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190

Arquivos de Zoologia

Ctenidial vein

34.    Width: 0= normal (discretely broader than

osphradium); 1= very broad (Doryssa spp.) (CI= 100, RI= 100).

The ctenidial vein may be a contractile organ, even so, the degree of dilatation appears to be a distinctive feature of examined Doryssa species. For instance, in D. ipupiara, the posterior region of this vessel is broader than the gili.

35.    Posterior region firce łrom gili: 0= long; 1= short

(thiarids, Supplanaxis nucleus, pleurocerids, cerithids, Finella dubia, Alaba incerta, Ceriłhidea costata) (CI= 50, RI= 87).

Most cerithioideans have the posterior end of the gili close to the pericardium and the ctenidial vein penetrates the pericardium immediately posterior to the gili. Somc other cerithioideans, such as Modulus, Turritella, Batillaria, Campanile and Serpulorbis, have a long section of the ctenidial vein between the gili and the pericardium, comparable to vetigastropods (e.g., Haliołis, Calliostoma, person, obs.) outgroups, is regarded as plesiomorphic.

36.    Attachment in osphradium: 0= absent; I = present

(Campanile symbolicum) (CI= 100, RI= 100). lt is possible that the ctenidial vein not only is attached, but also collects the blood coming ffom the osphradium leaflets as well usually from the gili leaflets. This matter merits further research.

Head and floor of pallial cavity

37.    Head size: 0= normal (about 1/2 offoot width);

1= narrow (about 1/4 of foot width) (Turritella hookeri)-, 2= broad (about same width as foot) (Doryssa atra, D. macapa, Cerithium atratum, Campanile symbolicum) (CI= 50, RI= 33, not additive).

38.    Food groove in doisal region ofhead-foot complex:

0= absent; 1= present (Turritella hookeri, Serpulorbis decussatus) (CI= 50, RI= 50).

39.    Food groove in right and ventral region of head:

0= absent; 1= present (Turritella hookeri, Serpulorbis decussatus) (Cl= 100, RI- 100).

The character food groove is separated in the present analysis in two regions: that of dorsal region ofhead-foot (#38), which are also found in other filter-feeding gastropods, such as Viviparidae, Crepidulidae and Struthiolariidae (person, obs.) (probably not homologous); and that part of the groove surrounding the right and ventral region of the head (#39), this part is absent in other groups.

Gili

40.    Base of filaments: 0= broad; 1= narrow

(pleurocerids, Turritella hookeri, M. modulus, Serpulorbis decussatus) (CI= 25, RI- 57).

41.    Tip position in filaments: 0= central; 1= right

(Aylacostoma exoplicata; Supplanaxis nucleus, Turritella hookeri) (CI= 33, RI= 0).

42.    Tip form: 0- sharp; 1 = rounded (pleurocerids);

2= fiat (Finella dubia) (CI= 100, RI= 100, not additive).

43.    Filament height and thickness: 0^ short and

thin; 1= tali and thin (Turritella hookeri, Serpulorbis decussatus); 2= tali and thick (M. modulus) (CI= 66, Rl= 50, not additive).

44.    Area between gili and rectum: 0= broad; 1=

narrow (Bittium varium, Finella dubia, Alaba incerta, Batillaria minima, Cerithidea costata, Serpulorbis decussatus) (CI= 20, RI= 33).

45.    Visible vessels between gili and rectum: 0=

absent; 1 = present (Aylacostoma exoplicata, A. tenuilabris, Doryssa atra, D. macapa, Campanile symbolicum) (Cl= 25, RI= 25). The gili of caenogastropods is greatly modified in relation to those of most examined archaeogastropod outgroups, making comparison difficult. Comparison with the Neritimorpha (Neritina, Nerita, person, obs.), and Addisonia enodis Simone, I996a (Cocculiniformia) were performed. The distance between the gili and rectum appears to increase in some cerithioidean groups, especially those groups with some environmental adversity, such as estuarine and fresh-water species. In some species, inclusive, transverse vessels are clearly present in this area. The transverse vessels the in roof of the pallial