Sachiko Tamura

Taxonomy and geographical distribution of Dugesia japonica and D. ryukyuensis in the Far East

Dugesia japonica Ichikawa et Kawakatsu, 1964, is a common and polymorphic species of freshwater planarian distributed widely in the Far East. In 1976 the geographic populations were separated into 2 subspecies (D.j.japonica and D.j. ryukyuensis). The taxonomy of this species is reconsidered once again from the morphological, anatomical, histological, and karyological viewpoints. From the result of these studies, D.j. ryukyuensis is elevated to the rank of species: D. ryukyuensis Kawakatsu, 1976. D. japonica (n = 8, 2x = 16, 3x = 24) differs from D. ryukyuensis (n = 7, 2x = 14, 3x = 21) in having an asymmetrical penis papilla without a well-developed valve surrounding its basal part, and a well-developed vagina (distribution: the Japanese Islands, Taiwan, the Korean Peninsula, China, and Primorskiy, Northeast Siberia, in Russia). D. ryukyuensis is characterized by an asymmetrical penis papilla with a well-developed valve surrounding its basal part, and a less-developed vagina (distribution: the Southwest Islands of Japan).

Karyological and taxonomic studies of Dugesia japonica Ichikawa et Kawakatsu in the Far East

A review of previous studies on the taxonomy, karyology and chorology of a polymorphic species Dugesia japonica from the Far East is presented. Two subspecies are now known: D. j. japonica (n = 8, 2x = 16, 3x = 24) and D. j. ryukyuensis (n = 7, 2x = 14, 3x = 21). An attempt has also been made to determine the definition of the B-chromosome as LB and SB and the variation of the karyotypes of both subspecies is described. Every known karyotype of D. japonica is classified into six groups (see Table 2). D. japonica from many localities has a diploid karyotype (2x), a triploid karyotype (3x) and an orthoploidic mixoploid karyotype of 2x & 3x. The origin and the karyological significance of these karyotypes are discussed.

A review of chromosomal variation in Dugesia japonica and D. ryukyuensis in the Far East

The chromosome numbers of Dugesia japonica Ichikawa et Kawakatsu, 1964, are n = 8, 2x = 16 and 3x = 24; those of Dugesia ryukyuensis Kawakatsu, 1976, are n = 7, 2x = 14 and 3x = 21. The karyotypes of both species include diploid, triploid and mixoploid; aneuploidic and mixoaneuploidic karyotypes may occur. In 785 specimens studied of D. japonica, the occurrence rates of specimens having each karyotype are substantially the same (29-37%). Diploid sexual specimens represented nearly 10% of the total and virtually no triploid or mixoploid sexual specimens were found. The diploid karyotype can be inherited by both sexual and asexual reproduction; the triploid and mixoploid karyotypes will be inherited only by asexual reproduction. In 51 specimens studied of D. ryukyuensis, the different karyotypes are: diploid (ca 39%), triploid (ca 57%) and mixoploid (ca 4%). Diploid sexual specimens represented nearly 25% of the total; sexual specimens with triploidic karyotypes made up nearly 27%. The diploid, triploid and mixoploid karyotypes were also found in juveniles hatched from cocoons. The diploid karyotype is inherited by both sexual and asexual reproductions; the other karyotypes may be inherited by parthenogenesis or self-fertilization (including pseudogamy) and asexual reproduction.

Karyological and taxonomic studies of Dugesia japonica from the Southwest Islands of Japan-II

The karyotypes of Dugesia japonica from the southern part of the Southwest Islands of J apan (the Nansei Shoto) include diploidy, triploidy, mixoploidy, and mixoaneuploidy. Animals having karyotypes based on n = 8 were found on Okinawa Island, Ishigaki Island, Iriomote Island, and Yonaguni Island, while animals having karyotypes based on n = 7 were found on Okinawa Island, Miyako Island, and Ishigaki Island. Toward the northern end of this island chain, at Tanegashima Island, Yakushima Island, and Amami-Oshima Island, karyotypes based on n = 8 occurred; and on one of these, Tanegashima Island, n = 7 also occurred. Our data provide further support of the karyotypical distinction between the two subspecies of D. japonica: D. j. japonica has karyotypes based on n = 8 and D. j. ryukyuensis has karyotypes based on n = 7. Taking into consideration the geological history of the Southwest Islands and the ties of their faunas to those of adjacent areas, we can explain the current geographical distribution of the two subspecies in these islands as the result of two separate invasions by D. japonica, one in the Miocene and one after the early Quaternary.

Chromosomes of Temnocephala minor, an ectosymbiotic turbellarian on Australian crayfish found in Kagoshima Prefecture, with karyological notes on exotic turbellarians found in Japan

Records of exotic turbellarian species found in Japan are reviewed from taxonomic and karyological viewpoints. Temnocephala minor Haswell, 1888, an ectocommensal on a freshwater crayfish of Australia, was found from culture ponds of Cherax tenuimanus (introduced from W. Australia) in Kagoshima Prefecture. T. minor had the chromosome number of 2x = 18 (2sm + 2m + 2m + 2sm + 2m + 2m + 2m + 2sm + 2m). The following 3 species of exotic freshwater triclads were recorded from tanks and ponds used for tropical fish culture: Dugesia austroasiatica Kawakatsu, 1985 (2x = 16), Dugesia tigrina (Girard, 1850) (2x = 16) and Rhodax? sp. (3x = 24; 3x = 24 & 3x + 1LB + 1SB = 25 + 1SB). The following 3 species of exotic terrestrial triclads were recorded: Bipalium nobile Kawakatsu et Makino, 1982 (2x = 10), Bipalium kewense Moseley, 1878 (2x = 18), and Platydemus manokwari de Beauchamp, 1962 (n = 6, 2x = 12). An extensive occurrence of P. manokwari in the Southwest Islands of Japan may be due to an unexpected introduction of the animal in very recent years.

Karyology and biogeography of Dugesia japonica and Dugesia ryukyuensis in Kyûshû, southern Japan

In southern Japan, two dugesiid species of freshwater planarians are known: Dugesia japonica Ichikawa et Kawakatsu, 1964, and Dugesia ryukyuensis Kawakatsu, 1976. D. japonica is a common and polymorphic species widely distributed in the Far East (karyotypes: n=8, 2x=16, 3x=24). D. ryukyuensis is a species recorded only from the Southwest Islands of Japan (Nansei Shotô) (karyotypes: n=7, 2x=14, 3x=21). Recently, small populations of D. ryukyuensis were found in the lowland areas in Kyûshû on the East China Sea (the Nishisonogi Peninsula, the Shimabara Peninsula, the Gotô Islands, the Satsuma Peninsula, and the Ôsumi Peninsula). The current geographical distribution of D. japonica and D. ryukyuensis in southern Japan can be explained from geological and faunal viewpoints, as follows: (1) two separate inversions by the ancestor of D. japonica, one in the Miocene and one after early Quaternary; (2) only one expansion of its domain by the ancestor of D. ryukyuensis in the Miocene.

Chromosomes of Phagocata kawakatsui and Bdellocephala annandalei from Lake Biwa-ko in Honshu, central Japan

Two lake-dwelling species of paludicolen triclads from Lake Biwa-ko (Honshû, Japan) were studied taxonomically and karyologically. (1) Phagocata kawakatsui Okugawa, 1956, is an epigean species usually inhabiting shallow springs and spring-fed streams in Central Japan. In Lake Biwa-ko, animals were obtained from several bottom stations of the littoral area in the southern part of the northern basin (3–70 m in depth). Chromosome numbers and karyotype: 2x=24 (2m+2sm+2sm+2m+2sm+2m+2sm+2m+2m+2sm+2m+2m). The first pair of metacentric chromosomes is very large in size. (2) Bdellocephala annandalei Ijima et Kaburaki, 1916, an endemic species, is distributed widely in the deep areas of the northern basin (30 to over 100 m in depth). Chromosome numbers and karyotype: 2x=28 (2m+2sm+2sm+2sm+2sm+2m+2m+2m+2m+2m+2m+2m+2m+2m) with the first pair of metacentric chromosomes very long.

Karyology of four land-planarian species of the genus Bipalium from Japan

We have empolyed a new scale for characterizing chromosomal forms in the karyotypes of four species of Bipalium from five localities in Japan. Specimens of Bipalium nobile Kawakatsu et Makino, 1982, from Yokohama had a diploid chromosome number of 2x = 10 (2m + 2sm + 2sm + st & sm + 2sm); specimens of the same species from Toyonaka had this number as well but with slightly different chromosomal form (2m + 2sm + sm & st + 2st + m & sm). An undescribed species from Sanjo, Bipalium sp. 2, with two dorsal stripes and a yellow head crescent, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m); and another undescribed species from Chichijima Island, Bipalium sp. 3, with five dorsal stripes, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m). A non-sexual bipaliid tentatively identified as Bipalium kewense Moseley, 1878, from Chichijima Island had 2x = 18 (2m + 2m + 2m + 2sm + 2st + 2sm + 2sm + 2sm + 2sm).

Variation in karyotypes of Dugesia japonica japonica (Turbellaria) from Osaka Prefecture, Central Japan

An analysis of the karyotypes of Dugesia japonica japonica Ichikawa et Kawakatsu, 1964, from 30 localities of seven river systems in Osaka Prefecture, Central Japan, revealed a total of 26 karyotypes of which 12 are new-found varieties. More than two karyotypes were found in many localities. The mixoaneuploidic triploid karyotype showed the widest distribution (21 localities), orthoploidic diploid karyotype and or- thoploidic mixoploid of diploid and triploid karyotype were next (13 localities, respectively), and other karyotypes (triploidic aneuploid, orthoploidic triploid and mixoploid of triploid & tetraploid) were also found. Some correlation of karyotype with elevation was also detected.