Twelve persons were indicted in Philadelphia yesterday after a federal investigation into what a prosecutor called "reptile smuggling." The probe involved animals at eight American zoos, including the National Zoo here.

None of the zoos nor any of their officials was indicted as a result of the 33-month investigation into aspects of a "multi-million dollar industry," according to David W. Marston, U.S. attorney in Philadelphia.

Based on the indictments issued, Marston said, he nevertheless thinks "it's clear . . . (that) the zoos acted wrongfully." He said the nature and degree of possibly wrongful conduct varied from zoo to zoo and case to case, but he declined to distinguish among them.

In a telephone interview, Marston said information about the zoos is being referred to the Interior Department "which has agreed to consider it for possible civil action under the Lacey Act!" The act prohibits interstate transportation of illegally taken wild life.

Edward H. Kohn, deputy director of the National Zoo, said the zoo invites full review and consideration of its policies. He declined further comment.

Among alleged ant, according to Marston, are the sale to the National Zoo on Aug. 6, 1973 of three blue-tongued skinks and two pygmy mulga monitors, and the sale on Aug. 17 of two green tree monitors, one tree monitor, one carpet python and four banded Fiji Island iguanas. Skinks and monitors are members of the lizard family.

Two green tree monitors and two Fiji iguanas, which have dinosaur-like heads and gimlet orange eyes, were on view last spring at the National Zoo's reptile house.

Marston said the indictments are the first under the international provisions of the endangered species act of 1973 and said he hoped they would help change the way American zoos do business.

He said the investigation stemmed from a 1974 incident in New York in which Customs agents spotted an allegedly mislabeled shipment of animals and tracked it to its destination.

Some animals in the investigation could not have been exported under laws of their country of origin, Marston said. In other cases, he said, animals could have been shipped legally if proper documents had been obtained. In those cases, he said, the so-called smuggling appeared to be a matter of convenience.