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Related FAQs; Flatworms/Planaria 1, Flatworms 2Flatworms 3, & FAQs on: Flatworm Identification, Flatworm ID 2, Flatworm ID 3, Flatworm Behavior, Flatworm Compatibility, Flatworm Control, Predator Control, Chemical Control, Flatworm Selection, Flatworm Systems, Flatworm Feeding, Flatworm Disease, Flatworm Reproduction,

Related Articles: Pest Flatworm Control by Anthony Calfo, Worm DiversityThe Flatworms That Are Flukes by Bob Fenner

/The Conscientious Reef Aquarist:

Flatworms, including "Planaria" & Marine Aquariums, Part 1

To: Part 2, Part 3, Part 4, Part 5, Part 6

By Bob Fenner

Thysanozoon nigropapillosum

Of the worms, the Platyhelminthes ("flat worms") are considered the prototypes, having developed such innovations as bilateral symmetry, a head, tail, and three germinal tissue layers (stinging celled animals, comb-jellies... only have two). These simple soft-bodied animals use their skin to breath through and only have one body opening, the mouth serving also as an anus. 

    The Flatworm Phylum includes two groups of well-known parasitic species of aquatic animals; the Tapeworms (Class Cestoda) and Flukes (Class Trematoda). These are important species to humans directly and indirectly through their negative interactions with food and ornamental animal life, including fishes. There are many species of both Cestodes and trematodes that live on/in fishes and their gill cavities. Fortunately, due to complex life histories and careful quarantine, dips/baths, most aquarists don't come in contact with these parasitic forms. 

    The free-living (i.e. non-parasitic) species of Flatworms, the Class Turbellaria are more of note... True, some of them do trend toward being pests when their numbers get out of control... and can be problematical should you provoke a poisonous variety to the point of toxin release... most are benign organisms that are best ignored. Most of us have had contact at High School science classes with the tiny freshwater genus Planaria. These are the remarkable worms that you cut in two and witnessed regeneration with.

Class Turbellaria: Mostly free-living Flatworms; about 3,000 described species. 

Acoel Flatworms: Simple, "gut-less", small worms... including the ones that "reproduce like rabbits" in reef tanks... best left alone... or selectively siphoned off (mainly) soft corals, out of reef systems.

Amphiscolops sp.,  a harmless Acoel that "shows up" at times in reef tanks. Photo by Mike Giangrasso

Does this look like fun to you? Here's an infestation of Acoel flatworms (perhaps Convolutriloba retrogemma) on someone's (Birch Aquarium, San Diego, California, USA) Corallimorphs... Best to... leave them alone, siphon off, seek a predator?

Waminoa sp. 1 Characterized by having a pumpkin silhouette appearance and a yellow dot at the base of their caudal notch (and a lack of other unknown members of the genus other coloring, marking characteristics...). Overall color due to algal symbionts (Dinoflagellates, diatoms?). Think you've seen infestations? Here are some images made in the Lembeh Strait in N. Sulawesi. Below: on Bubble Coral (Plerogyra), Goniopora (Flower Pot Coral) and a Fungiid (Heliofungia actiniformes). 
Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Polyclad Flatworms: Referring to their multi-branched digestive system. Similar to Nudibranchs, but lacking the latter's "naked gills"; flatworms are "flatter", and often much faster moving. 

Bulaceros sp. Transparent w/ a broken white line, random dark spots on body. To 20 cm. The genus is cryptic; but here seen feeding on a star during the day in S. Leyte 2013.

Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

Genus Maiazoon:

Maiozoon orsaki Newman & Cannon 1996. Creamy colored body, ruffled margin, with a thin white line down its back, skirted by black and burgundy edging. Raja Ampat 08.

To: Part 2, Part 3, Part 4, Part 5, Part 6

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