Contributions to Zoology, 83 (2) – 2014Pablo Hernández-Alcántara; Vivianne Solís-Weiss: Anatomical and morphometric analysis of a new species of Leitoscoloplos (Annelida: Orbiniidae) with numerous stomach papillae, from the Gulf of California, Eastern Pacific
Material and methods

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Morphological analysis

Some morphological characters have been used under different names in the family Orbiniidae after Hartman’s (1957) study; that is why the modifications proposed by Mackie (1987), as well as those introduced by Blake (1996) and Eibye-Jacobsen (2002), were used here to standardize the description of the species. The abdomen is considered to start where the neuropodia become cylindrical; besides, the abdominal neuropodia bear a few capillaries, while the thoracic neuropodia have fan-shaped bundles of numerous chaetae. A single postchaetal lobe is present in the notopodia, and the chaetiger at which this lobe appears can be a diagnostic character for some species. Contrary to the notopodia, an important number of morphological structures are helpful in the neuropodia for the identification of the different taxa. The number and distribution of papillae associated with the parapodia are important to identify several genera of Orbiniidae. In the course of this study, podal, subpodal and/or stomach papillae were observed in the neuropodia of specimens of Leitoscoloplos, and their distribution on the thorax and/or abdomen were considered significant to separate the taxa. In particular, the podal papillae are postchaetal processes, which are part of the subdivided neuropodial lobes proper; the term subpodal papilla refers to papillae immediately below the neuropodia, present in a transverse row, ventral and somewhat posterior to the neuropodia, while stomach papillae are papillae clearly placed close to the ventral midline of the body (Mackie, 1987; Eibye-Jacobsen, 2002). These stomach papillae have also been described by some authors as subpodal papillae extended almost to the ventral midline of the body (Eibye-Jacobsen, 2002).

Morphological differences among Leitoscoloplos panamensis, L. multipapillatus sp. nov. and Leitoscoloplos sp. are difficult to recognize, except for the number of stomach papillae. Usually, the subpodal and stomach papillae are separated by a gap, and the stomach papillae are counted from this gap to the ventral midline of the body, but in the new species described in this study, the distribution of the subpodal and stomach papillae is occasionally continuous (see discussion). This is why they look like additional papillae on the ventral surface, making it difficult to distinguish between them, as indicated by Mackie (1987) and Eibye-Jacobsen (2002).

The emendations of Eibye-Jacobsen (2002) to the genus Leitoscoloplos allow the inclusion of species with up to seven subpodal papillae; in the new species herein described, all the diagnostic characters corresponded to Leitoscoloplos, except for their numerous (up to 14) stomach papillae, which is why it was necessary to extend the diagnosis of the genus to include species with numerous stomach papillae.