First record of the alien invasive biofouling mussel mytella strigata (Hanley, 1843) (mollusca: Mytilidae) from Indian waters

Abstract

The invasive tropical American brackish water mussel Mytella strigata is recorded for the first time from the Indian sub-continent and this is the fourth report from the Indo-Pacific. The mussels were found attached in high densities (120 ± 24 ind. 25 cm-2) to floating plastic bottles, wooden pilings, walls of fish cages, hulls of boats and bottom sediment in the Cochin backwater, Kerala, India during summer 2019. The only other bivalve species found with this population was Perna viridis. The mean length to height ratio for the Cochin population of M. strigata was 2.06 ± 0.26 cm with the largest individual having a length of 5.9 cm. The general external colour of the shells in Cochin population was uniformly black when wet but they exhibit dark green over the dorsal and posterior areas with faint paler streaks when dry. In addition some of the individuals rarely form bright green colour and pattern as seen in Singapore populations. The mitochondrial DNA cytochrome c oxidase subunit I gene sequences of mussels from this study were consistent with specimens in their native range, from Colombia, and from Singapore where it has recently been reported as invasive. The invasion of this species in Cochin may be through ballast water or fouling on ships hulls from its native range or from Singapore where it has been established recently. Their rapid growth, early maturity and wide salinity tolerance make them a potentially alarming fouling species in all brackish waters of India and neighbouring countries.