Feeding ecology of the black coral, Antipathes Fiordensis, from
Doubtful Sound, Fiordland, and description of a new species, Thamnomolgus,
N.SP. (Poecilostomatoida: Thamnomolgidae), a Copepod associated
with A. Fiordensis.
This study was undertaken to investigate aspects of the feeding
ecology of the black coral, Antipathes fiordensis, from Doubtful
Sound, New Zealand. The focus was on feeding behavior during prey
capture and ingestion, the role spirocysts play in prey capture,
and changes that occur on a cellular basis during feeding action.
In addition, the diet of A. fiordensis was investigated.
Several laboratory experiments on black coral feeding were conducted
in 1998/1999, recording feeding posture, prey capture and handling.
Most prey of Antipathes fiordensis was larger than the tentacle
spacing (400 µm), and could, therefore, be retained by direct
interception which is likely to be the primary mode of particle
encounter. The feeding response of black coral polyps was elicited
by a combination of chemical and mechanical stimuli. Polyps responded
to water movement without chemical stimuli (e.g., when stirred with
a syringe) with increasing tentacle motion and increasing body size.
The same response was observed when adding live zooplankton to the
The expanded tentacles readily captured zooplankton and investigation
of the tentacular ultrastructure using transmission electron microscopy
showed that spirocysts play an important role in prey capture. An
increasing mucus layer on the polyps' tentacles functioned in trapping
the prey items that were ingested within a short time. In average,
ingestion time was 14.8 minutes (9.1 SD), and digestion time was
18 minutes (9.1 SD). The digestion time for various types of prey
in A. fiordensis was observed examining fresh collected samples
at two occasions, in September 22, 1998, and March 16, 1999. While
gelatinous prey was digested fastest (1.5 to 2.5 hours), bivalves
remained longest in the guts (>6.5 hours). Average digestion
time was 6.2 hours (±1.05 SE).
It has been demonstrated that nutrients (labelled with 14C) were
transported through the gastrovascular system of A. fiordensis,
which has not been shown for any antipatharian to this stage.
Dynamic changes in the tentacular ultrastructure during feeding
action were observed in A. fiordensis. Mucus cells transport vesicles
to the tentacle surface, and the deterioration of cnidae and mucus
cells result in a significant structural change in the epidermal
cytoplasm. The experiment showed furthermore, that columnar cells
containing prominent Golgi complexes with accompanying secretion
products developed in the epidermis during feeding action, providing
the insight that these cells are an induced and not persistent morphology.
The discovery of this type cell in the tentacular epidermis of
A. fiordensis suggests that there is, in addition to planktonic
prey, another nutritive source available for the black coral, which
is dissolved or colloidal organic material.
The diet of A. firodensis consisted mostly of epipelagic copepods
of the species Oithona, Oncaea, Paracalanus, and Clausocalanus.
The prey items were mostly larval stages with an average size of
500 µm, but larger copepods of the species Calanus australis
and Metridia were also occasionally found. Bivalves, appendicularia,
hydrozoa, and invertebrate eggs were also present in the coelenterons.
When examining gut contents of the black coral, a new species
of a symbiotic copepod was found and described in chapter 4. This
chapter has been reviewed and accepted for publication by the New
Zealand Journal of Marine and Freshwater Research.