File:American malacological bulletin (1987) (17970363919).jpg

Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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224 AMER. MALAC. BULL. 5(2) (1987)
Text Appearing After Image:
Figs. 17 and 18. Mantle/foot relationships of living Pleurobranchus peronii Cuvier. Both photographs depict the same individual (note scar on mantle behind left rhinophore) and were taken less than five minutes apart. Figure 17 shows the animal at rest and figure 18 shows it crawling actively. Specimen (48 mm extended crawling length) from an intertidal pool, Hastings Point, northern New South Wales, Australia, August 1984. Photographs by R. C. Willan. afferent vessel runs on the mesial edge closest to the body wall (Moquin-Tandon, 1870; Thompson and Slinn, 1959; Mor- ton, 1972). Blood flows within the pinnules in upwards- directed vertical vessels; as many vessels being present as there are pinnules. The rachal tubercles, besides producing mucus, act as "guides" for fine particles, each leading material off the rachis onto the pinna that arises next to it. The gill is attached to the lateral body wall by two con- tiguous suspensory membranes. In Tylodina and Anidolyta, only the anterior half of the gill is attached. Throughout the Pleurobranchidae, the gill is attached for more than half its length. In Umbraculum, the gill is attached for almost its en- tire length. The gill of Umbraculum extends from a mid- anterior point on the body in a continuous crescent, around the right side, well back into the right posterior quadrant. Such a situation of extreme branchial enlargement is most unusual and it appears to be another manifestation of the bodily reorganization undergone by Umbraculum; one probably necessitated by presence of the flattened, inflexible shell and tough, enlarged foot. The free posterior part of the gill is muscular and mobile in all pleurobranchs (Thompson and Slinn, 1959). The gill rachis of the Notaspidea is primitively smooth but it bears a series of tubercles in some genera (for example Pleurobranchus, see Fig. 19). A tubercle is present on the outer face of the rachis at the point a pinna arises laterally. That tubercles occur on the gill rachis in the otherwise not closely related genera Pleurobranchus (where their presence is correlated with the development of tubercles on the mantle) and Euselenops (where the mantle is smooth) demonstrates a case of convergent apomorphy. In Pleurobranchella, the gill rachis can apparently be smooth or weakly tuberculate de- pending on the species; however, in the species that do possess them, the tubercles are unlike those of Euselenops or Pleurobranchus, being merely a series of swellings that are separated by narrow, vertical, somewhat undulating grooves (pers. obs.).

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