Yann Quilichini

Ultrastructural study of the spermatozoon of Nicolla testiobliquum (Digenea, Opecoelidae) parasite of brown trout Salmo trutta (Pisces, Teleostei)

The present paper describes the spermatozoon of Nicolla testiobliquum (Digenea, Opecoelidae), an intestinal parasite of brown trout Salmo trutta, studied by transmission electron microscopy. The mature spermatozoon possess two axonemes of 9 + “1” pattern, two mitochondria, a nucleus, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. A comparative study between N. testiobliquum and Nicolla wisniewskii shows mainly two different dispositions of the two mitochondria in these two species of a same genera. Moreover, the comparison of each of these spermatozoon features with others digeneans, in general, and other Opecoelidae in particular, is also presented. It appears that the organisation of the posterior part of the spermatozoon, the disposition of cortical microtubules and external ornamentation associated with spine-like bodies could be interesting elements for phylogeny.

SPERMIOGENESIS AND SPERMATOZOON ULTRASTRUCTURE OF NICOLLA WISNIEWSKII (DIGENEA: OPECOELIDAE), AN INTESTINAL PARASITE OF BROWN TROUT SALMO TRUTTA (PISCES: TELEOSTEI)

Spermiogenesis and ultrastructure of spermatozoon of Nicolla wisniewskii (Digenea, Opecoelidae), an intestinal parasite of Salmo trutta, were studied by electron microscopy. Spermiogenesis follows the general pattern found in the Digenea. It begins with the formation of a differentiation zone, including striated rootlets associated with 2 centrioles and an intercentriolar body. The flagella undergo a rotation of greater than 90°. Then, their fusion with the median cytoplasmic process is proximodistal and asynchronous. A peculiarity was observed before the fusion of flagella, i.e., the attachment zones joined as 2 pairs by an electron-dense bridge. The mature spermatozoon is characterized by 2 axonemes, cortical microtubules, a nucleus, 2 mitochondria, external ornamentation, and spinelike bodies. At the posterior end of flagella, the spermatozoon is also characterized by the presence of a central element of the axoneme and without the 9 microtubule doublets. These results were compared with those of the other digeneans and, in particular, with other species of Opecoelidae. It appears that the number of cortical microtubules and their localization in the spermatozoon may be an interesting feature of their phylogeny.

Ultrastructural study of the spermatozoon of Pronoprymna ventricosa (Digenea, Baccigerinae), parasite of the twaite shad Alosa fallax Lacepede (Pisces, Teleostei)

In this paper, we describe the ultrastructural organisation of the spermatozoon of a Digenea Baccigerinae Pronoprymna ventricosa. This spermatozoon possesses the elements found in the others digeneans: two axonemes with 9 + “1” pattern, a mitochondrion, a nucleus, cortical microtubules and external ornamentations. However, this spermatozoon presents two particularities. The first is the presence of a single field of cortical microtubules disposed in the ventral side (mitochondrion side) of the spermatozoon. In the other digeneans, two fields of cortical microtubules are observed between the two axonemes. The second is the presence of external ornamentations not associated with cortical microtubules. These two points have, to our knowledge, never been described in another digenean. Moreover, a separation in two groups of the digenean spermatozoa is proposed in relation to the localisation of the external ornamentations. We propose to distinguish a first group exhibiting these elements in the proximal part of the spermatozoon and a second one with external ornamentations in a second part of the gamete.

Spermiogenesis and sperm ultrastructure of Deropristis Inflata Molin, 1859 (Digenea, Deropristidae), a parasite of Anguilla anguilla

To our knowledge, this paper describes the first ultrastructural results on spermiogenesis and the spermatozoon of a Digenea belonging to the family Deropristidae, Deropristis inflata. Spermiogenesis follows the usual pattern found in the digeneans, but a single noteworthy characteristic concerns the centriole, which presents a “prominent pear-shaped electron-dense region.” Spermiogenesis in D. inflata begins with the formation of a differentiation zone. The two centrioles give rise to flagella. These two flagella undergo a rotation of 90° and fuse with the median cytoplasmic process. The proximo-distal fusion occurs at the level of attachment zones. The mature spermatozoon of D. inflata possesses five regions and presents all the features found in the digenean gamete. However, several characteristics allow us to distinguish the spermatozoon of D. inflata from other digenetic trematoda, namely the external ornamentations of the plasmic membrane, the anterior and posterior extremities. Furthermore, the distal part of the nucleus in front of those of the mitochondria appears such a distinctive criterion in the spermatozoon of this species. Our ultrastructural investigations produce new data on the reproduction of D. inflata, which may be useful for the understanding of the phylogenetic relationships in the Deropristidae family.

ULTRASTRUCTURAL STUDY OF SPERMIOGENESIS AND THE SPERMATOZOON OF CREPIDOSTOMUM METOECUS (DIGENEA: ALLOCREADIIDAE), A PARASITE OF SALMO TRUTTA (PISCES: TELEOSTEI)

Spermiogenesis and the spermatozoon of Crepidostomum metoecus, an intestinal parasite of brown trout Salmo trutta, were studied by transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone in front of 2 centrioles associated by an intercentriolar body. Each centriole is linked to a striated rootlet, and gives rise to a flagellum. The rotation of flagella is greater than 90°; their fusion with the median cytoplasmic extension is proximodistal and asynchronous. The spermatozoon is formed after constriction of arched membranes. The spermatozoon possesses 2 axonemes of the 9 + “1” pattern, a nucleus, mitochondria, and glycogen. A major feature is the presence, in the anterior part, of external ornamentation and a lateral expansion associated with spinelike bodies. Another attribute is the presence of 2 mitochondria rather than just 1, as in most of the digenean spermatozoa. To our knowledge, this study is the first undertaken with a species of the Allocreadiidae.

Spermatozoon Ultrastructure of Gyliauchen sp. (Digenea: Gyliauchenidae), an Intestinal Parasite of Siganus fuscescens (Pisces: Teleostei)

The ultrastructure of the mature spermatozoon of Gyliauchen sp., a parasite of the dusky rabbitfish Siganus fuscescens, was studied by transmission electron microscopy. The spermatozoon possesses two axonemes of the 9+“1” pattern of Trepaxonemata, four attachment zones, one mitochondrion, a nucleus, cortical microtubules, external ornamentation of the plasma membrane, and spine-like bodies. The main characteristics of this spermatozoon are the presence of one mitochondrion, spine-like bodies not associated with the external ornamentation, and a posterior extremity of type 3 that is characterized by the following sequence: posterior extremity of the nucleus then posterior extremity of the second axoneme. Numerous other ultrastructural features are also discussed and compared to the digenean spermatology literature. This is the first study of a member of the Gyliauchenidae and the fourth within the Lepocreadioidea. The results show that many ultrastructural characters are variable within this superfamily and could be useful for phylogeny.

Sperm ultrastructure of the digenean Siphoderina elongata (Platyhelminthes, Cryptogonimidae) intestinal parasite of Nemipterus furcosus (Pisces, Teleostei)

The ultrastructure of the spermatozoon of Siphoderina elongata was studied by transmission electron microscopy. A description and drawings of the mature spermatozoon are presented in this paper. Several ultrastructural elements of this male gamete have been observed: a nucleus, two mitochondria, two axonemes of 9 + “1” pattern, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. The presence, the location or the number of these elements have been compared with other digenean spermatozoa. Moreover, a close attention was paid to the organization of the external ornamentation region. This zone presents a single row of cortical microtubules disposed in a semi-circle around a mitochondrion and associated with external ornamentation and spine-like bodies. The aim of this study is to highlight criteria which can be interesting in Platyhelminthes phylogeny.

Sperm ultrastructure of the gall bladder fluke Anisocoelium capitellatum (Digenea: Cryptogonimidae), a parasite of Uranoscopus scaber (Pisces: Uranoscopidae)

Ultrastructure of mature spermatozoon of Anisocoelium capitellatum is described with transmission electron microscopy. The description gave evidence of some characteristics of this digenean. The male gamete presents features allowing the distinction between A. capitellatum and other digenetic trematodes. It is characterized by original anterior and posterior extremities. The peripheral doublets appear prior to the central cores in the anterior extremity of axoneme. In the distal part of the spermatozoon, these ultrastructural features are also the first elements disappearing in the axoneme 1 and the last remaining in the axoneme 2. Another important peculiarity of the spermatozoon is the presence of three mitochondria.

Ultrastructure of the spermatozoon of Holorchis micracanthum (Digenea: Lepocreadiidae), an intestinal parasite of Plectorhinchus mediterraneus (Pisces, Teleostei) in Senegal

The mature Holorchis micracanthum spermatozoon exhibits an apical cone of electron-dense material forming a lateral extension, extramembranar ornamentations, and two fields of cortical microtubules, delimited by attachment zones. The axonemes, of the 9 + “1” pattern of the Platyhelminthes, are shifted longitudinally, one compared to the other. The nucleus, with a fibrous chromatin and a more or less circular section, granules of electron-dense material, and a moniliform mitochondrion are present. The latter, in longitudinal sections, appears in the form of successive bulges, connected to each other by a fine mitochondrial cord, and extends along almost the whole length of the gamete. To our knowledge, a moniliform mitochondrion has never been described before in a digenean. Likewise, the presence of a lateral extension of an apical cone of electron-dense material has never been previously reported in the Lepocreadioidea. In addition, in this work, we show for the first time the existence of extramembranar ornamentations in a species of the Lepocreadiidae.

Morphological, chemical and genetic differentiation of two subspecies of Cistus creticus L. (C. creticus subsp. eriocephalus and C. creticus subsp. corsicus).

Cistus creticus L., an aromatic species from the Mediterranean area, contains various diterpenes bearing the labdane skeleton. The production of essential oil from this species has potential economic value, but so far, it has not been optimized. In order to contribute to a better knowledge of this species and to its differentiation, the morphological characters, volatile chemical composition and genetic data of two subspecies (C. creticus subsp. eriocephalus and C. creticus subsp. corsicus) were investigated. The leaf trichomes were studied using scanning electron microscopy. The chemical composition of Corsican essential oil (C. creticus subsp. corsicus) has been reported using GC, GC/MS and 13C NMR; the main constituents were oxygenated labdane diterpenes (33.9%) such as 13-epi-manoyl oxide (18.5%). Using plant material (54 samples) collected from 18 geographically distinct areas of the islands of Corsica and Sardinia, the basis of variation in the headspace solid-phase microextraction volatile fraction and an inter-simple sequence repeat genetic analysis were also examined. It was shown that the two subspecies of C. creticus differed in morphology, essential oil production, volatile fraction composition and genetic data.