A note on the occurrence of Cremnochonchus conicus (Blanford, 1870) in Mumbai, India

The Caenogastropod family Littorinidae is almost exclusively marine, but a unique freshwater genus, Cremnoconchus, is known from India. Cremnoconchus conicus (Blanford, 1870) were observed on 11th of July, 2021 in healthy populations in Conservation Education Centre of Mumbai. The species preferred streams and smaller waterfalls (cascades) with stony substrate and dense riparian vegetation. The note emphasizes on extension of its present known range and habitat preferences.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) Members of the genus Cremnoconchus are known to be restricted to montane streams on the western escarpment of the Western Ghats, at altitudes between 300 m and 1,400 m (Rao 1989;Reid et al. 2013;Tripathy & Sajan 2020).
Four species and several varieties were described in the 19 th century (Blanford 1869). In 2013, only three described species-C. syhadrensis, C. conicus, C. canaliculatus, were considered valid and recognized from the northern Western Ghats in Maharashtra state, where all can occasionally be found sympatrically out of the nine recognized species from the genus Cremnoconchus (Reid et al. 2013;Tripathy & Sajan 2020).
The gastropod genus Cremnochonchus is endemic to the Western Ghats. The species being habitat specialist are exclusive to spray zones of waterfalls. C. carinatus was first recorded by Layard in the spray zones of waterfalls in Mahabaleshwar and is the only known range for the species. The species has since been known to be extirpated from that locality (Molur et al. 2011).
In 2013, C. carinatus was no longer considered a valid species and has been clubbed with C. conicus, which were considered sister species (Reid et al. 2013 The specimens were identified on the field and by shell specimens using the identification key by Reid et al. (2013) -turbinate shell shape; one shell rib at the shoulder (2 ribs observed in a specimen); wide columella; absence of pseudumbilicus; satin sheen shell surface with microstriae; weakly calcified operculum with no internal ridge.
The current known habitat preference of C. conicus is the spray zones of waterfalls and shallow pools of freshwater (Aravind et al. 2011). Our observations in CEC add on to this known habitat preference. C. conicus have been observed along the flowing, freshwater streams of CEC. They are found on the moist rocks present in between or along the flowing streams. They also lay eggs in clutches of 10-25 on these boulders. The egglaying starts in June and lasts up to late July.

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Discussion: C. conicus is a habitat specialist gastropod found in the spray zones of waterfalls of Mahabaleshwar Hills (Molur et al. 2011). In the light of this new record, C. conicus not only inhabits the waterfalls but also the freshwater streams originating from it. It even lays eggs on the rocks present on these streams just above the flowing water surface. The ecology of eggs needs to be studied further as the fate of the eggs in this new scenario is unknown. There may be two possibilities -either the eggs hatch underwater once the stream overflows due to heavy rains in the month of July or due to change in the habitat conditions, it has to alter its ecology and spawn in such streams that may overflow and destroy the eggs.
The current conservation status of C. conicus is Vulnerable (VU) (Aravind et al. 2011;Reid et al. 2013), but may require a re-evaluation as this specialist species, in a rapidly vanishing freshwater habitat, currently faces anthropogenic pressures (Shubham Yadav, pers. comm. August 2021). C. conicus as well as other snail species are harvested by the locals for consumption. Apart from that, the freshwater streams are quickly  being polluted due to waste disposal, effluent and organic discharge along and directly in these streams. The streams in Mahabaleshwar, from where Blanford collected his specimens, have since been polluted and hence, no species of Cremnocochus were found during a survey in 2010 (Aravind et al. 2011). Southern Coucal and Starling sp. predation has been observed on C. conicus. Furthermore, its range considering its niche can be estimated to be abundant in the pristine streams of northern Western Ghats. The species needs to be studied further to understand its ecology and importance as an indicator of freshwater habitat.

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