Entamoeba nezumia sp. n. and Other Parasites from a North Atlantic Fish

Abstract

Entamoeba, Coccidia, Myxosporida, Nematoda, Monogenea, and I copepod have been recovered from 4 specimens of the macrourid fish, Nezulmia bairdi, collected in the North Atlantic Ocean. The ameba, E. nezumia sp. n., from the stomach, has trophozoites that measure 8.5 by 12.2 ,u, and cysts that are 7.7 ,u in diameter. Most cysts are uninucleate. The relatively large number of species of parasites in this fish is consistent with the hypothesis that benthic fishes have more kinds and numbers of parasites than do midwater fishes. Six specimens of Nezumia bairdi Goode and Bean were collected on 9 March 1962, by the United States National Museum Eltanin Cruise No. 2, Station 10, as part of the University of Southern California Antarctic Research Program sponsored by the National Science Foundation. The collection was made before the cruise started southward. The location was long 44o30' N and lat 56?55' W off the coast of Greenland. These fish were made available to us for autopsy on 10 January 1969, and we found a total of seven species of parasites (Table I) in the four adult specimens. The other two fish were immature and without parasites. This paper is primarily concerned with a description of a new species of Entamoeba, and a short account of the parasitemix of the host. It is the first report, to our knowledge, of an ameba from a deepsea fish. Nine species of amebas have previously been described from fishes, four of these from marine hosts. One of the marine species (Amoeba mucicola Chatton, 1909) occurs in branchial mucus and on the skin of Symphodus tinca, a fish from Banyules (Mediterranean Sea). The other marine species were recovered from the intestines of their hosts. These species are: Proctamoeba salpae (Leger and Duboscq) Alexeieff (1912) from Box salpa and B. boops from Banyules; Entamoeba molae Noble and Noble (1966) from Mola mola from the coast of southern California; and E. gadi Bullock (1966) from Pollachius virens from the coast of New Hampshire. See Noble and Noble (1966) for a brief description of these species (except E. gadi) and those from freshwater hosts. Received for publication 7 January 1971. * Supported by NSF Grant 11859. MATERIALS AND METHODS The fish were collected in a beam trawl at a depth of 400 m over a bottom of sand and gravel, placed in 10% formalin, and later transferred to 40% isopropyl alcohol. The four adults were all females ranging in standard length (tip of snout to base of caudal fin) from 242 to 330 mm. The two immature specimens were 62 and 51 mm long. Small portions of the stomach previously found (by smears of its contents) to be infected with amebas and coccidia were dehydrated through an alcohol series, cleared in xylene, and embedded in paraplast. Sections were cut at 7 u and stained either with Heidenhain's iron hematoxylin or with Azan stain (Mallory's Heidenhain's, modified after Koneff). All measurements were made on fixed, stained, and sectioned material. We used a Zeiss Standard WL research microscope with phase contrast condenser and a built-in camera lucida.