Morphological and molecular characterisation of eggs and larvae of dark sleeper goby, Butis humeralis (Valenciennes, 1837), collected from a tropical estuary

Shameena, M K and Sruthy, V L and Ratheesh Kumar, R and Sajeela, K A and Kaladharan, P (2026) Morphological and molecular characterisation of eggs and larvae of dark sleeper goby, Butis humeralis (Valenciennes, 1837), collected from a tropical estuary. Journal of the Marine Biological Association of India, 68 (1). pp. 5-13. ISSN 2321-7898

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Abstract

Eggs of Butis humeralis (Valenciennes, 1837) were described for the first time from the west coast of India. A cluster of sparsely distributed eggs of B. humeralis was observed on a gritted glass panel submerged for biofouling studies in the Cochin estuary, Kerala. The egg mass covered an area of 62 cm2 with an average abundance of 120 ± 30 eggs/cm2. Molecular characterisation of the egg was performed to confirm species identification. The brownish-yellow, sticky, pyriform-shaped, transparent eggs of B. humeralis measured 0.41 ± 0.01 mm in diameter along the long axis and 0.36 ± 0.01 mm along the short axis. The newly hatched larvae of B. humeralis were slender and translucent with a total length of 1.01 ± 0.037 mm. The total length of the preflexion larvae was 2.08–2.12 mm. DNA barcoding using partial mitochondrial cytochrome oxidase subunit I gene sequences confirmed species identity, with 100% similarity to B. humeralis sequences from the Cochin estuary, which were deposited in GenBank. Genetic divergence analysis showed extremely low intraspecific variability (0.0%) and moderate interspecific divergence (5.7–24.7%), confirming genetic distinctness and clear taxonomic separation of B. humeralis. The first taxonomic description of the early life stages of this lesser-known species will facilitate future ichthyoplankton identification and contribute to assessing its conservation status within the ecosystem.

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