needed to belong to leisure organisations that both met their requirements for sport or physical activity and also allowed them to meet other social needs in relation to their leisure being distinctive and maintaining their class position and separation from the lower classes. The second group contains two sub groups: the upper middle class managers or owners of factories and secondly the allied groups of those involved in the running of organisations aiming to attract large memberships such as churches. Both these groups sought leisure activity for their employees or members that served as an attraction and incentive to attendance and also that was likely to have positive outcomes in relation to education, health and general behaviour. The third group are the working class individuals who sought leisure activity that was inexpensive, easy to access, provided some form of entertainment and provided respite from the constant effort of work and the harsh living conditions that many of them endured.

Health risks of early swimming pool attendance

Swimming pool attendance and exposure to chlorination by-products showed adverse health effects on children. We assessed whether early swimming pool attendance, especially baby swimming, is related to higher rates of early infections and to the development of allergic diseases. In 2003-2005, 2192 children were analysed for the 6-year follow-up of a prospective birth cohort study. Data on early swimming pool attendance, other lifestyle factors and medical history were collected by parental-administered questionnaire. Bivariate and multivariate logistic regression analyses were used to evaluate associations. Babies who did not participate in baby swimming had lower rates of infection in the 1st year of life (i) diarrhoea: OR 0.68 CI 95% 0.54-0.85; (ii) otitis media: OR 0.81 CI 95% 0.62-1.05; (iii) airway infections: OR 0.85 CI 95% 0.67-1.09. No clear association could be found between late or non-swimmers and atopic dermatitis or hay fever until the age of 6 years, while higher rates of asthma were found (OR 2.15 95% CI 1.16-3.99), however, potentially due to reverse causation. The study indicates that, in terms of infections, baby swimming might not be as harmless as commonly thought. Further evidence is needed to make conclusions if the current regulations on chlorine in Germany might not protect swimming pool attendees from an increased risk of gastrointestinal infections. In terms of developing atopic diseases there is no verifiable detrimental effect of early swimming.

In memory of Volker Lehmann (10 December 1956 to 26 May 2006)

In memory of Volker Lehmann (10 December 1956 to 26 May 2006)

Patterns in Early Embryonic Motility: Effects of Size and Environmental Temperature on Vertical Velocities of Sinking and Swimming Echinoid Blastulae

Early embryonic swimming is widespread among marine invertebrates, but quantitative information about swimming behaviors is scarce. Swimming may affect encounters with predators, positioning in the water column, and nutrient absorption. Measured rates and patterns of swimming and sinking for blastulae of four eastern Pacific echinoid species show that sinking speeds equal or exceed swimming speeds. Swimming speed scaled negatively with embryo size, though sinking speed did not scale with size. Analysis of swimming paths of Strongylocentrotus franciscanus revealed a temperature dependency in swimming pattern that affected speed of upward movement. Sinking speeds were significantly greater at 10 degrees C than at 14 degrees C for blastulae of all four species examined. In Dendraster excentricus, killing the blastulae annulled this temperature effect, indicating an active density regulation by these embryos. Finally, measurements of particle velocities around sinking and swimming D. excentricus blastulae show that swimming creates a more localized disturbance than sinking. Embryonic swimming may therefore decrease rather than increase encounters with pelagic predators. Results from subsequent experiments in which embryos were reared in low-oxygen environments suggest that any oxygen-absorption advantages of swimming have little, if any, effect on the development of D. excentricus embryos.

Further characterization of genes expressed during Ciona intestinalis metamorphosis

Metamorphosis of ascidians is a dynamic event by which a nonfeeding, mobile tadpole larva is transformed into a filter-feeding, fixed juvenile. This process usually begins with the settlement of the larva and is followed by a series of coordinated morphogenetic movements that rearrange organs, tissues, and cells. To identify genes that are involved in the initiation of metamorphosis, we conducted differential screening between mRNAs of swimming larvae and those of juveniles in Ciona intestinalis. This screening permitted the isolation of cDNA clones for genes whose expression is upregulated during metamorphosis, and the characterization of four such genes ( Ci-meta3, Ci-meta4, Ci-meta5 and Ci-meta6) is reported here. Ci-meta3 encodes a protein with a domain found in Sp1a and the RYanodine receptor. This gene is not expressed in early swimming larvae but is expressed in the endoderm region and part of the retractile tail region in metamorphosing juveniles. The predicted proteins encoded by Ci-meta4, Ci-meta5 and Ci-meta6 do not contain any known consensus motifs, nor do they show any similarity to known proteins. Ci-meta4 and Ci-meta5 are expressed weakly in mesenchyme cells of the early larva and strongly in the metamorphosing juvenile, while Ci-meta6 is expressed in the mesenchyme in the late larva. In addition, we characterized 53 independent cDNA clones whose expression was downregulated during the period from early swimming larvae to metamorphosing juveniles by taking advantage of the Ciona intestinalis cDNA project database and BLAST searches. The expression patterns of some of these clones were changed during the larval period.

Evolution of Fast Development of Planktonic Embryos to Early Swimming

Planktonic embryos of marine animals swim at an early stage and age. Although natural selection has apparently favored rapid development of structures for swimming, taxa have not converged on the same, minimal time from first cell division to first swimming. Comparisons of 34 species with planktonic embryos in 10 phyla revealed factors that account for variation in time to swimming. Time to first swimming correlated significantly with time from first to second cleavage (first cell cycle) in analyses of all embryos sampled and separately within the Spiralia and Echinodermata. Time to first swimming also correlated significantly with egg diameter in some clades, but not in all. Correlations between egg diameter and cell cycle duration were low except for the three species of Urochordata. Development to a feeding or nonfeeding larva did not affect time to first swimming beyond effects attributable to egg size. Time to first swimming did not correlate with type of locomotion developed (uniciliated cells, multiciliated cells, or muscle). Nonetheless, differences in locomotion are associated with changes in cell cycle durations prior to swimming. The ratios of time to first swimming and time for first cell cycle suggests that allocation of time to multiplication of cells versus differentiation of cells is resolved differently in species with different types of locomotion.

Variability as a characteristic of immature motor systems: an electromyographic study of swimming in the newborn rat

Swimming behaviour was studied in neonate rats by carrying out electromyographic recordings. The study showed that the early swimming pattern was characterized by highly instable temporal parameters. A decrease was found to occur with age in the variability of the instantaneous period in each leg and in that of the antiphase pattern. Moreover, a dissociation occurred during development between the foreleg and the backleg activity. While patterns involving the forelegs always remained extremely instable, a considerable improvement was found to occur with time in the hindlimb activity.

Development of early swimming in Xenopus laevis embryos: Myotomal musculature, its innervation and activation

The development of the axial musculature, its innervation and early locomotion in Xenopus laevis embryos are described. Between stages 17 and 40 some 45 myotomes are formed on each side of the body. During this period the animals develop from non-motile to free swimming embryos. Using fluorescein-conjugated bungarotoxin the acquisition of acetylcholine receptor-sites was studied. At stage 25 (early flexure stage) bound bungarotoxin was confined to the first seven intermyotomal clefts, in free swimming embryos (stage 33) to the first 20 clefts. Application of horseradish peroxidase to the intermyotomal clefts in embryos ranging from stages 25 to 3738 revealed that primary motoneurons were usually situated 100–400 μ m, i.e. 0.5–1.5 myotomes, rostral to the cleft they innervated. The motor axons left the spinal cord at the caudal side of each spinal segment where Neural crest was present between the cord and the myotomes. At stage 25 ventral root activity could be recorded extracellularly from only the first three intermyotomal clefts, at stage 3233 from the first 16 clefts. The first spontaneous rhythmic swimming-like activity could be recorded around stage 28. Between stages 27 and 3233 the initial swimming frequency and the swimming episode duration increased at least three-fold. Comparable results were obtained with high-speed cinematography and measurements with a photelectric transducer. Between stages 17 and 40 the number of myotomes increased by 0.9 myotome/h, approximately 11.4 h later followed by the innervation of the myotomes at 0.7 cleft/h. About 3.6 h after this, ventral root activity appeared at the rate of 0.6 cleft/h. This study shows that the early swimming pattern generating neuronal network, located within the rostral spinal cord, reaches a state of “critical mass” around stage 27, at which the first rhythmic swimming activity occurs. At least 6–10 functional spinal segments and adjacent myotomes are required for early swimming.

Structural and functional properties of reticulospinal neurons in the early-swimming stage Xenopus embryo

This study presents direct evidence that in Xenopus laevis embryos ipsi- and contralaterally descending reticulospinal fibers from the caudal brain stem project to the spinal cord, where they directly contact primary motoneurons. At stage 30, occasional contacts between primary motoneurons and descending axons are present. These contacts are possibly already functional since presynaptic vesicles were sometimes observed. Furthermore, the physiological data obtained in this study suggest that reticulospinal neurons in the caudal brain stem are involved in the central generation of early swimming. The first ingrowth of reticulospinal axons was observed in the rostral spinal cord after application of HRP to the caudal brain stem of stage 27/28 embryos. By stage 32, many supraspinal axons could be found in the spinal cord at the level of the 12/13th myotome, near the time of the first rhythmic swimming. Both lamellipodial and varicose growth cones were found. Intracellular recordings from the brain stem and extracellular recordings from the myotomal muscles in curarized embryos around stage 30 revealed neurons in the caudal brain stem which were active during early fictive swimming. After intracellular staining with Lucifer yellow neurons with descending axons were found in the brain-stem reticular formation. These reticulospinal neurons showed "motoneuron-like" phasic activity, producing one spike each swimming cycle. Rhythmically occurring spikes with swimming periodicity were superimposed on a sustained depolarization level of some 5-30 mV. Reticulospinal neurons in the brain stem resemble descending interneurons in the spinal cord by their morphology, projection pattern, and activity during early swimming. Reticulospinal neurons and descending interneurons might therefore form one continuous population of projecting interneurons with a different location but a similar function. In support of this we propose that the embryonic brain-stem reticular formation forms part of the swimming pattern generator.

Neural cell adhesion molecule expression in Xenopus embryos

The spatiotemporal pattern of expression of the neural cell adhesion molecule NCAM was mapped immunohistochemically in embryos of the frog Xenopus, from blastula to early swimming stages, using a polyclonal antibody that recognizes Xenopus NCAM. The neural plate stage was the earliest at which NCAM could be detected. The initial sites of NCAM immunoreactivity were neural ectoderm, somitic mesoderm, and chordamesoderm. During formation of the neural tube, NCAM immunoreactivity became restricted to the neuroectoderm and its derivatives. During closure of the neural tube and for 2–4 hr thereafter, NCAM was expressed in a distinctive radial pattern in coronal sections of the neural tube. NCAM was observed in neural crest cells before migration and after formation of cranial and spinal ganglia. During the period of initial neurite outgrowth, NCAM became concentrated in the developing central nerve fiber pathways. NCAM was seen on peripheral nerves from the time of their initial outgrowth and it was strongly expressed at neuromuscular junctions during the period of their formation. These results show that NCAM is expressed after neural induction and functions during morphogenesis of the neural plate and tube, some neural crest derivatives, development of nerve fiber tracts, and formation of neuromuscular connections.

Early British Swimming 55 B.C.-A.D. 1719 With the First Swimming Treatise in English, 1595.Nicholas Orme

<i>Early British Swimming 55 B.C.-A.D. 1719 With the First Swimming Treatise in English, 1595.</i>Nicholas Orme

Cow-Pup Behaviour of the Weddell Seal, Leptonychotes Weddelli (Pinnipedia), in Mcmurdo Sound, Antarctica.

Study was of the behaviour of 9 marked female Weddell seals, Leptonychotes weddelli, and their young in a colony of 35 to 40 such pairs at Turtle Rock, McMurdo Sound, off Ross Island, Antarctica. The young sucked first about 80 min after birth. Sucking was usually initiated by the young seal, which had to raise its head to reach either of the 2 nipples. After sucking for 10 to 20 sec the young seal dropped down to the ice and waited for 1 to 2 min before sucking again. It was not clear whether the young seal had to rest after supporting itself or whether it had cleared the milk from the gland cistern and had to wait while milk from alveoli and ducts refilled the cistern. For young more than 1 week old there was a diurnal pattern of sucking with peaks between 1200 and 2359 h and least between 0300 and 0600 h. When the young began to swim they used more energy, stored less fat and sucked less. Early swimming, resulting in lower bodyweight at weaning, could affect survival during the following winter. Published values for bodyweight increments of growing seals are given. Young Weddell seals accumulate less fat than some species but learn to catch food before they are weaned.

Myogenesis in the trunk and leg during development of the tadpole of Xenopus laevis (Daudin 1802)

Xenopus embryos pass through five behavioural stages between the end of neurulation (stage 20) and the accomplishment of free swimming (stage 33). These are (I) non-motile (stage 20-22) when the myotome muscle begins to differentiate; (II) pre-motile (stage 22-24) when the first striated fibrils are visible and contractions are possible; (III) early flexure (stage 24-27) when reflex responses are given and peripheral nerves are present; (IV) early swimming (stage 28-33); and (V) free swimming (stage 32-46) when co-ordinated swimming is possible but the myotome muscles are still uninucleate. At the onset of metamorphosis (stage 48-50) the myotome muscle becomes multinucleate, possibly by fusion with satellite cells at the ends of the fibres, and has the appearance of adult skeletal muscle. The hind limb of Xenopus passes through similar behavioural stages but at a later stage in development: (i) non-motile (stage 48-52) when little differentiation of the limb-bud has occurred but nerves are present; (ii) pre-motile (stage 53-54) when the limb trembles and muscles are just beginning to acquire striated fibrils; (iii) motile (stage 55-58) when the limb can make stepping movements and the muscles are striated and multinucleate; and (iv) fully functional (stage 60-63) when the limbs are fully differentiated. Unlike the myotome muscle the limb muscle becomes multinucleate before striated myofibrils are assembled. By stage 60 myotome and limb muscle are similar in appearance except that the myotome muscle has larger fibres with fewer nuclei than the limb muscle. In Xenopus, myotome and limb muscle become multinucleate at more or less the same time in the development of the tadpole. In the myotome this is long after contractility and nervous control have appeared, in the limb it precedes the formation of striated fibrils and the ability to contract. It is suggested that the difference in development of the myotome and limb muscles with respect to the stage at which they become multinucleate may be due to some substance produced just before or during metamorphosis.

Multiple Forms of Deoxyribonucleic Acid-dependent Ribonucleic Acid Polymerase in Xenopus laevis: LEVELS OF ACTIVITY DURING OOCYTE AND EMBRYONIC DEVELOPMENT

Abstract The amounts of the various forms of RNA polymerase (Ia, Ib, IIa, IIb, and III) have been determined in oocytes, eggs, and embryos of Xenopus laevis. During oogenesis the relative proportions of the enzymes remain nearly constant, although the absolute levels of all forms increase dramatically. As a result, the mature oocyte, as well as the unfertilized egg, contains 4 to 5 orders of magnitude more RNA polymerase activity than is present in an individual somatic cell. Both oocytes and eggs contain unusually high levels of forms III and IIa in addition to forms I and IIb which predominate in somatic cells. The amounts and relative proportions of the five enzymes in the unfertilized egg remain about the same up to gastrulation of the embryo. During subsequent stages of embryogenesis the total amounts of forms I and IIb increase about 10-fold while the amounts of forms IIa and III increase only slightly. The rapid increase in cell number along with this selective increase in forms I and IIb during early development re-establishes the same relative and absolute enzyme levels per cell in the swimming embryo that are present in adult somatic cells. Anucleolate mutant embryos at the early swimming stage have the same amount of each enzyme as do control embryos. Furthermore the relative amounts of the various enzymes in purified nuclei are the same in anucleolate embryos as they are in control embryos. Chromatographic heterogeneity in enzyme I was found at all stages of oocyte maturation and throughout embryogenesis of control and anucleolate mutant embryos.

Resistance of differentiating neurons to the antimetabolite, amethopterin

Ambystoma embryos were immersed in a 0.005% amethopterin solution from open neurula to early swimming stages. The degree of neural degeneration was related to dosage, duration of experiment, specific structure concerned, or to all. Gross head deformities were first visible at stage 37. Brain and optic cups were seriously affected; spinal ganglia, otic vesicles, and nasal placodes much less so. Although mitotic activity was depressed by stage 29 and pycnotic degeneration within the brain and optic cup appeared by stage 33, the over-all shape and size of the neural tube were normal through stage 35. Subsequently the forebrain structures degenerated, but the medullary wall, though reduced in thickness, continued to parallel the normal in shape because of a sufficient residue of dividing and differentiating cells. Mauthner's and other large resistant neurons underwent an apparently normal nucleolar and Nissl-substance development until the late phases of the experiment. We interpret inhibition at this dosage to be due largely to some effect on RNA metabolism, perhaps at a level involving nucleolar function. Any repression of DNA metabolism that directly affects mitosis occurs relatively late, is partial, and may be bound to other effects involving RNA and protein synthesis. A possible sequestering of the drug over long exposures may result in intracellular concentrations that inhibit different levels of nucleic acid metabolism. The largest cells, such as Mauthner's neuron, with the greatest potential for production of nucleoprotein are most able to resist prolonged periods of exposure to amethopterin.

Synthesis and accumulation of low molecular weight RNA during embryogenesis of Xenopus laevis

An egg of Xenopus laevis contains about 1% of its total RNA as 4 s RNA and approximately 1.5 to 2% as 5 s RNA. All 5 s RNA is bound to ribosomes, whereas less than 10% of the 4 s RNA is associated with ribosomes. Although the content of 4 s RNA in the unfertilized egg is high for a single cell, it is low relative to the egg's content of ribosomal RNA representing less than one molecule of transfer RNA for each ribosome in the whole egg. Since the 4 s RNA which is made during oogenesis is as stable as ribosomal RNA, the high content of the latter relative to the former in the egg reflects the remarkably high synthetic rate of ribosomal RNA which occurs during oogenesis. During ovulation and early cleavage, when there is no detectable synthesis of 4 s RNA, terminal addition of CCA groups to transfer RNA takes place. New synthesis of 4 s RNA begins at the late blastula stage, after which the embryo doubles its content of 4 s RNA with each doubling of the cell number. By the time the embryo has developed to early swimming stage, about 15% of its total RNA is 4 s RNA. At each developmental stage, about 10% of the total 4 s RNA of the embryo is associated with ribosomes. In contrast to 4 s RNA, the amount of 5 s RNA per ribosome remains constant throughout early development, and there is no detectable synthesis of 5 s RNA at early stages. The synthesis of 5 s RNA may be coordinated with that of ribosomal RNA.

Rhythmicity in the early swimming of anuran larvae

ABSTRACT Observations were made upon two species of anurans, Xenopus laevis and Rana pipiens, of the early body movements and their modification after making sections through various levels of the central nervous system. Bursts of muscle contractions, effecting swimming, occur spontaneously and are identical to those evoked by tactile stimulation. Bursts are usually consistent in duration and occur at fairly regular intervals. In Rana they are generated by the spinal cord as well as by the hind-brain, but with a decreasing frequency at successively posterior levels. Early behavior in Xenopus is unchanged by removal of the forebrain and mid-brain, or by removal of the most anterior portion of the hind-brain. More extensive hind-brain removal alters the swimming pattern in most cases so that the bursts become either prolonged or abortive. Complete removal results in continual rather than periodic muscular activity. The early amphibian central nervous system is concluded to consist functionally of several excitatory and inhibitory rhythms acting upon an efferent mechanism which is capable of generating pulses at a constant mean frequency. Sensory input is held to alter briefly the net level of central excitation resulting from these endogenous rhythms.

The Effect of Exercise on Mortality of Animals Poisoned with Diphosgene

ConclusionsIt is clear that the worst that can be said of swimming shortly after diphosgene gassing at mid- or somewhat above mid-lethal doses is that it had no influence on final mortality among mice and rats or on survival time in dogs. There was, in fact, some indication, especially from the finding of a significant difference between survival of moderate early and late exercised mice, that moderate early swimming was beneficial or late swimming deleterious or both. It is striking that in all of the pooled data (see tables), and very often in individual experiments, differences noted, though not statistically significant, are consistently in the direction of increased survival for moderate early exercise in all 3 species, and in the direction of increased mortality for moderate or heavy late exercise in mice and heavy early exercise in dogs.The dog survival times and lung weights suggest that “moderate” and “heavy” exercise as distinguished in these experiments are physiologically as well as quantitati...