MORPHOLOGICAL BASIS FOR MATERNAL NUTRIENT PROVISION TO EMBRYOS IN THE VIVIPAROUS FISH Ataeniobius toweri ( TELEOSTEI : GOODEIDAE )

2021 ◽  
Author(s):  
Mari Carmen Uribe ◽  
Paola‐Ivonne Cerda‐Jardón ◽  
Daniel G. Blackburn
Keyword(s):  
Viviparous Fish ◽  
Morphological Basis

Morphological Basis of the Disparity Between Muscle Length and Sarcomere Length in the Myocardium

1973 ◽  
Vol 31 ◽  
pp. 422-423
Author(s):  
G.E. Adomian ◽  
L. Chuck ◽  
W.W. Pannley
Keyword(s):  
Cardiac Muscle ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Contractile Force ◽  
Direct Function ◽  
Morphological Basis ◽  
Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

Memoirs: Observation on the Breeding and Development of the viviparous fish, Heterandria formosa

1940 ◽  
Vol s2-81 (324) ◽  
pp. 479-520
Author(s):  
ELIZABETH A. FRASER ◽  
RACHEL M. RENTON
Keyword(s):  
Early Stage ◽  
Late Development ◽  
Head Region ◽  
Mature Ovum ◽  
Entire Area ◽  
Short Account ◽  
Viviparous Fish ◽  
Large Size ◽  
Noteworthy Feature ◽  
Heterandria Formosa

1. A short account is given of the breeding habits of Heterandria formosa in an aquarium. 2. The ovary and the mature ovum are briefly described, the noteworthy feature of the ripe ovum being the small quantity of yolk. 3. Degeneration of ova is found to be a common occurrence in unfertilized females, and to a less extent in those full of developing embryos. 4. The method for ensuring the fertilization of the egg within the follicle is portrayed. Over the area where the spermatozoa have entered the cells of the ovarian epithelium and those of the follicle form a solid plug which eventually disrupts to enable the fully developed embryo to escape into the cavity of the ovary. 5. It is characteristic of early development that the egg is encircled by a unilaminar ectoderm before there is any visible differentiation into endoderm and mesoderm. 6. Owing to the scarcity of yolk only a few periblast cells arise and no syncytial layer is formed. 7. The primitive-germ cells are visible at an early stage within the apparently undifferentiated mesendoderm cells. 8. A striking feature is the large size of the pericardium and its growth upwards as a pericardium hood which completely surrounds the head region of the embryo. Over the walls runs a network of blood-vessels from which the maternal capillaries become eventually separated by only an attenuated layer of protoplasm. Both respiration and nutrition are effected through the follicle. 9. A remarkable specialization is the development of a urinary bladder which expands into a thin-walled vesicle of enormous dimensions, finally occupying almost the entire area formerly filled by the pericardium and the yolk-granules. 10. The development of Heterandria is compared with that of other viviparous fishes. 11. The significance of the unusual features in early and late development is discussed and some comparisons are made with the conditions in higher vertebrates.

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