Search

Start Over Coverage 60-70

2. Existují rasy?: nový pohled na fyzickou rozmanitost lidstva

Creator:
Salzmann, Zdeněk
Format:
print
Type:
model:internalpart and TEXT
Language:
Czech
Description:
The traditional terms „race“ and „racial group (type)“, referring to a division of humankind possessing a combination of physical traits that characterize it as a distinet human type, are no longer usable. Even in the past, the concept of race was far from unambiguous: Darwin gave examples of' classifications of' humans that ranged from two to sixty-three different varieties. The modern view of the concept of race recognizes that mass migrations as well as mixed marriages have occurred so frequently during the last several centuries that the so-called races are for the most part no longer definably distinet. Two approaches are now used to discuss human physical variety. One is clinal: a cline is a gradient of morphological or physiological change in a group of related organisms, usually along a line of geographical or environmental transition. For example, if one maps the distribution (presence or absence) of epicanthus or of the degree of skin pigmentation in the world's populations, one realizes that physical traits are not covariant. The second approach is to recognize that a breeding population has a noticeable frequency of' certain genes in comparison or contrast with other populations.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Experimental observations on the development of Anguillicola crassus (Nematoda: Dracunculoidea) in its definitive host, Anguilla anguilla (Pisces)

Creator:
Moravec, F., Di Cave, D., Orecchia, P., and Paggi, L.
Format:
print
Type:
model:internalpart and TEXT
Subject:
Nematoda, Anguillicola, eel, development, and definitive host
Language:
English
Description:
The development of the swimbladder nematode Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 in the definitive host (eels) was studied under experimental conditions. Small eels, Anguilla anguilla (L.) with body length 8-16 cm were infected by feeding them intermediate host copepods (Cyclops strenuus Fischer) harbouring third-stage larvae of this parasite. These experiments showed that, at 20-22° C, the development from the third-to the fourth-stage larvae lasted approximately three weeks, but some retarding third-stage larvae occurred in the wall of the host’s swimbladder or hyperparasitizing in the cuticle of adult nematodes as late as three months p.i. Young adults developed in the lumen of the swimbladder within approximately one month and noneinbryonated eggs first appeared in females 6-7 weeks p.i. The prepatent period was about three months and the patent period could be estimated to last no more than a month. Females degenerated soon after oviposition. The experiments confirmed that the size of mature A. crassus depends on the body size of its definitive host (eel).
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public