Two New Gyrodactylus (Trematoda : Monogenea) from Cyprinid Fishes with Synopsis of Those Found on North American Fishes

Abstract

Gyrodactylus atratuli from the blacknose dace (Rhinichthys atratulus) and the pearl dace (Semotilus margarita) is compared with known species of Gyrodactylus from North American fishes and described as a new species. Gyrodactylus margaritae from the pearl dace (Semotilus margarita) is compared with known species of Gyrodactylus from North American fishes and described as a new species. The average number of G. atratuli per blacknose dace in the natural habitat is 7.8 (1 to 32) and in the laboratory at the same water temperature after 55 days in captivity, 5.4 (0 to 11). G. atratuli and G. margaritae fail to live and reproduce on fish kept in nonrunning water at between 19 and 26 C in laboratory aquaria, but will live and reproduce in running spring water at 12 C in laboratory aquaria. An illustrated synopsis with a comparative table of measurements of known North American Gyrodactylus and a list of the species with brief reference to their differentiating characteristics are given. During the summer of 1962, two species of fish, the blacknose dace (Rhinichthys atratulus) and the pearl dace (Semotilus margarita), from the south branch of Leetown Run, Leetown, West Virginia, harbored Gyrodactylus species on the body and fins. One species of Gyrodactylus was found on both the blacknose and the pearl dace, while another species was found only on the pearl dace. After comparison with known species of Gyrodactylus found on North American fishes, they are here described as new species, Gyrodactylus atratuli from both the blacknose and pearl dace, and Gyrodactylus margaritae from the pearl dace. Following the new species descriptions is an illustrated synopsis of the genus Gyrodactylus and a comparative table showing the measurements in microns of known Gyrodactylus species found on North American fishes. MATERIALS AND METHODS Fish harboring the parasites were taken by seine from Leetown Run, which is spring fed with water 12 C throughout the year. For maintaining the parasites, the fish were kept in stainless-steel troughs with a small constant flow of spring water about the same temperature as the Leetown Run. Received for publication 12 March 1963. For obtaining the parasites for microscopy, fish were placed in petri dishes containing a solution of 1: 4,000 formalin (modification of Parker and Haley, 1960). After a few minutes the parasites dropped to the bottom of the dishes and were pipetted to slides for study or fixed for permanent preparation. The parasites were studied in living, fixed, and stained preparations. If permanent mounts were to be made, the parasites were changed from the 1: 4,000 formalin solution to a 10% formalin solution for thorough fixing. Various stains were employed for permanent mounts, but Harris' hematoxylin was preferred. For studying temporary stained mounts, methyl green (0.25% in 1.0% acetic acid) was used. A drop of this stain was placed on the slide at the edge of the cover slip and allowed to diffuse under. A progressive staining could be achieved with this method, and it was found to emphasize the cirrus pouch and its armature as well as other anatomical structures. Gross measurements were made in the living state and also after the parasites had been removed with the 1: 4,000 formalin solution. These measurements were made without the use of cover slips. Measurements of the more detailed anatomy were taken in the unstained and stained state, but with ample liquid beneath the cover slip to minimize distortion of the organism due to cover-slip pressure. For studying the hard parts in detail, the soft body parts were allowed to decompose under a vaseline-sealed cover slip (Ikezaki and Hoffman, 1957). All measurements (method of Malmberg, 1956)