Ocular migration and the metamorphic and postmetamorphic maturation of the retinotectal system in Xenopus laevis: an autoradiographic and morphometric study

Development ◽  
1986 ◽  
Vol 92 (1) ◽  
pp. 43-69
Author(s):  
S. Grant ◽  
M. J. Keating
Keyword(s):  
Visual Field ◽  
The Body ◽  
Eye Position ◽  
Larval Life ◽  
Larval Stages ◽  
Cell Counts ◽  
Metamorphic Climax ◽  
Retinal Growth ◽  
The Asymmetry ◽  
Thymidine Autoradiography

The growth of the retina and tectum during larval life in Xenopus has previously been studied extensively. These two structures continue to grow in metamorphosing and postmetamorphic animals. During these later stages there are marked changes in eye position. We have used histogenetic and morphometric techniques to monitor retinal and tectal growth in Xenopus aged from stage 58 of larval life to ten years postmetamorphosis. The relative eye migration was quantified with optical techniques. An attempt has been made to relate modes of retinal growth to problems associated with changing interocular geometry. The predominant mode of growth during this period is hypertrophic, that is, it is due largely to an increase in size and complexity of existing elements, rather than the histogenetic creation of new elements. In the retina, however, tritiated thymidine autoradiography reveals that histogenesis does persist until at least six months after metamorphosis. The rate of histogenesis is much decreased compared with that of larval stages but, like that of larval stages, it takes place at the ciliary margin. It is asymmetrically distributed in the retina, most histogenesis occurring at the ventral retinal pole and very little at the dorsal retinal pole. Some histogenesis occurs at the nasal and temporal retinal poles. Thymidine autoradiography and cell counts indicated that little significant histogenesis occurs in the tectum after metamorphic climax. Two possible biological reasons for the asymmetry of retinal histogenesis have been examined. The first was the suggestion that the asymmetry was related to the emergence, during this period, of a binocular visual field secondary to the relative migration of the two eyes. It is shown that the asymmetric pattern of histogenesis is not closely related to those retinal areas that come to view binocular visual space. It was found, however, that the asymmetry of retinal growth from metamorphic climax was that required to stabilize retinal visual field positions with respect to body position. It is suggested that this minimizes the requirements for visuomotor readjustments that would otherwise be necessary to compensate for a situation in which eye position, relative to the body, is changing.

Factors involved in the development of ipsilateral retinothalamic projections in Xenopus laevis

Development ◽  
1981 ◽  
Vol 65 (1) ◽  
pp. 199-217
Author(s):  
C. Kennard
Keyword(s):  
Visual Field ◽  
Xenopus Laevis ◽  
Visual Information ◽  
Experimental Manipulation ◽  
Larval Life ◽  
Optic Chiasma ◽  
Larval Stages ◽  
Ipsilateral Projection ◽  
Terminal Degeneration ◽  
Selective Pattern

The extent, and the development, of the ipsilateral retinothalamic projection in the frog Xenopus laevis have been studied using terminal degeneration and autoradiographic techniques. This ipsilateral projection derives only from those retinal areas receiving visual information from the binocular portion of the visual field. In Xenopus, the ipsilateral retinothalamic projection arises from a larger area of the retina than was found to be the case in earlier studies on Rana. This correlates with the fact that Xenopus has a larger binocular visual field than does Rana. The ipsilateral retinothalamic projection is just detectable at about stage 56 of larval life, considerably later than its contralateral counterpart. Experimental manipulation of the developing eye vesicle at early larval stages followed by histological studies of the ipsilateral retinothalamic projections showed, however, that the retinal areas which give rise to this projection are determined by stage 32 of larval life. Further studies, in which monocular enucleation was performed at different larval stages with subsequent examination of the retinothalamic projections from the remaining eye, indicated that the selective pattern of decussation and non-decussation of retinothalamic fibres at the optic chiasma does not require interactions, at the chiasma, between optic fibres from the two eyes.

The growth of the harvest mite, Trombicula autumnalis Shaw

Parasitology ◽  
1951 ◽  
Vol 41 (3-4) ◽  
pp. 229-248 ◽  
Author(s):  
B. M. Jones
Keyword(s):  
Room Temperature ◽  
Pupal Stage ◽  
The Body ◽  
Larval Life ◽  
Laboratory Findings ◽  
Absolute Size ◽  
Nymphal Stage ◽  
Holometabolous Insect ◽  
Larval Stages ◽  
Food Reserves

1. Rearing. Larvae of Trombicula autumnalis were fed on young mice (about 8 days old); after 48 hr. at 25° C. they began dropping off fully engorged.The post-larval stages were reared individually in separate filter-paper cells. At room temperature, 100% R. H., the engorged larvae were actively mobile for about 6–12 days, and for 12–20 days at 30° C., 100% R.H., before entering a quiescent stage (the developing nymphal stage). The nymphs emerged after about 33 days at room temperature, and 25 days at 30° C., from the time the engorged larvae dropped off the host.Of the nymphs which developed to adults, four fed on a mixture of yeast, molasses, and agar plus chicken faeces; one fed upon the exuded contents of the eggs of Aëdes aegypti; and another fed upon a mixture of all the ingredients mentioned. Young and old nymphs of Trombicula autumnalis appeared to be incapable of feeding upon intact insects' eggs; neither did they show any particular predilection for the exuded contents of insects' eggs offered as a soft mass, and only with some difficulty were they made to introduce this food into the gut. When chicken faeces were offered as food the nymphs did not feed upon it.A method of ‘forced feeding’ was adopted, that is to say, nymphs were placed upon or guided on to the periphery of the food mass provided. When a nymph moved away it was replaced upon the food, and the process was repeated until the nymph showed signs of introducing the food into the gut. Occasionally a nymph after being placed upon the food remained in situ and fed continuously for about 6–8 hr. until completely engorged.2. The post-embryonic forms. The features of the stages (the larva nymph and adult), are described with respect to their development and growth.The transition, or developing stages (the pre-nymph and pre-adult), are closed systems which resemble the pupal stage of a holometabolous insect. The developing mite is enclosed by the cuticular remains of the preceding mobile stage, and a second inner or intermediate cuticle. Large flattened cells of epidermal origin are present, usually lying against the inner surface of the intermediate cuticle. Emergence of the nymph and adult depends upon the combined effects of an active secretion, which causes a disintegration of the intermediate cuticle, and muscular exertion.3.Dimorphism. Two kinds of dimorphism are shown during the growth of T. autumnalis; sexual dimorphism associated with size, and nymphal dimorphism depending on marked differences in body shape and in the length of the posterior setae.Both kinds of dimorphism are initiated at the beginning of post-larval life (beginning of nymphal development).The time which the engorged larva takes to settle is inversely proportional to the size of the post-larval stages; in other words, the amount of activity and accompanying usage of acquired food reserves before the engorged larva settles appear to govern the absolute size of the individual during post-larval life. There is an indication of small forms becoming male and larger ones female.Two types of nymph (referred to in this paper as α-type and β-type nymphs) were bred from out-wardly identical larvae. The differences in the growth of the body as a whole and the posterior setae, which distinguish the two types of nymph, appear to be of developmental origin.4. The life cycle in the natural environment. Laboratory findings confirm the view that only one generation is produced each year, but that successive broods are produced throughout the season of incidence.

scholarly journals Seasonal occurrence of some larval stages of endoparasites in three cyprinids from the Nwanedi-Luphephe dams, the Limpopo River System, South Africa

2015 ◽  
Vol 52 (3) ◽  
pp. 229-235 ◽  
Author(s):  
E. M. Mbokane ◽  
J. Theron ◽  
W. J. Luus-Powell
Keyword(s):  
Developmental Stages ◽  
River System ◽  
Intestinal Wall ◽  
The Body ◽  
Seasonal Occurrence ◽  
Seasonal Fluctuations ◽  
Metazoan Parasites ◽  
Larval Stages ◽  
Parasite Communities ◽  
Third Stage

Abstract This study provides information on seasonal occurrence of developmental stages of endoparasites infecting three cyprinids in the Nwanedi-Luphephe dams, Limpopo River System. Labeobarbus marequensis (Smith, 1841), Barbus trimaculatus Peters, 1852 and Barbus radiatus Peters, 1853 were investigated seasonally from January 2008 to October 2008. The following larvae of metazoan parasites were collected: Diplostomum sp. from the eyes of L. marequensis and B. trimaculatus; Ornithodiplostomum sp. from the gills of B. trimaculatus; Posthodiplostomum sp. from muscle, skin and fins of B. trimaculatus and B. radiatus; third-stage Contracaecum larvae (L3) from the mesentery fats and on the liver lobes of L. marequensis and B. trimaculatus and gryporynchid cestode larvae from the outer intestinal wall of B. radiatus. All the flukes encountered were metacercariae. Diplostomum sp. and Contracaecum sp. dominated the parasite communities. Their prevalence exhibited seasonal fluctuations with maxima in summer. Factors likely to influence fish infection such as the body size of fish and their condition factors were also briefly considered in this study.

Neurogenesis in the thoracic neuromeres of two crustaceans with different types of metamorphic development

1998 ◽  
Vol 201 (17) ◽  
pp. 2465-2479 ◽  
Author(s):  
S Harzsch ◽  
J Miller ◽  
J Benton ◽  
RR Dawirs ◽  
B Beltz
Keyword(s):  
Embryonic Development ◽  
Larval Development ◽  
Neuronal Development ◽  
Temporal Patterns ◽  
Homarus Americanus ◽  
Spider Crab ◽  
Larval Life ◽  
Larval Stages ◽  
Metamorphic Development ◽  
Embryonic And Larval Development

The mode of embryonic and larval development and the ethology of metamorphosis in the spider crab and the American lobster are very different, and we took advantage of this to compare neuronal development in the two species. The goals of this study were to discover whether the differences in the maturation of the neuromuscular system in the pereopods and the metamorphic changes of motor behavior between the two species are reflected at the level of the developing nervous system ('neurometamorphosis'). Furthermore, we wanted to broaden our understanding of the mechanisms that govern neuronal development in arthropods. Proliferation of neuronal stem cells in thoracic neuromeres 4-8 of the lobster Homarus americanus and the crab Hyas araneus was monitored over the course of embryonic and larval development using the in vivo incorporation of bromodeoxyuridine (BrdU). Neuropil structure was visualized using an antibody against Drosophila synapsin. While proliferation of neuronal precursors has ceased when embryogenesis is 80 % complete (E80%) in the lobster thoracic neuromeres, proliferation of neuroblasts in the crab persists throughout embryonic development and into larval life. The divergent temporal patterns of neurogenesis in the two crustacean species can be correlated with differences in larval life style and in the degree of maturation of the thoracic legs during metamorphic development. Several unusual aspects of neurogenesis reported here distinguish these crustaceans from other arthropods. Lobsters apparently lack a postembryonic period of proliferation in the thoracic neuromeres despite the metamorphic remodeling that takes place in the larval stages. In contrast, an increase in mitotic activity towards the end of embryonic development is found in crabs, and neuroblast proliferation persists throughout the process of hatching into the larval stages. In both E20% lobster embryos and mid-embryonic crabs, expression of engrailed was found in a corresponding set of neurons and putative glial cells at the posterior neuromere border, suggesting that these cells have acquired similar specific identities and might, therefore, be homologous. None of the BrdU-labeled neuroblasts (typically 6-8 per hemineuromere over a long period of embryogenesis) was positive for engrailed at this and subsequent stages. Our findings are discussed in relation to the spatial and temporal patterns of neurogenesis in insects.

scholarly journals Morphological development of larvae and juveniles of Prochilodus argenteus

2017 ◽  
Vol 47 (4) ◽  
Author(s):  
Irũ Menezes Guimarães ◽  
◽  
Vinícius Augusto Dias Filho ◽  
Ana Helena Gomes da Silva ◽  
Rafael Silva Santos ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Linear Regression Analysis ◽  
The Body ◽  
Morphological Development ◽  
Body Proportions ◽  
Juvenile Phase ◽  
Larval Stages ◽  
Larvae And Juveniles ◽  
Rate Of Increase ◽  
Environmental Importance

ABSTRACT: Prochilodus argenteus is an endemic fish species from the São Francisco River basin that is of high economic and environmental importance. The present study aimed to contribute with information to the taxonomic identification of larvae and juveniles of this species. Larvae , obtained from induced spawning of wild animals, were reared in ponds. Individuals were collected daily and classified into larval stages or juvenile phase. Morphological descriptions and morphometric measurements were performed, together with a piece wise linear regression analysis of the body proportions throughout the development process. Individuals in the preflexion stage had a standard length (SL) of 4.48 to 6.64mm, long to moderate body (BH/SL), small to moderate head (HL/SL), and a small to moderate eye (ED/HL). In the flexion stage, the SL varied from 6.60 to 11.00mm, long to moderate body, moderate head, and small to moderate eye. Larvae in the postflexion stage presented SL of 10.54-19.93mm, moderate body, moderate to big head and small eye. The juvenile phase included specimens with a SL of 18.27 to 42.21mm which presented a moderate to high body, big head and small to moderate eye. Regression analysis showed significant moments of change in rate of increase of the body proportions, presenting a change in the growth pattern from allometry to isometry during the early development.

scholarly journals Observations on the predatory potential of Lutzia fuscana on Aedes aegypti larvae: implications for biological control (Diptera: Culicidae)

2016 ◽  
Vol 48 (2) ◽  
pp. 137
Author(s):  
Soujita Pramanik ◽  
Sampa Banerjee ◽  
Soumyajit Banerjee ◽  
Goutam K. Saha ◽  
Gautam Aditya
Keyword(s):  
Biological Control ◽  
Aedes Aegypti ◽  
Biological Control Agent ◽  
Instar Larva ◽  
Control Agent ◽  
The Body ◽  
Larval Habitats ◽  
Larval Stages ◽  
Augmentative Release ◽  
Predatory Potential

Among the natural predators, larval stages of the mosquito <em>Lutzia fuscana (</em>Wiedemann, 1820) (Diptera: Culicidae) bear potential as a biological control agent of mosquitoes. An estimation of the predatory potential of the larva of <em>L. fuscana</em> against the larva of the dengue vector <em>Aedes aegypti</em> (Linnaeus, 1762) (Diptera: Culicidae) was made to highlight its use in vector management. Laboratory experiments revealed that the larva of<em> L</em>. <em>fuscana</em> consumes 19 to 24 <em>A. aegypti</em> larvae per day, during its tenure as IV instar larva. The consumption of <em>A. aegypti</em> larvae was proportionate to the body length (BL) and body weight (BW) of the predatory larva<em> L. fuscana</em> as depicted through the logistic regressions: y = 1 / (1 + exp(-(-2.09 + 0.35*BL))) and y = 1 / (1 + exp(-(0.4+ 0.06*BW))). While the prey consumption remained comparable among the days, the net weight gained by the <em>L</em>. <em>fuscana</em> larva showed a decreasing trend with the age. On the basis of the results, it is apparent that the larva of the mosquito <em>L. fuscana</em> can be used in the regulation of the mosquito <em>A. aegypti</em> through augmentative release, particularly, in the smaller mosquito larval habitats.

Morphological descriptions of the egg and larval stages of Trichuris suis Schrank, 1788

Parasitology ◽  
1973 ◽  
Vol 67 (3) ◽  
pp. 263-278 ◽  
Author(s):  
R. J. S. Beer
Keyword(s):  
Reproductive System ◽  
Intestinal Tract ◽  
Vas Deferens ◽  
Ejaculatory Duct ◽  
The Body ◽  
Vitelline Membrane ◽  
Initial Development ◽  
Larval Stages ◽  
Trichuris Suis ◽  
System L

The egg and larval stages of Trichuris suis can be briefly characterized as follows: The egg: barrel shaped, possesses a thick shell consisting of three thick outer layers and an inner thin vitelline membrane, is operculate at each end and is unsegmented and unfertilized when freshly deposited. L. 1 within the egg: presence of an oral spear, a poorly denned oesophagus and an intestinal tract consisting of undifferentiated granulated material. L. 1 within the host: initial differentiation of an oesophagus, cell body, intestine and rectum. L. 2: further differentiation of the body organs and the appearance of the rudiments of the reproductive system. L. 3: initial development of reproductive system and development of a cloaca in the male thus distinguishing the sexes. L. 4: differentiation of reproductive system into vagina, uterus, oviduct and ovary in the female, and testis, vas deferens, ejaculatory duct, spicule and spicular muscle, sheath and tube in the male. L. 5 or adult stage: completed development of the sexual organs including formation of the vulval orifice and eggs in the female and seminal vesicle in the male.

scholarly journals Sign language experience redistributes attentional resources to the inferior visual field

2019 ◽  
Author(s):  
Chloé Stoll ◽  
Matthew William Geoffrey Dye
Keyword(s):  
Visual Field ◽  
Visual Attention ◽  
Visual System ◽  
Visual Fields ◽  
The Body ◽  
Language Experience ◽  
Bayesian Hierarchical ◽  
Signed Languages ◽  
Covert Visual Attention ◽  
Deaf Signers

While a substantial body of work has suggested that deafness brings about an increased allocation of visual attention to the periphery there has been much less work on how using a signed language may also influence this attentional allocation. Signed languages are visual-gestural and produced using the body and perceived via the human visual system. Signers fixate upon the face of interlocutors and do not directly look at the hands moving in the inferior visual field. It is therefore reasonable to predict that signed languages require a redistribution of covert visual attention to the inferior visual field. Here we report a prospective and statistically powered assessment of the spatial distribution of attention to inferior and superior visual fields in signers – both deaf and hearing – in a visual search task. Using a Bayesian Hierarchical Drift Diffusion Model, we estimated decision making parameters for the superior and inferior visual field in deaf signers, hearing signers and hearing non-signers. Results indicated a greater attentional redistribution toward the inferior visual field in adult signers (both deaf and hearing) than in hearing sign-naïve adults. The effect was smaller for hearing signers than for deaf signers, suggestive of either a role for extent of exposure or greater plasticity of the visual system in the deaf. The data provide support for a process by which the demands of linguistic processing can influence the human attentional system.

scholarly journals Larval form of the genus Thubunaea Seurat, 1914 from the body cavity of an insect, Supella sp., at Meerut (U.P.), India

2011 ◽  
Vol 3 (1) ◽  
pp. 54-57
Author(s):  
H.S. Singh ◽  
Malti Malti ◽  
Anshu Chaudhary
Keyword(s):  
Body Cavity ◽  
The Body ◽  
Present Communication ◽  
Larval Form ◽  
Larval Stages

The present communication deals with a larval nematode belonging to the genus Thubunaea Seurat, 1914, from the body cavity of an insect, Supella sp., at Meerut, U.P. Both encysted and free larval stages were recovered. Morphology of the larvae is described in detail.

Optokinetic Memory in the Crab, Carcinus

1966 ◽  
Vol 44 (2) ◽  
pp. 233-245
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Visual Feedback ◽  
Opposite Direction ◽  
Feedback Loop ◽  
Closed Loop ◽  
Dark Period ◽  
Eye Position ◽  
Movement Perception ◽  
Memory Experiment

1. A crab is held at the centre of an illuminated stationary striped drum or any visual field with strong contrasts. After a time all lights are turned off and the drum is moved in the dark. The light is restored when the drum is stationary in its new position. The animal responds by a movement of the eyes. 2. Stimuli of 0.5° over a dark period of 2 min. or 1° over 15 min. give a response. The response depends on the angle of the drum movement, and is slower in performance and less in total amount for longer periods of darkness. 3. On re-illumination the movement of the eye relative to the stationary drum is such that the visual field moves across the eye in the opposite direction to the eye's movement, but nevertheless the perception of small drum oscillations is not impaired. 4. When the visual feedback loop is opened by clamping the seeing eye and painting over the moving one, eye movements can be greater than drum movements, as in movement perception. Comparison of calculated with experimental closed-loop conditions shows that in the memory experiment there is no attenuation or amplification in the visual feedback loop. 5. Perception of very slow movements and stabilization of eye position could, but do not necessarily, depend on this accurate but short-lived directional memory.

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