Karyotype Differentiation within the Elephant Pupinid Snail, Pollicaria mouhoti (Pfeiffer, 1862) (Caenogastropoda: Pupinidae)

Abstract

Mitotic chromosomes of Pollicaria mouhoti were analyzed from gonad tissue. The diploid chromosome number is n = 13, 2n = 26, the fundamental chromosome number is FN = 50. However, intraspecific variation was found between populations of P. mouhoti located in different regions of Thailand. Specimens of the northern dark form possess karyotypes of (7m+3sm+2st+1t) with five large and seven median chromosomes, whereas the southern typical forms are (6m+4sm+2st+1t) with nine large, three medium and one small chromosome. Likewise, differences in the relative length (RL) and centromeric index (CI) between these two allopatric morphs were noted. The existence of heteromorphic chromosome pairs in females but not males supports a potential ZZ (male) – ZW (female) sex chromosome system, as reported for other species in this genus. The dark form specimens, from Loei and Nongbualamphu Provinces, exhibited smaller shells which were black in color throughout their shell, while the typical form specimens from Chaiyaphum, Khon Kaen, Phetchabun and Phitsanulok Provinces had larger shells with a brown body and a whorl which was orange colored on the three last whorls. The results of this study are consistent with the two allopatric morphological forms being distinct subspecies.