Turbellarian taxonomic database

Abstract / Notes

"A karyological survey of Japanese freshwater planarian P. auriculata was made with 14 local populations
covering the northern 1_2 of Honshu and the southern 1_2 of Hokkaido. A series of highly complicated
chromosomal polymorphisms was found including 2n _ 6 (tentatively denoted as karyotype A), 3n _ 9 (karyotype
B), 3n with secondary modified chromosomes by centric fusion and pericentric inversion (karyotypes C-H),
polyploids (3n, 4n and 6n) with chromosomal deletion (karyotype I-M) and various mixoploids involving
karyotypes B-H (B_D, B_C_E, B_E_F_G_H, etc.). The detailed karyotypic analyses revealed the karyotypes C, D
and G were derived from the B by 3 successive centric fissions. Some supernumerary chromosomes (so-called
B-chromosomes) were observed in the karyotypes D, E, F and J. The karyotype A was widely observed in most of
all populations examined; others were more or less restricted in distribution, the karyotype B-H were found in
the population at Mt. Iwaki, the K-M at Mt. Hakkoda, and the I and J at Mt. Iwaki, Sendai and Mt. Bandai. The
karyotype A (2n _ 6) is probably the basic karyotype of this species and others (B-H, K-M, I and J) were
independently induced from the basic stock A. The complicated polyploids and mixoploids found in P. auriculata
may be resulted from the fact this species often reproduces asexually by fission. The karyologically different
worms occasionally showed some morphological polymorphisms in head shape, body shape, body length, body color
and eye spot number. Two noteworthy morphological variants were found, an eyeless morph which was
characteristically found in the worms with the karyotype F having a large subtelocentric chromosome derived
from the submetacentric of the karyotype B by pericentric inversion, and an unpigmented morph with milk-white
body color, which was found in the karyotype I and possibly caused by a gene mutation."

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