UNIVERSITY OF MICHIGAN MUSEUM OF ZOOLOGY
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November 2022 - Fieldwork in Rangiroa, Tuamotu Archipelago
[English version/Tahitian version/French version]
Diana Vergara and Tom Duda traveled to Avatoru in the northwest part of Rangiroa where they studied the ecology and evaluated the occurrence of cone snail species in nearshore habitats of lagoon and seaward areas. They recorded the presence of cone species and microhabitats where the snails occurred, collected and preserved egg capsules, measured individuals, placed snails in small containers with sea water. They then collected feces from individuals that defecated, photodocumented specimens, obtained tissue clips from individuals, and preserved up to five individuals per species to serve as voucher specimens. DNA sequences will be obtained from fecal materials, tissues, and egg capsules to determine diets of individuals, evaluate the potential presence of cryptic cone snail species, and determine which species were reproducing (i.e., depositing egg capsules) at the time of the fieldwork.
The fieldwork primarily took place at sites on lagoon and seaward sides of Avatoru that were approximately 500 m from each other (click here to see the area on Google Maps). The lagoon site was to the southwest of the western part of the airport runway while the seaward site was to the northwest of the same part of the runway.
The lagoon site consisted of a gradually sloping subtidal area that was occasionally subject to waves when conditions were windy. The microhabitats included areas with sand and rubble as well as a mix of subtidal platforms, boulders and reef areas. Above water images of this area are shown below.
The seaward site was subject to constant wave action with approximately 1-2 ft waves during the time of the fieldwork. The site consisted of a rather large, gradually sloping intertidal bench with algal bound sand and occasional small pockets of sand or small boulders. Areas out closer to the fringing reef contained a more heterogeneous assemblage of deeper sand pockets, larger boulders and rubble. Above water images of this area are shown below; the first shows the bench area during low tide, while the latter shows the area near where waves break.
Diana and Tom collected more than 2000 cone snail specimens and measured more than 1100 of them. Many species occurred at both sites and most species were larger in size and exhibited much greater encrustation by coralline algae at the lagoon site. Conus ebraeus and Conus sponsalis were extremely abundant at both sites. Lots of juvenile and subadult individuals of Conus ebraeus were observed at the seaward site which suggests a recent recruitment event here for this species. Images below show individuals of Conus ebraeus from the lagoon and seaward sites, respectively.
Māuruuru roa to all of those who helped make this work possible especially Christophe Brocherieux from the Direction de l'environnement de la Polynésie Française; Tamatoa Bambridge, Serge Planes, Béatrice Tanseau, and Tiphanie François from CRIOBE; Ben Hess and Taehwan Lee from UM; and Didi for facilitating the work in Rangiroa.
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