Environmental Microbiology of Aquatic and Waste Systems

80 4 Taxonomy, Physiology, and Ecology of Aquatic Microorganisms

5. Suctoria
   The juvenile forms are ciliated and motile, while the
   adult forms are sessile and capture food by tentacles.
   They feed by extracellular digestion and lack cilia in
   the adult phase. The adult have structures called hap­
   tocysts at the tip which attach to the prey. The prey’s
   cytoplasm is then sucked directly into a food vacuole
   inside the cell, where its contents are digested and
   absorbed. Most suctoria are around 15–30 mm in size,
   with a non­contractile stalk and often a shell. Suctoria
   reproduce primarily by budding, producing swarmers
   which lack both tentacles and stalks but have cilia.
   Once the swarmers (motile young) have found a place
   to attach themselves, they quickly develop stalks and
   tentacles and lose their cilia. Because of the presence
   of cilia in the young of suctoria, some authors group
   the suctoria among ciliates.

Suctoria are found in both freshwater and

marine environments, and some which live on the

surface of aquatic animals, and typically feed on

ciliates. Some marine species form symbiotic rela­

tionships with crustaceans and even some fish.

One species, Ephelota gemmipara lives on the

external parasite of salmon, Lepeophtheirus sal­

monis (salmon louse).

4.1.6.2 Fungi

Fungi are eukaryotic microorganisms which

(a) Are non­photosynthetic and hence do not contain

chlorophyll

(b) Contain chitin and/or cellulose in their cell walls

(c) Are usually filamentous (called molds), but they

may be unicellular (called yeasts)

(d) Reproduce asexually with spores

Mastigophora

Apicomplexa

Ciliophora

Sarcodina

Flagellum

Pseudopodia

Cilia

Euglena

Chlamydomonas

Paramecium

Vorticella

Plasmodium in red blood cells

Amoeba

Arcella

Fig. 4.21 Protozoan groups. Illustrations of some Protozoa (From http://www.cliffsnotes.com/study_guide/topicArticleId-
8524,articleId-8461.html; Anonymous 2010 b. With permission)