1063-0740/05/3106- © 2005 Pleiades Publishing, Inc.
Russian Journal of Marine Biology, Vol. 31, No. 6, 2005, pp. 352–358.
Original Russian Text Copyright © 2005 by Biologiya Morya, Timofeev.
The size of animal eggs is an important index widely
used in ecological and evolutional studies, while in the
theory of life cycles, this is one of the basic parameters
. To date, the dynamics of eggs size in crustaceans
in the process of embryogenesis has been studied in
detail; interspecies and intraspecies differences have
been analyzed, as well as latitudinal trends and trends
stemming from gradients in environmental factors, etc.
Euphausiaceans have received much less attention in
this respect, which is due, primarily, to difﬁculties in
species identiﬁcation of eggs, whose development in
most species of Euphausiacea occurs in the water col-
umn, without any connection with the parental organ-
ism. A few papers dealing with the size characteristics
of euphausiacean eggs have solved the problem of species
identiﬁcation of the eggs [11, 15]. The one exception is
; but for this species a comparative
analysis of egg size from different parts of its geographical
range has been performed and the rate of embryonic mor-
tality was estimated [12, 18, 21, 22, 40, 41].
In the Barents Sea, two species occur in large quan-
Both species are neritic,
but the former one prefers coastal areas, bays, bights,
and seamounts, whereas the latter displays a more
“oceanic” distribution pattern and the localization of its
aggregations in the sea depends, to a certain degree, on
the advection of Atlantic waters . In this connection,
it is of interest to perform a comparative analysis of egg
from populations hundreds and thou-
sands of kilometers away from each other.
In this project, we studied the egg sizes of
from samples collected in different areas of the Barents
and Norwegian seas, i.e., the interspecies (intrapopula-
tion) variability of egg size in a euphausiacean.
MATERIALS AND METHODS
Zooplankton samples were collected in the spring–
summer period in different areas of the Barents and
Norwegian seas (Table 1); as a sampling device, we
used a Juday net (opening area 0.1 m
; made of 168
capron mesh). The following water layers were sam-
pled: 100, 100–75, 75–50, 50–25, 25–100, and 10–0 m.
The samples were ﬁxed with 4% neutral formalin.
We identiﬁed the eggs of euphausiaceans to species
level, determined the stage of development, and mea-
32 magniﬁcation (using dissection micro-
scopes MBS-1 or MBS-10) accurate to 25
m. It was
almost impossible to identify in the formalin-ﬁxed
materials the stages of embryonic development of
euphausiaceans belonging to the genus
proposed by Ponomareva  and Zelikman , espe-
cially in the early stages of embryogenesis. Therefore,
we used a method that was somewhat simpliﬁed. The
eggs of euphausiaceans were separated into three
groups: (I)—from hatching (zygote) to transition from
blastula to gastrula (at this stage the embryo has
rounded shape); (II)—beginning of the formation of
nauplius; and (III) completely developed nauplius
within the egg envelope. The size of eggs increases in
Egg Size and Formation of the Geographical Range
(Krøyer, 1846) (Crustacea:
Euphausiacea) in the Norwegian and Barents Seas
S. F. Timofeev
Murmansk Marine Biological Institute, Kol’ski Scientiﬁc Center, Russian Academy of Sciences, Murmansk, 183010 Russia
Received May 4, 2005
—Using materials on the euphausiacean
collected in the Norwegian and Barents
seas (from 60
N to 73
N) we studied the variability of size characteristics in the eggs (diameter of embryos and
egg capsules and the width of the perivitelline space) and their correlations with water temperature and salinity.
The size of embryos showed almost no variability irrespective of the location of the sampling site and the water
temperature and salinity; the perivitelline space performs a protective function, and its width showed a tendency
to decrease with increasing water temperature and salinity. The similarities in the size of embryos in
populations thousands of kilometers away from each other might be explained, ﬁrst, by the relatively small age
of the populations (the age of the population from the Barents Sea did not exceed 6000–7000 years) and second,
by movement of the crustaceans with currents from the Norwegian Sea to the Barents Sea.
, embryo, perivitelline space, temperature, salinity.