Pelvic-fin brooding in a new species of riverine ricefish (Atherinomorpha: Beloniformes: Adrianichthyidae) from Tana Toraja, Central Sulawesi, Indonesia

Abstract

A new species of ricefi sh is described from a hill stream in Tana Toraja, Sulawesi. Oryzias eversi, new species, is distinguished from all other adrianichthyids in Sulawesi by having a low number of fi n rays in anal (17-18 (19)) and dorsal (10-12) fi ns, only 33-36 scales in lateral midline, ½14 transverse scale rows at dorsal fi n origin, 30-32 (33) vertebrae, small eyes (28.2-35.5% of head length), a conspicuous blackish male courtship colouration, and pelvic brooding behaviour similar to lacustrine ricefi shes. Female Oryzias eversi carry the eggs until the embryos hatch, and show a conspicuous abdominal concavity and extended pelvic fi ns, accommodating and holding the clutch of eggs. The eggs are connected to the female for the whole time of development by attaching fi laments that protrude from the female's urogenital pore. A mitochondrial haplotype phylogeny suggests that the new species is closely related to another "pelvic brooder", the lake-dwelling O. sarasinorum from Lake Lindu in Central Sulawesi. However, the haplotype group of O. eversi and O. sarasinorum is nested within a clade of egg-depositing Oryzias from central, southwest, and southeast Sulawesi, whereas another pelvic brooder, Adrianichthys oophorus from Lake Poso, forms a distinct, second lineage of Sulawesi's ricefi shes. Accordingly, the pelvic brooding strategy has probably evolved more than once and may be realised in river habitats, which represents a new evolutionary trajectory in the radiation of ricefi shes in Sulawesi. The present discovery adds another new ricefi sh species to Sulawesi's still only partially known ichthyofauna, and highlights the island's role as hotspot of adrianichthyid diversity.