Maiazoon orsaki Newman and Cannon, 1996
Species diagnosis: The diagnostic characters for this species are the presence of two male gonopores posterior to the pharynx and the presence of three to five female gonopores. The transparent light brown or cream background with a thin white median line is also a diagnostic character for this species.
Type material museum: The holotype is a whole mount of an entire specimen (G210715), and the paratype is a set of serial histological sections (G210648) deposited at the Queensland Museum in Brisbane, Australia.
External anatomy: Elongate oval body, raised medially with marginal ruffles and slightly tapered posteriorly. Transparent light brown or cream background with a thin white median line starting anteriorly to the cerebral eyespot and ending just prior to the posterior margin. An indistinct marginal band, intensifying into orange-brown with a narrow black rim. The ventral surface has the same dorsal color pattern without the median line. The pseudotentacles are laterally ruffled, square, pointed with transparent tips with four scattered clusters of 30-50 eyes. A big cerebral cluster of eyes and a simple pharynx anteriorly located. Two male gonopores posterior to the pharynx and three to five female gonopores equidistant, located posterior and well separate from the male pores.
Internal anatomy: The male complex consists of two male gonopores, each one leading to an independent male system. Each system consist of branched vas deferens with a large and oblong seminal vesicle connected to a long and uncoiled ejaculatory duct, a small and round prostatic vesicle oriented anteriorly, and a small penis papilla bearing a thin sclerotized penis stylet. The female gonopores are connected to a common uterus and each female system has a deep antrum, with a short and narrow vagina surrounded by the cement glands.
Ecology and Distribution
This species has been reported for Madang, Papua New Guinea, the Maldives and the Marshall Island in Micronesia.
This species is commonly found on the exposed edge of the reef crest and in boulders covered with coralline algae
Evolution and Systematics
Maiazoon orsaki is the only species of this genus which is morphologically similar to the species belonging to the genus Pseudobiceros with regards to marginal ruffling, type and shape of pharynx, and the presence of two male gonopores, but they differ one to another in the number of female gonopores. M. orsaki also resembles the monotypic genus Nymphozoon described by Hyman (1959) in which N. bayeri has about eight female gonopores. The color of N. bayeri is black and white with a median black line and lateral bands grayish black, different from M. orsaki which has a transparent background and a white middle line. Additionally, in the revision of the holotype of N. bayeri made by Newman & Cannon (1996) there was neither evidence of a sclerotized stylet nor presence of sucker as seen in M. orsaki.
Hyman, L.H. (1959) A further study of Micronesian polyclad flatworms. Proceedings of the United States National Museum, 108: 543–597.
Newman, L.J. & Cannon, L. R. G. (1996) New genera of pseudocerotid flatworms (Platyhelminthes, Polycladida) from Australian and Papua New Guinean coral reefs. Journal of Natural History, 30: 1425–1441.