Stichodactyla mertensii (Merten's Carpet Anemone) Breeding & Propagation Guide

Reproduction of Stichodactyla mertensii, the largest sea anemone: pelagic sexual spawning unreachable at home and the infrequent asexual fission of sea anemones. Realistic hobby expectations.

Overview

Stichodactyla mertensii is regarded by Wikipedia as the largest sea anemone, with a diameter exceeding 1 m. It attaches to rocky or coral substrate across the Indo-Pacific from Mauritius to Fiji. It contains obligate symbiotic zooxanthellae and is a highly generalist host to around half of all anemonefish species plus a damselfish. Its short 1–2 cm tentacles and immense size frame any propagation discussion.

Reproductive Mode

As a sea anemone, S. mertensii can in principle reproduce both sexually and asexually. Wikipedia's general account states that males release sperm to stimulate females to release eggs, with fertilization in the water column or internally, and the resulting planula larva drifts before settling and metamorphosing. No captive spawning method specific to this species is documented in the consulted sources.

Asexual Propagation

The asexual options of sea anemones are longitudinal fission into identical clones, the rarer transverse fission, and pedal laceration, in which fragments from the pedal disc regenerate into clones. Such large host anemones divide only occasionally, so deliberate fragmentation is not a practical or recommended propagation route.

Sexual Reproduction

Sexual reproduction is broadcast and pelagic: gametes are released into open water and planula larvae drift in the plankton before settling on rock. This open-water larval stage cannot be reproduced in an aquarium, so home sexual breeding of S. mertensii is not feasible.

Common Challenges

Its eventual size demands a very large reef with strong light and rock for attachment. Given the pelagic larval phase and infrequent division, the realistic aim is long-term health of a single specimen rather than reproduction.