ISSN 1063-0740, Russian Journal of Marine Biology, 2006, Vol. 32, No. 6, pp. 386–388. © Pleiades Publishing, Inc., 2006.
Original Russian Text © S.D. Kashenko, 2006, published in Biologiya Morya.
The heart sea urchin,
(Pennant) is a recent member of spatangoid urchins,
which are mostly extant now. This species is widely
distributed in temperate latitudes of the Paciﬁc and
Atlantic oceans, at depths of 0.5 to 230 m deep [7–11,
etc.]. This species is a typical member of infauna; it pre-
fers silty–sandy or sandy grounds, where it burrows
down to a depth from several millimeters to 15–20 cm.
In Russian waters
inhabits Peter the Great
Bay, the Sea of Japan where it develops mosaic popula-
tions [1, 3].
Under conditions of monsoon climate, with storms
often occurring during the summer period, adult speci-
sometimes become transferred
onto hard substrates or even stranded; i.e., they enter an
environment that is not suitable for their existence. As
a result of sharp changes in both salinity and tempera-
ture, the sea urchins perish.
The goal of this study was to determine the resis-
tance of adult specimens of the sea urchin
to extreme environmental conditions, i.e., absence of a
suitable substrate (where animals cannot burrow) and
sharp decrease in seawater salinity.
MATERIALS AND METHODS
The study was performed at the Vostok Marine Bio-
logical Station of the Institute of Marine Biology, Far
East Division, Russian Academy of Sciences (Vostok
Bay, Sea of Japan) in June and August 2004.
In June, adult specimens of the sea urchin
in prespawning condition were
collected from a depth of 8–10 m, at a water tempera-
ture of 13
C and salinity of 33.2‰ in Srednyaya Bight.
The sea urchins stayed in ﬁne sand, at a depth of 10–
15 cm from the ground surface. Collected animals were
placed onto the bottom of an aquarium (hard substrate)
with running seawater, whose temperature and salinity
C and 33.2‰, respectively. Thus, a situa-
tion was simulated in which, during spawning, the sea
urchins coming out of the sand, onto the surface, are
transferred onto a hard substrate. One day later the
spawning was completed. In the experiment, where we
studied the capability for survival without sand and,
therefore, food, 50 animals were used. By the end of the
experiment, the water temperature in both the aquarium
and the sea gradually increased up to 14.8
C; the salinity
remained unchanged. The duration of experiments was
taken as the period from the moment when sea urchins
were introduced into the aquarium up to the death of
100% of the animals. Death was registered when no
responce of ambulacral podia was observed after a prick
with a needle and spines on the test stopped moving.
In the second stage, in August, we determined salin-
ity tolerance and resistance of adult specimens of
to a sharp decrease in salinity under a sta-
ble temperature of 19
C, which corresponded to water
temperature in the bay, close to the bottom, during this
time of the year. The animals were collected from 7–
8 m deep, at a salinity of 33.1‰, in ﬁne silted sand,
from a depth of 15–20 cm from the ground surface.
Salinity tolerance of
by the number of active animals (100%) 1 h after they
were introduced into 20-l aquariums with seawater of
different salinity (33‰ and from 30 to 16‰ at intervals
of 2‰) . A preliminary study of the capability of
heart sea urchin to turn from the dorsal side of the body
onto the ventral side (righting) showed that such an
action is very difﬁcult for this species of sea urchins;
thus, of 20 specimens turned upside down, only one
Resistance of the Heart Sea Urchin
(Echinoidea: Spatangoida) to Extreme Environmental Changes
S. D. Kashenko
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received March 24, 2006
—The ability to survive under extreme environmental conditions was studied in the adults of the heart
(Pennant). At seawater temperatures of 13.3 to 14.8
C and salinity of 33.2–
33.4‰, being devoid of the possibility to burrow into the sand or eat, some sea urchins died on day 5 and all
individuals had perished by the end of day 8. At a temperature of 19
C, the salinity tolerance range of adults
was limited to 33–28‰. Only 30 to 20% of sea urchins transferred to a solid substrate survived for 7 days at a
salinity of 33 to 24‰, but all of them perished toward the end of day 8.
sea urchins, Echinocardium cordatum, temperature, salinity, substrate.