scholarly journals Embryonic Development of Eye Lens in Mosquito fish Gambusia affinis (Baird and Girard, 1853)

2007 ◽  
Vol 4 (4) ◽  
pp. 505-511
Author(s):  
Baghdad Science Journal
Keyword(s):  
Embryonic Development ◽  
Posterior Pole ◽  
Equatorial Region ◽  
Gambusia Affinis ◽  
Eye Lens ◽  
Anterior Pole ◽  
Posterior Edge ◽  
Terrestrial Vertebrates ◽  
Mosquito Fish ◽  
Lens Vesicle

The embryonic development of the Mosquito fish(Gambusia affinis) eye lens was investigated using light microscopy .The results indicated that the embryonic development of the lens does not correspond to that of the non spherical lenses of terrestrial vertebrates .This study showed that a very small cavity in the lens vesicle appears during development ,but it differs from that of the mammalian lens. The most important aspect in this study is that ,the posterior edge of the simple cuboidal epithelium which covers the anterior half of the surface of the lens is situated well beyond the equatorial region of the lens .As a result , the germinal and transitional zones became closer to the posterior pole rather than the anterior pole of the lens. This might be an important factor in causing the lens to be spherical rather than being biconvex.

Embryology of the teleost (Oncorhynchus mykiss) lens

1994 ◽  
Vol 72 (4) ◽  
pp. 689-701 ◽  
Author(s):  
J. A. West ◽  
J. G. Sivak ◽  
R. D. Moccia
Keyword(s):  
Rainbow Trout ◽  
Embryonic Development ◽  
Light Microscopy ◽  
Oncorhynchus Mykiss ◽  
Anterior Pole ◽  
Lens Development ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Lens Vesicle ◽  
Lens Placode

Embryological studies of the teleost lens have attracted little attention. The morphology of the rainbow trout (Oncorhynchus mykiss) lens during embryonic development was investigated using light microscopy. Results indicate that in general, the embryology of the rainbow trout lens proceeds much like that which has been described for other vertebrates. However, evidence in this study indicates that both layers of the lens placode invaginate, forming a lens pit, contradicting earlier descriptions of lens development in fishes. Furthermore, a hollow lens vesicle does not appear during development, as is typically described for the mammalian lens. Most importantly, the posterior limit of the anterior epithelium is situated well beyond the equator, three-quarters of the distance from the anterior pole of the lens. As a result, the germinative and transitional zones are located more posteriorly than traditionally described. The consequence of these features and their relevance to the shape of the lens are discussed.

Anterior Movement of the Crystalline Lens in the Process of Accommodation in Children

2007 ◽  
Vol 17 (4) ◽  
pp. 515-520 ◽  
Author(s):  
B.J. Kaluzny
Keyword(s):  
Refractive Error ◽  
Axial Length ◽  
Crystalline Lens ◽  
Posterior Pole ◽  
Anterior Pole ◽  
Forward Movement ◽  
Ophthalmic Examination ◽  
Lens Thickness ◽  
Lens Position ◽  
Refractive Status

Purpose To investigate changes of crystalline lens position during accommodation in children with emmetropia, myopia, and hyperopia. Methods A total of 188 children (372 eyes) from 4 to 19 years old (mean age 11.3±4.43) with cycloplegic refractive error within a range +9.00 D to −9.00 D were enrolled. After a general ophthalmic examination, ultrasound biometry was performed, with the eye at a maximal accommodative effort. Cycloplegia was induced by triple installation of 1% tropicamide drops and 30 minutes later the biometric examination was repeated. Results In emmetropic eyes in the process of accommodation, the anterior pole of the crystalline lens moved forward by 0.144±0.14 mm (p ≤ 0.001); the position of the posterior pole did not change. In myopic eyes, the anterior pole moved forward by 0.071±0.13 mm (p≤0.001) and the posterior pole moved backward by 0.039±0.10 mm (p=0.003). In hyperopic eyes, the whole lens translocated anteriorly: anterior pole moved forward by 0.242±0.16 mm (p≤ 0.001) and posterior pole moved forward by 0.036±0.09 mm (p≤0.001). Differences among emmetropia, myopia, and hyperopia were statistically significant. Forward movement of the posterior pole correlated with a low axial length of the eye, and also with plus refractive error and with a smaller accommodative increase of lens thickness. Conclusions In children, accommodative changes of the crystalline lens position depend on refractive status.

Induction of primitive streak and Hensen's node by the posterior marginal zone in the early chick embryo

Development ◽  
1998 ◽  
Vol 125 (17) ◽  
pp. 3521-3534 ◽  
Author(s):  
R.F. Bachvarova ◽  
I. Skromne ◽  
C.D. Stern
Keyword(s):  
Chick Embryo ◽  
Marginal Zone ◽  
Lower Layer ◽  
Primitive Streak ◽  
Normal Embryo ◽  
Anterior Pole ◽  
Posterior Edge ◽  
Amphibian Embryo ◽  
Midline Cells ◽  
Marginal Zones

In the preprimitive streak chick embryo, the search for a region capable of inducing the organizer, equivalent to the Nieuwkoop Center of the amphibian embryo, has focused on Koller's sickle, the hypoblast and the posterior marginal zone. However, no clear evidence for induction of an organizer without contribution from the inducing tissue has been provided for any of these structures. We have used DiI/DiO labeling to establish the fate of midline cells in and around Koller's sickle in the normal embryo. In the epiblast, the boundary between cells that contribute to the streak and those that do not lies at the posterior edge of Koller's sickle, except at stage X when it lies slightly more posteriorly in the epiblast. Hypoblast and endoblast (a second lower layer formed under the streak) have distinct origins in the lower layer, and goosecoid expression distinguishes between them. We then used anterior halves of chick prestreak embryos as recipients for grafts of quail posterior marginal zone; quail cells can be identified subsequently with a quail-specific antibody. Anterior halves alone usually formed a streak, most often from the posterior edge. Quail posterior marginal zones without Koller's sickle were grafted to the anterior side of anterior halves. These grafts were able to increase significantly the frequency of streaks arising from the anterior pole of stage X-XI anterior halves without contributing to the streak or node. Stage XII anterior halves no longer responded. A goosecoid-expressing hypoblast did not form under the induced streak, indicating that it is not required for streak formation. We conclude that the marginal zone posterior to Koller's sickle can induce a streak and node, without contributing cells to the induced streak.

Memoirs: The Early Embryonic Development of Rhodnius Prolixus (Hemiptera, Heteroptera)

1935 ◽  
Vol s2-78 (309) ◽  
pp. 71-90
Author(s):  
HELEN MELLANBY
Keyword(s):  
Relative Humidity ◽  
Embryonic Development ◽  
Early Development ◽  
Constant Temperature ◽  
Germ Cells ◽  
Rhodnius Prolixus ◽  
Posterior Pole ◽  
Early Embryonic Development ◽  
Temperature And Humidity ◽  
Cent Relative Humidity

1. Eggs of Rhodnius prolixus were incubated at constant temperature and humidity (21° C. and 90 per cent, relative humidity). Eighty-five per cent, was the lowest record of the controls hatched successfully under these conditions. 2. The processes of maturation and fertilization were not studied. 3. Cleavage begins 12-13 hours after incubation. At 25 hours there are 32 nuclei. Yolk-cells are derived from cleavage nuclei, and they multiply by mitosis up to 50 hours. Blastoderm formation is complete after 55-60 hours of incubation. 4. The ventral embryonic rudiment is similar to that of many other insects. As soon as it is formed, germ-cells are budded off at the posterior pole of the egg. 5. The first stage in blastokinesis is fully described. 6. The formation of the mesoderm is by invagination and overgrowth. 7. The endoderm arises from two proliferating areas situated anteriorly and posteriorly. 8. Numerous cells are given off into the yolk during the early development of the embryo. There they disintegrate.

Expression pattern ofBrachyuryin the molluscPatella vulgatasuggests a conserved role in the establishment of the AP axis in Bilateria

Development ◽  
2002 ◽  
Vol 129 (6) ◽  
pp. 1411-1421 ◽  
Author(s):  
Nicolas Lartillot ◽  
Olivier Lespinet ◽  
Michel Vervoort ◽  
André Adoutte
Keyword(s):  
Expression Pattern ◽  
Bilateral Symmetry ◽  
Growth Zone ◽  
Posterior Pole ◽  
Axis Formation ◽  
Posterior Edge ◽  
Cell Stage ◽  
Posterior Growth Zone ◽  
Erk Activity ◽  
Anterior Posterior

We report the characterisation of a Brachyury ortholog (PvuBra) in the marine gastropod Patella vulgata. In this mollusc, the embryo displays an equal cleavage pattern until the 32-cell stage. There, an inductive event takes place that sets up the bilateral symmetry, by specifying one of the four initially equipotent vegetal macromeres as the posterior pole of all subsequent morphogenesis. This macromere, usually designated as 3D, will subsequently act as an organiser. We show that 3D expresses PvuBra as soon as its fate is determined. As reported for another mollusc (J. D. Lambert and L. M. Nagy (2001) Development128, 45-56), we found that 3D determination and activity also involve the activation of the MAP kinase ERK, and we further show that PvuBra expression in 3D requires ERK activity. PvuBra expression then rapidly spreads to neighbouring cells that cleave in a bilateral fashion and whose progeny will constitute the posterior edge of the blastopore during gastrulation, suggesting a role for PvuBra in regulating cell movements and cleavage morphology in Patella. Until the completion of gastrulation, PvuBra expression is maintained at the posterior pole, and along the developing anterior-posterior axis. Comparing this expression pattern with what is known in other Bilateria, we advocate that Brachyury might have a conserved role in the regulation of anterior-posterior patterning among Bilateria, through the maintenance of a posterior growth zone, suggesting that a teloblastic mode of axis formation might be ancestral to the Bilateria.

Instability of the anteroposterior axis in spontaneous double abdomen (sda), a genetic variant of Chironomus samoensis (Diptera, Chironomidae)

Development ◽  
1987 ◽  
Vol 101 (3) ◽  
pp. 591-603 ◽  
Author(s):  
K.L. Kuhn ◽  
J. Percy ◽  
M. Laurel ◽  
K. Kalthoff
Keyword(s):  
Genetic Variant ◽  
Laboratory Strain ◽  
Posterior Pole ◽  
Mirror Image ◽  
Anterior Pole ◽  
Spontaneous Formation ◽  
Pole Cells ◽  
Anterior Segments ◽  
Egg Polarity

We have isolated a laboratory strain of Chironomus samoensis in which determination of the anteroposterior egg polarity is disturbed. Most conspicuous is the spontaneous formation of ‘double abdomen’ embryos where head and thorax are replaced by a mirror image of the abdomen. Such double abdomens are found in about half of the egg clusters in this strain, which we call the spontaneous double abdomen (sda) strain as opposed to the normal (N) strain. Also observed in the sda strain, although less frequently, are ‘double cephalon’ embryos showing a mirror-image duplication of cephalic segments in the absence of thorax and abdomen. Moreover, embryos from the sda strain tend to form cells at the anterior pole resembling the pole cells at the posterior pole. Reciprocal crossings between the sda and the N strain indicate that the sda trait is inherited maternally. Spontaneous double abdomen formation is correlated with signs of disturbed egg architecture, including extruded yolk and detached cells. Double cephalons can also be generated by centrifuging embryos from the N strain, whereas centrifugation of sda embryos produces mostly double abdomens. Double abdomen formation can be induced experimentally by anterior u.v. irradiation of embryos from either strain. The sda trait and u.v. irradiation act in a synergistic fashion. The data suggest that the sda trait may be caused by one or more genomic mutations interfering indirectly with the activity of anterior determinants, i.e. cytoplasmic RNP particles necessary for the development of anterior segments. The sda defects may be ascribed to alterations in cytoskeletal components involved in anchoring anterior determinants and segregating them into anterior blastoderm cells.

Salsuginus bermudae sp.n. (Monogenea: Ancyrocephalidae) from Fundulus bermudae Gunther and Gambusia affinis (Baird and Girard) in Bermuda

1987 ◽  
Vol 65 (7) ◽  
pp. 1847-1852 ◽  
Author(s):  
Thomas G. Rand ◽  
Michael Wiles
Keyword(s):  
Accessory Piece ◽  
Physicochemical Characteristics ◽  
Gambusia Affinis ◽  
Mosquito Fish ◽  
Isolating Mechanism

Salsuginus bermudae sp.n. is described from gills of mangrove minnow, Fundulus bermudae Gunther, and mosquito fish, Gambusia affinis (Baird and Girard), from Bermuda. It differs from S. angularis by its shorter ventral hamuli (20–23 versus 22–26 μm); from S. fundulus, S. spirae, and S. heterocliti by its shorter dorsal and ventral hamuli (17–21 versus 22–26, 22–26, 20–24 μm, respectively, for dorsal hamuli and 20–23 versus 23–29, 23–27, 25–28 μm, respectively, for ventral hamuli); from S. bahamianus by its longer ventral hamulus superficial root (6–10 versus 5–6 μm); and from S. umbraensis by its shorter dorsal hamuli and dorsal bar (17–21 versus 23–24 and 19–26 versus 30–31 μm, respectively). It is indistinguishable morphometrically from S. seculus, yet differentiable from other species of Salsuginus by its dorsal and ventral hamuli and by its accessory piece. Mangrove minnows may be distributed in separate populations in the various Bermudian lakes. Differences in accessory piece morphology allowed discrimination of two morphotypes isolated in separate small mangrove minnow populations from two lakes (Mangrove and Lover's) which have different physicochemical characteristics. A possible isolating mechanism is discussed.

Genotoxic effects of produced waters in mosquito fish (Gambusia affinis)

Ecotoxicology ◽  
2008 ◽  
Vol 18 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Ilaria Caliani ◽  
Serena Porcelloni ◽  
Gabriele Mori ◽  
Giada Frenzilli ◽  
Maria Ferraro ◽  
...  
Keyword(s):  
Gambusia Affinis ◽  
Genotoxic Effects ◽  
Mosquito Fish ◽  
Produced Waters
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