Possible involvement of hemolytic activity in the contact-dependent lethal effects of the dinoflagellate Karenia mikimotoi on the rotifer Brachionus plicatilis

Abstract

We investigated the effects of two strains (SUO-1 and FUK) of the dinoflagellate Karenia mikimotoi on the rotifer Brachionus plicatilis. The SUO-1 strain was highly toxic to rotifers, whereas the FUK strain was less toxic. After 10-hour incubations, the survivorship of rotifers exposed to SUO-1 and FUK was 20% and 95%, respectively.Both the cell-free culture supernatant and the ruptured cell suspension prepared from these strains were not toxic to rotifers. Furthermore, when direct contact between K. mikimotoi and rotifers was interrupted with a cell-impermeable membrane (3-m pores), the toxicity of both the SUO-1 and FUK strains of K. mikimotoi to rotifers were completely inhibited even after a 24-h exposure. Cell suspensions of SUO-1 showed hemolytic activity toward horse erythrocytes, but the FUK strain did not. The cell-free supernatant and the ruptured cell suspension of SUO-1 showed no significant hemolytic activity. These results suggest that this highly toxic strain of K. mikimotoi causes lethality in rotifers by direct contact in which live cell-mediated hemolytic activity might be a contributing factor.

The toxic effects of three dinoflagellate species from the genusKareniaon invertebrate larvae and finfish

“…Chattonella marina and Heterosigma akashiwo (Yang et al 1995;Ishimatsu et al 1996;Oda et al 1997). Zou et al (2010) indicated that ROS production depended on the K. mikimotoi strain and two other Japanese strains did not generate ROS. In the present Notes: LT 50 , least time for 50% of larvae to become moribund after exposure to specified cell concentration (mean 9 SEM from curve fit); LC 50 , lowest cell concentration for 50% of larvae to become moribund after exposure time of 2 or 24 h (estimate; 50% moribund defined as mean toxicity score of 2.5); , survival of all larvae at longest observation time or highest cell concentration used; 1 estimate (insufficient data for curve fit); 2 Pacific oyster; 3 Greenshell TM mussel.…”

“…Karenia mikimotoi is one of the most common fish-killing toxic dinoflagellates in both the Atlantic and Pacific regions (Honjo 1995;Silke et al 2005;Gentien et al 2007;Zou et al 2010). The cell concentration in a typical K. mikimotoi bloom can easily reach millions of cells per litre (1Á20)10 6 cells L Á1 ) (Silke et al 2005; International Council for the Exploration of the Sea 2006; Davidson et al 2009;Ulrich et al 2010).…”

“…Karenia mikimotoi can produce several potentially toxic compounds, including gymnocins, haemolysins and reactive oxygen species (ROS) (Yasumoto et al 1990;Satake et al 2002;Haywood et al 2004;Munday et al 2004;Yamasaki et al 2004;Satake et al 2005). It is a cosmopolitan species and there may be a range of sub-species with varying toxicities and modes of action (Zou et al 2010). The strain of K. mikimotoi used in the present study was isolated from the northern coast of New Zealand and is maintained in the CICCM.…”

Differential inimical effects of Alexandrium spp. and Karenia spp. on cleavage, hatching, and two larval stages of Japanese pearl oyster Pinctada fucata martensii

“…On the other hand, the activity of D-larvae and pre-settling larvae was significantly decreased following exposure to K. mikimotoi for 24 h at 5 Â 10 3 cells ml À1 and 24 h at 5 Â 10 2 cells ml À1 , respectively. No morphological anomalies were observed in embryos or in larvae, thereby excluding lytic activity in favor of toxicity of brevetoxins (PbTx) and/or other organic compounds, although K. mikimotoi is known to produce hemolysin activated via cell contact (Neely and Campbell, 2006;Zou et al, 2010). Brevetoxins (PbTx) responsible for the neurotoxic shellfish poisoning (NSP) in humans are produced by Karenia brevis, and other Kareniacea, including K. papilionacea, are suspected to produce PbTx or PbTx-like compounds (Furey et al, 2007;Ramsdell, 2008;Brand et al, 2012).…”

Karenia: The biology and ecology of a toxic genus

“…Environmental differences in the water masses that led to the bloom occurring in some water masses and not others in the first place may also play a role. K. mikimotoi has also been observed to be toxic to rotifers (Zou et al, 2010) and have a negative effect on some ciliates (Hansen, 1995), however in some mesocosm experiments, reduction of grazing pressure has resulted in an increase in K. mikimotoi numbers (Turner and Graneli, 2006). It should also be noted that some dinoflagellate species can have an adverse impact on K. mikimotoi.…”