Turret Shell

Maoricolpus roseus has a spiral cone shape shell that grows up to 87 mm in length and 25 mm in width. Maoricolpus roseus is brownish/purple in colour with a tint of marble. The protoconch of the shell has three to four tiny round sections and does not have a visible nucleus. The teleoconch of the shell has about 18 whorls which forms a shape with two angles and a slightly indented middle. The texture of the shell involves three thick ridges with the middle appearing first followed by the lower one, then the upper. The shell is covered with very fine and coarse lines. The base of the shell is flat with many strong lines and growth marks.

Maoricolpus roseus is native to New Zealand but inhabits large parts of Australian waters. It can be found off the coast of New South Wales, the Eastern coast of Victoria, Tasmania and around New Zealand. It is tolerant in different temperatures and depths allowing the distribution to extend down the coast of Australia. Many samples have been found at beaches in Australia such as Botany Bay in 1999 and in the D’Entrecasteuax Channel in 1935.

Maoricolpus roseus are suspension feeders that forage for food by filtering small particles from the water column. It is common that for other Turritellidae, when phytoplankton abundance levels are low, they are able to switch to a ‘deposit feeding’ system; however, it is unknown whether M. roseus can switch modes. Analysis from isotopes done off species off the coast off southeast Australia, compared with organic matter and sediment reveals that the food source for M. roseus originates from lower trophic levels.

Maoricolpus roseus can either have direct or indirect embryonic development. Direct embryonic development is where the veliger stage occurs within the egg capsule. Indirect embryonic development involves a veliger larvae spending a longer time in the water which is suggested by the multispiral protoconch. The egg capsule is held onto by the adults right before or just after the eggs hatch. A study done on M. rosues in Otago 1969, showed that each shell stored between 100 and 150 egg capsules, each containing 120 embryos. However, only 7–8 embryos per capsule developed into veligers and the rest were abortive. It takes over a year for M. roseus to mature with the fastest growth occurring in the first two years. Some planktonic veligers of M. roseus can began shell coiling and doubling in size after two weeks. Growth rates are positively related to the levels of planktonic microalgae.