Embryogenesis in ascidians is the classic example of mosaic development, yet within this phyla a number of colonial species exist which as adults can reproduce entire bodies asexually. The colonial ascidian Botryllus schlosseri is an excellent model to study this process: on a weekly basis it regenerates all somatic and germline tissues, and while these processes have been characterized morphol...

We investigated the physical role of the extracellular matrix (ECM) in vascular homeostasis in the basal chordate Botryllus schlosseri, which has a large, transparent, extracorporeal vascular network encompassing an area >100 cm2 We found that the collagen cross-linking enzyme lysyl oxidase is expressed in all vascular cells and that in vivo inhibition using β-aminopropionitrile (BAPN) caused a...

Invertebrate model systems, such as nematodes and fruit flies, have provided valuable information about the genetics and cellular biology involved in aging. However, limitations of these simple, genetically tractable organisms suggest the need for other model systems, some of them invertebrate, to facilitate further advances in the understanding of mechanisms of aging and longevity in mammals, ...

The colonial ascidian Botryllus schlosseri possesses an innate immunity, which plays fundamental roles in its survival, adaptability, worldwide spread and ecological success. Three lines of differentiation pathways circulating haemocytes are known to be present the haemolymph, starting from undifferentiated haemoblasts: (i) phagocytic line (hyaline amoebocytes macrophage-like cells), (ii) cytot...

In a primitive chordate model of natural chimerism, one chimeric partner is often eliminated in a process of allogeneic resorption. Here, we identify the cellular framework underlying loss of tolerance to one partner within a natural Botryllus schlosseri chimera. We show that the principal cell type mediating chimeric partner elimination is a cytotoxic morula cell (MC). Proinflammatory, develop...

It has been widely recognized that mammal brain size predominantly increases over evolutionary time. Safi et al. [Biol Lett 2005;1:283-286] questioned the generality of this trend, arguing that brain size evolution among bats involved reduction in multiple lineages as well as enlargement in others. Our study explored the direction of change in the evolution of bat brain size by estimating brain...

The variety of theories that have attempted to define the mechanisms of aging and life span can be broadly divided into two alternative but nonexclusive viewpoints. The first stipulates that random changes of cellular and molecular structures lead to death following progressive "wear and tear." The second argues that life span is, at least in part, genetically programmed, and therefore aging ma...

The source of tissue turnover during homeostasis or following injury is usually due to proliferation of a small number of resident, lineage-restricted stem cells that have the ability to amplify and differentiate into mature cell types. We are studying vascular regeneration in a chordate model organism, Botryllus schlosseri, and have previously found that following surgical ablation of the extr...

A new mechanoreceptor organ, the "coronal organ," located in the oral siphon, is described by light and electron microscopy in the colonial ascidians Botryllus schlosseri and Botrylloides violaceus. It is composed of a line of sensory cells (hair cells), accompanied by supporting cells, that runs continuously along the margin of the velum and tentacles of the siphon. These hair cells resemble t...