GENETIC POPULATION STRUCTURE OF THE INVASIVE TIGER SHRIMPS Penaeus monodon FROM NIGERIA COASTAL WATERS

In the last decade, the giant black tiger shrimp (P. monodon) suddenly became an invasive species of interest to the global research community. Since they invaded Nigeria, there has been no information on phylogenetics and phylogeography of this non-indigenous species as far as we know. This invasive species could help to improve food security and molecular studies could help to aid in the selection of founder stocks for hatchery management or effective aquaculture practice. Therefore, this research aims to study the molecular diversity of P. monodon and assess the population structure and migration pattern within the Nigerian coastal waters.

Tiger shrimp samples were obtained from Ten locations covering five coastal states of Nigeria vis-à-vis Lagos Makoko (LM), Lagos Apapa (LA), Lagos Takwabay (LT), Lagos Tincan (LC), Lagos Folu (LF), Ondo Aiyetoro (AO), Bayelsa Brass (BB), Rivers Bonny (RB), Rivers Kaa (RK) Akwa Ibom Ibeno (AB). Pleopod samples were preserved and transported to United States Geological Survey for molecular analysis. A total of 192 DNA samples were used for microsatellite study. Out of 28 United States invasive tiger shrimp microsatellite markers used for screening the Nigerian invasive samples, 11 markers with highest PIC values and best amplification result were selected for the population studies. A high degree of allelic polymorphism was observed with an average of 12 allelels and total of 140 alleles. The Pmo-1 marker had the highest number of alleles.  Among populations, expected heterozygosity (H_e) was highest in RB population and lowest in LT population. Principal Coordinate Analysis of Fst and Nei's genetic distance showed that majority of the populations clustered together, with the AB and OA populations being more genetically distant. However distance values were not significant which may suggest isolation by distance effect on these populations. This study shows an inherent high genetic diversity typified by allelic richness in the gene pool, possibly contributing to the survival and establishment of tiger shrimps in the Nigerian coastal waters. However, lack of significant genetic distance values among populations reflects their homogeneity, suggesting a limited number of founding individuals.