Serpenomonas
Serpenomonas Triemer, 1986 (ref. ID; 4226 original paper)
[ref. ID; 4226]
Diagnosis; Colorless cells, rigid with slight dorso-ventral flattening. Pellicle with prominent ridges. Two unequal, subapically inserted, heterodynamic flagella. The sorter flagellum directed anteriorly during swimming and the longer, thicker flagellum trailing posteriorly. Cells move along the substrate with a creeping motion. Ingestion apparatus composed of separate ribs extending the length of the cell and incorporated into the ventral ridge of the pellicle, independent of the canal and reservoir; not in the form of a protrusible siphon. (ref. ID; 4226)
Remarks; The morphology of the genus, Entosiphon, is most similar to that of the proposed genus Serpenomonas with one major exception. The major distinctive feature of the genus Entosiphon is the feeding apparatus. This structure is a tube or "siphon" composed of a number of rods fused together. In living cells it can be extended outward beyond the edge of the cell body and then retracted into the cytoplasm. This structure with its distinctive movement is characteristic for the genus. Light microscopic observations of living cells and electron microscopic observations of fixed cells demonstrate that the feeding apparatus in Serpenomonas is not protrusible or retractable and exhibits an ultrastructure distinctly different from that of the Entosiphon feeding apparatus. Additionally, I have examined the feeding apparatus in Serpenomonas and in two species of Entosiphon with the scanning electron microscope. In both of the Entosiphon species, the siphon is independent of the pellicle and is not closely associated with it as it is in Serpenomonas. Morphologically, the feeding apparatus of Serpenomonas is most similar to that reported in Isonema nigricans, a colorless flagellate suspected of having euglenoid affinities. The presence or absence of a feeding apparatus is currently used as one of the primarily criteria for establishing an organisms as a member of the suborder Heteronematina. If such a criterion is justified in establishing suborders, then it would seem warranted that significant morphological differences in the structure of the feeding apparatus could be utilized in establishing generic characters. Therefore, the differences between Entosiphon and the organism described in this report are sufficient to justify the establishment of a new genus, Serpenomonas, the "creeping monad". (ref. ID; 4226)
Type species; Serpenomonas costata n. g., n. sp. (ref. ID; 4226)
- Serpenomonas costata Triemer, 1986 (ref. ID; 4226 original paper)
Serpenomonas costata Triemer, 1986 (ref. ID; 4226 original paper)
Diagnosis
Cells ovate in dorsal view. 21-25 um long x 18 um wide. Slightly flattened on the ventral surface. Cells nonmetabolic with five grooves in the cell surface, each containing a crenate ridge. Two flagella arise from the groove on the ventral surface. The anterior flagellum 0.5 x the cell length and a thicker trailing flagellum 1.5-2.0 x the cell length. Cells move with a creeping motion. Prominent feeding apparatus extends the length of the cell body and tapers posteriorly. Collected from standing pools on salt marsh. (ref. ID; 4226)
Descriptions
Serpenomonas costata is a unicellular, colorless euglenoid, often found among fragments of rotting plants and algae in standing ponds on the salt marsh. The cells measure 21-25 um in length and are about 18 um wide, with slight dorso-ventral flattening. Five prominent ridges mark the pellicular surface, with the outermost portion of each ridge bearing crenate ornamentation. Each cell has two subapically inserted flagella projecting from the ventral ridge of the pellicle. The leading flagellum is about 1/2 the length of the cell and, while swimming, beats with a rapid flickering motion throughout its entire length. Often it appears to have a "fuzzy" coating. The trailing flagellum is approximately 1.5 to 2 times the length of the cell and is twice as thick as the leading flagellum. During forward motion this flagellum appears to be dragged along behind as the cell glides along the substrate. Frequently, however, the trailing flagellum can flex rapidly causing a sudden jerk which changes the direction of forward motion. A large feeding apparatus, visible with the light microscope extends nearly the entire length of the cell and tapers towards the posterior end. Observations of living feeding cells indicate that the apparatus is maintained close to the substrate during swimming, but at no time is it extended or retracted by the cell. Scanning electron micrographs reveal that the apparatus is closely associated with the margin of the ventral pellicular ridge opposite the crenate ornamentation. The anterior end of the apparatus is capped by a C-shaped thickening. Transmission electron micrographs show that supporting ribs of the feeding apparatus (usually six) are arranged in the form of a partial rosette. The cytoplasmic organelles found in Serpenomonas costata are typical of those found in other euglenoids. A large nucleus with condensed chromosomes is present near the center of the cell; a layer of endoplasmic reticulum underlies the pellicle, and the mitochondria bear plate-like cristae. In addition, number of electron-dense vesicles are found adjacent to the feeding apparatus. (ref. ID; 4226)
Etymology
The type species Serpenomonas costata has been given the species epithet "costata" due to the distinct ridges on the pellicular surface. (ref. ID; 4226)
Type locality
This was collected from a standing pond on the salt marsh in Tuckerton, NJ, in March 1984. (ref. ID; 4226)