PARASITES OF THE COMMERCIAL SHRIMPS, PENAEUS AZTECUS IVES, P. DUORARUM BURKENROAD AND P. SETIFERUS (LINNAEUS) i--DWAYNE NATHANIEL KRUSE, Department of Biological Sciences, Florida State University, Tallahassee, Florida Introduction The U. S. Fish and WildHfe Service Fish-ery Statistics of the United States for 1956 show that shrimp are by far the leading sea-food industry in the United States. The total catch for 1956 was worth $70,894,000. The Gulf of Mexico produced $62,499,000 of this amount. Though the importance of shrimp in the fishing economy has been in-creasing steadily since 1956, little is known about their parasites. Knowledge concern-ing deleterious effects, distribution and host specificity of shrimp parasites is desirable for both academic and economic interests. The specific goals of this preliminary sur-vey were: (1) description and identification of the parasites of P. aztecus, P. duorarum and P. setiferus from Alligator Harbor and Apalachicola Bay, Florida; (2) determina-tion of the incidence and site of infection of these parasites; and (3) recording observa-tions regarding host specificity and life his-tories of these parasites. After the present paper had been sub-mitted for publication Hutton, et al ( 1959) published a preliminary report dealing with parasites of shrimp in Florida waters. For a historical review of the subject the reader is referred to this work. Materials and Methods Collection of Hosts The shrimp hosts, Penaeus duorarum, P. aztecus and P. setiferus, were collected from three locations along the northwest Gulf coast of Florida between June and Novem-ber, 1958. Most P. duorarum were collected at approximately monthly intervals from July through October in Alligator Harbor, Franklin County, Florida. These shrimp were collected in the grassy flats on the sand bar in the mouth of the harbor with either a push net or a small beam trawl. One collection of ten specimens of P. duo-rarum was made in Apalachicola Bay, Frank-lin County, Florida in October; another col-lection of four shrimp was made in the grassy flats near the mouth of the St. Marks River, Wakulla County, Florida in Septem-ber. All specimens of P. aztecus and P. seti-ferus examined were collected from Apa-lachicola Bay with a large shrimp trawl. The collections were made at seven different stations in the bay that varied from shallow grassy flats near its head to a depth of 40 feet near St. George's Island. P. aztecus and P. setiferus were collected at approximately monthly intervals from June through Oc-tober. The shrimp were identified with the aid of the keys to the family Penaeidae by Anderson and Linder (1934) and Voss (1955). Examination of Hosts All of the shrimp caught were macro-scopically examined for evidence of a micro-sporidian infection locally known as "cotton shrimp", "blue shrimp" or "milk shrimp". The incidence of this infection in relation to the total catch was noted. The infected specimens were either preserved in 10% formalin or brought back alive to the labo-ratory at Florida State University for further study. A representive sample of normal "non-cotton shrimp" was taken from each station; these were transported alive in three gallon glass jars to the laboratory for com-plete examination. The shrimp were dissected alive in petri dishes in a small amount of sea water or physiological saline. Hosts which had been iced or preserved in formalin proved to be unsatisfatcory for examination. The diges-tive gland in iced shrimp liquefies rapidly and fills the hemocoel with cytolized yellow tissue making small translucent parasites 1 A portion of a thesis submitted to the g^raduate Council of Florida State University in partial fulfillment of the requirements for the degi-ee of Master of Science. -A contribution from the Department of Biological Sciences and the Oceanographic Institute (No. 120), Florida State University.