File:American malacological bulletin (1987) (17968648168).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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MORTON: MANTLE CAVITY ORGANS OF PERNA 161 THE MANTLE Mantle fusion only occurs between the inhalant and exhalant apertures. The latter is conical (Figs. 2, 3: ES), the former (IA) long and without the sensory papillae typical of other mytilids, e.g. Mytilus (Soot-Ryen, 1955) and Xenostrobus (Wilson, 1979). The mantle is variably patterned dark brown, but usually with a darker stripe decorating each side of the outer surface of the exhalant siphon and the inner surfaces of the inhalant aperture. The mantle contains much of the gonad and the ventral mantle margin, seen in transverse sec- tion in Figure 4, comprises the usual three folds (Yonge, 1957, 1982): inner (IMF), middle (MMF) and outer (OMF). The outer and middle folds are of the typical plan and fulfill typical func- tions (Yonge, 1983). Of interest, however, is the inner fold which is greatly enlarged and divided into two components; inner (IMF(I)) and outer (IMF(O)). The inner component has an extensive haemocoel and probably can be inflated with blood. Between it and the general mantle surface is a deep, densely ciliated, rejectory tract (RT). The outer component of this fold is secretory and possesses a large sub-epithelial gland (MG), the basiphilic cells of which are some 20 ^m in diameter. It is believed that these glands, along with other glands in the foot (not illustrated), produce the copius amounts of mucus that are characteristic of Perna viridis.
Text Appearing After Image:
Fig. 4. Perna viridis. A transverse section through the right mantle margin at the pedal gape and showing the extent of the mucous gland (MG) in the outer component of the inner mantle fold (IMF(O)), (IMF(1), IMF(2), inner and outer components of the inner mantle fold; MG, mucous gland; MMF, middle mantle fold; OMF, outer mantle fold; P, periostracum; PN, pallial nerve; PRM, pallial retractor muscle; RT, rejectory tract). THE CTENIDIA Unlike the majority of bivalves where the larger pro- portion of the mantle cavity is located lateral to the visceral mass, that of the Mytilacea, including Perna viridis, is largely beneath the body in the expanded ventral component of the shell. The ctenidia are generally typical of the Mytilacea and are flat, homorhabdic, non-plicate, filibranch and comprise approximately equal inner and outer demibranchs (Figs. 2, 3). The gill ciliation is of type B(1) (Atkins, 1937). The ctenidia are removed from the anteriormost apex of the shell and the anterior filaments of the ctenidia are unusually arranged. In the boring mytilid Adula falcata (Gould), Fankboner (1971) showed that the outer demibranchs are typically some 10 filaments shorter at their anterior ends than the inner demibranchs. Material arriving at the ctenidial-labial palp ter- minus on the outer demibranch, therefore, must pass onto the inner demibranch before proceeding to the palps and mouth. Similar situations exist in other mytilids, e.g. Lim- noperna, Musculista, Modiolus and Arcuatula (Morton, 1973, 1974, 1977a, b, 1980). This is not the case in Perna viridis. Anteriorly (Figs. 5, 6), the demibranchs (ID; OD) are of the same length, but particles arriving at the terminus in the ven- tral margin food groove of the outer demibranchs stop about 14 filaments from the end. Moreover, the cilia in the ventral marginal food groove of the anteriormost 14 filaments, beat posteriorly so that the two streams meet and from this point (Figs. 5, 6: star) transported particles can fall onto the palps (RILP, ROLP) for resorting.

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