Pyrgophorus parvulus

Invasion History

First Non-native North American Tidal Record: 2015
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 2015

---

General Invasion History:

The crown snail Pyrgophorus parvulus is a small, taxonomically difficult, morphologically variable snail, native to the Caribbean rim, including Cuba, the Lesser Antilles, Venezuela, and Mexico.  It occurs in fresh brackish water in creeks, swamps and marshes (Harrison 1984). In 2015, it was discovered in one brackish pond on Hilton Head Island, South Carolina.  Retention ponds in coastal South Carolina contain several exotic species of freshwater snails, probably introduced by aquarium releases of aquatic plants (Dillon et al. 2024; Gooding et al. 2018).  Other invasions of this snail in fresh or brackish coastal waters have probably been overlooked.

North American Invasion History:

Invasion History on the East Coast:

In 2015, the crown snail Pyrgophorus parvulus was discovered in surveys of fresh and brackish ponds and ditches in South Carolina. This crown snail occurred only in one strongly brackish (14–18 PSU)  pond on Hilton Head Island, which is heavily developed as a luxury resort. The exotic snails, Melanoides tuberculata, Bellamya japonica, often kept in aquariums, were also present in many of these ponds. Accidental transport and release with aquarium animals and plants are the likeliest vector for P. parvulus (Dillon 2015; Dillon et al. 2024; Gooding et al. 2018, USGS Nonindigenous Aquatic Species Program 2024)

---

Description

Pyrgophorus parvulus (a crown snail) is a small, fresh-brackish water tropical snail. The shell is dextral with 6–7 whorls, with a well-marked keel-like spiral ridge on the shoulders of the whorls. Individuals can either have a plain, smooth shell or have calcareous spines projecting from the spiral ridges, on the shoulder of the whorls. The spines are most developed on the middle whorls. The spines are blunt, and hollow, continuous with shell interior, but the periostracum usually extends to make sharper points. In the genus Pyrgophorus, the occurrence of spiny forms gave rise to the common name 'crown snail', but the frequency of the spiny forms vary among populations. The variation in shape had led to numerous synonyms, but the morphology of the radula is a species characteristic (Harrison 1984). The introduced population in South Carolina contains both smooth and spiny specimens (Dillon et al. 2024). The operculum is horn-like in color and texture. Adult shells are 3.4–4.8 mm (Harrison 1984). Shells are yellowish- to reddish-brown. The body is yellowish, with a black head and red eye-tentacles (Harrison 1984; Dillon et al. 2024).

Snails in the genus Pyrgophorus were once included in the family Hydrobiidae, but that family has been broken up, with many New World species now placed in the family Cochliopidae, including the genera Littoridinops, Spurwinkia, and Pyrgophorus, among others (Hershler, et al. 2017; WoRMS Editorial Board 2018). Records of this species from Florida (treated as native in the USGS Nonindigenous Aquatic Species Database 2024), and possibly some records in coastal Texas (in GBIF 2024) refer to P. platyrachis, native to Florida (Dillon et al. 2024).

---

Taxonomy

Ecology

General:

Pyrgophorus parvulus is native to tropical climates, but appears to have established a population in subtropical South Carolina (Dillon et al. 2017). Its native habitats include fast- and slow-flowing streams, marshes, and the edges of mangroves (Harrison 1984; Dillon et al. 2024). Like other 'hydrobioid' snails, they feed on detritus, algae, and microbes adhering to sediment particles (Lopez and Kofoed 1980).

Food:

Detritus, algae

Consumers:

Other hydrobioid snails

Trophic Status:

Deposit Feeder

DepFed

---

Habitats

General Habitat	Nontidal Freshwater	None
General Habitat	Fresh (nontidal) Marsh	None
General Habitat	Salt-brackish marsh	None
General Habitat	Canals	None
General Habitat	Coarse Woody Debris	None
General Habitat	Grass Bed	None
General Habitat	Mangroves	None
Salinity Range	Limnetic	0-0.5 PSU
Salinity Range	Oligohaline	0.5-5 PSU
Salinity Range	Mesohaline	5-18 PSU
Vertical Habitat	Epibenthic	None

---

Life History

Pyrgophorus parvulus (a crown snail) is a small tropical fresh and brackish water snail. Sexes are separate, and fertilization is internal. Eggs are brooded internally, within an enlarged oviduct or 'uterus'. (Dillon et al. 2024).

---

Tolerances and Life History Parameters

Minimum Salinity (‰)	0	This is a freshwater species.
Maximum Salinity (‰)	17.5	Field, Dillon et al. 2006
Minimum Length (mm)	3	Harrison 1984
Maximum Length (mm)	4.8	Harrison 1984
Broad Temperature Range	None	Tropical-Subtropical
Broad Salinity Range	None	Limnetic-Mesohaline

General Impacts

Only one small, isolated population of Pyrgophorus parvulus is known from North America (Dillon et al. 2024), and no impacts have been reported. However, this snail is easily overlooked.

---

References

Gooding, Elizabeth L.; Fowler, Amy E.; Knott, David; Dillon, Robert T.; Brown, Tiffany; Kendrick, Michael; Kingsley-Smith, Peter R. (2018) Life history and phenological characteristics of the invasive island apple snail Pomacea maculata (Perry, 1810) in stormwater retention ponds in coastal South Carolina, USA, Journal of Shellfish Research 238(1): 229
https://doi.org/10.2983/035.037.0121

Dillon, R. T. Jr.; Watson, B.T.; Stewart, T. W.; Reeves, W. K. 2006-2024 The freshwater gastropods of North America. https://www.fwgna.org/



Dillon, Rob 2015 The many invasions of Hilton Head. https://fwgna.blogspot.com/2015/12/the-many-invasions-of-hilton-head.html



Harrison, A. D. (1984) Redescription of Pyrgophorus parvulus (Gastropoda: Hydrobiidae) from St. Vincent, St. Lucia, and Grenada, West Indies, Proceedings of the Academy of Natural Sciences of Philadelphia 136: 145-151

Hershler, Robert; Davis, Cheryl L.; Kitting, Christopher L.; Liu, Hsiu-ping (2007) Discovery of introduced and cryptogenic cochliopid gastropods in the San Francisco estuary, California., Journal of Molluscan Studies 73: 323-332

Lopez, G. R.; Kofoed, L. H. (1980) Epipsammic browsing and deposit feeding in mud snails Hydrobiidae., Journal of Marine Research 38(4): 585-600

Nava Ferrer, Mario L.; López, Cesar; Hernández, Mora, Dayrana C.; Pares, Guillermo; Manzano Marcano, José M.; Macías Serpa, Moisés S.; Sanchez, Roxana (2018) [Maximum salinity tolerance of the gastropod Pyrgophorus platyrachis (Littorinimorpha: Cochliopidae) in the Laguna Las Peonías, Maracaibo Lake system Venezuela, Ecotropica 30(e0004): Published online

Rosenberg, Gary 1995-2023 Malacolog 4.1. http://www.malacolog.org/



USGS Nonindigenous Aquatic Species Program 2003-2024 Nonindigenous Aquatic Species Database. https://nas.er.usgs.gov/



WoRMS Editorial Board 2022-2024 World Register of Marine Species. https://www.marinespecies.org


https://doi.org/10.14284/170

---