Abstract
A new species and the first confirmed record of a true pygmy seahorse from Africa, Hippocampus nalu sp. nov., is herein described on the basis of two specimens, 18.9-22 mm SL, collected from flat sandy coral reef at 14-17 meters depth from Sodwana Bay, South Africa. The new taxon shares morphological synapomorphies with the previously described central Indo-Pacific pygmy seahorses, H. colemani, H. japapigu, H. pontohi, and H. satomiae, and H. waleananus, including diminutive size, twelve trunk rings, prominent cleithral ring and supracleithrum, spines on the fifth and twelfth superior and lateral trunk ridges, respectively, and prominent wing-like protrusions present on the first and/or second superior trunk rings posterior to the head. Hippocampus nalu sp. nov. is primarily distinguished from its pygmy seahorse congeners by highly distinct spine morphology along the anterior segments of the superior trunk ridge. Comparative molecular analysis reveals that the new species demonstrates significant genetic divergence in the mitochondrial COI gene from the morphologically similar H. japapigu and H. pontohi (estimated uncorrected p-distances of 16.3% and 15.2%, respectively). Hippocampus nalu sp. nov. represents the eighth member of the pygmy seahorse clade to be described from the Indo-Pacific, the first confirmed record from the African continent and the Indian Ocean, and an extension of more than 8000 km beyond the previously known range of pygmy seahorses from the Central and Western Indo-Pacific.