Phylogeography and genetic diversity of the copepod family Cyclopidae (Crustacea: Cyclopoida) from freshwater ecosystems of Southeast Nigeria.

BACKGROUND: Copepods are key components of aquatic ecosystems and can help regulate the global carbon cycle. Much attention has been paid to the species diversity of copepods worldwide, but the phylogeography and genetic diversity of copepods in Nigeria is unexplored. RESULTS: Using a mitochondrial cytochrome c oxidase subunit I marker, we preformed phylogenetic and phylogeographic analyses for Cyclopidae copepods in Southeast Nigeria. A high species diversity of Cyclopidae in Nigeria: 5 species of Tropocyclops, 5 species of Mesocyclops and 2 species of Thermocyclops from Cyclopidae were identified in 15 populations. Moreover, we detected 18 unique haplotypes, which fell into two distinct clades. Pairwise genetic distances (uncorrected p-distances) among the species of Cyclopidae ranged from 0.05 to 0.257. Several species co-existed in the same lake, and some haplotypes were shared among different geographic populations, suggesting a dispersal of Cyclopidae in our sampling region. Finally, we found that the population genetic diversity for each species of Cyclopidae was low in Nigeria. CONCLUSIONS: Our findings explored the species diversity and distribution of copepods within the family Cyclopidae for 15 Nigerian freshwater ecosystems: a high species diversity of Cyclopidae copepods was detected over a small geographic sampling range. Results from this study contribute to a better understanding of copepod diversity of Nigerian freshwater ecosystems.

Hematological and immunological responses in the African catfish Clarias gairepinus exposed to sublethal concentrations of herbicide Ronstar®.

The aim of the study was to investigate the effects of sublethal concentrations (0.3, 0.6 and 1.2 mg L-1) of the herbicide Ronstar on the hematology and some immune parameters in Clarias gariepinus juvenile (mean weight and length 58.72 ± 2.46 g and 27.60 ± 1.62 cm, respectively). The hematological and some immune parameters were studied for 21 days in a static renewal bioassay system in which the water and the herbicide were changed daily. The erythrocyte count, hemoglobin concentration (Hb), and packed cell volume (PCV) were significantly (p < 0.05) reduced in the treatment groups. When compared with the control, there were significant (p < 0.05) leucocytosis, lymphocytosis, neutropenia and monocytopenia in the treatment groups. Both the mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV) were reduced ((p < 0.05) in the Ronstar-exposed fish. The result showed that the treated fish suffered hypochromic microcytic anemia. The total immunoglobulin and phagocytic indices (phagocytic capacity and phagocytic index) were significantly (p < 0.05) reduced in the treatment groups. while the respiratory burst was significantly (p < 0.05) increased in the treatment groups. The result showed that exposure to Ronstar had adverse effects on the hematology and immunocompetency of the fish.