'Cup cell disease' in the colonial tunicate Botryllus schlosseri

Abstract

A new progressive, fatal disease called 'cup cell disease' was characterized in ex situ cultures of Botryllus schlosseri, a colonial tunicate. The disease originated as a few dark spots growing within zooids. The infected colonies then started to deteriorate, morphologically diagnosed by ampullar retraction, lethargic blood circulation and by a swollen and soft tunic matrix. In later stages of the disease, developed buds were also affected. Many large black dots were scattered within the tunic matrix, and zooids were transformed to opaque, dilated, sac-like structures, signaling impending death. Colonies were infected periodically, even without direct tissue contact. The time course from first appearance to colony death ranged between 30 and 45 d. Histological studies, in vitro culturing of blood cells and blood smears revealed the existence of numerous cup-like cells (up to 4.8 µm diameter on average) with a yellowish cell wall and transparent cytoplasm that was not stained by various dyes (except azocarmine-G). Cells were refractive under bright-field illumination and revealed a flattened wall with flanges, characteristic of species of the phylum Haplosporidia. Cup cells aggregated in blood vessels and in internal parts of zooids and buds and were phagocytosed by blood cells. In a single case, plasmodia-like structures were found only in the tunic matrix of an infected colony. This is the first record in botryllid ascidians of an infectious lethal disease associated with haplosporidian protists.KEY WORDS: Ascidians · Botryllus · Disease · Haplosporidia · Mariculture Resale or republication not permitted without written consent of the publisherDis Aquat Org 60: [77][78][79][80][81][82][83][84] 2004 Using the laboratory facilities at Haifa, we maintain and culture Botryllus schlosseri colonies first established in 1988. The culture conditions, which have improved with time (Rinkevich & Shapira 1998), maintain the tunicates in good condition (i.e. fast growth rate), and support sexual reproduction, high survivorship of young individuals and long-term maintenance under laboratory conditions. However, occasionally, the entire stock of colonies growing in one of the culturing tanks (17 l standing-seawater tanks; Rinkevich & Shapira 1998) or the entire set of colonies growing in the culture room (20°C) dies simultaneously without the emergence of any known agent. Diseases causing mortality to urochordates have rarely been reported (Monniot 1990). Herein, we describe 'cup cell disease' in cultured Botryllus schlosseri colonies that is associated with the appearance of a haplosporidian protist. Infected colonies characteristically exhibited swollen zooids with dark pigmentation that gradually deteriorated and died. MATERIALS AND METHODSAnimal maintenance. Botryllus schlosseri colonies (originating from Monterey, Half Moon Bay and Moss Landing, Marinas, California, USA, and from the Istra Peninsula, Croatia) were kept in the laboratory at Haifa in 17 l standing-seawater, glass tanks (up to 20 colonies per t...

Identification of the Endostyle as a Stem Cell Niche in a Colonial Chordate

“…Colonies were fixed and sections from paraplast embedded tissues were made, cross and longitudinal sections (5μm) were stained with Azan Heidenhain or Hematoxyline Eosin as described (Moiseeva et al, 2004). …”

Further portrayal of epithelial monolayers emergent de novo from extirpated ascidians palleal buds

“…schlosseri is an important experimental model system for the study of a variety of scientific disciplines. While most studies on botryllid ascidians involved in vivo approaches (for recent reviews, see Rinkevich 2004Rinkevich , 2005aManni et al 2007;Ballarin 2008), the use of in vitro methodologies, either the development of cell cultures or the use of primary cultures made from different organs for in-depth research (Rinkevich and Rabinowitz 1993, 1994, 1997Kamer and Rinkevich 2002;Rinkevich 2003, 2004;Moiseeva et al 2004;Kawamura et al 2006), has been proven to be highly informative. We previously studied the in vitro fate of developing primary buds extirpated from large colonies of B. schlosseri at all blastogenic stages Rinkevich 2003, 2004).…”

The occurrence of haplosporidian parasites, Haplosporidium nelsoni and Haplosporidium sp., in oysters in Ireland

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