Liliane Frenkiel

Gill filament differentiation and experimental colonization by symbiotic bacteria in aposymbiotic juveniles of Codakia orbicularis (Bivalvia: Lucinidae)

Summary Codakia orbicularis is a tropical lucinid harboring gill endosymbionts which are environmentally transmitted from a free living-symbiont form to the new host generation after metamorphosis. Structural changes occurring in the cellular organization from incomplete gill filaments in young aposymbiotic juveniles to full differentiated gill filaments containing bacterial endosymbionts in reared symbiotic juveniles, were analyzed for juveniles from 250 μm to 2 μm shell-length. Aposymbiotic juveniles possess differentiated gill filaments with ciliated, intermediary, and lateral zones similar to those described in wild juveniles, except for the bacteriocytes which are lacking. Granule cells, which progressively differentiate during the morphogenesis of the gill filament, do not appear as a consequence of symbiosis. Experimental colonization of aposymbiotic juveniles by the free-living symbiont form has been obtained through the addition of unsterilized sand collected from the natural habitat of C. orbicu...

COCCIDIAN (APICOMPLEXA) PARASITE INFECTING STROMBUS GIGAS LINNÉ, 1758 DIGESTIVE GLAND

Abstract This study reports on a new parasite of the digestive gland of the queen conch, Strombus gigas. An intense and generalized sporozoan infection was detected during a reproductive study of S. gigas in San Andres island (Colombia). The parasite was found in the digestive gland of every sampled S. gigas, with a heavy intensity of infection (invasion of every cell) in many animals. The infection of the digestive gland began in the cryptic cells and later secretory cells were also infected, giving way to discharge of sporocysts to the stomach through the digestive gland ducts. Apicomplexa-like trophozoites were embedded in the digestive gland epithelial cells and attached to host cell wall by their conoid end. Several stages were detected: trophozoites, sporocysts, and gamonts containing macrogametes or microgametes. Given the presence of multiple stages at the same time, the entire life cycle of the parasite is assumed to occur within the same host and tissue. The taxonomic position of the parasite should be ascertained by DNA analysis.

Ultrastructural study of the spermatozoon in a tropical lucinid bivalve: Codakia orbicularis L.

Summary In Codakia orbicularis, the spermatozoon has a short cylindrical acrosome separated from a long, curved, tapered nucleus by a large subacrosomal region. The cinetic apparatus is made of a complex system of fibrillar processes linking the distal centriolar satellite bodies to a microtubule-like ring which, in turn, is anchored to the plasma membrane through a fibrillar network issued from the secondary satellites at the basal part of the middle-piece where it is encased in a circular flange. The tail contains a normal axonemal pattern; moreover, a large undulating membrane, oriented in the same plane as the central microtubules, is differentiated along the flagellum. The elongated nucleus together with the differentiation of the middle piece and tail represent a significant modification of the primitive type of spermatozoon.

Storage tissue and reproductive strategy in Lucina pectinata (Gmelin), a tropical lucinid bivalve adapted to a reducing sulfur-rich, mangrove environment

Summary The large Lucinidae Lucina pectinata (Gmelin) is a dominant species in the most confined areas of mangrove swamps where it lives deeply burrowed in reducing mud. In most female individuals, the gonads of this protandric species are in an apparently permanent state of maturity, having a various proportion of small previtellogenic oocytes together with larger oocytes undergoing vitellogenesis and full-grown oocytes which are characterized by their thick jelly coat. Oocyte resorption is also frequent in these gonads. Such a maturation schedule results in a continuous reproductive competence. Resorption of spermatozoa and simultaneous oogonia multiplication take place in spent male gonads allowing for a progressive sex change. In spent and developing stages, gonad-wall cells constitute a thick pseudo-stratified epithelium which gets progressively thinner with gonad maturation and thickens again soon after spawning. The complex cycle of these follicular cells is the result of two complementary function...

Occurrence of Apicomplexa-like structures in the digestive gland of Strombus gigas throughout the Caribbean.

The queen conch, Strombus gigas, is a marine resource of ecological and economical importance in the Caribbean region. Given its importance in this region, and the critical status of most populations, the reproductive biology of this species has been studied to support management decisions. It was from these studies that a generalized sporozoan infection was detected. This study describes the geographic distribution of a coccidian (Apicomplexa) parasite infecting the digestive gland of S. gigas throughout the Caribbean. The parasite was present in every location sampled. Based on histological analysis, the parasites from all locations are similar and appear to complete their life cycle within the digestive gland. The highest occurrence of the parasites was registered in samples from Puerto Rico (54 parasites per field) and Martinique (45 parasites per field). The lowest incidence was registered on the Mexican coast of Yucatan peninsula, at Alacranes and Chinchorro with 17 parasites per field. Data showed significant differences among sites (Kruskal Wallis H=106.957; p ≤ 0.05). The abundance of parasites found in the digestive ducts and in the faeces suggests the liberation of parasites to the environment. A gradual decrease in abundance was found from East to West of the Caribbean sea.

Attenuated reproduction of Strombus gigas by an Apicomplexa: Emeriidae-like parasite in the digestive gland

An intense and generalized sporozoan infection was detected in every population of the queen conch, Strombus gigas through the Caribbean. In this contribution we establish the relationship between occurrences of an Apicomplexa: Emeriidae-like organism and reproductive activity at San Andres archipelago, Colombia. Occurrence of the parasites was estimated counting the feeding stage Merozoites and cysts Sporozoites at 40× magnification. Nonmetric multidimensional scaling analysis (NMDS) was made to correlate the parasites stages abundance with frequency of the reproductive stages. Gametogenesis and spawning were always low coinciding with high numbers of Merozoites, a positive correlation was established between parasite abundance with reabsorption and undifferentiated stages, and negative correlation was observed between parasite abundance with maturity and spawning stages. The nonmetric multidimensional scaling (NMDS) shows that gametogenesis, maturity and spawning increase as the number of parasites decrease, factor that could be threatening reproduction of S. gigas through the Caribbean.

Gill structure and adaptation to high-sulfid environment in the lucinidae, Lucina pectinata

The human articular cartilage is a fundamental tissue in the function of the synovial articulation, has a complex arrangement of cells, as well as collagen fibrils and other elements of the matrix. Grafting has become an accepted method of treating specific clinical problems. Tansplantation of viable articular cartilage cryopreserved would seem to be promising, a means of preserving the donor material in a viable, functional state is highly desirable, but limited progress has been made with fragments of the articular cartilage cryopreserved. Previously, we developed a cryoprotect ion procedure for the c ryopreserva t ion of art icular cart i lage fragments. ( S. Tapia, Cryobiology 30 ( 6 ) : 628, 1993 ), recently we developed a new method for cartilage preservation : SETAMU. ( S. Tapia, Cryobiology 31 ( 6 ) : 5 8 2 , 1994). In the present study, we report the ultrastructural changes of the human articular cartilage cryopreserved, using SETAMU, method developed recently by our unity of cryobiology. The uttrastructural analysis the specimens were realized by transmission electron microscopy (T .E .M. ) , fixed by immersion in glutaraldehyde with ruthenium ( I I I ) hexamine trichtoride (R.H.T.) , and post-fixed in osmium tetroxide with R.H.T., that improved cellular and matrix preservation. Ours results show that SETAMU, play an important role for the cryopreservat ion of the human articular cartilage, preserving the ul t rastructure of the chondrocytes and the matrix. The good cryopreservation of the human cartilage is of particular importance in morphologic research and also in the study of reparation of articular surfaces lbr individuals clinically attain. L IGHT M I C R O S C O P Y A N D L T S E M S T U D I E S OF FUSARIUM R O O T ROT IN BEANS