Neritina pulligera

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Neritina pulligera
Neritina pulligera.jpg
A live specimen of Neritina pulligera.
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Neritimorpha
Order: Cycloneritida
Family: Neritidae
Genus: Neritina
Species:
N. pulligera
Binomial name
Neritina pulligera
(Linnaeus, 1767) [2]
Synonyms [3]

Nerita rossmassleriana Récluz, 1846
Nerita rubella O. F. Müller, 1774
Neritina brandtii R. A. Philippi, 1849
Neritina bruguieri G. B. Sowerby II, 1849
Neritina larga Hombron & Jacquinot, 1848
Neritina subcanalis Mousson, 1865

Contents

Neritina pulligera, also known as dusky nerite, black racer, black helmet snail, or steel helmet snail, is a species of freshwater snail of the family Neritidae. [1] The snail was first described in 1767 by Carl Linnaeus and is the type species (reference species) of the genus Neritina. [4]

N. pulligera has a thick, olive-green to black shell typically 20 - 26 mm long. The shell covers almost the entire body and only the tentacles stick out. This species has an operculum, a "trapdoor" used by the snail to close its shell. Females have a specialised organ called the crystal or reinforcement sac, which stores solid material used to produce a hardened egg capsule. [5]

N. pulligera is native across the Indo-west Pacific and lives in fast-flowing streams and rivers. It is sold worldwide as part of the aquarium trade, raising concerns about potential biological invasions, but has not been recorded outside of its native range as of 2023. [6]

Females attach their eggs on the shells of other living snails, an unique behaviour shared by neritids. Together with the reinforced egg capsules, this helps protect the eggs from predation by other snails. [5] Like other neritids, the larvae drift downstream to the sea and juveniles migrate back upstream to reproduce. Juveniles of Neritina asperulata often save energy in this migration by "hitchhiking" on the bigger N. pulligera. [7]

The snail is a popular ornamental species in aquariums and often introduced to combat algae growth. However, N. pulligera feeds exclusively on algae and biofilm and individuals may starve if algae don't regrow fast enough or if their diet is not complemented e.g. with algae stones. [8] [9] Because juveniles do not develop in fresh water, all traded individuals are wild caught, which raises concerns about impacts on local N. pulligera populations. [10]

Taxonomy and nomenclature

19th century drawing of Neritina pulligera by Jean-Charles Chenu Neritina pulligera.png
19th century drawing of Neritina pulligera by Jean-Charles Chenu

N. pulligera was first described in 1767 by Swedish biologist Carl Linnaeus from a specimen found in India. [2] The specific epithet pulligera comes from the Latin words pullus ("dark coloured") and gero ("to carry") referring to its shell. [11] [12] It is the type species (reference species) of the Genus Neritina, a monophyletic and well-established group. [4] [13]

In the 19th century several authors described new snail species based on shell features such as morphology, size, and colour. Many of these species were later placed as synonyms or subspecies of N. pulligera as researchers noticed that mollusc shells frequently showed phenotypic plasticity. [13] However, in the 21th century morphometric and genetic analyses have confirmed that several of these snails are actually separate species. This includes Neritina petitii, Neritina canalis, Neritina iris, Neritina asperulata, and Neritina powisiana in 2009 [14] as well as former subspecies Neritina stumpffi and Neritina knorri in 2017. [13]

Molecular phylogeny of Neritina and related genera after Abdou et al., 2017. [13]

Description

Shell of Neritina pulligera from various angles. The operculum is absent. Neritina pulligera 01.JPG
Shell of Neritina pulligera from various angles. The operculum is absent.

Shell

The shell of N. pulligera is thick and typically measures 20 - 26 mm in length, although some individuals can reach 40 mm. [15] [16] The colour varies from pale olive-green to dark brown or black. [17] [18] These snails present sexual dimorphism (morphological differences between male and female individuals), in the sense that males are smaller in size and generally display a more vibrant shell colouration. [10]

In both sexes, the shell is oval with a large opening (aperture) and an orange band running along the inside of the aperture. [19] The spire (coiled tip of the shell) is very low, but has a distinct apex (pointed tip of the shell). [18] [17] At the aperture, the outer margin (lip) forms a small ridge toward apex. The inner lip is broad and has a thick, flat area (callus) which covers part of the aperture. This callus has a bluish-black colour on the outer side which gradually fades toward the inner side. It is also slightly toothed at the inner edge. [19] [20] The shell covers almost the entire body of the snail, such that the foot barely shows and only the tentacles stick out. [21]

The operculum, a "trapdoor" used by the snail to close its shell, is slightly convex on the outside with fine lines running lengthwise. Its back end is pale tan, while the front is pinkish with dark blue circular streaks in-between. From the inside, the operculum is slightly concave and dirty green with rosy white spots. [22]

Like other members of the subfamily Neritimorpha, N. pulligera presents a particularly convoluted protoconch (the earliest shell formed during the larval stage), with each new whorl overlapping the earlier one. Specifically in N. pulligera, it displays prominent ridges running lengthwise along the last half-whorl. [23]

Radula

In addition to the shell, another structure useful in gastropod taxonomy is the radula, a tongue-like structure covered with rows of chitinous teeth used by snails to feed by scraping the surface. [24] The only description of N. pulligera's radula is given by Horace Burrington Baker in 1923. According to him, the structure is similar to that of Neritina punctulata , but the first lateral tooth next to the central one (A-central) is broader and the third lateral tooth (C-central) has much smaller cusps. The inner lateral teeth are strongly modified and carry 45 vestigial cusps that extend behind the body of the tooth. The outer lateral teeth, or uncini (numerous closely packed marginal teeth) are long and narrow, and have smooth tips and long cusps. [25]

Reproductive system

E. A. Andrews (1937) provided the most detailed description of N. pulligera’s reproductive system. Within the genus Neritina, the anus is closer to the opening of the oviduct (passageway which transports the eggs to the outside) than in related genera. Specifically in N. pulligera, it is conjoined with the oviduct opening and extends laterally rather than forming a round shape. [26]

Females of N. pulligera have a specialised organ called the crystal or reinforcement sac. This organ stores solid particles used to produce a hard calcareous egg capsule in which the eggs are laid. [5] These particles can include sand, sponge spicules, diatoms, or foraminifera shells, depending on the snail’s location. Females also have an external structure called the female ridge, a fleshy fold of skin next to the right eye and tentacle. Andrews (1937) theorises that it may help guide sperm transfer during mating, yet there are no recorded observations.

Males of N. pulligera produce a spermatophore, a sperm packet transferred entirely to the female during reproduction. In N. pulligera, it is a long double tube filled with granular matter, bent in a wide loop and ending in thin filaments. Spermatophores are introduced into the female one or two at a time, and several can be stored within her reproductive tract, such that they can reproduce continuously. [26] [10]

Distribution

N. pulligera originated in Southeast Asia, based on fossils of the Pliocene and Pleistocene ages found in Java. It occurs as a native species across the Indo-west Pacific. Records include India (Andaman and Nicobar Islands), Madagascar, northern Australia, Mozambique, South Africa (KwaZulu-Natal), and the Comoro Islands. [27] [28] [29] It has also been reported as a native from Japan. [30]

Following the IUCN Freshwater Biodiversity Assessment between 2003 and 2009, N. pulligera was classified as a species of Least Concern (LC) for southern Africa, [31] but as Near Threatened (NT) [32] in the pan-African scope.

N. pulligera is sold worldwide as part of the aquarium trade. As with other pet trade species, its international commerce raises concerns about a potential biological invasion leading to the decline of native species. Nevertheless, the species has not been documented outside of its native range as of 2023. [6] Studies from the European Union and the United Kingdom indicate a low temperature suitability for N. pulligera in these regions, even under future climatic scenarios. [33] [34]

Ecology

Habitat

N. pulligera lives in fast-flowing streams and rivers with rocky substrates. [1] It colonises the entire freshwater course and can be found as far downstream as areas near the tidal influence of the ocean, such that it is also found in brackish waters. [35] [36] It is often found in groups on boulders or coral blocks under moderate currents (20 – 50 cm/sec), but take shelter next to the stones facing away from the current when it becomes too strong (1 m/sec). [35] N. pulligera is most commonly reported under warm water temperatures (between 23 - 29 °C), [35] [37] such that it is mostly found in low elevational zonations. [38]

Reproduction

A collection of N. pulligera shells covered in egg capsules. Naturalis Biodiversity Center - RMNH.MOL.152173 - Neritina pulligera (Linnaeus, 1767) - Neritidae - Mollusc shell.jpeg
A collection of N. pulligera shells covered in egg capsules.

Like other neritids, N. pulligera has separate sexes. [39] The female is fertilised internally [10] and lays its eggs inside a hard calcareous capsule, which is relatively large compared to other Neritidae, about 2.11 x 1.57 mm on average, and elliptical in shape. They are laid in clusters of 9 - 39 capsules. Like other neritids, N. pulligera presents a unique egg-laying behaviour by preferably laying its eggs on the shells of other living snails. This, together with the reinforced capsules, helps protect the eggs from predation by other snails. These snails must scrape the capsule surface with their radula for several minutes to access the eggs, which is made especially difficult when they are on moving shells. [5] Like other neritids, N. pulligera has an amphidromous life cycle: larvae drift downstream into the marine environment, and juveniles migrate upstream to mature and reproduce. [7] [40]

Interspecific interactions

Predation on adult N. pulligera has not been documented. Taylor (1976) suggested that the thick shell of neritids provides an effective defence from the shell-boring predatory muricid snails. [41] However, the closely related genera Clithon and Vittina facultatively feed on the eggs of N. pulligera. [5]

Neritina asperulata and, to a lesser extent, Neritina petitii engage in an obligatory “hitchhiking” behaviour with larger neritids such as N. pulligera. Juveniles attach to the shell of the host and are carried upstream as it migrates. [7] This behaviour spares the juveniles from expending energy in migration (since both are also amphidromous species) and protects them from predators along the way. [42]

Human relevance

Aquarium trade

N. pulligera is traded as an ornamental species in the aquarium industry. [33] [6] It is popular for its peaceful nature and ease of care and is often introduced as part of a “clean-up crew” to combat algae growth. However, these snails feeds exclusively on algae and biofilm, and may starve once the algae infestation is taken care of and food availability declines. [8] Newly imported individuals often arrive famished. [9] N. pulligera will not eat conventional fish or invertebrate food but will graze on homemade algae stones. [9] [43] Because juveniles do not develop in fresh water, the species was not yet successfully bred in captivity as of 2025 and all traded individuals are wild caught. This practice raises concerns about impacts on local N. pulligera populations. [10] [43]

Other uses

N. pulligera is used for food in some parts of Viti Levu, Fiji. [44]

Reference

  1. 1 2 3 IUCN (June 2016). Neritina pulligera: Gerlach, J., Madhyastha, A., Köhler, F. & Van Damme, D.: The IUCN Red List of Threatened Species 2016: e.T165773A91284470 (Report). International Union for Conservation of Nature. doi:10.2305/iucn.uk.2016-3.rlts.t165773a91284470.en . Retrieved 3 October 2025.
  2. 1 2 Linnaeus, C. (1767). Systema naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Ed. 12. 1., Regnum Animale. 1 & 2. [The system of nature through the three kingdoms of nature: according to classes, orders, genera, species, with characters, differences, synonyms, places. Ed. 12. 1., Animal Kingdom. 1 & 2]. Holmiae [Stockholm], Laurentii Salvii. pp. 1-532 [1766] pp. 533-1327 [1767]., available online at http://www.biodiversitylibrary.org/item/83650#5 page(s): 1253
  3. ↑ "MolluscaBase - Neritina pulligera (Linnaeus, 1767)". www.molluscabase.org. Retrieved 3 October 2025.
  4. 1 2 "WoRMS - World Register of Marine Species - Neritina Lamarck, 1816". www.marinespecies.org. Retrieved 6 October 2025.
  5. 1 2 3 4 5 Kano, Y.; Fukumori, H. (November 2010). "Predation on hardest molluscan eggs by confamilial snails (Neritidae) and its potential significance in egg-laying site selection". Journal of Molluscan Studies. 76 (4): 360–366. doi:10.1093/mollus/eyq018. ISSN   0260-1230.(subscription may be required or content may be available in libraries)
  6. 1 2 3 Dickey, James W. E.; Liu, Chunlong; Briski, Elizabeta; Wolter, Christian; Moesch, Simon; Jeschke, Jonathan M. (2023). "Identifying potential emerging invasive non-native species from the freshwater pet trade". People and Nature. 5 (6): 1948–1961. Bibcode:2023PeoNa...5.1948D. doi:10.1002/pan3.10535. ISSN   2575-8314.
  7. 1 2 3 Kano, Yasunori (August 2009). "Hitchhiking behaviour in the obligatory upstream migration of amphidromous snails". Biology Letters. 5 (4): 465–468. doi:10.1098/rsbl.2009.0191. ISSN   1744-9561. PMC   2781923 . PMID   19411267.(subscription may be required or content may be available in libraries)
  8. 1 2 Garnelio. "Our top 6 algae eaters in the aquarium". Garnelio EN. Retrieved 9 October 2025.
  9. 1 2 3 "Anthrazit-Napfschnecke". ZOOBOX (in German). Retrieved 9 October 2025.
  10. 1 2 3 4 5 Aquadiction (January 2024). "Dusky Nerite Snail - Neritina pulligera Snail Profile & Care Guide". Aquadiction. Archived from the original on 27 June 2025. Retrieved 9 October 2025.
  11. ↑ "Latin Definition for: pullus, pulla, pullum (ID: 32278) - Latin Dictionary and Grammar Resources - Latdict". latin-dictionary.net. Retrieved 6 October 2025.
  12. ↑ "Latin Definition for: gero, gerere, gessi, gestus (ID: 21464) - Latin Dictionary and Grammar Resources - Latdict". latin-dictionary.net. Retrieved 6 October 2025.
  13. 1 2 3 4 Abdou, Ahmed; Galzin, René; Lord, Clara; Denys, Gaël P. J.; Keith, Philippe (2017). "Revision of the species complex 'Neritina pulligera' (Gastropoda, Cyclonetimorpha: Neritidae) using taxonomy and barcoding". Vie et Milieu / Life & Environment.
  14. ↑ Kano, Yasunori (August 2009). "Hitchhiking behaviour in the obligatory upstream migration of amphidromous snails". Biology Letters. 5 (4): 465–468. doi:10.1098/rsbl.2009.0191. ISSN   1744-9561. PMC   2781923 . PMID   19411267.
  15. ↑ Ramakrishna & Dey, A. (2007). Handbook on Indian freshwater molluscs. 399 pp. Zoological Survey of India, Kolkata.
  16. ↑ "Shell Encyclopedia - Conchological MegaDatabase Iconographic Overview on Mollusks | ConchologyNERITIDAE | Conchology". www.conchology.be. Retrieved 1 October 2025.
  17. 1 2 Beu, AG; Marshall, BA (March 2011). "New Cenozoic records of genera and families from New Zealand (Mollusca, Gastropoda): highlights from Phillip Maxwell's collection". New Zealand Journal of Geology and Geophysics. 54 (1): 13–34. Bibcode:2011NZJGG..54...13B. doi:10.1080/00288306.2011.536517. ISSN   0028-8306.
  18. 1 2 "Neritina pulligera". keys.lucidcentral.org. Retrieved 30 September 2025.
  19. 1 2 Rao, N. S., Das, A. K., & Mitra, S. C. (1979). On freshwater molluscs of Andaman and Nicobar islands. Records of the Zoological Survey of India, 215-245.
  20. ↑ HAUSER, M. H., & KOWALKE, T. (2001). Early Miocene brackish-water Mollusca from the Eastern Mediterranean and from the Central Paratethys–a faunistic and ecological comparison by selected faunas. Journal of the Czech Geological Society, 46, 3-4.
  21. ↑ "Black racer nerite snail | Neritina pulligera care & info". The Shrimp Farm. July 2022. Retrieved 2 October 2025.
  22. ↑ Récluz, M.C.A. (1842). "Descriptions of various species of Navicella, collected by Mr Cuming in the Philippine Islands". Proceedings of the Zoological Society of London. 10: 154-160.
  23. ↑ HAUSER, M. H., & KOWALKE, T. (2001). Early Miocene brackish-water Mollusca from the Eastern Mediterranean and from the Central Paratethys–a faunistic and ecological comparison by selected faunas. Journal of the Czech Geological Society, 46, 3-4.
  24. ↑ Andrews, E. A. (1935). "The egg capsules of certain Neritidae". Journal of Morphology. 57 (1): 31–59. Bibcode:1935JMorp..57...31A. doi:10.1002/jmor.1050570103. ISSN   1097-4687.(subscription may be required or content may be available in libraries)
  25. ↑ Baker, H. B. (1923). Notes on the radula of the Neritidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 75, 117-178.
  26. 1 2 Andrews, E. A. (December 1937). "Certain reproductive organs in the Neritidae". Journal of Morphology. 61 (3): 525–561. Bibcode:1937JMorp..61..525A. doi:10.1002/jmor.1050610307. ISSN   0362-2525.
  27. ↑ Ramakrishna & Dey, A. (2007). Handbook on Indian freshwater molluscs. 399 pp. Zoological Survey of India, Kolkata.
  28. ↑ Haynes, A. (1988). Notes on the stream neritids (Gastropoda; Prosobranchia) of Oceania. Micronesica, 21, 93-102.
  29. ↑ Fischer-Piette, E. & Vukadinovic, D. (1974). Les Mollusques terrestres des Iles Comores. Mémoires du Museum National d'Histoire Naturelle, Nouvelle Série, Série A, Zoologie, 84: 1-76, 1 plate. Paris.
  30. ↑ Higo, Shun'ichi; Callomon, Paul; Gotō, Yoshihiro (1999). Catalogue and bibliography of the marine shell-bearing mollusca of Japan: Gastropoda, Bivalvia, Polyplacophora, Scaphopoda. Ōsaka-fu, Yao-shi: Elle Scientific Publ. ISBN   978-4-901172-01-1.
  31. ↑ Kristensen, T.K., Stensgaard, A.S. and Appleton, C. 2010. Neritina pulligera (S. Africa FW assessment). The IUCN Red List of Threatened Species 2010: e.T165773A6114595. Accessed on 02 October 2025.
  32. ↑ Appleton, C., Kristensen, T.K., Lange, C.N. & Stensgaard, A-S. 2010. Neritina pulligera (Pan-Africa assessment). The IUCN Red List of Threatened Species 2010: e.T165773A6115214. Accessed on 02 October 2025.
  33. 1 2 Patoka, Jiří; Kopecký, Oldřich; Vrabec, Vladimír; Kalous, Lukáš (July 2017). "Aquarium molluscs as a case study in risk assessment of incidental freshwater fauna". Biological Invasions. 19 (7): 2039–2046. Bibcode:2017BiInv..19.2039P. doi:10.1007/s10530-017-1412-6. ISSN   1387-3547.(subscription may be required or content may be available in libraries)
  34. ↑ Guilder, James; Copp, Gordon H.; Thrush, Mark A.; Stinton, Nicholas; Murphy, Debbie; Murray, Joanna; Tidbury, Hannah J. (October 2022). "Threats to UK freshwaters under climate change: Commonly traded aquatic ornamental species and their potential pathogens and parasites". NeoBiota. 76: 73–108. Bibcode:2022NeoBi..76...73G. doi: 10.3897/neobiota.76.80215 . ISSN   1314-2488.
  35. 1 2 3 Starmühlner, F. (1976). Beiträge zur Kenntnis der Süsswasser-Gastropoden pazifischer Inseln. Annalen des Naturhistorischen Museums in Wien, 473-656.
  36. ↑ Aravind, N. A., Madhyastha, N. A., Rajendra, G. M., & Anirudha, D. (2011). The status and distribution of freshwater molluscs of the Western Ghats. The status and distribution of freshwater biodiversity in the Western Ghats, India, 21-42.
  37. ↑ Suratno; Susilo, V E; Doviyana, V; Mujiono, N (February 2020). "The diversity of gastropoda in meru betiri national park". Journal of Physics: Conference Series. 1465 (1) 012011. Bibcode:2020JPhCS1465a2011S. doi:10.1088/1742-6596/1465/1/012011. ISSN   1742-6588.
  38. ↑ Benstead, Jonathan P.; March, James G.; Pringle, Catherine M.; Ewel, Katherine C.; Short, John W. (June 2009). "Biodiversity and ecosystem function in species-poor communities: community structure and leaf litter breakdown in a Pacific island stream". Journal of the North American Benthological Society. 28 (2): 454–465. doi:10.1899/07-081.1. ISSN   0887-3593.(subscription may be required or content may be available in libraries)
  39. ↑ Andrews, E. A. (1937). "Certain reproductive organs in the Neritidae". Journal of Morphology. 61 (3): 525–561. Bibcode:1937JMorp..61..525A. doi:10.1002/jmor.1050610307. ISSN   1097-4687.(subscription may be required or content may be available in libraries)
  40. ↑ Bandel, K.; Riedel, F. (June 1998). "Ecological zonation of gastropods in the Matutinao River (Cebu, Philippines), with focus on their life cycles". Annales de Limnologie - International Journal of Limnology. 34 (2): 171–191. doi:10.1051/limn/1998017. ISSN   0003-4088.
  41. ↑ Taylor, J. D. (September 1976). "Habitats, abundance and diets of Muricacean gastropods at Aldabra Atoll". Zoological Journal of the Linnean Society. 59 (2): 155–193. doi:10.1111/j.1096-3642.1976.tb01013.x.(subscription may be required or content may be available in libraries)
  42. ↑ Heller, Joseph (2015). Sea Snails: A natural history. Cham: Springer International Publishing. doi:10.1007/978-3-319-15452-7. ISBN   978-3-319-15451-0.(subscription may be required or content may be available in libraries)
  43. 1 2 Tim (March 2021). "Anthrazit-Napfschnecke - Neritina pulligera". Das Garnelen Aquarium (in German). Retrieved 9 October 2025.
  44. ↑ Nadarivatu Hydropower Scheme - Consolidated EIA. "Appendix G - Hydrological Assessment." Retrieved from: https://documents1.worldbank.org/curated/en/172641468029359688/pdf/E14640v80Nadar1ient0Issue0220Oct007.pdf
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