Title: Interjurisdictional competition in emission taxes under imperfect competition of local firms
Abstract: Setae and setal-like structures are found only in a few bilaterian taxa. In the past, the close similarity of brachiopod and annelid setae even on the ultrastructural level has been taken to indicate homology of these structures in Brachiopoda and Annelida. Therefore, annelid and brachiopod setae are often considered as synapomorphic characters. The present investigation of the setae of different developmental stages of the inarticulate lingulid brachiopod, Lingula anatina Lamarck, 1801, and two articulate species, Notosaria nigricans (Sowerby, 1846) and Calloria inconspicua (Sowerby, 1846) provides the first comparative study of brachiopod setae. Two different types, larval and adult brachiopod setae, are identified. All setae-bearing developmental stages of L. anatina and the adult articulate brachiopods investigated have adult setae, built within an ectodermal invagination (setal follicle). The chaetoblast as well as the seta-surrounding follicle cells are secreting different components of setal material. Lecithotrophic larvae of N. nigricans and C. inconspicua have larval setae built exclusively by a chaetoblast. Each larval seta pierces a single epidermal invaginated cell, which is not involved in the production of setal material. Follicle cells are lacking in the setal sacs of these brachiopod larvae. In terebratellaceans larval setae are part of a sensory complex. The lack of larval setae in Lingulacea supports the hypothesis that lingulaceans do not have larvae, but so-called 'pelagic juveniles'. The lack of larval setae in Annelida does not necessarily reflect homoplasy of annelid and brachiopod setae, but in accordance with morphological characters other than setae the results may support the hypothesis of convergent evolution of setae in both taxa.
Publication Year: 1995
Publication Date: 1995-01-01
Language: en
Type: preprint
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