Pseudobiceros ferrugineus Hyman, 1959 (33mm)

Featured Invertebrate Data


Frequency on Okinawa: Collection Data:
[brackets indicate range for all Okinawa-collected specimens of the species]

Species Account:

        The "Fuchsia Flatworm" Pseudobiceros ferrugineus is considered to be rare on Okinawa as I have seen only a few animals and collected but a single individual over a period of numerous years of diving in Okinawan waters. It's, at best, difficult to pick out the most attractive flatworm as there are so many beautiful species, but certainly P. ferrugineus ranks quite high in the "attractive flatworm" category. It was collected from an area of mixed sand and coral rubble from 140ft during a morning SCUBA excursion. [note the small white bi-lobed structure(egg sacs) on the upper perimeter of the above image. A very small parasitic copepod; the females carry a pair of sausage-shaped egg sacs on their tail]

        The following original description of Pseudoceros ferrugineus (now known as Pseudobiceros ferrugineus, Faubel, A., 1984.) is taken from Hyman (1959).

Material: The single specimen was taken by the Stanford team at Sta. 236a, in Iwayama Bay, Palau Islands, Oct. 20, 1955, crawling in about a meter of water on the rocky shelf of the east end of Koror Island, in Oyster Pass.

General characters: The worm is of elongated oval shape, measuring 18 mm. in length by 11 mm. in width, preserved. The tentacular foldings appear slightly developed, both in the preserved worm, and on the color photograph of the live worm. The brilliant coloring in life is preserved on the photograph taken by F. M. Bayer, but, alas, the preserved worm is a dull grayish brown. In life the general color is a bright rusty red blending into a narrow margin of brilliant orange. The dorsal surface is liberally flecked with white on the rusty background and here and there these flecks fuse to form nebulous patches of clear white or tinged with pink in places. The white flecks diminish towards the margin where the rusty red background is much more in evidence. The bright orange marginal line is free from spots. There is some indication of a narrow mid dorsal line of pale rust that fades away posteriorly.

In the cleared worm there could be seen the sightly bilobed cluster of cerebral eyes, the ruffled pharynx having the butterfly shape that I have noticed in some species of Pseudoceros, the pair of male pores in the concavity of the last lobulations of the pharynx, the female pore close behind the male pores, and the sucker slightly behind the middle, about 10 mm, from the anterior end.

Differential diagnosis: The color pattern is distinctive.

Holotype: USNM 28654, in alcohol.

In addition, the following information is from Wikipedia:

Description: Pseudobiceros (Hyman, 1959) ferrugineus can reach a length of about 18-48 mm. It has an enlarged oval shape. The upper surface of the body is fuchsia (hence the common name) with small white dots and two marginal bands red and orange without dots.

Morphology: External anatomy: Large body with several marginal deep ruffles. The color is dark red with the dorsal surface covered by compacted small white dots given the appearance of a brilliant pink surface. There are not two marginal bands, red and orange without white dots. Ventrally, the color is red being more intense towards the margin. Pseudotentacles formed by simple broad folds of the anterior margin with numerous marginal eyes. Cerebral cluster made of a large number of eyespots. Small pharynx with elaborated folds.

Internal anatomy: The male reproductive system consists of a branched vas deferens, a long seminal vesicle connected to a short ejaculatory duct, a small prostatic vesicle with two chambers, a muscular prostatic duct, and a small stylet housed in a shallow male antrum. The female system has a shallow antrum with a short vagina directed backwards surrounded by a thick and strong mass of cement gland on its first portion.

Distribution: This species is widespread in the tropical Indo-Pacific, from the Indonesian Archipelagos to Central Great Barrier Reef in Australia, Palau in Micronesia, Philippines and the islands of Hawaii.

Habitat: It can be found in the external slope or top coral reef, at a depth of 1-15 m.

Behaviour and feeding: These flatworms are benthic and diurnal. Because of their aposematic colors, they have no fear to crawl around to feed. Pseudoceros ferrugineus feeds on various colonial ascidians.

Newman & Cannon (2003) Have several excellent photographs of P. ferrugineus on pp. 1, 32, 38, and 74. In addition, Gosliner, et al, 1996, have a photograph (p. 106) as well There are also numerous photographs of P. ferrugineus on-line, two of these sites are:

  • Reef Guide
  • Pseudoceros_ferrugineus

            I've added a second page w/ several additional images of Pseudobiceros ferrugineus.

            In addition, there's a page w/ links to misc. phyla including this species' phylum, as well as additional resources.


    • Hyman (1959) chose the specific name in reference to parts of the body being rusty in appearance (L. ferruginis, iron rust, ferruginus, rusty). [Portions of the upper body are fuchsia colored (therefore the common name)].

    Literature Cited:

    • Faubel, A., 1984. The Polycladida, Turbellaria. Proposal and establishment of a new system. Part II. The Cotylea. Mitteilungen des hamburgischen zoologischen Museums und Instituts 80. 189-259.
    • Gosliner, T.M., D.W. Behrens, & G.C. Williams. 1996. Coral Reef Animals of the Indo-Pacific. Sea Challengers, Monterey, California.
    • Hyman, Libbie H., 1959. A further study of micronesian Polyclad flatworms. Proceedings of The United States National Museum, vol. 108, n. 3410, p. 571.
    • Newman & Cannon 2003. Marine Flatworms: The World of Polyclads. CSIRO PUBLISHING, Collingwood VIC, Australia.
    • Wikipedia. https://en.wikipedia.org/wiki/Pseudoceros_ferrugineus.

    Page Date: 01 Jun '17
    Page Modification Date: 01 Jun '17
    Digitally manipulated photo
    Copyright © 2017 Robert F. Bolland