Pigment compositions and toxic effects of three harmful Karenia species, Karenia concordia, Karenia brevisulcata and Karenia mikimotoi (Gymnodiniales, Dinophyceae), on rotifers and brine shrimps

Karenia concordia, Karenia brevisulcata and Karenia mikimotoi are anomalously-pigmented gymnodinoids characterised by having fucoxanthin and two acyl-oxyfucoxanthin derivatives, instead of having peridinin as in the majority of photosynthetic dinoflagellates. HPLC pigment analyses of all three species, cultured in identical conditions, revealed two different patterns of pigmentation: (1) 19′-hexanoyl-oxyfucoxanthin-rich with very little fucoxanthin, as represented by K. concordia and K. brevisulcata, and (2) fucoxanthin-rich with much less acyl-oxyfucoxanthins, as represented by K. mikimotoi. Moreover, zeaxanthin was detected in both K. concordia and K. brevisulcata, but only trace amount in K. mikimotoi (generally not detected in this species). Both K. concordia and K. brevisulcata lacked carotene-β,ɛ and carotene-ɛ,ɛ. These differed from K. mikimotoi which generally produced all three carotenes (β,β; β,ɛ and ɛ,ɛ). At exponential growth phase, chlorophyll a content on a per cell basis of K. mikimotoi was more than double that of K. concordia and six times greater than that of K. brevisulcata. Toxicological tests conducted on rotifers elicited distinct responses - single-strength lipophilic cell extracts of both K. concordia and K. brevisulcata killed rotifers in tens of minutes (fast-acting), while that of double-strength K. mikimotoi, in tens of hours (slow-acting). Additionally, mature and nauplii forms of brine shrimps exposed to lipophilic cell extract of K. concordia appeared to be temporarily 'anaesthetised', but recovered in c. 45 min and 3 h respectively. No such 'anaesthetic' effect was observed on both forms of brine shrimps exposed to lipophilic extracts of either K. brevisulcata or K. mikimotoi. The former, however, killed both forms of brine shrimps in a matter of tens of hours, while those of the latter, did not cause any harm to either form tested.