Gregarine Cephaloidophora communis Mawrodiadi, 1908 in the Barnacle Euraphia rhyzophorae, Oliveira, 1940 from Brazil

The gregarine Cephaloidophora communis was observed for the first time in Brazil in the barnacles Euraphia rhyzophorae collected in Angra dos Reis, Rio de Janeiro, Brazil, between 1990 and 1996. Histological studies showed growth phases of the parasite in specific parts of the digestive system. The intracellular forms occurred in the vacuoles of the intestinal cells. Syzygy was frequent, and the most common form following syzygy was cylindrical, with a single membrane. The cytoplasm of the gregarines was always irregular, dense, and occasionally presenting a dark stoch area.

The gregarines were arranged in the traditional phylum Sporozoa, renamed Apicomplexa by Levine (1970). They are parasitic protoctists, all endoparasites of invertebrate or vertebrate hosts. They show different degrees of host specificity (Vivier & Desportes 1989).
Dusznski (in Vivier & Desportes 1989) estimates that there are about 500 species in the class Gregarinia. The wide majority of gregarines are monoxenous, but some species may be heteroxenous because their life cycles are still unknown.
Gregarines in the intestine of barnacles were first reported by Kölliker (1848), and described in the intestine of Balanus pallidus as Gregarina balani. Mawrodiadi (1908) demonstrated C. communis in B. eburneus, B. amphitrite, B. crenatus andMegabalanus tintinnabulum. Tregouboff (1912) and Kamm (1922) pointed out that the members of the family Cephaloidophoridae are parasites of crustaceans and develop within the cells, producing one or more oval spores. Ball (1973) and Henry (1938) also studied gregarines in barnacles. Tuzet and Ormières (1964) contributed to their morphology and Barnes (1953) to the developmental physiology of barnacle larvae and their gregarines. Reger (1966) and Reger et al. (1967) studied the spores of C. communis in the cells of the intestine of M. tintinnabulum using electron microscopy. Arvy and Nigrelli (1969), reported the gregarines in intestine of B. nubilis and B. eburneus collected on Coney Island, New York, near the Osborn Laboratory of Marine Science.
Gregarines in barnacles have been studied by various authors in the United States of America, England, France and Germany. In Brazil there has been relatively little interest in these sessile crustaceans. Since, this is the first report of gregarine in the intestine of the barnacle Euraphia rhyzophorae, Oliveira (1940) collected on the shore in Angra dos Reis, near the city of Rio de Janeiro.

MATERIALS AND METHODS
Approximately 150 adult barnacles of E. rhyzophorae were collected from the roots of Rhyzophora mangle on the shore in Angra dos Reis, State of Rio de Janeiro, Brazil, between 1990 and1996. The barnacles, with or without substrate, were immediately immersed in a fixative such as Bouin's (according to Duboscq-Brasil) or Heidenhein's original of Susa.

RESULTS AND DISCUSSION
C. communis gregarines were observed in the mid and hind gut of the barnacles E. rhyzophorae ( Fig. 1, GR, INT). This species of gregarine was described by Mawrodiadi (1908) from other species of barnacles: B. improvisus, B. amphitrite, B. eburneus and M. tintinnabulum, in which oval spores 50 to 60 µm in size were observed inside. In gregarines of the family Cephaloiphoridae these organisms can be seen associated during their growth in groups of usually two individuals, or may develop singly (Fig. 1), as reported by Vivier and Desportes (1989).
The gregarines in E. rhyzophorae were always numerous in the digestive tube and exhibited different growth phases. Although almost all organs of the host may be infected by apicomplexan zoites or other forms, there is always a motile stage that may penetrate the target or-gans, where the development may be completed (Vivier & Desportes 1989). Fig. 1 shows deuteromites (GR) containing dark round bodies (MR) of stock material in the lumen of the midgut (INT). NU identifies the nucleus of one of the epithelial cells.
The forms seen next to the epithelial cells (Fig. 2 EP) are limited to the plasma membrane that lines the intestinal lumen. The epithelial wall of the intestine in barnacles has extended narrow cells. Their cytoplasm is dense, with Intestine of Euraphia rhyzophorae midgut. a central nucleus, round and rich in chromatin. Within the cytoplasm clear vacuoles are seen (Fig. 3, VC). These contain one or more sporocysts measuring about 40 µm which stand out as dark bodies in the hyaline vacuoles (ESP). They emerge into the lumen throughout the entire intestine.
These gregarines of rounded forms (Fig. 4, GR) emerge from the duct (TB) of the pancreatic gland (GE). This picture shows where the duct of the pancreatic gland comes in contact with the epithelium of the intestine and two spherical gregarines. Some gregarines (Fig. 5, GR) are seen in the intestinal folds (DB). Others appear to be passing from the midgut into the proctodeum, remaining in the posterior intestine close to the fecal mass (Fig. 6, BL). In this longitudinal section one sees the sphincter (VL) that separates the midgut from the posterior intestine. Fig. 7 shows a giant gregarine (GR), about 150 µm long, close to a row of epithelial cells. In the mid part of the deutomerite (Fig. 8, DT) there is a disctinct nucleus (NU), spherical, poor in chromatin (CR) but with an accentuated nuclear membrane. A dense nucleolus (NUC) is present. The cytoplasm is granular (CT), almost alveolar but it may also show dark spots, as in Fig. 1 (MR).
Some gregarines present matching posterior parts, familiar figures of syzygy, as can be seen in Figs 2 and 8.
The gut parts of E. rhyzophorae, can be observed in Fig. 9, where within the enteron (ENT) a round gregarine (GR), the esophagean valve (VL), a part of the esophagus (ES) and the pharynx (FA), which constitutes the foregut are detected; the pancreatic gland (GE) is always lateral to the intestinal wall.
C. communis found in the barnacles E. rhyzophorae in Brazil may be another giant gregarine like Porospora giganteal and Didymophyes gigantea that parasitizes coleopterans larva (Grassé 1953). In barnacles there was no evidence of cellular damage associated with the presence of these gregarines.