Egg development and lifecycle timing in the noble crayfish (Astacus astacus) (original) (raw)
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Turkish Journal of Fisheries and Aquatic Sciences, 2004
In this study, freshwater crayfish (Astacus leptodactylus, Esch, 1823) eggs were incubated starting seven weeks after spawning, at three different temperatures (11.8 ºC, 16±1ºC and 20±1 o C) and the results were compared with respect to hatching time and survival rate. The eggs hatched between days 116 and 125, 88 and 97, and 69 and 74, at 11.8 ºC, 16 ±1 ºC, and 20 ±1 o C, respectively. The survival rates at these temperatures were 22.4%, 46.9% and 32.5%. In conclusion, it was found that A. leptodactylus eggs could hatch 1.5 months earlier than under natural conditions by increasing water temperature, starting in March, up to 20 o C, but the optimum temperature for maximum hatching rate was found to be around 16 o C.
Reviews in Fish Biology and Fisheries, 2009
The development of artificial incubation techniques in astacid crayfish has attracted attention from scientists in many countries ever since the nineteenth century. It is only in the last few years that these techniques, along with studies on egg storage and transport, have provided reliable options for improving the reproductive phase in farming. The juveniles produced need to be reared until they reach a sufficient size both for restocking and for growing purposes. In view of the current level of knowledge of rearing juvenile astacids, two 80-day experiments were carried out under controlled conditions to compare the survival and growth of Stage 2 juvenile signal crayfish (Pacifastacus leniusculus) from two origins: maternal or artificial incubation. In the first experiment, three treatments were tested: juveniles from artificially incubated eggs with formaldehyde treatments, juveniles from maternal incubation and a mixture from both origins (50% each). Survival rates ranged from 87.8% to 93.3% with no significant differences among treatments. Crayfish from artificial incubation grew significantly faster (11.47 mm carapace length (CL), 373.80 mg weight) than crayfish from maternal incubation. In the second experiment, a bifactorial design included four treatments: the crayfish was derived from artificial or from maternal incubation and was fed once a day or twice a day. Final survival rates ranged from 68.89% to 77.78%, with no significant differences among treatments. Crayfish from artificial incubation grew significantly faster than crayfish from maternal incubation. The highest CL (14.54 mm) and weight (780.13 mg) were reached by the juveniles from artificial incubation that were fed once a day. No significant differences were found between the two feeding frequencies. Results showed that artificial incubation with formaldehyde treatments had no harmful effects and made it feasible to get a better performance from the juveniles obtained.
Aquaculture Research, 1998
One of the main limiting factors in the use of artificial incubation techniques on crayfish farms has been the widespread belief that eggs should be stripped from females in the late stages of embryogenesis. In order to disprove this idea, three different times for egg removal were tested in white-clawed crayfish, Austropotamobius pallipes (Lereboullet): (1) just before the gastrulation process (mean degree days ϭ 335, 34 days after spawning); (2) when the embryo was between the closing of the blastopore and the appearance of mandibular rudiments (mean degree days ϭ 524, 56 days after spawning); and (3) when the embryo had thoracic appendage rudiments (mean degree days ϭ 810, 92 days after spawning). The results showed that it is possible to attain acceptable survival rates up to juvenile stage 2 (51%), even when eggs have been detached at the earliest time (34 days after spawning), in such a way that artificial incubation is used for more than three-quarters (75.7%) of the total duration of the embryonic development. Factors such as the incubation device, water quality and incubation conditions have a major influence on the success of the process. Finally, a critical period was observed during the last stages of development in the present study, particularly between the eyed stage and juvenile stage 2, with mortality rates of between 26.7% and 56%.
Aquaculture, 1999
The development of artificial incubation techniques for freshwater crayfish eggs and the incorporation of these practices to the working scheme in production centres would have numerous advantages. This study evaluates the efficacy of one particular device, designed by this Ž. research group, for the artificial incubation of white-clawed crayfish Austropotamobius pallipes eggs. Comparisons between maternal and artificial incubation demonstrated the suitability of the tested system for artificial incubation for eggs of this species, during a period of 42% of the total duration of the embryonic development. Overall survival rate to juvenile stage 2 was significantly Ž. Ž. higher P-0.05 in artificially incubated eggs 68.2% compared with those attached to the Ž. maternal pleopods throughout the embryonic development 56.2%. It can be seen that artificial incubation provides, at least, similar results to those of maternal incubation. It was observed that most mortalities during artificial incubation were between eyed stage and juvenile stage 2.
Aquaculture, 1992
Carral, J.M., Celada, J.D., Gonzalez, J., Gaudioso, V.R., Femandez, R. and Lbpez-Baisdn, C., 1992.
Aquaculture and Fisheries Management, 1994
In artificial incubation (AI) of astacid species, which have a long embryonic development, eggs have to remain during long periods without maternal care and it is recommended to remove the dead ones. With the aim to test the effect on final stage 2 juvenile production of different removal frequencies, four treatments were tested: removal every 4 days, every 7 days, every 10 days and no removal. Using an egg density of 2.2 eggs/cm 2 , stage 2 juvenile production rate was significantly better (70.3%) with removal every four days than with less frequent removals. However there were not detected statistical differences between the control (no egg removal) and the other treatments. The relatively low incubation density (2.2 eggs/cm 2 ) could partially explain the general good results achieved, even when dead eggs were not removed.
Bulletin Français de la Pêche et de la Pisciculture, 2006
We comprehensively describe the fecundity and time of embryonic development of the spiny-cheek crayfish (Orconectes limosus). Linear relationships between female size and ovarian fecundity, pleopodal fecundity, and production of juveniles at the 3 rd stage, were confirmed. The ovarian fecundity was evaluated for the smallest as well as largest females in the sampled population (43-93 mm of body length); the number of oocytes (eggs) ranged widely, between 46 and 505. No significant difference was found between the ovarian and pleopodal fecundity observed just after egg laying. The value of the female gonadosomatic index just before laying was 4.2 ± 1.8% (0.8-7.7%). The mean diameter of eggs on female pleopods was 1.8 ± 0.2 mm (1.45-2.15 mm). A statistically significant difference was found between the numbers of eggs carried on individual pairs of pleopods. Mean time from laying to hatching was 46 ± 3.8 days (37-56 days), i.e. 647 ± 39.9 CTU (Celsius Temperature Units = degrees Celsius × days). Mean production of juveniles at the 3 rd stage was found to be 135.7 ± 67.24 (15-243) juveniles. The early sexual maturation and also high number of juveniles at the 3 rd stage per female gives this species a good predisposition for quick establishment in new localities.
Polish Journal of Natural Science, 2008
Wild living spawners of dace Leuciscus leuciscus (L.), ide L. idus (L.) and chub L. cephalus (L.), were obtained from rivers of central (the Pisa River basin) and northern (the Pasłęka River basin) Poland and next transported to a hatchery for artificial reproduction. The obtained eggs were dry fertilized and next incubated in water as different constant temperatures ranging from 4.5 to 29.0 o C. The hatched embryos were kept at the same temperatures until the moment of complete yolk sac resorption and later fed ad libitum on live nauplial Artemia sp. stages. The power function was applied for determination of the relation between the temperature and time until and achievement of each of the thirteen characteristic stages of embryonic development. It was shown that the pace of embryonic development increased with the temperature increase. In the majority of cases, at identical thermal conditions, both the incubation time and the pace of embryonic development were much less diversified among individual of the same species originating from different population than between the individual species. The obtained data finds application in optimization of early raring process and as a consequence will be an important tool in protection of endangered species.
Aquaculture International, 2009
In the present study, the effect of darkness on the timing of mating and pleopodal egg production in Astacus leptodactylus was investigated. Crayfish were exposed to three different light regimes: natural day light regime (control, mean 10.04-h light/13.96-h dark); 24-h dark (24 h D); 8-h light/16-h dark (8 L:16 D). Experiments were carried out between November 2006 and January 2007 with 36 males and 144 females. The results showed that darkness did not have an effect on the onset of mating and pleopodal egg production in the groups, but it did affect significantly the timing of individual matings; the higher percentage of ovigerous females in the darkness group at the first observation means that on average females under this condition mated and spawned earlier than in the other groups (P \ 0.01). The percentage of ovigerous females exposed to constant darkness in the first observation in which crayfish started to mate and spawn was 62.50. These figures for those exposed to 16 D:8 L and control were 43.75 and 37.50%, respectively. Therefore, it can be concluded that the reproduction efficiency (i.e., rate of ovigerous females) of A. leptodactylus can be enhanced under controlled conditions by exposing broodstock to constant darkness in their mating and spawning season. Keywords Freshwater crayfish Á Astacus leptodactylus Á Light Á Mating Á Pleopodal egg production Á Darkness This study is a part of Master Thesis of Tuba Ç AKMAK DURAN (FÜ BAP-Project No: 1324).