Ultrastructure of the spermatozoon of Macvicaria obovata (Digenea: Opecoelidae), a parasite of Sparus aurata(Pisces: Teleostei) from the Gulf of Gabès, Mediterranean Sea. | LitMetric
The ultrastructural organization of the spermatozoon of the digenean Macvicaria obovata (Opecoelidae) is described by transmission electron microscopy. Alive digeneans were collected from the digestive tract of Sparus aurata (Teleostei, Sparidae), caught from the Gulf of Gabès in Chebba, Tunisia (Eastern Mediterranean Sea). The male gamete of M. obovata is a filiform cell, tapered at both extremities and exhibits typical characters such as two axonemes of different lengths showing the 9+'1' trepaxonematan pattern, a nucleus, mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. Cortical microtubules are absent in the anterior spermatozoon extremity and appear after the disappearance of the electron-dense material. The first mitochondrion is of moniliform type and it is associated with the external ornamentation of the plasma membrane and spine-like bodies. The second mitochondrion is more posteriorly located, reaching the nuclear region. The present study provides new data on the mature male gamete of M. obovata that may be useful for the understanding of digenean relationships and phylogenetic studies.
The ultrastructural organization of the spermatozoon of the digenean Macvicaria obovata (Opecoelidae) is described by transmission electron microscopy. Alive digeneans were collected from the digestive tract of Sparus aurata (Teleostei, Sparidae), caught from the Gulf of Gabès in Chebba, Tunisia (Eastern Mediterranean Sea). The male gamete of M.
Maturation of trematode larval stages is expected to be temporally and spatially adapted to maximise the encounter with the adequate downstream host, i.e. the host, which will be infected by this parasite stage.
Morphological and molecular characterisation of specimens of Macvicaria spp. (Digenea: Opecoelidae) from five species of Mediterranean sparids (Teleostei: Sparidae) sampled in the Bizerte Lagoon and the Bay of Bizerte (Tunisia) revealed the presence of two species complexes designated as "obovata" and "crassigula" groups. Detailed comparative morphological and phylogenetic analyses revealed that two of the specimen sets, one from each complex, represent species new to science.
Due to their shallow and confined nature, lagoons provide excellent conditions for the transmission of digenean trematode parasites that require two or more intermediate hosts for the completion of their complex life cycles. However, these unstable environments are characterised by an internal heterogeneity and a large variation of a range of abiotic variables. We conducted a series of experiments in a comparative framework to assess the effect of a number of exogenous factors known to exhibit marked fluctuations in the lagoonal environment, i.
In a study of the digeneans parasitising molluscs in the Els Alfacs lagoon (Ebro Delta, Western Mediterranean) we found heavy infections with sporocysts emitting two types of cotylocercous cercariae in the prosobranch trochid gastropod Gibbula adansonii and with metacercariae in the prosobranch nassariid gastropod Cyclope neritea. A comparative analysis using ITS ribosomal DNA sequences from these larval stages and published sequences of 17 larval and adult opecoelid stages allowed us to elucidate the life-cycle of Macvicaria obovata and to confirm the identification of Cainocreadium labracis based on cercarial morphology. We provide molecular evidence for the identification and the first detailed morphological descriptions of the intramolluscan larval stages of the two opecoelid species as well as partial 28S rDNA sequences to aid future studies on systematic relationships within the Opecoelidae.
