甲藻的异养营养型

综述了甲藻的异养类型。目前已知异养营养型在甲藻中广泛存在,只有很少几种甲藻营严格自养营养方式。有近一半的甲藻物种是没有色素体的,还有很多甲藻即使具有色素体也会有异养营养需求,称为兼养营养类型。这些兼养类群不一定主要以有机物作为其获取碳的来源,而仅仅是补充一些生长必需的有机物如维生素、生物素等。兼养类群以渗透营养和腐食营养方式进行,同时也可以寄生方式和共生方式进行兼养生活。无色素体的甲藻以有机物作为碳的唯一来源,仅仅依靠异养方式生存,属于严格异养营养方式,又称有机营养型。它们是甲藻异养营养型的主体,其主要类型有寄生、渗透营养和吞噬营养。由于吞噬营养是甲藻异养的主要类型,因此论述了3种吞噬营养型:吞噬营养方式、捕食茎营养方式和捕食笼营养方式。吞噬营养方式在无甲类和具甲类甲藻中都有存在,主要通过甲藻细胞的纵沟或底部对猎物进行吞噬,也有研究发现吞噬部位为顶孔或片间带。捕食茎营养方式是通过捕食茎刺穿猎物细胞膜并吸食其细胞质来获取营养,在异养甲藻中也较常见。捕食笼营养方式只在原多甲藻属(Protoperidinium)和翼藻属(Diplopsalis)里发现,是甲藻通过鞭毛孔分泌细胞质到胞外形成捕食笼将猎物包裹并进行消化来摄食的。甲藻摄食对象尺寸范围变化较大,小至几微米,大至几百微米。有些甲藻具有摄食选择性,通过感应猎物释放的化学物质来判断猎物的位置并进行摄食,摄食完成后由于体积的增加经常会发生细胞分裂和蜕鞘。对于甲藻异养的其他形式如拦截摄食营养方式、伪足摄食营养方式、口足摄食营养方式、触手摄食营养方式等只作简单介绍。还就甲藻异养的研究方法、其生态学意义和进化学意义进行简要论述,并对相关研究进行展望。

Dinoflagellate heterotrophy

The state art of dinoflagellate heterotrophy are reviewed in this paper. Heterotrophic dinoflagellates are widespreadly in dinoflagellates, only few species are living on autotrophic mechanism sensu stricto (autotrophic amphitrophy) alone. Nearly half of the dinoflagellate species are apochlorotic, and the rest dinoflagellate species have organic nutritional needs even if they have chloroplasts, called mixotrophy. These mixotrophy dinoflagellates do not necessarily uptake organic compounds as the major carbon sources, but vitamins, biotin and so on for growth and reproduction. The mixotrophy dinoflagellates can live not only on actively uptaking dissovled organic matters (osmotrophy) and extracellular digestion of food with subsequent uptake of the dissolved products (saprotrophy), but also parasitic (parasitism) and symbiotic (symbiosis) way to support their growth. Most apochlorotic dinoflagellates live on organic matters as their only carbon source, called heterotrophic amphitrophy sensu stricto, or organotrophy, which are the majority of heterotrophic dinoflagellates. There are three types of organotrophy, parasitic organotrophy, symbiosis organotrophy and phagotrophy. This article discusses the three kinds of phagotrophy in detail: phagotrophic feeding, peduncle feeding and pallium feeding. Phagotrophic feeding is commonly found in either thecate or athecate apochlorotic dinoflagellates, phagotrophic dinoflagellates mainly feed through the junction of the flagellar grooves in sulcus or the bottom of the hypotheca for the prey, but through the apical hole and suture are also found. Peduncle feeding dinoflagellates feed by means of an extinsible, tube-like "peduncle/phagopod", by which attached to unicellular algae, ciliates and even small metazoans, pierce through their prey cytoplasmic membrane and suck their cytoplasma to get the nutrition. Peduncle feeding is the majority of phagotrophy in dinoflagellates. Pallium feeding only is found in Protoperidinium and Diplopsalis, feeding on other plankton with a pallium (sac) extruded from a microtubular basket outside the cell, wrapping and digesting the prey in pallium. The sizes of dinoflagellates prey have a wide range, from a few microns to hundreds of microns. Some dinoflagellates feed selectively. They locate and feed on special prey by chemical sensing, and consequently increase the biovolume and ecdysis. Other types of heterotrophic feeding by dinoflagellates, such as filter/interception feeding, pseudopodial feeding, stompopd feeding, tentacle/piston feeding etc., is briefly introduced in this article. The methodology of dinoflagellate heterotroph study, an attempt to understand the evolutionary meaning of these heterotrophic manifestations, their implications on the marine ecosystem, and future research topics are also briefly discussed.