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Nerita histrio (Linnaeus, 1758)

Richard Dylan Corner 2018


Nerita histrio (synonym Nerita squamulata), the scaly nerite, is a herbivorous marine gastropod inhabiting rocky shores and mangroves in tropical and subtropical areas of Asia and Australasia (Wilson, 2013). This gastropod shows a huge range of phenotypic variation in regards to its shell colour and patterns, and is commonly confused with Nerita chameleon. However N. histrio can typically be identified by its rough or scaly shell (Tan & Clements, 2008).

It is unclear whether this species undergoes direct fertilisation or sperm casting, however it is known that internal fertilisation occurs (Paruntu & Mutsunori, 2003). The planktotrophic larvae of this species is typically smaller than other members of the Nerita genus, leading to a generally smaller adult (Fukumori & Yasunori, 2014). The radula present is a modified rhipidoglossate used to scrape algae, diatoms and cyanobacteria during high tide (Macey, Brooker & Cameron, 1997).

The classification for N. histrio is as follows:
Kingdom : Animalia
Phylum : Mollusca
Class : Gastropoda
Subclass : Neritimorpha
Order : Cycloneritida
Family : Neritidae
Genus : Nerita
Species : N. histrio

Physical Description


N. histrio are described to have the shell width of up to 2.5cm (Wilson, 1993). This is relatively small compared to some of the larger species in the genus Nerita, which can have a shell size of up to 4cm, seen in Nerita balteata (Wilson, 1993).

There was some variation present in the size of the N. histrio collected from Wellington Point, Queensland (figure 1). This is most likely due to difference in the age of the individuals. From the 15 individuals collected, the length of the shell ranged from 1.3cm to 1.8cm, with the average being 1.64cm. The height of the shell was less variable than the length, ranging from 0.7cm to 1.1 cm tall, with an average of 0.93cm. Shell width was the least variable parameter measured, ranging from 1.2 cm to 1.5 cm, with the average shell width being 1.36cm. Figure 2 shows the definitions of length, width and height. 

Figure 1: Random sample of 12 Nerita histrio individuals collected from Wellington Point, Queensland Australia.Note the variation in size, colour and pattern.

Figure 2: Example N. histrio shell showing definitions of length, width and height measurments.


It is well documented that N. histrio shows a great deal of variation in shell colours and patterns, and this was clearly seen in the individuals collected. Colours ranged from orange to dark brown, and the patterns varied from almost one solid colour, to alternating stripes of colours, to seemingly random speckles of two or more colours (figure 3). The shell for all individuals collected had a depressed spire (figure 3), and had some degree of flare at the shell opening (figure 4).