Effect of extenders and
osmotic pressure on storage of eggs of ornamental common carp Cyprinus
carpio at ambient and refrigerated temperatures
D.A.
Glenn, T.R. Tiersch-2002
Journal of the World Aquaculture Society, 33(3):
254-267 (from Current Contents)
Abstract :
The eggs of ornamental (koi) common carp Cyprinus
carpio were stored at ambient temperature (similar to 22-25°C) and at
refrigerated temperatures (0-20°C) in extenders at different osmolalities.
The treatments evaluated were dry (control), calcium-free Hanks' balanced
salt solution (C-F HBSS), salt (NaCl), synthetic ovarian fluid (SOF), and
Kurokura #2 (K2). In the first study, eggs were placed in extenders at
osmolalities ranging from 130 to 450 mOsmol/kg and were fertilized after 2
h. The percent-age of eyed embryos (our measure of fertilization capacity)
was calculated 24 h later, and percent hatching was calculated at 60 h.
Fertilization capacity of eggs suspended in C-F HBSS (28%) or SOF (37%) was
highest (P = 0.0001) at 250 mOsmol/kg, while eggs stored dry (control) had a
fertilization capacity of 24%. Fertilization capacity of eggs suspended in
NaCl (40%) or K2 (39%) was highest (P = 0.0001) at 200 mOsmol/kg. The
percent of eyed embryos and percent hatch were found to be positively
correlated (r = 0.9914). In the second study, eggs were stored in these
extenders with the most effective osmolality from the previous study to
evaluate percent eyed embryos and hatching over time. Samples of eggs were
fertilized at every hour for 7 h. Eggs in the extenders C-F HBSS and SOF
yielded the highest (P = 0.0001) percent eyed embryos during 7 h. Percent
hatch of these eggs was not significantly different (P = 0.1258) among
treatments at each time interval. Eggs stored in the extenders SOF, C-F
HBSS, and NaCl had higher fertilization capacity (P = 0.0271) at 7 h than
did the dry control. Eggs were also stored at refrigerated temperatures in
these four extenders at the most effective osmolalities from the first
study. A dry control (no extender) was also compared. The third study
compared quality of eggs stored for 0, 2, 4, or 6 h in each of the extenders
at 5°C or at ambient temperature (similar to 22-25°C). Eggs suspended in
C-F HBSS had significantly higher fertilization capacity at ambient
temperature over time than did eggs stored in NaCl, SOF, K2, or the dry
control. Eggs suspended in C-F HBSS and the dry control had significantly
higher fertilization capacity at 5°C over time than did eggs stored in
NaCl, SOF, or K2. Eggs held dry had higher hatch at ambient temperatures (P
= 0.0001) and at 5°C (P = 0.0002) over time than did eggs stored in any
extender. At 6 h, fertilization capacity with eggs in C-F HBSS or K2 was
higher than with NaCl, SOF, or the dry control. The fourth study used C-F
HBSS (250 mOsmol/kg) as the extender to evaluate fertilizing and hatching
ability during storage at temperatures 0, 5, 10, 15, 20, or 25°C. Eggs were
fertilized after 0, 1, 3, 6, 9, or 12 h of storage. Eggs stored at 15°C had
significantly higher fertilization capacity (P = 0.0001) than at any other
temperature. Eggs stored at 15°C and 10°C had significantly higher hatch
(P = 0.0001) than at any other temperature. Fertilization capacity at 12 h
was significantly higher in eggs stored at 10°C (33%) or 15°C (29%) than
at any other temperature. Storage of koi carp eggs in C-F HBSS at
refrigerated temperatures extended fertilizing ability for as long as 12 h
compared to storage in NaCl, SOF, K2, or the dry control.
(Louisiana State Univ; Aquaculture Res Stn; 2410 Ben
Hur Rd; Baton Rouge; LA 70820; USA, e-mail of T.R. Tiersch: ttiersch@agetr.lsu.edu)