INTRODUCTION Several of the common ocean fishes off the California coast are heavily infested with the isopod Livoneca vulgaris. Little is known about Livoneca except that it is a protandrous hermaphrodite; while young, it is a male with functional testes and as it matures. certain tissue in the body developes into ovaries, while the testes degenerate. It is distinquished morphologically from others of the same genus, by the following characteristics: its eyes are sep- arated by three times their width, the head terminates in a broad, subtruncate lobe about twice the width of the eye, the telson is twice as broad as it is long, the total body length is up to 32mm. (Hatch,1947). Most of the species of flatfish in Monterey Bay were infested with Livoneca. This study is based on two of the flatfishes most commonly caught, the Pacific sanddab, Citharichthys sordidus and the starry flounder, Platichthys stellatus. These are both bottom dwelling fish, which are born with one eye on each side of the head, one of which migrates to the other side by the time they are inch in length. They are found from southern California to Arctic Alaska (Miller, 1972). Their underside is white and smooth, their upper side is rough and a brownish-green color. The objectives of this investigation were to examine the diet and the nature of attachment of Livoneca to its hosts. METHODS AND MATERIALS Flatfish were caught in Monterey Bay by pole-fishing and otter trawling and kept alive in sea water tanks with constant running sea water ataapproimately ,1%. Isopods from dead fish were kept in a separate aerated tank with constant flowing sea water at 1400. To study the position of the iso- pod on the gill, infested fish were quick-frozen in liquid nitrogen. The gill flap was then cut away, exposing the isopod in place in the gill chamber. The gut and diverticula were removed from livoneca vulgaris by dissection after they had been rendered motionless by immersion in magnesium chloride. This prevented rapid emptying of gut and diverticula. Examination of gut and diverticula contents took place under 10X and 100X power. The presence of blood in the diverticula was determined by the Wilkinson and Peters Benzidine Peroxidase Reaction. Benzidine di Hydrochloride was first added to the diverticula, then a few frops of glacial acetic acid, and then a few drops of hydrogen peroxide. The immediate appearance of a dark blue color indicated the presence of hemoglobin. Blood pigments were extracted from the diverticula by adding sodium carbonate to a sample, heating to boiling, and centrifuging for fifteen minutes at 200 rpm. The supernatant was poured off and a few drops of concentrated sulfuric acid was added to the diverticula to further extract the pigments. Two mls. of water was added and the contents centrifuged for another fifteen minutes at 200 rpm. The supernatant was run on a Beckman DB-G spectro- photometer to obtain wavelengths at which the hemochromogen absorbed. The same extraction procedure was performed on samples of flat- fish blood and spectra was taken to compare with the spectra of the blood in the diverticula. RESULT Eighty two fish were examined and all but one were infested with livoneca in both gills. Generally the size of the isopod in the gill was proportional to the size of the fish, but there were too many exceptions for this data to be statistically significant. Usually one Livoneca per gill was found, but up to four isopods were found in a gill. Since the two sides of the flatfish markedly differ, isopods in the lower and upper gill were compared. The dorsal side of the isopod matched the color of the side of the fish it was on. No relationship was found between the number of isopods or their sex and the side of the fish they occupied. Female Livoneca were found with their heads in the anterior part of the gill chamber, facing the anterior end of the host, with the dorsal surface lying next to the outer side of the gill chamber. Males were generally found with their heads facing the anterior end of the fish, but their dorsal side could be facing either the inner or outer side of the chamber. Young isopods, two to five mm. in length were often found crawling on the outer gill filaments. Externally, parasitized fish couldn't be distinquished from non-infected fish. Ovigerous females with large brood pouches leave an indentation in the gill chamber where the brood pouch rests. Both males and females have hooked pereiopods which they use to attach to the host. These leave holes of about one mm. diameter in the inner side of the gill. Sometimes the distal parts of the gill filaments are destroyed by the isopod. Females in the date-brooding stages contained no food in their guts or diverticula. Diverticulas of males and females in the early brooding stages contained blood, which was determined to be hemoglobin by comparing adsorption peaks of blood pigments ex- tracted from the blood of Citharichthys sordidus and the blood in livoneca's diverticula. Mouthparts of Livoneca are very similar to those in the family Aegidae, which are very frequently found with their guts and thoracic segments full of blood. (Bowman,1960). Examina¬ tion of the gut revealed no other food preference; all guts were empty except for minute fragments of what looked like bacteria. Young Livoneca, up to three to four mm. would consume young dead flatfish. DISCUSSION The gill chamber is a favorable place for Livoneca to live; it is protected from predation unless its host is consumed, it is provided with a good supply of oxygenated water, food particles, and a convenient blood supply is available. It's characteristic orientation could be keyed to catching small food particles that pass through the gill. It would be advantageous for Livoneca not to destroy this chamber by consuming it. Possibly the gill fila- ments are destroyed to make more room for the growing isopod or as a result of Livoneca raking them for food. Other damage to the fish could be caused by the fact that large, ovigerous females occupy most of the gill chamber, possibly obstructing the flow of water through the gill, thus reducing oxygen uptake. Results show that young isopods just hatched consume dead fish until they are at least three to four mm. in length. However, males larger than this and females will not eat the flesh, although they may cling to it. Eventually, isopods deprived of a blood supply, die. This implies that during their free-living stage, young Livoneca can scavange for food while searching for a host. After a certain life stage Livoneca must find a host or perish. Blood sucking continues until the female enters the late brooding stage. It then ceases, although there is no change or degeneration of mouth parts. Since t he hosts blood provides a steady diet, it would not be necessary for Livoneca to gorge itself. This might explain the empty gut. It was not determined why blood is stored in the diverticula and never in the gut. Possibly there are enzymes present in the diverticula to digest the blood. It is also a convenient place to store blood and use it a little at a time. Livoneca has biting and sucking mouthparts which enable it to draw blood. It bores through the tissue until it reaches a blood supply; this could account for the small holes in the fish found under the mouthparts when the isopod is removed. SUMMARY A study of the attachment of Livoneca vulgaris to its hosts, Citharichthys sordidus and Platichthys stellatus, showed that their characteristic orientation is with the head in the anterior part of the gill chamber, pointed toward the anterior of the host and its dorsal surface lies against the outer flap of the chamber. A parasitized gill chamber may be missing gill filaments or have an indentation on the inner side as a result of the female's swollen brood pouch. Livoneca's diet is fish blood which it stores in its diverticula. 370 A 255 3900 — D aou 40mu 700 A 409 100. 100 KEY TO THE FIGURES Figure 1. Livoneca vulgaris: A, maxilliped, ovigerous female; B, second maxillae, ovigerous female; C, first maxillae. ovigerous female; D, mandibles, ovigerous female Figure 2. Spectra of hemochromogen: A, Hemochromogen extract from blood of Citharichthys sordidus, peak at 409 mu.; B, Hemochromogen extract from blood in diverticula of Livoneca vulgaris, peak at 409 mu. LITERATURE CITED 1. Bowman, Thomas E.. 1960. Description and notes on the Biology of Lironeca Puhi, N. Sp. (Isopoda: Cymothoidae). Crustaceana. 1:83-91 2. Hatch, Melville, 1947. Chelifera and Isopoda of Washington and Adjacent Regions. U. of W. Publications. 10:207,211 3. Light, Smith, Pitelka, Abbott, Weesner, 1964. Intertidal Inver- tebrates of the Central California Coast. University of Calif- fornia Press. Berkeley and Los Angleles. 387p. 4. Menzies R., Thomas Bowman and Franklin Alverson. 1955. Studiese on the Biology of the Fish Parasite Livoneca convexa Richardson (Crustacea, Isopoda, Cymothoidae). Wasman J. Biol.. 13. 277-294 5. Miller, Daniel J. and Robert N. Lead, 1972. Guide to the Coastal Marine Fishes of California. Fish Bulletin 156. State of Calif- ornia Department of Fish and Game. 80p. 6. Norman, J. R. 1934. A Systematic Monograph of the Flatfishes. Oxford University Press. London. 435p.