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Arquivos de Zoologia

The kidney is obviously morę complex in freshwater groups. In pleurocerids several compIex folds appeared, representing a large increase of renal surface. In thiarids, beyond folded chambers, the kidney is divided into 2 lobes; in Melanoides the anterior lobe of the kidney stays within the membranę between the kidney and the pallial cavity, while in Aylacostoma spp the anterior lobe runs anterior-right, attached to the rectum. Apparently the thiarid bilobed kidney is not equivalent to the bilobed kidney of othergastropods (e.g., tonnids, see Simone, 1995b), because the rectum does not cross between both lobes. The disposition and type of the renal inner folds, in both families, are of great value for species comparison, but of little value in higher systematics. Observing the details of the pleurocerid and thiarid kidneys, it is difFicult infer any close relation between them.

The kidneys of marinę forms are generally very simple and short, appearing as a undifferentiated solid tissue. Campanile, however, is an exception in having a very large, complex kidney.

55. Nephrostome: 0= slit-like, situated about in center of membranę; 1= slit-like, situated close to rectum (thiarids); 2= wide opened, protected by a flap of gonoduct (pleurocerids) (Cl= 100, RI= 100, not additive).

In most cerithioideans, like other caenogastropods, the nephrostome is a slit, surrounded by thin muscular fibers, and is located approximately in the center of the membranę that separates the kidney from the pallial cavity. This condition is considered plesiomorphic. However, in the two freshwater groups, this condition is modified. In the thiarids the nephrostome is located to the right, very close to the rectum and partially closed by it. The pleurocerids have also the nephrostome close to the rectum, but it is very wide, apparently without muscular fibers, and protected on the left and vcntrally by a flap inserted in the outer lamina of the pallial gonoduct. This flap may be the homologue of the cyrtophore organ or se-minal receptacle of Pleurocera acuta and Goniobasis livescens (see Dazo, 1965, fig. 9 and pl. 4). The kidney of the ingroup animals could an interesting structure for histological and ultrastructural comparative study, and it is possible that several other characters could appear, including the possibility that pleurocerids have an ureter.

Heart

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56.    Aortas attachment: 0= free from stornach; 1= j

in style sac and adjacent intestine (all i cerithioideans except Campanile symbolicum) (CI= 50, RI= 80).

The heart of the cerithioideans, although of normal monotocardian type, present a great value for the identity of the superfamily, in having the aortas attached directly to the style sac (only separated by pericardium membranę), and sometimes in adjacent intestinal loops. This condition was not found in any other examined gastropod, which have, in generał, a portion of gonad and digestive gland, or even kidney tissue, between stornach and pericardium. The cerithioidean condition may be due the great dcvelopment of stornach, but is not cxplained by this phenomenon I alone. The examined hydrobioids, which present also | a proportionally large stornach, there is somel separation (even smali) between style sac and I pericardium (see, e.g., Simone & Moracchioli, 1994,1 on Pothamolithus spp.). Among the cerithioideans, I the attachment of the aortas to the style sac is less I evident in those species with reduction of style sac, I such as Serpulorbis and Campanile.    I

57.    Site: 0= anterior-left from kidney; 1 = posteriori

to kidney (all cerithioideans) (Cl= 100, RI= 100). I The position of the pericardium posteriori to the kidney is a character shared with some other I caenogastropods such as littorinids.    I

Digestive system    I

Buccal mass    I

58.    Site: 0= posterior to snout; 1 = part within snoui I

(thiarids, Supplanaxis nucleus, pleurocerids, I cerithids, Finella dubia, A laba incertaM Baiillaria minima, Cerithidea costata) (CI=1 100, RI= 100).    I

This character has relation to the length ofl the orał tubę, which connects the mouth with the H buccal mass. The orał tubę is very short and wideł in abovc listed species.    I

59.    Jaw size: 0= normal; 1= very large (Campanile I

symbolicum)-, 2= smali, inserted in al membranę (Supplanaxis nucleus, Baiillaria I minima) (01= 66, RI-" 0, not additive). I