The spermatozoon of Thaumastoderma moebjergi with the description of the sperm model for the family Thaumastodermatidae (Gastrotricha, Macrodasyida)

The spermatozoon of Thaumastoderma moebjergi (Gastrotricha, Macrodasyida, Thaumastodermatidae) was described, and its structural features were compared to those of the other thaumastodermatid sperm models so far described. Although many of the sperm characters were present in different macrodasyidan species, the following complete set of characters was only found in all the thaumastodermatid spermatozoa at now described: a tubular structure within the acrosome formed by a pile of disks, the mitochondria arranged inside the nuclear spring, the striated cylinder in the flagellum, and a perinuclear helix. Thus the family Thaumastodermatidae appears uniform as far as sperm characters are considered.