302
G. La Spada et al.
sions is present, so that it is impossible to distinguish the origin of each of them. Alternatively, a
difference between species could be hypothesized. Our results and those of Watson and
Hessinger (1992) and Mire-Thibodeaux and
Watson (1994) strongly contrast with those of
Rifkin (1996) who indicated the absence of
cnidocil in Anthozoa.
The method of isolation by treatment with
SCN- made it possible to obtain cellular elements which essentially consisted of microbasic-mastigophore nematocytes, anatomically
intact but lacking in mechanosensitive apparatus and this differs notably from that observed
in nematocytes isolated with the physical
method. However, it must be considered that
after treatment with SCN-, when nematocytes
are still in situ and only partially extruded. they
do show their mechanosensitive apparatus,
which afterwards disappears in the extruded
nematocytes.
The exposure of the nematocytes, isolated
with the two above-mentioned methods, to
hyposmotic shock corresponding to 35% resulted in different responses. In fact, in nematocytes
isolated by treatment of the tentacle with SCNthe cell swelling gradually decreased, while still
keeping hypotonic conditions unvaried, showing
therefore mechanisms of RVD. Obviously the
value of osmotic swelling is moderate, considering their particular anatomy. In fact, given that
the cell volume is taken up by the nematocyst
(-85%) CA. Saileo, unpublished}, the volume of
which does not vary under hyposmotic shock.
the cell profile only varies to a moderate extent,
as the cytoplasm is situated in a thin rim in an
equatorial, and sometimes apical, position. It
must also be considered that these cell have a
higher capacity for volume regulation, compared
to that seen in other cells (Park et al. 1994; De
Smet et al. 1995). This result can be evaluated
taking into account the great variability,
observed in limited areas, of the seawater salinity of the brackish pond Faro, due to both the
poor communication with the sea and anthropic
intervention.
In nematocytes isolated by heat dissociation,
cell swelling, which took place over a longer time
than that in isolation with SCN-, was constant for
the entire duration of the hyposmotic shock. The
absence of RVD in nematocytes isolated in this
way could be attributed to some possible conformational modifications of the channel-proteins
through which RVD mechanisms take place.
Such modifications could be attributed to the
degree of temperature and duration to which the
tentacle was subjected.
From the present study we can conclude that:
nematocytes isolated from Aiptasia diaphana by
heat dissociation are anatomically intact, have
mechanosensorial apparatus but lose a property,
the RVD. that depends on integrity of ion transport mechanisms, while the general physiological integrity of nematocytes isolated with SCNis better maintained, with the exception of the
mechanosensitive function.
Acknowledgements. We are grateful to Prof. Alberto Salleo of
Institute of General Physiology (University of Messina) for
helpful discussion and revision of the manuscript.
References
Anderson PAY, McKay Me (1987) The electrophysiology of cnidocytes. J Exp BioI 133: 215-230
Barra PFA, Musd G. Salleo A (1997) Control of discharge of acontial nematocysts in Aiptasia diaphana. In: Proc 6th Int Conf
Coelenterate BioI (1995), pp 39-46
Burnett JW (1991) Clinical manifestations jellyfish envenomation. Hydrobiologia 216/217: 629-636
De Smet P, Simaels J, Van Driessche W (1995) Regulatory volume
decrease in a renal distal tubular celliioe (A6). I. Role of K+.
and CI- pflngers Arch 430: G, Schaller H, Trenker E (1972)
regeneration of Hydra from reaggregated cells. Nat New BioI
239 (91): 98-101
Hidaka M (1993) Mechanism of nematocyst discharge and its cellular control.Arlv Comp Environ Physioll5: 45-76
Holstein T, Tardent P (1984) An ultrahigh-speed analysis of exocytosis: nematocyst discharge. Sciences 22.3: 830-833
Lang F. Gillian L, Busch Ritter M, Vlilkl H, Waldegger S, Gulbins E,
Haussinger D (1998) Functional significan.ce of cell volume
regulatory mechanisms. Physiol Rev 78; 247-306
La Spada G, Biundo T, Nardella R, Meli S (1999) Regulatory volume decrease in nematocytes isolated from amntia of
Aiptasia diaphana. Cell Mol BioI 45: 249-258
Long KO, Burnett JV (1994) Characteristics of ialuronidase and
hemolitic activity in fishing tentacle nematocyst venom of
Grhysaara quinquecirrha. Toxicon 32: 165-174
Mariscal RN (1974) Nematocysts. In: Muscatine L, Lenhoff HM
(eds) Coelenterate biology. Academic Press, New York, pp
129-178
McKay MC,Anderson PAY (1988) Preparation and properties of
cnidocytes from the sea anemone Anthopleura elegantissirna. BioI Bull Mar Bioi Lab Woods Hole 174: 47-53
Mire-Thibodeaux P, Watson GM (1994) Morphodynamic hair
bundles arising from sensory ceI1Jsupporting cell complexes
frequency-tune nematocyst discharge in sea anemones. J
Exp Zoo1278: 282-292
Morris CE (1990) Mechanosensitive ion channels. J Membr BioI
113: 93-107
Norton RS (1991) Structure and structure function relationships
of the sea anemone proteins that interact with the sodium
channel. Toxicon 29: 1051-1084
G. La Spada et al.
sions is present, so that it is impossible to distinguish the origin of each of them. Alternatively, a
difference between species could be hypothesized. Our results and those of Watson and
Hessinger (1992) and Mire-Thibodeaux and
Watson (1994) strongly contrast with those of
Rifkin (1996) who indicated the absence of
cnidocil in Anthozoa.
The method of isolation by treatment with
SCN- made it possible to obtain cellular elements which essentially consisted of microbasic-mastigophore nematocytes, anatomically
intact but lacking in mechanosensitive apparatus and this differs notably from that observed
in nematocytes isolated with the physical
method. However, it must be considered that
after treatment with SCN-, when nematocytes
are still in situ and only partially extruded. they
do show their mechanosensitive apparatus,
which afterwards disappears in the extruded
nematocytes.
The exposure of the nematocytes, isolated
with the two above-mentioned methods, to
hyposmotic shock corresponding to 35% resulted in different responses. In fact, in nematocytes
isolated by treatment of the tentacle with SCNthe cell swelling gradually decreased, while still
keeping hypotonic conditions unvaried, showing
therefore mechanisms of RVD. Obviously the
value of osmotic swelling is moderate, considering their particular anatomy. In fact, given that
the cell volume is taken up by the nematocyst
(-85%) CA. Saileo, unpublished}, the volume of
which does not vary under hyposmotic shock.
the cell profile only varies to a moderate extent,
as the cytoplasm is situated in a thin rim in an
equatorial, and sometimes apical, position. It
must also be considered that these cell have a
higher capacity for volume regulation, compared
to that seen in other cells (Park et al. 1994; De
Smet et al. 1995). This result can be evaluated
taking into account the great variability,
observed in limited areas, of the seawater salinity of the brackish pond Faro, due to both the
poor communication with the sea and anthropic
intervention.
In nematocytes isolated by heat dissociation,
cell swelling, which took place over a longer time
than that in isolation with SCN-, was constant for
the entire duration of the hyposmotic shock. The
absence of RVD in nematocytes isolated in this
way could be attributed to some possible conformational modifications of the channel-proteins
through which RVD mechanisms take place.
Such modifications could be attributed to the
degree of temperature and duration to which the
tentacle was subjected.
From the present study we can conclude that:
nematocytes isolated from Aiptasia diaphana by
heat dissociation are anatomically intact, have
mechanosensorial apparatus but lose a property,
the RVD. that depends on integrity of ion transport mechanisms, while the general physiological integrity of nematocytes isolated with SCNis better maintained, with the exception of the
mechanosensitive function.
Acknowledgements. We are grateful to Prof. Alberto Salleo of
Institute of General Physiology (University of Messina) for
helpful discussion and revision of the manuscript.
References
Anderson PAY, McKay Me (1987) The electrophysiology of cnidocytes. J Exp BioI 133: 215-230
Barra PFA, Musd G. Salleo A (1997) Control of discharge of acontial nematocysts in Aiptasia diaphana. In: Proc 6th Int Conf
Coelenterate BioI (1995), pp 39-46
Burnett JW (1991) Clinical manifestations jellyfish envenomation. Hydrobiologia 216/217: 629-636
De Smet P, Simaels J, Van Driessche W (1995) Regulatory volume
decrease in a renal distal tubular celliioe (A6). I. Role of K+.
and CI- pflngers Arch 430: G, Schaller H, Trenker E (1972)
regeneration of Hydra from reaggregated cells. Nat New BioI
239 (91): 98-101
Hidaka M (1993) Mechanism of nematocyst discharge and its cellular control.Arlv Comp Environ Physioll5: 45-76
Holstein T, Tardent P (1984) An ultrahigh-speed analysis of exocytosis: nematocyst discharge. Sciences 22.3: 830-833
Lang F. Gillian L, Busch Ritter M, Vlilkl H, Waldegger S, Gulbins E,
Haussinger D (1998) Functional significan.ce of cell volume
regulatory mechanisms. Physiol Rev 78; 247-306
La Spada G, Biundo T, Nardella R, Meli S (1999) Regulatory volume decrease in nematocytes isolated from amntia of
Aiptasia diaphana. Cell Mol BioI 45: 249-258
Long KO, Burnett JV (1994) Characteristics of ialuronidase and
hemolitic activity in fishing tentacle nematocyst venom of
Grhysaara quinquecirrha. Toxicon 32: 165-174
Mariscal RN (1974) Nematocysts. In: Muscatine L, Lenhoff HM
(eds) Coelenterate biology. Academic Press, New York, pp
129-178
McKay MC,Anderson PAY (1988) Preparation and properties of
cnidocytes from the sea anemone Anthopleura elegantissirna. BioI Bull Mar Bioi Lab Woods Hole 174: 47-53
Mire-Thibodeaux P, Watson GM (1994) Morphodynamic hair
bundles arising from sensory ceI1Jsupporting cell complexes
frequency-tune nematocyst discharge in sea anemones. J
Exp Zoo1278: 282-292
Morris CE (1990) Mechanosensitive ion channels. J Membr BioI
113: 93-107
Norton RS (1991) Structure and structure function relationships
of the sea anemone proteins that interact with the sodium
channel. Toxicon 29: 1051-1084