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Leiostracus Albers, 1850 was established to allocate land snails from Central America and Northern South America. Currently, approximately 19 species are considered valid. However, for most of them, the internal morphology is unknown. Leiostracus obliquus was described as a species of Bulimus from the state of Bahia based on shell characters. Until now, knowledge of this species has been scarce. The discovery of ethanol-preserved specimens from MZSP of this species allowed us to characterize, for the first time, the internal anatomy of this species and update its distribution. The shell of L. obliquus has seven to eight whorls and a wide pale-pink disrupted band all over the teleoconch. The rachidian tooth is small rectangular, symmetric, with round edges, and without differentiated cusps. After comparing the anatomy and radular characters between the shells of L. obliquus and L. carnavalescus, we found remarkable similarities in the morphology and color pattern.

Obeliscus sylvaticus (Spix & Wagner, 1827) Bulimus sylvaticus Spix & Wagner, 1827: 11, pl. 5, fig. 4. Obeliscus sylvaticus ��� Pilsbry 1906: 248, pl. 34, figs 54, 55. ��� Salgado & Coelho 2003: 155. ��� Simone 2006: 188, fig. 692. MUSEUM DEPOSITS. ��� Brazil ��� ZSM/MOL 110009 ��� 3; donor Brown, A. D.; ANSP 3065 ��� 2; 4.VI.1908; donor Anthony, J. G.; ANSP 59332 ��� 1; 4.VI.1908; donor Anthony, J. G.; ANSP 59333 ��� 4; Bahia, Bom Fim, Fazenda Ambroter; 22.XI.1907; Haseman J. D. leg.; CMNH 62.16564 ��� 2; CMNH 62.14869 ��� 1; FMNH 103188 ��� 1 shell; HIST.370 (RBINS) ��� 1 shell; HIST.346 (RBINS) ��� 1 shell; HIST.110 (RBINS) ��� 1 shell; MCZ 27322 ��� 1 shell; MCZ 27321 ��� 3; USNM 117495 ��� 1; USNM 20275 ��� 1 shell; ZMA. MOLL.32567 (NBCN). French Guiana ��� 1; Cayenne; FMNH 36245 ��� 1; Cayenne; FMNH 36173 ��� 1; Cayenne; soft parts pre- served in ethanol, dry shell; MB-A053789 (SANBI). TYPE LOCALITY. ��� Brazil: Piau��, in woods. OTHER LOCALITIES. ��� French Guiana: Cayenne (FMNH 36173; MB-A 053789). ILLUSTRATION. ��� Spix & Wagner (1827: pl. 5, fig. 4); Pilsbry (1906: pl. 34; figs 54, 55). REFERENCES. ��� Pilsbry (1906); Salgado & Coelho (2003)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 169, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["SPIX J. B. & WAGNER J. A. 1827. - Testacea fluviatilia quae in itinere per Braziliam. 36 p. + 29 pls.","PILSBRY H. A. 1906. - Manual of Conchology. vol. 18. Achatinidae, Stenogyrinae and Coeliaxinae. Philadelphia (USA). Academy Natural Sciences xii + 357 p + 51 p. https: // www. biodiversitylibrary. org / item / 76495 page / 310 / mode / 1 up","SALGADO N. C. & COELHO A. C. S. 2003. - Moluscos terrestres do Brasil (gastropodes operculados ou nao, exclusive Veronicellidae, Milacidae e Limacidae. Revista de Biologia Tropical 51 (Suppl. 3): 149 - 189.","SIMONE L. R. L. 2006. - Land and freshwater mollusks of Brazil. EGB, Fapesp. Sao Paulo, 390 p."]}

Obeliscus planospirus (Pfeiffer, 1852) Bulimus planospirus Pfeiffer, 1852: 108, pl. 34, fig. 3. Obeliscus planospirus ��� Pilsbry 1906: 247, pl. 34, fig. 44. ��� Salgado & Coelho 2003: 155. ��� Simone 2006: 187. MUSEUM DEPOSITS. ��� Brazil ��� Esp��rito Santo, Rio Doce; ANSP A9714 ��� 2 shells; Esp��rito Santo, Rio Doce; 24.V.1910; ANSP 100535 ��� 1 shell; CM: Mollusks 62.13330. TYPE LOCALITY. ��� Unknown. OTHER LOCALITIES. ��� Brazil: head waters of the Mucury river in eastern Minas Gerais (Pilsbry, 1906). Brazil: Esp��rito Santo, Rio Doce (ANSP 100535). ILLUSTRATION. ��� Pfeiffer (1852: pl. 34, fig. 3); Pilsbry (1906 pl. 34; fig. 44). REFERENCES. ��� Pfeiffer (1852); Pilsbry (1906); Salgado & Coelho (2003)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on pages 168-169, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["PFEIFFER L. 1852. - Die Gattungen Bulimus, Partula, Achatinella, Achatina und Azeca, in Abbildungen nach der natur mit beschreibungen. Systematisches Conchylien-Cabinet 3: 1 - 395. https: // doi. org / 10.5962 / bhl. title. 119525","PILSBRY H. A. 1906. - Manual of Conchology. vol. 18. Achatinidae, Stenogyrinae and Coeliaxinae. Philadelphia (USA). Academy Natural Sciences xii + 357 p + 51 p. https: // www. biodiversitylibrary. org / item / 76495 page / 310 / mode / 1 up","SALGADO N. C. & COELHO A. C. S. 2003. - Moluscos terrestres do Brasil (gastropodes operculados ou nao, exclusive Veronicellidae, Milacidae e Limacidae. Revista de Biologia Tropical 51 (Suppl. 3): 149 - 189.","SIMONE L. R. L. 2006. - Land and freshwater mollusks of Brazil. EGB, Fapesp. Sao Paulo, 390 p."]}

Obeliscus latispira Pilsbry, 1944 Obeliscus latispira Pilsbry, 1944: 127, pl. 11, fig. 18. ��� Clench & Turner 1962: 84. MUSEUM DEPOSITS. ��� Paratypes. Peru ��� 1 shell; Junin Dept., Huacapistana; 1800 m; 1942; Weyrauch W. leg.; ANSP 451843 ��� Junin Dept., Huacapistana, river Tarma; FLMNH 110894 ��� same collection data as for preceding; FLMNH 203092. TYPE LOCALITY. ��� Peru: Huacapistana. OTHER LOCALITIES. ��� Peru: Dept. Junin, River Tarma, Huacapistana (FLMNH 110894; 203092). ILLUSTRATION. ��� Pilsbry (1944: pl. 11, fig. 18). REFERENCES. ��� Clench & Turner (1962)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 167, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["PILSBRY H. A. 1944. - Peruvian land Mollusca II. Nautilus 57 (4): 118 - 127.","CLENCH W. J. & TURNER R. D. 1962. - New names introduced by H. A. Pilsbry in the Mollusca and Crustacea. Academy of Natural Science of Philadelphia, Special Publication 4: 1 - 218. https: // doi. org / 10.5962 / bhl. title. 6489"]}

Obeliscus virescens (Da Costa, 1898) Stenogyra (Spiraxis) virescens Da Costa, 1898: 82, pl. 6, fig. 10. Obeliscus virescens ��� Pilsbry 1906: 257, pl. 36, fig. 81. TYPE LOCALITY. ��� Colombia: Valley of the Cauca River. OTHER LOCALITIES. ��� Species known only from the type locality. ILLUSTRATION. ��� Da Costa (1898: pl. 6, fig. 10); Pilsbry (1906: pl. 36, fig. 81). REFERENCES. ��� Pilsbry (1906)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 169, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["DA COSTA S. I. 1898. - Remarks on some species of Bulimulus, sect. Drymaeus, and descriptions of new species of land-shells from Bolivia, Ecuador and the U. S. of Colombia. Proceedings of the malacological Society of London 3: 80 - 84.","PILSBRY H. A. 1906. - Manual of Conchology. vol. 18. Achatinidae, Stenogyrinae and Coeliaxinae. Philadelphia (USA). Academy Natural Sciences xii + 357 p + 51 p. https: // www. biodiversitylibrary. org / item / 76495 page / 310 / mode / 1 up"]}

Obeliscus boitata Simone & Salvador, 2016 Obeliscus boitata Simone & Salvador, 2016: 25, 29 (figs 77-79). MUSEUM DEPOSITS. ��� Holotype. Brazil ��� 1; Minas Gerais, Nanuque; 17��51���S, 40��23���W; 120 m a.s.l.; very close to the borders with the states of Bahia and Esp��rito Santo, very small fragment of Atlantic Forest; MZSP 106169. Paratypes. Brazil ��� 39 shells; same collection data as for holotype; MZSP 106170. TYPE LOCALITY. ��� Brazil: Minas Gerais, Nanuque. OTHER LOCALITIES. ��� Species known only from the type locality. REFERENCES. ��� The only bibliographic reference is the original description of the species., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on pages 166-167, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["SIMONE L. R. L. & SALVADOR R. B. 2016. - Taxonomical study on a sample of land snails from Nanuque (Minas Gerais, Brazil), with descriptions of three new species. Stuttgarter Beitrage zur Naturkunde A, Neue Serie 9: 9 - 30. https: // doi. org / 10.18476 / sbna. v 9. a 2"]}

Obeliscus blandi (Pfeiffer, 1852) Bulimus blandi Pfeiffer, 1852: 85. Obeliscus blandi ��� Pilsbry 1906: 257, pl. 36, figs. 83, 84. TYPE LOCALITY. ��� Colombia: Baranquilla, in the Andes. OTHER LOCALITIES. ��� Species known only from the type locality. ILLUSTRATION. ��� Pilsbry (1906: pl. 36, figs 83, 84). REFERENCES. ��� Pilsbry (1906)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 166, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["PFEIFFER L. 1852. - Die Gattungen Bulimus, Partula, Achatinella, Achatina und Azeca, in Abbildungen nach der natur mit beschreibungen. Systematisches Conchylien-Cabinet 3: 1 - 395. https: // doi. org / 10.5962 / bhl. title. 119525","PILSBRY H. A. 1906. - Manual of Conchology. vol. 18. Achatinidae, Stenogyrinae and Coeliaxinae. Philadelphia (USA). Academy Natural Sciences xii + 357 p + 51 p. https: // www. biodiversitylibrary. org / item / 76495 page / 310 / mode / 1 up"]}

Obeliscus moderatus Pilsbry, 1933 Obeliscus moderatus Pilsbry, 1933: 152. ��� Clench & Turner 1962: 99. MUSEUM DEPOSITS. ��� Dominican Republic ��� Barahora Province, Sierra de Bahoruco, 4 km North Polo; 12.IX.1983; Thompson F. leg.; FLMNH 045777 ��� Barahora Province, Sierra de Baho- ruco, 4 km North Polo; 19.III.1974; Thompson F. leg.; FLMNH 045778 ��� Barahora Province, Sierra de Bahoruco, 5 km North Polo; 19.III.1974; Thompson F. leg.; FLMNH 210623 ��� Barahora Prov- ince, 7 km NNE of Polo; 19.III.1974; Thompson F. leg.; FLMNH 210624 ��� Estrelleta Province; 9 km North East of La Descubierta; 02.VI.1974; Thompson F. leg.; FLMNH 210625 ��� Barahona Prov- ince; 2 km NNE of Polo; 19.III.1974; Thompson F. leg.; FLMNH 210626 ��� Estrelleta Province, 6 km NW of Postrer Rio; 02.VII.1974; Thompson F. leg.; FLMNH 210627 ��� Independencia Province, 4 km North East of El Aguate; 30.VI.1974; Thompson F. leg.; FLMNH 210628 ��� Barahona Province, 14 km South of Cabral, 7 km NNE of Polo; 18.VI.1974; Thompson F. leg.; FLMNH 210629 ��� Estrelleta Province, 3 km North East of El Aguacate; 30.VI.1974; Thompson F. leg.; FLMNH 210630. TYPE LOCALITY. ��� Dominican Republic: Santo Domingo - Del Monte plantation, 5-6 min W of Barahona. OTHER LOCALITIES. ��� Dominican Republic: Barahona Province, Sierra de Bahoruco, 4 km North of Polo (FLMNH 045777; 045778); Barahona Province, 5 km North East of Polo (FLMNH 210623); Barahona Province, 7 km North East of Polo (FLMNH 210624); Estrelleta Province, 9 km North East of La Descubierta (FLMNH 210625); Barahona Province, 9 km North East of Polo (FLMNH 210626); Estrelleta Province, 6 km NW of Postrer Rio (FLMNH 210627); Independencia Province, 4 km North East of El Aguacate (FLMNH 210628); Barahona Province, 14 km of Cabral, 7 km North East of Polo (FLMNH 210629); Estrelleta Province, 3 km North East of El Aguacate (FLMNH 210630). REFERENCES. ��� Clench & Turner (1962)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 167, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["PILSBRY H. A. 1933. - Santo Domingan land mollusks collected by Daniel C. Pease, 1932, and by A. A. Olsson, 1916. Proceedings of the Academy of Natural Sciences of Philadelphia 85: 121 - 162. https: // www. jstor. org / stable / i 385995","CLENCH W. J. & TURNER R. D. 1962. - New names introduced by H. A. Pilsbry in the Mollusca and Crustacea. Academy of Natural Science of Philadelphia, Special Publication 4: 1 - 218. https: // doi. org / 10.5962 / bhl. title. 6489"]}

Obeliscus abbotti Vanatta, 1918 Obeliscus abbotti Vanatta, 1918: 238, fig. 3. MUSEUM DEPOSITS. ��� Lectotype. Haiti ��� 1 shell; near The Generals Cave, 1 mile west of Jeremie; 1918; Abbott W. L. leg.; ANSP 118244. Puerto Rico ��� 2 shells; USNM 252558. TYPE LOCALITY. ��� Haiti: General���s Cave, west of Jeremie. Found in debris. OTHER LOCALITIES. ��� Puerto Rico. ILLUSTRATION. ��� Vanatta (1918: fig. 3). REFERENCES. ��� The only bibliographic reference is the original description of the species., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 166, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["VANATTA E. G. 1918. - Two new shells from Hayti. Proceedings of the Academy of Natural Sciences of Philadelphia 70: 237 - 238. http: // www. biodiversitylibrary. org / page / 26374556 page / 250 / mode / 1 up"]}

Obeliscus pattalus Pilsbry, 1906 Obeliscus pattalus Pilsbry, 1906: 249, pl. 36, fig. 70. ��� Clench & Turner 1962: 115. ��� Salgado & Coelho 2003: 155. ��� Simone 2006: 188 (fig. 690). MUSEUM DEPOSITS. ��� Lectotype. Brazil ��� 1; 4.VI.1908; ANSP 59335. Paralectotype. Brazil ��� 1; 21.VIII.2015; ANSP 465076. TYPE LOCALITY. ��� Brazil, no specific locality. OTHER LOCALITIES. ��� Species known only from the type locality. ILLUSTRATION. ��� Pilsbry (1906: pl. 36, fig. 70). REFERENCES. ��� Clench & Turner (1962); Salgado & Coelho (2003)., Published as part of D'��vila, Sthefane, Simone, Luiz Ricardo L., Oliveira, Luiz Fernando Cappa de, Charles, Laurent & Maestrati, Philippe, 2020, Rediscovery of Obeliscus agassizi Pilsbry, 1906 (Gastropoda, Subulinidae, Obeliscinae), annotated checklist of species of Obeliscus Beck, 1837 and first description of the anatomy for the genus, pp. 159-172 in Zoosystema 42 (12) on page 168, DOI: 10.5252/zoosystema20v42a12, http://zenodo.org/record/3762441, {"references":["PILSBRY H. A. 1906. - Manual of Conchology. vol. 18. Achatinidae, Stenogyrinae and Coeliaxinae. Philadelphia (USA). Academy Natural Sciences xii + 357 p + 51 p. https: // www. biodiversitylibrary. org / item / 76495 page / 310 / mode / 1 up","CLENCH W. J. & TURNER R. D. 1962. - New names introduced by H. A. Pilsbry in the Mollusca and Crustacea. Academy of Natural Science of Philadelphia, Special Publication 4: 1 - 218. https: // doi. org / 10.5962 / bhl. title. 6489","SALGADO N. C. & COELHO A. C. S. 2003. - Moluscos terrestres do Brasil (gastropodes operculados ou nao, exclusive Veronicellidae, Milacidae e Limacidae. Revista de Biologia Tropical 51 (Suppl. 3): 149 - 189.","SIMONE L. R. L. 2006. - Land and freshwater mollusks of Brazil. EGB, Fapesp. Sao Paulo, 390 p."]}

Snails of the family Lymnaeidae act as intermediate hosts in the biological cycle of Fasciola hepatica, which is a biological agent of fasciolosis, a parasitic disease of medical importance for humans and animals. The present work aimed to update and map the spatial distribution of the intermediate host snails of F. hepatica in Brazil. Data on the distribution of lymnaeids species were compiled from the Collection of Medical Malacology (Fiocruz-CMM, CPqRR), Collection of Malacology (MZUSP), “SpeciesLink” (CRIA) network and through systematic surveys in the literature. Our maps of the distribution of lymnaeids show that Pseudosuccinea columella is the most common species and it is widespread in the South and Southeast with few records in the Midwest, North and Northeast regions. The distribution of the Galba viatrix, G. cubensis and G. truncatula showed a few records in the South and Southeast regions, they were not reported for the Midwest, North and Northeast. In addition, in the South region there are a few records for G. viatrix and one occurrence of Lymnaea rupestris. Our findings resulted in the first map of the spatial distribution of Lymnaeidae species in Brazil which might be useful to better understand the fasciolosis distribution and delineate priority areas for control interventions. Moluscos da família Lymnaeidae são hospedeiros intermediários no ciclo biológico de Fasciola hepatica, agente etiológico da fasciolose, doença parasitária de importância médica para humanos e animais. O presente trabalho teve como objetivo datar e mapear a distribuição espacial dos hospedeiros intermediários de F. hepatica no Brasil. Os dados de distribuição das espécies de limneídeos foram obtidos das Coleções de Malacologia Medica (Fiocruz-CMM, CPqRR) e de Malacologia do Museu de Zoologia da Universidade de São Paulo (MZUSP), rede “SpeciesLink” (CRIA) e através de pesquisas sistemáticas na literatura. Os mapas de distribuição dos limneideos mostram que Pseudosuccinea columella é a espécie mais comum e distribuída nas regiões Sul e Sudeste com poucos registros nas regiões Centro-Oeste, Norte e Nordeste. Além disso, na região Sul os registros para G. viatrix são escassos e existe apenas um único relato de ocorrência para L. rupestris. Os dados obtidos resultaram no primeiro mapa de distribuição espacial das espécies de Lymnaeidae no Brasil, informação básica e relevante para estruturação de políticas de controle da fasciolose humana e animal.

O objetivo deste trabalho foi verificar a existência de comportamento agregativo na espécie Subulina octona (Brugüière, 1789) e obter evidências da mediação química desse comportamento. Foram utilizados 150 animais adultos, distribuídos em 15 caixas com terra vegetal (10 animais por caixa). Em cada caixa foram colocados quatro discos plásticos identificados, em posição eqüidistante, os quais serviram como abrigos para os animais. No experimento I, foram colocados 10 animais no centro de cada caixa. Após 24, 48, 96, 120, 144 e 168 horas foram observados o número de agregados formados, a posição dos agregados (sob qual abrigo), o número de indivíduos por agregado e o número de indivíduos isolados. No experimento II, todos os indivíduos foram transferidos para outras caixas contendo terra vegetal, três novos discos e o disco que continha o maior agregado após as 168 horas do experimento I (denominado disco condicionado). Foi verificado, após 24 e 48 horas, o número de indivíduos sob o disco condicionado. Em todas as caixas utilizadas e em todos os intervalos de tempo observados no experimento I, houve a formação de agregados. Houve um aumento significativo do número de indivíduos por agregado e uma diminuição do número de indivíduos isolados com o passar do tempo (ANOVA, p < 0,005). No experimento II, após 24 horas, seis das 15 caixas apresentavam agregados sob o disco condicionado, e após 48 horas, sete caixas, sendo esses os agregados com maior número de indivíduos, o que sugere o condicionamento dos discos usados por algum fator, possivelmente um composto químico. The current study aimed to verify the existence of aggregative behavior in Subulina octona (Brugüière, 1789) and to obtain behavioral evidence of chemical mediation of this behavior. We used 150 adult animals allocated in 15 boxes with humus (10 animals per box). In each box we placed four identified plastic disks in an equidistant position. These disks worked as shelters for the animals. In experiment I, 10 animals were put in the middle of each box. After 24, 48, 96, 120, 144, and 168 hours we observed the number of formed aggregations, as well as the position of the aggregates (in each shelter), the number of individual per aggregation and the number of isolated individuals. In order to test the hypothesis of conditioning of disks by chemicals compounds, the experiment II was carried out. All the individuals were transferred to other boxes with humus, three new disks and the disk containing the larger aggregate after the 168 hours of the experiment I (denominated conditioned disk). We verified, after 24 and 48 hours, the number of individuals below the conditioned disk. In experiment I, aggregations were observed in every used box and in every time intervals. In all boxes, there was a significant increase in the number of individuals per aggregation and a reduction in the number of isolated individuals until the end of the experiment (ANOVA, p < 0.005). In experiment II, after 24 hours, six from 15 boxes presented aggregations under the conditioned disk, and after 48 hours, seven boxes presented aggregations under conditioned disk. These were the aggregations with a larger quantity of individuals, which suggests the conditioning of the used disks by some factor, possibly a chemical compound.

O objetivo deste estudo foi verificar a influência da umidade do substrato sobre o crescimento e a reprodução de Subulina octona (Brugüière, 1789), criada em areia, argila e terra vegetal. Sobre o grupo experimental, constituído por três grupos tratados (substrato umedecido com 10ml de água a intervalos de cinco dias) e três grupos controle (substrato umedecido com 10ml de água a intervalos de um dia), foram realizadas observações a cerca do crescimento, expresso pelo comprimento da concha; do número de ovos produzidos e do comprimento da concha no primeiro evento reprodutivo. O grupo tratamento e o grupo controle constituíram-se de 210 indivíduos recém-eclodidos, distribuídos aleatoriamente em caixas diferenciais em função do substrato utilizado: caixa 1 e controle 1, com areia; caixa 2 e controle 2, com argila; caixa 3 e controle 3, com terra vegetal. Cada caixa continha 35 indivíduos. Os indivíduos do grupo controle (substrato umedecido a intervalos de um dia) apresentaram um ritmo de crescimento mais rápido. A umidade do substrato foi um fator de maior influência sobre a reprodução dos indivíduos criados em caixas com areia e argila. Houve diferença significativa entre as médias do comprimento da concha e do número de ovos produzidos, no primeiro evento reprodutivo dos indivíduos da caixa 1 (areia) e do grupo controle 1. Os indivíduos da caixa 2 (argila) apresentaram menor comprimento de concha no primeiro evento reprodutivo do que os indivíduos do grupo controle 2. Os gastrópodes terrestres perdem água pelo tegumento e, do mesmo modo, se reidratam pelo tegumento, através da chamada reidratação por contato. Neste contexto, a umidade do substrato influencia a manutenção da homeostase por estes organismos e conseqüentemente seu crescimento e reprodução. The aim of this study was to observe the influence of substrate moisture on growth, number of eggs produced and shell length of Subulina octona (Brugüière, 1789)in its first reproductive event. For this, two groups of moluscs were observed under laboratorial conditions. The trated group, manteined in substrate moinstened at five-days intervals and the control group, manteined in substrate moistened at one-day intervals, were both constituted by 210 newly hatched individuals distributed in boxes with different substrates. The box one and control one contained sand, the box two and control two, clay and the box three and control three, humus. Each box contained 35 snails. The individuals of the control group exhibited a faster growth rhythm than those of the trated group. The substrate moisture was a major influence over the individuals reared in sand and clay. It's probable due to the fact that these substrates loose water by evaporation more quickly than humus. The land snails loose water by their skin and by the same means they rehidrate by contact. So, the humidity of the substrate on wich the snails live influence their homeostasis. Substrates that retain water for a smaler time period offer fewer oportunities to rehidration. The waterloos by the skin, without later rehidration can causes changes in hemolinph osmolarity, with implications over the feedind control, hearth beating and locomotion. By this way, snails submited to dessication exhibes reduced activity and consequently smaler growth and produtivity.