Raja Ben Ahmed

Sexual behavior, insemination and development of the freshwater leech Helobdella stagnalis (Annelida, Hirudinea, Glossiphoniidae)

Abstract The reproductive biology of the Glossiphoniidae leech Helobdella stagnalis, under laboratory conditions, the structure of its eggs and its developmental stages were studied. Sperm transfer and insemination are made by hypodermic injection: one or numerous spermatophores were attached to the skin of the partner during copulation and sperm is injected through it. The leeches can copulate repeatedly with several partners. Each leech produces 4–8 cocoons containing 20–60 eggs whose are attached to the ventral side of the parent and carried around. At 22 °C, the developmental duration is 24 days from the oviposition until the juveniles leave the parent leech. Three (3) major stages have been distinguished: Eggs cleavage, germinal band generation, and juveniles hatching. The sexual behavior of Hellobdella stagnalis was described with a special attention given to parental care.

Effects of oil-related environmental pollutants on gonads of the freshwater leech Limnatis nilotica (Annelida, Hirudinea)

Abstract The main objective of this study was to determine the association between exposure to a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) and reproductive toxicity in the freshwater leech Limnatis nilotica. It was observed that exposure to 1.4 and 2.8 mg L−1 BTEX had a significant effect on previtellogenic and vitellogenic oocytes, but no effect on oogonia or early oocytes. In the 1.4 mg L−1 treatment group, previtellogenic and vitellogenic oocytes were characterized by clumping and shrinkage of the cytoplasm. In the 2.8 mg L−1 treatment group, the effect was more severe and the number of degenerating oocytes increased. The oocytes were easily identified by the vacuolization of their cytoplasm and nuclei. Exposure to 1.4 mg L−1 BTEX affected spermatogenesis by damaging spermatogenic cysts. 2.8 mg L−1 BTEX treatment caused severe damage to spermatogenesis manifested by the complete loss of normal cysts. The histopathological effects were confirmed by the comet assay because DNA damage was detected in both ovarian and testicular cells and was BTEX dose-dependent. The greatest DNA damage was recorded at 2.8 mg L−1 of BTEX in both ovarian and testicular cells compared to the control.

Annotations on marine and freshwater leeches (Annelida, Clitellata, Hirudinea) from North Africa

The purpose of this study is to provide information on the leech fauna of North Africa. This overview is based primarily on collected material, data from the literature and material in museum collections. A total of 37 species belonging to 6 families and 19 genera are presently known. Among these species, eight represent new records for North African countries. This report includes the first records for Tunisia of one freshwater leech, Helobdella stagnalis (Linneaus, 1758), and one marine leech, Trachelobdella lubrica (Grube, 1840). Four taxa are reported as new for Algeria: two marine species (Pontobdella muricata Linnaeus, 1758 and Branchellion torpedinis Savigny, 1822) and two freshwater subspecies (Dina punctata punctata Johansson, 1927 and Dina punctata maroccana Nesemann & Neubert, 1994). Pontobdella muricata is reported for the first time from Morocco and Alboglossiphonia iberica Jueg, 2008, previously known only from the Iberian Peninsula, is now reported from Morocco.

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.