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Marine Animal Encyclopedia

Neptune's necklace Hormosira banksii

Neptune’s necklace is one of the many brown seaweeds endemic (unique) to New Zealand and the cooler waters around Australia. Its distinctive fronds, which look like a string of brown beads, are made up of chains of ovoid, hollow segments joined by thin constrictions in the stalk. Small reproductive structures are scattered over each “bead.”

Dense mats composed almost entirely of Neptune’s necklace can be found on seashore rocks. The fronds are attached to the rock by a thin, disk-shaped holdfast. Neptune’s necklace also lives unattached among mangrove roots. The shape of its segments varies according to habitat. They are spherical and about in (2 cm) wide in fronds growing on sheltered rocks, in mussel beds on tidal flats, or in mangrove swamps. Fronds of Neptune’s necklace growing on subtidal rocks on moderately exposed coasts have smaller segments that are just in (6 mm) long.

Neptune's Necklacezoom image
  • Kingdom Phaeophyta
  • Length Up to 12 in (30 cm)
  • Habitat Lower shore and subtidal rocks
  • Water_temperature 50–68°F (10–20°C)
  • Distribution Coasts of southern and eastern Australia and New Zealand
Neptune's Necklace Habitat Mapzoom image