Reference: Biol. Bull 175: :-i A New, Disjunct Species of Triclad Flatworm (Turbellaria: Tricladida) From a Spring in Southern New England DOUGLAS G. SMITH \fn.\cinii nl /i>i>/di;\: I /;/Y<v\;/r . / I/</\M/< Ini^eiis. Amlwrst. Massachusetts 01003-0027 and Museum 1 ( 'imii'tiniiivi' /.tioloxy. Harvard L'nivcrsity. Cumhrulxe. Mu^aelinsetts 02138 Abstract. An undescribed species of tlatworm belong-ing to the genus /Wru'//.\ (family Planaridae) is reported from a spring in western Massachusetts. The new species represents the first recorded occurrence of Pol reel i\ in eastern North America. I he morphological uniqueness and geographical disjunction of the new species suggests that it has been isolated from congeneric forms for a con-siderable length of time. However, it is alternatively pos-sible that the species' existence in western Massachusetts is the result of introduction from some as yet unknown "natural" range elsewhere. If in fact naturally occurring in New England, the new species could be a survivor of a pre-glacial fauna that survived glacial advances by liv-ing in groundwater habitats under the ice sheet. Introduction The freshwater flatworm genus /WmV/v as recently denned by Gourbault ( 1972 land Kenk (1973). ischarac-tcii/cd bv certain morphological features which vary lit-tle among described species. Within the genus, two sub-genera are recogni/cd (l'<<l\< e/i\ and \< /<///</). the basis of distinction being founded in the degree of musculature associated with the genital atrium (Kenk. 1953. 1973). Only a lew species are prcsentlv assigned to Seicllia. in which the atrium is provided with an extensive and thick musculature Apart from the differences in atrial muscu-lature sep.' elis( \en striclo). without exten-sive atrial nnr< ilature. and S'i /<///</. the distinctions among the sevei n species in the genus are 1 1 m i ted to differences in the ipe and position of \anous com-cd 2(> (eh. ' lul ponents of the male reproductive system and. to a lesser extent, the presence or absence of muscular prostatic or-gans also known as adenodactyls. The distribution of Polyet'li.\ covers a large portion of the Northern Hemisphere (Kenk. 1953: Ball. 1975). In North America, the known species are restricted to the western third of the continent. Kenk (1953) proposed that the North American distribution of Pol reel is is a re-sult of pre-glacial dispersal from Asia across the Bering Strait when a land bridge existed during periods of lower sea stands. According to Kenk ( 1953). subsequent glacia-tions have controlled or adjusted the distribution of cer-tain species. Kenk's ( 1953) synthesis of Polyeelis distri-bution has been adopted by Ball ( 1975). Recent investigations of springs in western Massachu-setts, in the northeastern United States, have revealed the existence of an undescribed species of Polyeelis. The new species possesses, among other distinctive morphological features, a speciali/ed gland situated near the reproduc-tive structures, termed the ventral gland, which is unlike that of any other described species of /WroY/.s or any other known North American triclad species. This paper provides a description of the new species and attempts to explain the disjunct occurrence of the new species in New Fngland. Materials and Methods The spring in which the new species was found is in Sunderland. Franklin County, Massachusetts and repre-sents the i\ pe locality. The spring is the principal source of water for a state-owned fish hatchery. Specimens were collected on 25 August, 22 September, 30 October, 1987, l<
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