Heterosigma
Heterosigma Hada, 1968 (ref. ID; 3497 original paper)
[ref. ID; 3497]
The primitive naked dinoflagellates with discal chromatophores have a single marked forward flagellum starting at the subapical depression of the end of the sigmoidal groove, which is a scarcely developed sulcus. The girdle, another transverse one, is seen distinctly or not. In forms of the Diniferina, the longitudinal flagellum is typically stretching posteriorly along the sulcus, but the species of the new genus have a forward flagellum and no difinite transverse one. Pulsing vacuoles near root of flagella are observed or not. In the Diniferina the new genus is the special form, carrying a forward longitudinal flagellum, therefore, it is easily distinguishable by this fact from published genera similar in general contour such as Hemidinium and Oxyrrhis. (ref. ID; 3497)
- Heterosigma akashiwo (Hada) (ref. ID; 3497)
Syn; Entomosigma akashiwo Hada, 1967 (ref. ID; 3497)
- Heterosigma inlandica Hada, 1968 (ref. ID; 3497 original paper)
Synonym
Entomosigma akashiwo Hada, 1967 (ref. ID; 3497)
Comments
It is different from the other, Heterosigma inlandica, in carrying a posterior bristle and in weak development of a longitudinal and absence of a transverse groove. Therefore, it seems that the species is more primitive as compared with the H. inlandica in structure of the cell. (ref. ID; 3497)
Descriptions
The fusiform body is more or less compressed and usually tapering to the distal end in active specimens. The longitudinal groove, sulcus, typically starts from the subapical depression and goes obliquely to the center, from which a short transverse groove, girdle is branched, then down posteriorly, but does not extend to the distal end. The pulsing vacuole, of which the opening is located by the root of the forward longitudinal flagellum, is generally situated near the surface in the anterior half of the body, and the other connecting with the girdle is rarely observed, though a transverse flagellum has been unable to detect. The large ovate nucleus characteristic to dinoflagellates is usually seen in the center of the motile body, and a number (10-20) of greenish brown discal chromatophores and small grains of reserved substance are scattered in the cell. (ref. ID; 3497)
Comments
The new form is distinguished from the published species of the Diniferina by differences regarding flagella and grooves. Being delicate and changeable in form, the body of the new species is easily broken. It is so difficult to examine in detail, that the presence of a transverse flagellum has been impossible to certify. (ref. ID; 3497)
Measurements
Length 10-18 um, breadth 8-12 um, thickness 7 um; diameter of the nucleus 6-7 um; one of a chromatophore 3.5-4.0 um. (ref. ID; 3497)