Nephtheis (oxycorynia) fascicularis(DRASCHE, 1882)
Author: Bob Goemans
Range: Tropical Western Pacific Ocean
Natural Environment: This suspension feeder is found in protected areas receiving gentle water movement and usually inhabits areas on reef drop-offs and those under overhangs. Color depends upon its area of origin.
Captive Care: Unfortunately this and most others in this phylum require heavy concentrations of suspended food particles and/or bacteria-laden waters. For those that want to maintain them in aquaria, these creatures require numberous feedings per day of live and/or preserved commercial phytoplankton products or that of animal and plant powders that produce suspended products in the bulk water. Proper placement is also quite important. Generally, most prefer low light and do better with indirect light and gentle water movement.
Besides being difficult to maintain, they have a very short life span, usually about one year and sometimes far less. Only those willing to provide for their demanding level of care should attempt keeping them in closed systems. Actually, 99.9 percent of these animals should be left in the wild.
Notes: This phylum is actually divided into three subphyla, however only one is of interest to marine hobbyists—the subphylum Tunicata, which contains the tunicates and ascidians, or "sea squirts" as they are often called.
There are over 1500 speces in this subphylum, and the class Ascidiacea contains two major divisions that interest hobbyists, Enterogona and Pleurogona; these contain colonial and solitary sea squirts.
Most sea squirts are found on reef drop-offs and/or under overhangs, with some found at the base of corals, where various forms of particulate matter tends to collect. Occasionally, they are found attached to live rock or corals entering the aquarium. They are called "sea squirts" because a jet of water is expelled when they contract. Very few of these beautiful creatures in aquaria are sustainable for more than a few months, and in fact, their general life span is generally no longer than a year.
Many tunicates have male and female reproductive organs, therefore producing both sperm and eggs. Following a free-swimming or planktonic larval stage, the adults live a sessile lifestyle. Their bodies are encased in a protective firm substrate, e.g., rock, seaweed, or even other animals.
There are two openings in the tunic; one is often larger than the other. The larger one, called the buccal siphon, is where beating cilia draw in water. The water enters a chamber called the pharyngeal basket, which filters it for oxygen and foodstuffs. The filtered water is then expelled through the smaller opening called the atrial siphon. Food particles are mixed with mucus, drawn into the oesophagus, and digested. Resulting waste products also leave through the smaller opening.
I should also note that the taxonomy encompassing these animals is somewhat confusing; I've used the Checklist Ascidiacea published by the Australian Government Department of the Environment and Heritage to help properly place this species.
Water Requirements: Calcium 380 to 430 ppm, alkalinity 3.5 meq/l, pH 8.1 to 8.2, specific gravity 1.024 to 1.026, and a temperature range of 72° to 83°F (22° to 28°C).