The Use of Gill Pore Papillae in the Taxonomy of Lampreys
The structures within the gill pore of lampreys are shown to be a new taxonomic character. Papillae along the posterior margin of the gill pore cup, termed marginal papillae, vary in number, size, shape, and arrangement among species. The size and shape of a central process that extends posteriorly from the mid-lateral area of the wall of the gill pore cup is also of taxonomic significance. Examples are provided to show that there is stability of the character within an individual and among populations of a particular species. However, an example of the variation in counts over the range of Lampetra ayresii indicates that it is the average number of papillae, their arrangement, shape, and associated size in addition to the shape and size of the central process that may be of taxonomic significance. Examples of the usefulness of the new characters are provided for L. pacifica and Entosphenus folletti. The numbers and size of the marginal papillae readily distinguish L. pacifica from L. richardsoni. The number of marginal papillae and shape of the central process indicate that the holotype and paratypes of E. folletti may not be the same species. The full taxonomic value of these structures remains to be determined, but these initial studies indicate that the structures within the gill pore cup provide a method of improving the interpretation of speciation in lampreys, particularly for nonparasitic species.Abstract
(A) Schematic diagram of a longitudinal transverse section through the head region of an adult lamprey (adapted from Dawson, 1905a, 1905b; and Randall, 1972). The gill pore cup has been drawn to be larger than the actual size so that the structures can be shown. (B) Drawing of the gill pore cup showing the marginal papillae, central process, ental and ectal valves, and the approximate position of the external branchiopore. (C) Photograph of gill pore #3 of E. macrostomus from Mesachie Lake, British Columbia showing the structures in (B). (D) Interpretative drawing of (C) showing the large central process and 72 marginal papillae. (E) Diagram of shapes used in the description of papillae.
Relationship between total body length and the number of marginal papillae in gill pore #3 for E. macrostomus (n = 30).
(A) Line drawing of the gill pore papillae (n = 30) and central process of L. ayresii, from a specimen (237 mm) collected in the Strait of Georgia in February 2008. (B) Interpretative drawing of a typical gill pore cup structure for L. ayresii with 32 marginal papillae. Marginal papillae form a continuous row with papillae grouped at the dorsal and ventral ends of the row. Papillae in between these groups are usually in pairs or single. (C) Line drawing of the marginal papillae of L. pacifica, from paratype 86-0797 from the Canadian Museum of Nature, showing eight marginal papillae. (D) Line drawing of the marginal papillae of L. richardsoni from the Puntledge River, British Columbia, length 126 mm, showing 28 marginal papillae. (E) Line drawing of the marginal papillae of E. folletti holotype, from specimen 75-1549 from the Canadian Museum of Nature, showing 34 marginal papillae and (F) line drawing of the marginal papillae of L. folletti, from paratype 86-0806 from Fall Creek near Copco Lake, showing 43 marginal papillae.
(A) Relationship between the length and number of marginal papillae in gill pore #3 for L. ayresii from four locations (n = 60, from Tables 2 and 3). (B) Relationship between the length and number of marginal papillae in gill pore #3 for L. ayresii from the Strait of Georgia (n = 43, from Tables 2 and 3).
Photographs of the gill pore cups of E. tridentatus from (A) off the coast of Siberia, Russia and (B) the Merced River, California. The marginal papillae in (A) numbered 68 and in (B), 64. (C) Line drawing of the marginal papillae of E. tridentatus, from a specimen from the Columbia River, showing 72 marginal papillae and the large central process.
Contributor Notes
Associate Editor: D. Buth.