Methodical aspects of rearing decapod larvae,Pagurus bernhardus (Paguridae) andCarcinus maenas (Portunidae)

Abstract

Improved methods for experimental rearing of Pagurus bernhardus and Carcinus maenas larvae are presented. Isolated maintenance was found essential for reliable statistical evaluation of results obtained from stages older than zoea-1. Only by isolated rearing is it possible to calculate mean values +_ 95 % confidence intervals of stage duration. Mean values (without confidence intervals) can only be given for group-reared larvae if mortality is zero. Compared to group rearing, isolated rearing led to better survival, shorter periods of development and stimulated growth. Due to different swimming behavior P. bemhardus zoeae needed larger water volumes than Carcinus maenas larvae. P. bernhardus zoeae were reared with best results when isolated in Petri dishes (ca. 50 mI). They fed on newly hatched brine shrimp nauplii (Artemia spp.). P. bernhardus megalopa did not require any gastropod shell or substratum; it developed best in glass vials without any food. C. maenas larvae could be reared most sucessfully in glass vials (ca 20 ml) under a simulated day-night regime (LD 16:8); constant darkness had a detrimental effect on development, leading to prolonged stage-duration times. C. maenas larvae were fed a mixture of newly hatched brine shrimp naupli and rotifers (Brachionus plicatilis).

On the morphology of the central nervous system in larval stages ofCarcinus maenas L. (Decapoda, Brachyura)

“…In the laboratory, animals were kept in a flow-through system, in natural seawater. Newly hatched larvae were immediately separated from the adults and individually reared in glass vials at a constant 18 ~ They were fed on a diet of brine shrimp nauphi, Artemia spp., and the rotifer, Brachionusplicatilis (Dawirs, 1982). This method allows an exact determination of the larval stage and age of the animals.…”

Experimental studies on the larval development of the shrimpsCrangon crangon andC. allmanni

“…In C. crangon it appears particularly strong, and it reflects minor differences in environmental conditions. Crowding effects, for example, often occurring in mass cultures may be observed in mortality and moulting rates (Table 1; for reviews see also Reeve, 1969;Odai et al, 1978;Emmerson & Andrews, 1981;Dawirs, 1982;Shumway et al, 1985). When these effects are weak however, they may only be found in larval morphogenesis (Table 2).…”

Development of larval culture techniques for the shore crab, Carcinus maenas (L)

“…Early efforts to culture C. maenas determined that Artemia nauplii were a suitable larval food source for the development of the zoeal and megalopa stages through to the first crab stage, provided there was inclusion of a smaller food source during development from zoeae stage I to zoeae stage II (Williams 1968). Consequently, Artemia nauplii have been the most commonly used diet for the culture of C. maenas larvae, either as the sole diet or supplemented with the rotifer Brachionus plicatilis (Dawirs 1982;Dawirs 1985;Mohamedeen and Hartnoll 1989;Harms et al 1994). Dawirs (1985) achieved a survival rate of 70% to the megalopa stage on just Artemia nauplii in individually reared larvae, and Dawirs (1982) achieved a similar survival rate on a diet of Artemia nauplii and rotifers (70%), whilst Mohamedeen and Hartnoll (1989) achieved a survival rate of approximately 90% using the same diet, also in individually reared larvae.…”

“…Consequently, Artemia nauplii have been the most commonly used diet for the culture of C. maenas larvae, either as the sole diet or supplemented with the rotifer Brachionus plicatilis (Dawirs 1982;Dawirs 1985;Mohamedeen and Hartnoll 1989;Harms et al 1994). Dawirs (1985) achieved a survival rate of 70% to the megalopa stage on just Artemia nauplii in individually reared larvae, and Dawirs (1982) achieved a similar survival rate on a diet of Artemia nauplii and rotifers (70%), whilst Mohamedeen and Hartnoll (1989) achieved a survival rate of approximately 90% using the same diet, also in individually reared larvae. The difference in survival between Mohamedeen and Hartnoll (1989) and Dawirs (1982) could be attributable to the rearing methods used; Mohamedeen and Hartnoll (1989) held larvae in a larger water volume that was increased as the larvae developed.…”

“…Larval culture techniques for larval C. maenas are well documented at the laboratory scale (Williams 1968;Dawirs 1982Dawirs , 1985Dawirs and Dietrich 1986;Mohamedeen and Hartnoll 1989;Harms et al 1994). However, many of these studies have been concerned with physiology and developmental biology and hence have focused on the culture of individual animals in isolation.…”