Synedra inaequalis, previously reported by H. KOBAYASI from the Ara-kawa ( Ara River ), Japan, was re-examined using scanning electron m icroscopy ( SEM ). A type is designated, thereby validating this previousl y invalid name. Synedra lanceolata Utz., new to Japanese rivers is also examined by SEM.
A clone of Nitzschia levidensis grown in petri dishes formed belt-shaped chains in culture. The valve-half carrying the raphe is concave, and the other half is convex in the external view. On cells in a chain, a half-copula bearing rough slits is attached to the margin of the rapheless valve-half. To make the compact chains, the corner carrying the raphe of a valve is inserted to the space between the copula and the convex valve-half of the neighboring valve. The shape of valves and the raphe of this diatom seen by SEM differs evidently from Nitzschia tryblionella.
Ecological studies of benthic diatoms in coastal regions were performed by collecting the samples from 110 localities divided in 16 regions throughout Japan. In order to discriminate the characters between species whose distribution is limited by salinity and substratum, environmental gradient analyses were executed. By examination of 94 diatoms, it was found that the distribution of 7species were evidently confined by salinity,6 by the nature of substrata and 26 by the both factors. All species were divided into 11 groups on the basis of similarities in adaptation to salinity and substratum. The determination of limiting factors and the grouping of species will offer some preliminary knowledge on each diatom as biological indicators in studies of. paleoecology and water pollution.
The present contribution is based on collections from five lakes, e. g. L. Manindjau, L. Singkarak, L. Dibaruh, L. Diatas, L. Talang and their outflows and inflows in Central Sumatra, from November 24 to December 9,1984. Concerning L. Talang and L. Manindjau, additional samples were obtained by R. Usman on September,1985. About 160 taxa from 26 genera are recorded. The following three taxa are described as new variety: Epithemia turgida var. sumatraense nov. var., Gomphonema vibrio var. maior nov. var. and Navicula adnata var. rostrata nov. var. Microphotographs of 164 taxa from the materials are given in 17 plates.
The samples examined were collected from the rivulet in Cuzco, Peru. Almost 380 valves were analyzed by light microphotographs. Margins of the valves almost linear to slightly widened toward the center of the valve. Two types are distinguished in the form of the valves. The first type is Navicula type, of which valve is symmetrical with respect to the raphe and the second type is Cymbella type, of which valve is asymmetrical. Most of the valves belong to the Navicula type. Valve with capitate ends is more common than that with rostrate ends. Thirty seven percent of the valve have crooked protruding ends. Striae, at the center of the valve, mostly parallel ( 65% ). The relative frequencies of each characteristics are similar to the specimens from Taitong, Taiwan. Length,9-18μm, breadth 3.5-4.5μm, striae in 10, am,20-25 at dorsal margin,20-24 at ventral margin. The valves in Cuzco are smaller and have denser striae than those in Taitong and previously reported data.
Variation in characteristics of Mastogloia exigua at three localities, Lake Nakaumi in San'in district, Lake Notoroko and Lake Fuurenko in Hokka ido was compared. A range of variation of M. exigua is relatively wide, and it varies with populations. Valve outline is not analogous among populations. Characters of M. exigua are grouped into two categories. The one contains characters, valve outline, valve breadth, number of partecta per semi-partectal ring, length of row of partecta, shape of central area and degree of development of lateral line. The other contains characters, arrangement of partecta, length of partectum, P value ( relative length of row of partecta per valve length )arrangement of striae and density of striae and puncta. The former characters are not static, but they vary with valve length, and the later ones are the static characters. M. paludium VOIGT and M. pseudexigua CHOLN. are included in a range of variation of M. exigua. They are considered synonymous with M. exigua.
The diatom community attached to the rock of stone, chamber of Ishibutai ( a destroyed ancient tomb in Asuka Town, Nara Prefecture, Japan ) was investigated. The community was composed of 21 taxa ( three centric taxa and 18 pennate taxa ), and predominated by Navicula contenta and Melosira muscigena, both of which have been reported from moist rocks or moss. Light and electron micro-photographs of M. muscigena IWAHASHI from Ishibutai tomb showed that Melosira ruttneri described by HUSTEDT ( 1937 ) from Java and Sumatra is a later synonym of M. muscigena.
Diatoms collected from seven springs in Okinawa were studied. A total of 77 forms belonging to 21 genera were recorded. The diatom community was organized by 12-33 forms at each station. Nitzschia amphibia was only the d iatom distributed in all stations. Dominant species were as follows; Gomphonema angustum, G. angustatum, G. gracile, Navicula germainii, N. confervacea, N. contenta, Synedra fasciculata var. truncata, Achnanthes brevipes var. intermedia.