Invasion HistoryFirst Non-native North American Tidal Record: 2003
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 2003
General Invasion History:
Hyotissa hyotis has a very wide native range, in the Indian and Pacific oceans from the Red Sea and southern South Africa, to northern Australia, Hawaii, and the eastern Pacific from Mexico to Ecuador (Bieler et al. 2004; Duprat-Bertazzi and Garcia-Dominguez 2005; Academy of Natural Sciences of Philadelphia 2010; Stella et al. 2010; Tan et al. 2010; US National Museum of Natural History 2010). It had been reported in earlier literature from the Atlantic, but the Atlantic form was recognized as a distinct species (H. mcgintyi) in 1985 (Harry 1985, cited by Bieler et al. 2004), although some authors continued to list H. hyotis from the Atlantic. In 2003, genuine specimens of H. hyotis were identified by molecular methods from the Florida Keys (Bieler et al. 2004).
North American Invasion History:
Invasion History on the East Coast:
In 2001, a shell, later identified as H. hyotis, was found off West Palm Beach, Florida in the Atlantic Ocean. In 2003, in an investigation of fouling communities on shipwrecks, divers found some exceptionally large attached oysters on the wreck of the RV 'Thunderbolt', near Marathon Key, on the Gulf side of the Florida Keys. The largest specimens were later identified as H. hyotis, using molecular comparisons with specimens from Guam. The native oyster (H. mcgintyi, McGinty oyster) was also found on the wreck (Bieler et al. 2004). Subsequent collections of H. hyotis were made on the wreck of the USGC Cutter 'Duane,' off Key Largo, and on the wreck of the freighter Eagle in the Florida Keys National Marine Sanctuary, both in 2005, on the Atlantic side of the keys. This oyster is considered established in the Florida Keys (USGS Nonindigenous Aquatic Species Program 2011).
Invasion History Elsewhere in the World:
Hyotissa hyotis was reported from New Zealand, on the hull of a wrecked fishing vessel 10 nautical miles off Cape Brett on the North Island. This and other fouling organisms on the ship were not considered to be likely to become established (Williams et al. 2008). This oyster was also reported from a shipwreck off Pernambuco, Brazil (Lira et al. 2011). However, it is not clear whether H. hyotis was distinguished from the native H. mcgintyi.
Hyotissa hyotis is a very large oyster, with the two unequal valves. The shape is irregular, according to the substrate and conditions of growth. The animal is cemented to the substrate by the left valve. Both valves are solid and thick. The shell is very deeply ridged, with ridges extending to the shell margin, making it strongly saw-toothed. The arches of the valves interlock. The area of attachment of the ligament has a shallow median groove. The hinge is without teeth. The external coloration of the shell is purplish black, while the interior is bluish-white in the center, and bluish-black towards the margin. There is a single purplish adductor muscle scar, located towards the hinge (Bieler et al. 2004; Stella et al. 2010). Living animals are frequently heavily overgrown with fouling organisms. Hyotissa hyotis has been reported to reach 300 mm in size (Thomson 1954, cited by Duprat-Bertazzi and Garcia-Dominguez 2005), although other authors give maxima of 102 (Stella et al. 2010) and 180 mm (Bieler et al. 2004).
Potentially Misidentified Species
This Western Atlantic native oyster (McGinty Oyster) was frequently confused in older literature with its Indo-Pacific relative H. hyotis, but was identified as a distinct species. Recently, in a molecular study of that species, specimens of H. hyoti were discovered in Florida (Bieler et al. 2004).
Hyotissa hyotis has separate sexes; males and females can be distinguished by the color of the gonads (Sevilla et al. 1998, cited by Duprat-Bertazzi and García-Domínguez 2005). The mode of larval development is unknown, but spawning in the Gulf of California continued year-round, peaking in the warmest months (Duprat-Bertazzi and Garcia-Dominguez 2005).
This oyster is widespread on tropical rocky shores, coral reefs and shipwrecks. It appears to be limited to warm, high-salinity environments (Bieler et al. 2004; Duprat-Bertazzi and García-Domínguez 2005; Academy of Natural Sciences of Philadelphia 2010; Stella et al. 2010; Tan et al. 2010; US National Museum of Natural History 2010). It is frequently encrusted with fouling organisms, including other oysters (Bieler et al. 2004).
|General Habitat||Coral reef||None|
|General Habitat||Vessel Hull||None|
|General Habitat||Oyster Reef||None|
|Salinity Range||Euhaline||30-40 PSU|
Tolerances and Life History Parameters
|Minimum Reproductive Temperature||20||Field observations, Gulf of California|
|Maximum Reproductive Temperature||28.5||Field observations, Gulf of California|
|Maximum Length (mm)||300||Maximum sizes variously given as 102 (Stella et al. 2010) and 300 mm (Thomson 1954, cited by Duprat-Bertazzi and Garcia-Dominguez 2005).|
|Broad Temperature Range||None||Warm temperate-Tropical|
|Broad Salinity Range||None||Euhaline|
General ImpactsHyotissa hyotis is an important local fisheries species in its native range, because of its large size and good flavor. However, it does not appear to be cultured or deliberately introduced in other locations (Duprat-Bertazzi et al. 2010). This species has no reported impacts in North American waters.
Regional Distribution Map
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|CAR-I||Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida||2003||Def||Estab|
|S206||_CDA_S206 (Vero Beach)||2003||Def||Estab|
|S196||_CDA_S196 (Cape Canaveral)||2003||Def||Unk|
References2002-2016a Malacology Collection Search. http://clade.ansp.org/malacology/collections/
2006-2014b OBIS Indo-Pacific Molluscan Database. http://data.acnatsci.org/obis/
Bieler, Rudiger; Mikkelsen, Paula; Lee, Taehwan; O"Foighil, Diarmid. (2004) Discovery of the Indo-Pacific oyster Hyotissa hyotis (Linnaeus , 1758) in the Florida Keys (Bivalvia: Gyphaeidae), Molluscan Research Molluscan Research 24: 149-159
Duprat-Bertazzi, Gabriela; Garcia-Dominguez, Federico (2005) Reproductive cycle of the rock oyster Hyotissa hyotis (linne´, 1758) (Griphaeidae) at the La Ballena Island, Gulf of California, Mexico., Journal of Shellfish Research 24(4): 987-993
Lira, Simone Maria de Albuquerque; Farrapeira, Cristiane Maria Rocha; Amaral, Fernanda Maria Duarte; Ramos, Carla Alecrim Colaço (2011) Sessile and sedentary macrofauna from the Pirapama Shipwreck, Pernambuco, Brazil, Biota Neotropica 10(4): 155-165
Paulay, Gustav (1995) New records and synonymies of Hawaiian bivalves (mollusca), Bishop Museum Occasional Papers 45: 18-29
Ruiz, Gregory M.; Geller, Jonathan (2018) Spatial and temporal analysis of marine invasions in California, Part II: Humboldt Bay, Marina del Re, Port Hueneme, and San Francisco Bay, Smithsonian Environmental Research Center & Moss Landing Laboratories, Edgewater MD, Moss Landing CA. Pp. <missing location>
Stella, C.; Murugan, A.; Vijayalakshmi, S. (2010) New distributional records of Hyotissa hyotis (Linnaeus, 1758) family: Gryphaeidae from Mandapam area-south east coast of India, World Journal of Fish and Marine Sciences 2(1): 42-43
Tan, Siong Kiat; Woo, Henrietta P. M. (2010) <missing title>, Raffles Museum of Biodiversity Research, Singapore. Pp. <missing location>
2002-2021 Invertebrate Zoology Collections Database. <missing description>
2003-2022 Nonindigenous Aquatic Species Database. Gainesville, FL. http://nas.er.usgs.gov
Williams, Rissa; Gould, Brendan; Christian, Sheree (2008) Shipwrecks: an international biosecurity risk?, Surveillance 35(1): 1-6