0000000000178416
AUTHOR
Rudolf Reinboth
Observations on a new species of Unicapsula (Myxosporida) in the fish Maena smaris (L.) by conventional and electronmicroscopy
A myxosporidian parasite believed to be congeneric with Unicapsula muscularis Davis (1924), type (and only) species of this genus, was found in the dorsal muscles of the fish Maena smaris (L.) at Banyuls-sur-Mer, France. The spores were tripartite, with corresponding components of the three parts differentially developed. One part consisted of a small shell valve overlying no more than a trace of sporoplasm but covering a polar apparatus with well-developed polar capsule. Each of the other two parts consisted of a long shell valve covering a large sporoplasm and a polar apparatus with only the rudiment of a polar capsule. Electron microscope pictures of the trophozoite showed evidence of pi…
Physiological problems of teleost ambisexuality
The normal occurrence of spontaneous sex inversion among teleosts is a recent item within current concepts on vertebrate reproductive physiology. Investigations on the subject are mostly descriptive and deal with morphological and behavioral aspects. The concept of social control of sex inversion has been received with great interest. However, research on physiological processes that take place inside a fish when it changes sex must be rated as fragmentary. Steroid hormones are supposed to play a major role in sex inversion. But a cause and effect relationship has not yet been established. More experimental studies on more types of ambisexual species are badly needed. Future work will show …
Material und Methode
Die Untersuchungen wurden an drei Species der Centrarchidengattung Lepomis durchgefuhrt. Lepomis cyanellus wurde in Kiesgruben in der Umgebung von Mainz gefangen. Lepomis gibbosus und L. macrochirus stammten aus Fischteichen in ihrer naturlichen Heimat in den US-Staaten New York und New Jersey. Alle Versuche an L. cyanellus wurden in Mainz, die Experimente an L. macrochirus und gibbosus in den USA durchgefuhrt. Der vollstandige Jahrescyclus konnte nur bei Lepomis cyanellus verfolgt werden.
The occurrence of serological H-Y antigen (Sxs antigen) in the diandric protogynous wrasse, Coris julis (L.) (Labridae, Teleostei)
Abstract The serological sex-specific (Sxs) antigen (previously called ‘H-Y antigen’) has been shown, in various vertebrate species ranging from fish to mammals, to be characteristic of the heterogametic sex. We studied a protogynous hermaphrodite, Coris julis , in order to examine whether the change of a female to a secondary male also involves a change in the Sxs-antigen phenotype. The (homogametic) females of this species were found to be Sxs negative, while both primary and secondary males were Sxs positive. This was true not only for gonads but also for nongo-nadal tissues. The administration of androgen to females is known to cause sex inversion in this species; we were able to demons…
Mikroskopisch-anatomische Untersuchungen nach experimentellen Eingriffen
Alle Untersuchungen bei Knochenfischen stimmen darin uberein, das Hypophysektomie zur Gonadenregression fuhrt. Testes und Ovarien verlieren nach der Hypophysektomie an Grose, die Spermatogenese wird auf dem Spermatogonien-stadium sistiert (Vivien, 1941; Matthews, 1939; Pickford, 1953a). Grosere Oocyten degenerieren, wahrend kleinere nicht uber ein bestimmtes Stadium hinaus zur Entwicklung kommen (Vivien, 1939a, b, 1941). Sekundare Geschlechtscharaktere werden reduziert oder nach Hypophysektomie nicht ausgebildet (Vivien, 1938, 1941; Pickford, 1953a, b). Substitutionstherapie fuhrte in der Mehrzahl der untersuchten Falle zumindest zur teilweise Wiederherstellung der Gonadenfunktion (vgl. Pic…
Mikroskopisch-anatomische Untersuchungen an unbehandelten Tieren
Wahrend sich bei Lepomis cyanellus der Jahrescyclus in monatlichen Untersuchungen verfolgen lies, konnten bei L. gibbosus und L. macrochirus nur in den Monaten September, Oktober, Dezember, April und Juni Stichproben gemacht werden. Bei allen drei untersuchten Species stimmt der deutlich jahreszeitlich bestimmte Aktivitatsrhythmus der Gonaden weitgehend uberein.
H-Y antigen in the teleost.
H-Y antigen, presumably the product of mammalian testis-determining genes, has been detected in three species of teleost fish, Xiphophorus maculatus, Haplochromis burtoni, and Oryzias latipes, and in hybrids of the genus Tilapia. In X. maculatus H-Y was most readily detected in YY males, suggesting that a genetic determinant of H-Y antigen expression may exist on the teleost Y-chromosome. Although H-Y was detected in males and not in females in each of the species that we studied, male heterogamety has not been firmly established for H. burtoni. Thus despite the extreme phlyogenetic conservation of H-Y genes and their association with the Y-chromosome, it remains open to question whether H-…
Can Sex Inversion Be Environmentally Induced?
Among teleosts simultaneous hermaphroditism and spontaneous sex inversion (either protogyny or protandry) occur in many families that inhabit tropical and subtropical marine waters. The tooth-carp Rivulus marmoratus is unique among these in being self-fertilizing. Most studies are descriptive work on gonad histology and reproductive behavior. Experimental investigations are scanty and do not yet provide fruitful ideas that might help to understand what is occurring in a fish when it changes sex. Behavioral observations and experiments led to the hypothesis that in certain coral reef fish sex inversion may be under social control. The term sex inversion requires closer examination in order t…
The Peculiarities of Gonad Transformation in Teleosts
In teleosts the problem of sex determination and sex differentiation is more puzzling than in other vertebrates. It is not known whether the intriguing variety in the conditions of sex results from the position of these fishes within the vertebrate pedigree. They represent the final products of actinopterygian evolution toward the end of the age of reptiles, that is late in the Jurassic era. However, with that evolutionary fact in mind it is more plausible that teleosts deviate in many ways from the pattern that we are used to attribute to vertebrates in general. The following features of sex differentiation are striking examples of teleost peculiarity: (1) In both sexes there is no morphol…