Effects of rare earth element samarium doped zinc oxide nanoparticles on Mytilus galloprovincialis (Lamarck, 1819): Filtration rates and histopathology

BACKGROUND

Doping was reported to improve the photo catalytic performance, antioxidant, antibacterial and other biological properties of nanoparticles. While, improving the nanoparticle properties, doping could change toxicity profile to living organism. Hence, the aim of this work was to assess the effects of samarium doped zinc oxide nanoparticles (Sm doped ZnO NPs) on the edible mussel Mytilus galloprovincialis.

METHODS

Sm doped ZnO nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) techniques. 156 mussels were exposed during 7 days to a low, intermediate and high concentration of Sm doped ZnO NPs (0.5, 1 and 1.5 mg/L, respectively). The filtration rates were assessed after 1 and 2 h. Histopathological alterations were determined in gills, digestive glands and gonads using a quantitative analysis.

RESULTS

The filtration rates decreased in all individuals exposed to Sm doped ZnO NPs, a significant decrease was noted with the low and intermediate concentration (0.5 and 1 mg/L) of Sm doped ZnO NPs after 1 and 2 h, respectively. The histopathological index (Ih) estimated for gills, digestive glands and gonads showed differences depending on the organ and the nanoparticle concentration. The highest Ih were reported for digestive glands and female gonads exposed to the intermediate concentration (1 mg/L) of Sm doped ZnO NPs. As for gills and male gonads, the highest Ih were noted with the high concentration (1.5 mg/L) of Sm doped ZnO NPs.

CONCLUSION

Results from this study revealed the toxicity of Sm doped ZnO NPs in Mytilus galloprovincialis gills, digestive glands and gonads. The toxicity induced by this nanoparticle varies depending on the organ and the concentration.

Placobdella nabeulensis sp. nov. (Hirudinea: Glossiphoniidae), a new glossiphoniiform leech from Palearctic North Africa

BACKGROUND

Herein, we describe a new species of turtle blood-feeding leech, Placobdella nabeulensis sp. nov. from Palearctic North Africa (Tunisia and Algeria). The new species is described based on detailed morphological analyses using light and scanning electron microscopes.

RESULTS

Apart from the detailed morphology of the atrium, morphological features alone do not sufficiently separate the species from congeners due to the absence of distinct diagnostic characters. Therefore, we turned to molecular data to better distinguish this new species from other members of the genus and establish a basis for its genetic separation. Four DNA fragments were successfully amplified, including mitochondrial COI and 12S rDNA, as well as nuclear 28S rDNA and histone H3. We then provided the molecular descriptor of the taxon, based on redundant diagnostic nucleotide combinations in DNA sequence alignment within the Folmer region. Results of the phylogenetic analysis and species delimitation methods (ABGD, ASAP, and bPTP) based on the COI locus support the species rank of the Tunisian-Algerian Placobdella.

CONCLUSIONS

The new species is most closely related to the European species Placobdella costata (Fr. Müller, 1846) and the present study indicates that Placobdella nabeulensis sp. nov. has likely been confused with the European counterpart in several previous studies. This article is registered at www.zoobank.org under urn:lsid:zoobank.org:pub:4A4B9C1D-2556-430F-8E4B-0CE99F2012F5.

An ultrastructural study of the ovary cord organization and oogenesis in the amphibian leech Batracobdella algira (Annelida, Clitellata, Hirudinida)

This study reveals the ovary micromorphology and the course of oogenesis in the leech Batracobdella algira (Glossiphoniidae). Using light, fluorescence, and electron microscopies, the paired ovaries were analyzed. At the beginning of the breeding season, the ovaries were small, but as oogenesis progressed, they increased in size significantly, broadened, and elongated. A single convoluted ovary cord was located inside each ovary. The ovary cord was composed of numerous germ cells gathered into syncytial groups, which are called germ-line cysts. During oogenesis, the clustering germ cells differentiated into two functional categories, i.e., nurse cells and oocytes, and therefore, this oogenesis was recognized as being meroistic. As a rule, each clustering germ cell had one connection in the form of a broad cytoplasmic channel (intercellular bridge) that connected it to the cytophore. There was a synchrony in the development of the clustering germ cells in the whole ovary cord. In the immature leeches, the ovary cords contained undifferentiated germ cells exclusively, from which, previtellogenic oocytes and nurse cells differentiated as the breeding season progressed. Only the oocytes grew considerably, gathered nutritive material, and protruded at the ovary cord surface. The vitellogenic oocytes subsequently detached from the cord and filled tightly the ovary sac, while the nurse cells and the cytophore degenerated. Ripe eggs were finally deposited into the cocoons. A comparison of the ovary structure and oogenesis revealed that almost all of the features that are described in the studied species were similar to those that are known from other representatives of Glossiphoniidae, which indicates their evolutionary conservatism within this family.

Microscopic analysis of spermatogenesis and mature spermatozoa in the amphibian leech Batracobdella algira (Annelida, Clitellata, Hirudinida)

Spermatogenesis and spermatozoa ultrastructure of the amphibian leech Batracobdella algira Moquin-Tandon, 1846 (Hirudinida: Glossiphoniidae) have been investigated by means of electron and fluorescent microscopy. In B. algira, there are seven pairs of testisacs (testes) that are located latero-ventrally throughout the body. Each testis contains numerous cysts with developing germ cells. The germ cells in a given cyst are in the same developmental stage (i.e., there are spermatogonial, spermatocytic, and spermatid cysts); however, there is no developmental synchrony between the cysts, and therefore, all of the developmental stages occur simultaneously in the same testis. In the cysts, each germ cell is connected to acentral cytoplasmic mass, the cytophore, by one intercellular bridge. The spermatozoa of the studied species conform to the general organization plan that is known for Hirudinida: they are filiform cells that are formed in sequence by an elongated and twisted acrosome that consists of an anterior and posterior acrosome, a fully condensed and helicoid nucleus, a midpiece composed of a single and twisted mitochondrion that is characteristically surrounded by an electron-dense sheath, and a flagellum with the conventional 9 × 2 + 2 axonemal pattern. Using a comprehensive approach, we compared our findings with the ultrastructural data that had been obtained from the spermatozoa of the other hirudinids that have been studied to date. Only minor differences in the length and shape of the studied organelles were found which seems to be connected with the different ways of insemination, specific properties of female reproductive tracts, and physiology of fertilization. Additionally, we studied the organization of the microtubular cytoskeleton in male germline cysts at consecutive stages of spermatogenesis using fluorescent and electron microscopy. By comparing the present data with those from Oligochaeta, Branchiobdellida, and Acanthobdellida, we found that only the presence of an anterior acrosome characterizes the true leeches and that, at present, should be regarded as an autapomorphic character of Hirudinida. Our results showed that the arrangement of the microtubules changed dynamically during spermatogenesis.

<p class="A2">TAXONOMY OF SUBTIDAL MARINE POLYCLADS FROM TABARKA (NORTHWEST TUNISIA) WITH REMARKS ON THEIR HABITAT PREFERENCES

The Polyclad fauna of the northwest Tunisian coasts is still unexplored. This is the first investigation of Polyclad flatworms collected by scuba diving in Tunisian waters. Three species belonging to three different families and three different genera are reported and re-described. Echinoplana celerrima (Haswell, 1907) was found to feed on the ascidian Ciona intestinalis (Linnaeus, 1767) at 20 m of depth and Thysanozoon brocchii (Risso, 1818) was observed to eat on sponges Dysidea tupha (Martens, 1824) at 16 m of depth. Prosthiostomum siphunculus (Delle Chiaje) was found creeping on stones at 29 m of depth. Some anatomical data of living specimen of P. siphunculus and fixed specimens of T. brocchii were provided for the first time.

Ultrastructural study of spermatogenesis and sperm in the African medicinal leech Hirudo troctina Johnson, 1816 (Annelida, Hirudinida)

This paper presents the process of spermatogenesis in the leech Hirudo troctina Johnson, 1816 using light, fluorescent and transmission electron microscopy. At the onset of spermatogenesis in testes, the pear-shaped spermatogonia divide mitotically without full cytokinesis and as a result isogenic groups are formed (clusters, clones) with 2, 4, 8, 16, 32, 64, 128 spermatogonia and, finally, 256 primary spermatocytes occur. The final meiotic divisions of spermatocytes give rise to clones with 1024 spermatids. There are hundreds of developing germ-line clones in each testis. In each clone, the male germ cells divide in full synchrony and they are in the same phase of spermatogenesis. During complex spermiogenesis each spermatid becomes a filiform spermatozoon with a helicoid nucleus, which is characterized by the presence of a long acrosome with two regions - anterior and posterior, which are followed by a helicoid nucleus, a midpiece with only one mitochondrion and a long flagellum. Our results were compared to those on other clitellate annelids that have been studied to date, especially to sperm formation in Hirudo medicinalis Linnaeus, 1785. Only minor differences were found in the length and the diameter of different organelles and the number of spermatids in germ-line clones.

CHECKLIST AND DISTRIBUTION OF MARINE AND FRESHWATER LEECHES (ANNELIDA, CLITELLATA, HIRUDINEA) IN TUNISIA WITH IDENTIFICATION KEY

In this study 13 leech species from Tunisia are listed. They belong to 2 orders, 2 suborders, 4 families and 11 genera. The paper includes also data about hosts and habitats, distribution in the world and in Tunisia. Faunistic informations on leeches were found in literature and in the results of recent surveys conducted by the authors in the North East and the South of the country. The objectives of this study were to summarize historical and recent taxonomic data, and to propose an identification key for species signalized. This checklist is to be completed, taking into account the hydrobiological network of the country especially the North West region, which may reveal more species in the future

Erpobdellid leeches (Annelida, Clitellata, Hirudinida) from Tunisia: new records with the description of a new Trocheta species

Up to now in Tunisia, freshwater Hirudinida are represented by two mainly haematophagous families: Hirudinidae and Glossiphonidae, and a predatory one: the family Erpobdellidae. The present study provides new information on the diversity and taxonomy of erpobdellid leeches. Identification was based, in addition to morphological data, on the length of sperm ducts and the lengths of ovisacs in relation to the neurosomite (ns) and on the shape and size of the male atrium. Five taxons are found. Two subspecies are reported for the first time in the country: Dina punctata punctata Johansson, 1927 and Dina punctata maroccana Nesemann and Neubert, 1994. Tunisian populations of two species, Erpobdella testacea (Savigny, 1820) and Trocheta africana Nesemann and Neubert, 1994, are described, with records of new localities. The new Trocheta tunisiana n. sp. is discovered and described in detail. Trocheta species live in springs in elevated areas while Erpobdella seem to prefer low altitude reservoirs. A comprehensive comparison of the three genera is presented. The disparity between the actual systematics and phylogeny is discussed. This study gives also a detailed distribution of the five species in the north of Tunisia with notes on ecological preference of the genus Dina. Finally a key for the determination of freshwater erpobdellid species from Tunisia is proposed.

Batracobdella algira Moquin-Tandon, 1846 (Hirudinida: Glossiphoniidae)--morphometric analysis and internal morphology

There has been very few papers on leeches of Batracobdella algira. The aim of the presently reported study was to provide the measurements and, for the first time, description and characteristics of the reproductive and digestive systems of B. algira. The material used in this study was collected from frogs, Rana saharica Boulenger, 1913, in April 1987 by H. Hotz in Béja in Tunisia (11 individuals) and by R. Ben Ahmed in 2008 from the skin of Bufo mauritanicus Schlegel, 1841 in Nabeul in Tunisia (18 individuals). The relative length of the specimens ranges between 1.48 and 4.07. The digestive system of leeches has a standard structure for the species from the family Glossiphoniidae. Male and female gonopores are separated by two annuli. Ovisacs are as long as 5 neurosomits. The characteristic features of the male reproductive system of Batracobdella are sperm ducts, which are twisted in a small area and placed near to atrium. This study will hopefully contribute to a better understanding of the host-parasite relation.