Tag Archives: biology

Defecation behaviour

A short research note was recently published by Carvalho & Oliveira. It is about the defecation behaviour of a terrestrial snail from Brazil, Cochlorina aurisleporis (Bruguière, 1792).

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After noting the overall scarcity of data in literature on this behaviour in many animals, the authors describe the process in this arboreal snail, which uses it muscles to form a more or less spherical pellet and finally drops the pellet onto the substrate beneath. They suggest as hypothesis to explain this behaviour that it may be a strategy to prevent detection by chemically oriented predators. Although this hypothesis is interesting, it would need further testing in the field. For a start, the predators of this species are unknown as the biology of Neotropical land snails is hardly documented in literature. The authors also made a statement its distribution, viz. “a purported (and unexpected) disjunct distribution”, being known from Madagascar and Brazil. It is simply based on an erroneous original locality in Bruguière (in the 18th and 19th century species were often described based on material collected by others and many times with vague, imprecise or even erroneous localities). Cochlorina aurileporis is purely a Brazilian species; it is unfortunate that the reviewers have overlooked this.

Reference:
Carvalho de Lima, T. & Oliveira, C.D. de Castro, 2020. Unusual shaping: The defacation bahavior in Cochlorina aurisleporis (Bruguière, 1792) (Gastropoda: Bulimulidae). – The Nautilus 134(1): 57-59.

Demography Tikoconus

Due to oversight I missed the recent paper by Barrientos on the biology one of the new euconulid species; time to report it now.

Introduction: Ecology and natural history of neotropical land snails is almost unknown. Objetive: In this paper, I analyse the population dynamics of Tikoconus (Tikoconus) costaricanus Barrientos, an understory endemic euconulid.
Methods: I compared T. costaricanus’ demography patterns in tropical montane forests in central Costa Rica in three habitats with different restoration techniques: a mature forest, a secondary forest and a Cuppressus lusitanica plantation. I collected data in three month periods during a year. I analysed population size in relation with habitat, sampling date, leaf litter humidity, depth and quantity; and specimen size in relation with habitat and sampling date. I also kept some specimens in terraria and described part of their natural history.
Results: The species is more abundant in mature forest (Ø = 0.174 ind/m2). The number of specimens in each habitat was constant throughout the year (Kruskall-Wallis = 2.0118, p = 0.57, NS) and hatching occurs in the middle and last months of the rainy season (Kruskall-Wallis = 17.3061, P = 0.00061, **). Number of specimens is related with leaf litter humidity (Spearman correlation, r = 0.3524, n = 232, P < 0.001, **), quantity (Spearman correlation, r = 0.3922, n = 232, P < 0.001, **) and depth (Spearman correlation, r = 0.2543, n = 232, P < 0.001, **). This relationship is explained by the high and stable humid environment provided by leaf litter. Some specimens migrate from foliage to leaf litter during the drier months. Eggs (Ø = 1mm) are laid on moss or soil and the young spend the first 2 or 3 weeks of their life on moss. Egg masses are small (Ø = 4 eggs), and shells look bubbly. Egg development time (20 days) was longer than in other tropical species. Adult pigmentation appears around two months after hatch. In the only case observed, egg laying began 5 months after hatching and the specimen lived 9 months.
Conclusions: Restorations techniques should consider leaf litter features in order to protect endemic neotropical humid dependent diversity
“.

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This is an excellent ecological study of one of the new species recently described by her. And although the resulting data are not completely unexpected given the (very scarce) literature data, this study may have wider application than just the Costa Rican case. Albeit these studies are difficult to execute (especially if species are small and not occurring in abundant numbers), I hope that more Neotropical malacologists with endeavour them during field work.

Reference:
Barrientos, Z., 2019. Demography of the land snail Tikoconus (Tikoconus) costaricanus (Stylommatophora: Euconulidae) in tropical low montane and premontane forests, Costa Rica. – Revista de Biología Tropical, 67(6): 1449-1460.

Avoiding canopy gaps

Only now a paper turned up which was already published in 2014. Bloch & Stock reported on a Puerto Rican species from the Solaropsidae related to ecological research. Unfortunately the paper is text-only…

The abstract is “Because canopy gaps are characterized by elevated temperature and decreased humidity relative to closed-canopy forest, terrestrial gastropods may be exposed to greater desiccation stress in gaps than in undisturbed forest. We placed individuals of Caracolus caracolla at the edges of canopy gaps in montane forest in Puerto Rico and observed their movements. Individuals preferentially moved out of gaps except in one gap on the first night of the study, and the proportion of individuals recaptured inside gaps decreased over time. Individuals moved, on average, farther into forest than into gaps. Juveniles and adults responded similarly. These results suggest that C. caracolla actively avoids canopy gaps, and that its activity and ability to disperse are restricted in a post-disturbance environment“.

Reference:
Bloch, C.P. & Stock, M., 2014. Avoidance of Canopy Gaps by a Common Land Snail, Caracolus caracolla (L.), in Montane Forest in Puerto Rico. – Caribbean Naturalist, 8: 1-13.

Life history of subulinids

Just published: a paper on the life history of some subulinid species by D’ávila et al. The abstract reads: “In the present study, we aimed to characterize the life history of the land snail Subulina octona integrating information on life- history traits and morphology. We also compared the histology of the free-oviduct and spermoviduct of ovoviviparous and egg-retaining species of subulinids. We considered as ovoviviparous the species in which the complete embryonic development as well as egg hatching occurs inside the parent’s body and, at the end of this process, the parent releases juveniles instead of eggs. We considered as egg-retaining the species in which a great part of the embryonic development takes place inside the parent’s body and the eggs laid contain well-developed embryos. The results showed that the free-oviduct of both ovoviviparous and egg-retaining species shows a histological arrangement that confers greater strength to its walls and is probably related to egg retention. The wall of the spermoviduct is formed by pseudostratified columnar epithelium, with cell apical processes (probably cilia), and by underlying secretory cells. In gravid egg-retaining snails, the eggshells appear in close contact with the secretory cells of the spermoviduct. This fact suggests that these cells play a role in eggshell formation. The present study is the first account for histological features of S. octona, Allopeas gracile and Allopeas micra. The life history of S. octona is a combination of long life-span, early sexual maturity, indeterminate growth and egg reten- tion. Egg retention limits the number of young that can be produced in one reproductive event. However, the reproductive strategy adopted by S. octona, associating egg retention and K-strategism, compensates this cost of retaining eggs, because the reproductive success may be enhanced as a result of the higher survival of juveniles and the possibility of performing sev- eral reproductive events during the year”.

Since there are too many papers on the life history of land snails, this a welcome contribution. Especially since these subulinids are wide-spread, this paper is also of interest to non-Neotropical malacologists.

Reference:
D’ávila, S. et al., 2018. Life history of Subulina octona (Brugüière) (Gastropoda: Pulmonata: Subulinidae) based on four-year laboratory observations and a comparative histological analysis of egg-retaining and ovoviviparous subulinids. – Journal of Natural History 52 (23-24): 1551-1569.

Scavenging by macaws

A peculiar observation, already reported in ornithological literature, was repeatedly found in the scavenging of Megalobulimus shells by the Lear’s macaw, Anordorhynchus leari Bonaparte, 1856. The shells were broken and little pieces were eaten, presumable for the uptake of calcium.

The observations were made in northeastern Brazil.

Reference:
Lima, D.M. et al., 2017. Observation on scavenging events on shells of Megalobulimus (Gastropoda: Pulmonata) by Lear’s macaws. – The Festivus, 49(4): 329-331.

Reproductive biology of a Megalobulimus species

Fontenelle & Miranda have just published a paper on Megalobulimus. Their abstract reads “We studied the reproductive biology of Megalobulimus paranaguensis (Pilsbry & Ihering, 1900), a large and long-lived land gastropod from the Atlantic Rainforest of Brazil. The study was conducted at an urban park in the city of Santos, state of São Paulo. For 4 years, we counted the egg postures and annual eclosion rate of 32 captive snails and looked for associations between egg posture and the climatical variables of the period. The annual mean posture of 8.7 eggs per snail obtained in our results is a small number, but typical of Brazilian macromollusks. The annual eclosion rate was 31%. The beginning of the annual activity period of snails occurred in the middle of March, and lasted 33.97±3.02 weeks. The dormancy period started in the beginning of November, and lasted 18.39±3.11 weeks. There were two egg posture peaks, a minor peak between March and May, and a major peak between August and November, with greater values in September. Megalobulimus paranaguensis has a well-defined seasonal reproductive pattern influenced by environmental temperature and temperature range. Furthermore, in this snail, reproduction is negatively influenced by temperature increasing and temperature range”.

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Reference:
Fontenelle, J.H. & Miranda, M.S., 2017. Aspects of biology of Megalobulimus paranaguensis (Gastropoda, Acavoidea) in the coastal plain of the Brazilian southeast. – Iheringia, Zoologia, 107: e2017004 (5 pp.). DOI: 10.1590/1678-4766e2017004

Population dynamics of a Megalobulimus species

The recent study by Miranda & Fontanelle (2015) is a welcome addition to our knowledge of Megalobulimus species.

ABSTRACT. The population dynamics of Megalobulimus paranaguensis (Pilsbry & Ihering, 1900), a large and long-lived land gastropod from Brazil’s Southeast (Atlantic Forest) was studied between 2006 and 2009, at an urban park in the city of Santos, state of São Paulo. The study included biometry, weighing, and marking and recapture of adult individu- als. The variables obtained from specimens were correlated with the environmental variables of the study period. The survival rate of the adult snail population was 96.7%. Recruitment showed several peaks during the year, and was concentrated between April and August, except in 2009, when there was only one peak in August. Specimen abun- dance progressively increased from 2006 on, with a trend towards relative stability during that period. The condition factor remained relatively stable as well, decreasing from December to February. The potential evapotranspiration and precipitation influenced the number of captures, and the mean temperature influenced the condition factor. Megalobulimus paranaguensis goes through a period of dormancy in the tropical summer, which is between November and February, but remains active in the winter. The survival rate of M. paranaguensis was high, and may be the result of having its annual cycle synchronized with the tropical climate of the Atlantic forest.

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Reference:
Miranda, M.S. & Fontenelle, J.H., 2015. Population dynamics of Megalobulimus paranaguensis (Gastropoda: Pulmonata) in the southeast coast of Brazil. – Zoologia 32 (6): 463–468.
Available at http://dx.doi.org/10.1590/S1984-46702015000600005

Reproductive cycle in a Cerion species

To illustrate the statement in my previous post of the Cerionidae being well-studied, another paper by Suárez Torres (2015) may be mentioned.

“Gonads of 144 mature specimens of Cerion mumia chrysalis were examined. Between January-December, 2012 were collected 12 specimens per month. Two reproductive cycles were recognized, one from January to April, and another from July to September. Both male and female reproductive cells were observed inside the acini, which defines the species as hermaphrodite. During May-June and subsequently in October-November no follicular activity was observed. In December, the acini decreased notably in size”.

Cerionmummia

It is only by the interests of local malacologists that the biology of species, in this case a Cuban one, can be furthered.

Reference:
Suárez Torres, A., 2015. Ciclo reproductivo de Cerion mumia chrysalis (Pulmonata: Stylommatophora: Cerionidae). – Solenodon 12: 21–27.

Copulation in Cuban Jeanneretia

The biology of Neotropical land snails is largely unknown, and data on copulation is only hard to find. Recently a study on the mating behaviour of some Jeanneretia in Cuba was done, which received the Unitas Malacologica Student Research Award 2014 (Hernández Quinta, 2015).

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Major findings of the study are the variability in the location of the accessory copulation organ between different taxa, and the absence of a sensitive zone as observed in Polymita. The total duration of courtship appears to be relatively short compared to data from literature. A brief version of the study just appeared in the UM Newsletter.

Reference:
Hernández Quinta, M. (2015) Mating behaviour in Jeanneretia ss. (Helicoidea: Cepolidae), endemic of the western region of Cuba. – Unitas Malacologica Newsletter 35: 7-9.