Gammarus Salinus - Einige Daten Über Den Umwelt-Einfluss Auf Wachstum, Häutungsfolge, Herzfrequenz Und Eientwicklungsdauer

Abstract

[Experimental data are presented on growth, molting frequency, rate of heart beat and incubation time, in Gamamrus salinus exposed to different temperature and salinity conditions. The specimens tested were members of a population living in a brackish water pond (Kleiner Kiel, Kiel, North Germany) or their F1-generation. At temperatures between 19.0° and 20.0°C and a salinity of 10‰, females attain sexual maturity (first oviposition) 20 to 30 days after hatching; their average length, measured in a straight line from tip of rostrum to base of telson, is then 7 to 8 mm (fig. 1, table I). Males reach maturity 1 or several weeks later. The molting frequency varies greatly with temperature (fig. 2, table III), the intervals being longer in males than in females. Females kept without a male show a progressive prolongation of the intervals beginning with the 3rd or 4th interval following isolation (table IV). Females kept together with males, in pairs, exhibit under constant conditions practically constant intervals, except for very old or sick individuals. No significant differences were obtained in the three salinity levels: 5‰, 10‰ and 30‰. The rate of heart beat (fig. 3) is roughly the same in adult females and males; no significant differences between individuals exposed to the different salinities were observed. Incubation time (number of days between oviposition and hatching) depends largely on the temperature (fig. 4, table V) ; the data available do not indicate significant differences at the three salinity levels. Exposed to an identical environment, G. salinus grows faster, molts at shorter intervals and exhibits a higher frequency of heart beat than does G. duebeni. Its eggs also develop in a shorter time., Experimental data are presented on growth, molting frequency, rate of heart beat and incubation time, in Gamamrus salinus exposed to different temperature and salinity conditions. The specimens tested were members of a population living in a brackish water pond (Kleiner Kiel, Kiel, North Germany) or their F1-generation. At temperatures between 19.0° and 20.0°C and a salinity of 10‰, females attain sexual maturity (first oviposition) 20 to 30 days after hatching; their average length, measured in a straight line from tip of rostrum to base of telson, is then 7 to 8 mm (fig. 1, table I). Males reach maturity 1 or several weeks later. The molting frequency varies greatly with temperature (fig. 2, table III), the intervals being longer in males than in females. Females kept without a male show a progressive prolongation of the intervals beginning with the 3rd or 4th interval following isolation (table IV). Females kept together with males, in pairs, exhibit under constant conditions practically constant intervals, except for very old or sick individuals. No significant differences were obtained in the three salinity levels: 5‰, 10‰ and 30‰. The rate of heart beat (fig. 3) is roughly the same in adult females and males; no significant differences between individuals exposed to the different salinities were observed. Incubation time (number of days between oviposition and hatching) depends largely on the temperature (fig. 4, table V) ; the data available do not indicate significant differences at the three salinity levels. Exposed to an identical environment, G. salinus grows faster, molts at shorter intervals and exhibits a higher frequency of heart beat than does G. duebeni. Its eggs also develop in a shorter time.]