scholarly journals An ontogenetic perspective on the evolution of shell size and shell shape in the land snail genus Plectostoma

2014 ◽  
Author(s):  
Thor-Seng Liew ◽  
Menno Schilthuizen
Keyword(s):  
Parallel Evolution ◽  
Land Snail ◽  
Character Evolution ◽  
Growth Trajectory ◽  
Shell Shape ◽  
Shell Size ◽  
General Issue ◽  
Shell Form ◽  
Developmental Program

The rampant convergent and parallel evolution in shell form in the Gastropoda is well known. Many studies focus on the functional drivers which have been regarded as a major force in shell evolution. There is, however, a scarcity in studies that aim at understanding shell form evolution with respect to their ontogeny. Hence, we investigated the evolution of shell form in the micro-landsnail genus Plectostoma (Diplommatinidae) from the viewpoint of shell ontogeny. We examined the aperture ontogeny profiles that describe how aperture form and growth trajectory change along the shell ontogeny, and how the aperture ontogeny profiles relate to the observed shell forms. We also estimated the phylogeny of Plectostoma species, and examined patterns of character evolution for shell form. Our study revealed a general issue in the characterisation of shell shape and demonstrated how shell shape differences can be expressed as differences in the ontogeny of morphospace. It is clear that in Plectostoma the phylogenetic history does not prevent the course of shell ontogeny, and the resultant form. Finally, each species has a unique aperture ontogeny profile that determines its shell shape while retaining a conserved developmental program that maintains shell size.

scholarly journals An ontogenetic perspective on the evolution of shell size and shell shape in the land snail genus Plectostoma

2014 ◽  
Author(s):  
Thor-Seng Liew ◽  
Menno Schilthuizen
Keyword(s):  
Parallel Evolution ◽  
Land Snail ◽  
Character Evolution ◽  
Growth Trajectory ◽  
Shell Shape ◽  
Shell Size ◽  
General Issue ◽  
Shell Form ◽  
Developmental Program

The rampant convergent and parallel evolution in shell form in the Gastropoda is well known. Many studies focus on the functional drivers which have been regarded as a major force in shell evolution. There is, however, a scarcity in studies that aim at understanding shell form evolution with respect to their ontogeny. Hence, we investigated the evolution of shell form in the micro-landsnail genus Plectostoma (Diplommatinidae) from the viewpoint of shell ontogeny. We examined the aperture ontogeny profiles that describe how aperture form and growth trajectory change along the shell ontogeny, and how the aperture ontogeny profiles relate to the observed shell forms. We also estimated the phylogeny of Plectostoma species, and examined patterns of character evolution for shell form. Our study revealed a general issue in the characterisation of shell shape and demonstrated how shell shape differences can be expressed as differences in the ontogeny of morphospace. It is clear that in Plectostoma the phylogenetic history does not prevent the course of shell ontogeny, and the resultant form. Finally, each species has a unique aperture ontogeny profile that determines its shell shape while retaining a conserved developmental program that maintains shell size.

Notodiscus (Charopidae) on South Georgia: some implications of shell size, shell shape, and site isolation in a singular sub-Antarctic land snail

2011 ◽  
Vol 23 (5) ◽  
pp. 442-448 ◽  
Author(s):  
P.J.A. Pugh ◽  
R.I. Lewis Smith
Keyword(s):  
East Coast ◽  
Land Snail ◽  
Shell Shape ◽  
Shell Size ◽  
Site Isolation ◽  
South Georgia ◽  
North East ◽  
Larus Dominicanus ◽  
Close Proximity ◽  
Georgia Population

AbstractMultivariate analysis shows that shells of Notodiscus sp. (Charopidae: Pulmonata) reported from South Georgia are smaller and proportionately taller than, but otherwise similar to, populations of Notodiscus hookeri (Reeve) from Iles Crozet and Iles Kerguelen. The origin of this solitary, and spatially limited, South Georgia population is enigmatic. It is confined to a remarkably small coastal lowland site which was glaciated at Last Glacial Maximum, precluding a Tertiary relict origin, and on the leeward north-east coast, ruling out post-glacial ocean rafting. The site is close to the King Edward Point settlement, yet the absence of any logistics connections with the Iles Crozet or Iles Kerguelen mitigates against anthropogenic introduction. The close proximity of the population to nests of blue-eyed shag (Phalacrocorax atriceps), Dominican gull (Larus dominicanus) and light-mantled sooty albatross (Phoebetria palpebrata) could imply the snail was originally introduced to South Georgia via these ocean transiting seabirds.

scholarly journals Intrapopulation variation in shell morphological traits and banding polymorphism of the land snail Cepaea vindobonensis (Gastropoda; Pulmonata; Helicidae)

2020 ◽  
Vol 10 (5) ◽  
pp. 114-121
Author(s):  
A.S. Kramarenko ◽  
Zh.V. Ignatenko ◽  
O.I. Yulevich
Keyword(s):  
Morphological Traits ◽  
Shell Height ◽  
Spatial Differentiation ◽  
Spatial Arrangement ◽  
Land Snail ◽  
Shell Shape ◽  
Shell Size ◽  
Intrapopulation Variation ◽  
Phenetic Diversity ◽  
High Level

The main goal of this paper was to analyze intrapopulation variation of both morphological traits and shell banding polymorphism using the example of a continuous population (a metapopulation) of the land snail Cepaea vindobonensis (Férussac, 1821). A total of 14 samples of the land snail C. vindobonensis from a population located in the “Dubki” Park (Ukraine, Mykolayiv) were collected in May-July 2007. The land snail collection sites are divided into three areas by buildings and asphalt roads, indicated by the Latin letters A, B and C. The major diameter of shell (MJD), the minor diameter of shell (MID) and the shell height (SH) were measured with a digital calliper to the nearest 0.05 mm. Two shell shape indices (SF1 and SF2) were also computed. A high level of the intrapopulation variation of the land snail C. vindobonensis was found in our study. Significant differences between sample means were found for all shell traits and indices used (except for SF1), however, maximum difference was noted for SH and SF2 (in both cases: P ≤ 0.001). About 80% of the total variation of the variance-covariance matrix was explained by the 1st and 2nd Principal Components (PC1 and PC2). The PC1 was characterized by high positive factor loadings of MJD, MID and SH and thus can be interpreted as “shell size dimension” and the PC2 had a high correlation with SF2 and thus it can be interpreted as “shell globularity”. The PC1 and PC2 determined a high level of spatial differentiation of intrapopulation morphological variation of the land snail C. vindobonensis. Samples with small (area A) and large (areas B and C) shells were separated from each other according to the PC1. Areas B and C were characterized by individuals with flatness and globularity shells, respectively. The areas A, B and C differed significantly in the total number of morphs, average number of morphs and frequency of rare morphs (Kruskal-Wallis H-test; in all cases P ≤ 0.010). At the same time, the highest value of phenetic diversity was noted for samples collected within A and C areas. In general all phenetic diversity estimators showed a positive correlation with sample size (Spearman's correlation coefficient; in all cases P ≤ 0.05). It was found that the type of biotope did not likely affect the frequency of individual morphs with respect to the shell banding polymorphism pattern. With regard to the most common morphs two patterns of the spatial arrangement of the intrapopulation variation were found – clinal pattern was for the frequency of pallescens morph and chaotic pattern was for frequency of “12345” morph.

scholarly journals Some Morphological Variations in The Land Snail Monacha cantiana (Montagu,1803) within Baghdad Province

2013 ◽  
Vol 10 (1) ◽  
pp. 1-12
Author(s):  
Baghdad Science Journal
Keyword(s):  
Population Density ◽  
Shell Height ◽  
Calcium Content ◽  
Land Snail ◽  
Shell Morphology ◽  
Shell Size ◽  
Aperture Diameter ◽  
Morphological Variations ◽  
Shell Diameter ◽  
Soil Calcium

The present work includes investigation of some features of shell morphology; shell size, shell thickness, shell colour of the land snail Monacha cantiana, in addition to the correlation between height and diameter of shell and between shell aperture diameter and shell diameter at four sites within Baghdad Province, Iraq. Also, measurements of three environmental variables were made; soil temperature, soil moisture and soil calcium content in adition to population density. Shell Aperture Index (Ia) and Shell Index (SI) for individuals from size class ranged between (9-12)mm were measured. The results showed that the deference in shell size by using (Ia) within population related to temperature, moisture and population density but, the value of Shell Index decreased in AL-Kadhimiya site (0.81-0.97) due to increase in population density. The species was characterized by shell colour variation (creamy white, white ,creamy). Also, The results showed strong and positive correlation between shell height and diameter and between shell aperture diameter and shell diameter for all size classes.

scholarly journals The energetic costs of living in the surf and impacts on zonation of shells occupied by hermit crabs

2020 ◽  
Vol 223 (16) ◽  
pp. jeb222703 ◽  
Author(s):  
Guillermina Alcaraz ◽  
Brenda Toledo ◽  
Luis M. Burciaga
Keyword(s):  
Water Flow ◽  
Wave Action ◽  
Hermit Crabs ◽  
Energetic Cost ◽  
Shell Shape ◽  
Energetic Costs ◽  
Shell Size ◽  
Conical Shells ◽  
Drag Forces ◽  
Submerged Body

ABSTRACTCrashing waves create a hydrodynamic gradient in which the most challenging effects occur at the wave breaking zone and decrease towards the upper protected tide pools. Hydrodynamic forces depend on the shape of the submerged body; streamlined shapes decrease drag forces compared with bluff or globose bodies. Unlike other animals, hermit crabs can choose their shell shape to cope with the effects of water flow. Hermit crabs occupy larger and heavier shells (conical shape) in wave-exposed sites than those used in protected areas (globose shape). First, we investigated whether a behavioral choice could explain the shells used in sites with different wave action. Then, we experimentally tested whether the shells most frequently used in sites with different wave action reduce the energetic cost of coping with water flow. Metabolic rate was measured using a respirometric system fitted with propellers in opposite walls to generate bidirectional water flow. The choice of shell size when a large array of sizes are available was consistent with the shell size used in different intertidal sites; hermit crabs chose heavier conical shells in water flow conditions than in still water, and the use of heavy conical shells reduced the energetic cost of coping with water motion. In contrast to conical shells, small globose shells imposed lower energy costs of withstanding water flow than large globose shells. The size and type of shells used in different zones of the rocky shore were consistent with an adaptive response to reduce the energetic costs of withstanding wave action.

Land snails on Porto Santo: adaptive and non-adaptive radiation

1996 ◽  
Vol 351 (1337) ◽  
pp. 309-327 ◽  
Keyword(s):  
Distribution Patterns ◽  
Land Snail ◽  
Land Snails ◽  
Regional Differentiation ◽  
Similar Species ◽  
Adaptive Responses ◽  
Shell Size ◽  
A Value ◽  
Allopatric Divergence ◽  
Evolution Proceeds

A survey has been made of the land snail fauna of Porto Santo, Madeiran archipelago. Porto Santo is an isolated island about 12 km long by 5 km wide. The fauna is exceptionally species-rich and characterisied by radiations of species in several families, especially the Helicidae. Sixty-five samples from the mainland and five offshore islets yielded 56 species, 84% of them endemic, with a mean of 11.5 species per site, and marked regional differentiation in faunal composition. A given site produces on average only approximately one fifth of the number of species possible, equivalent to a value for Whittaker’s index of diversity of 4.5. Patterns of localization occur on the peaks to the east and west of the island, with numerous cases of replacement by congeneric and morphologically similar species. Local areas have assemblages of species differing in shell size and shape, which probably exploit different niches, the pattern in one area paralleling that in others. The low-lying sandy areas which separate these areas are now unfavourable to many endemic species; those which do occur in them tend to have island-wide distributions. Morphological variation in such species appears to have ecological rather than geographical correlates. We conclude that adaptive responses have occurred, but that much of the species richness can be interpreted as non-adaptive, that is, due to allopatric divergence in isolation by species which retain similar niches. Even on so small a land mass the topography is such that for many land molluscs it represents a cluster of refuges intermittantly connected through impermanent and often unfavourable sandy environments, on each of which evolution proceeds independently. Differences in distribution patterns between families probably arise because they evolved at different times in the island’s history. These results are compared with those from snail faunas in other parts of the world, some of which are similar to them.

Late-glacial to Holocene transition in northern Spain deduced from land-snail shelly accumulations

2012 ◽  
Vol 78 (2) ◽  
pp. 373-385 ◽  
Author(s):  
Yurena Yanes ◽  
Igor Gutiérrez-Zugasti ◽  
Antonio Delgado
Keyword(s):  
Shell Growth ◽  
Late Glacial ◽  
Land Snail ◽  
Balance Model ◽  
Adult Size ◽  
Northern Spain ◽  
Shell Size ◽  
Juvenile Stages ◽  
Climate Fluctuation ◽  
Extreme Seasonality

AbstractShells of the helicid Cepaea nemoralis were studied using taphonomic, isotopic and morphometric measurements to estimate late glacial–Holocene (~ 12.1–6.3 cal ka BP) environmental conditions in northern Spain. Higher taphonomic alteration among Holocene shells suggests lower sedimentation rates or higher shell-destruction rates than during glacial conditions. Shells preserved the aragonitic composition despite differing degree of skeleton damage. Shell δ13C values were − 10.3 ± 1.1‰, − 8.2 ± 2.3‰, and − 7.3 ± 1.6‰ for modern, Holocene and late-glacial individuals, respectively. Higher δ13C values during the late-glacial and some Holocene periods imply higher water stress of C3 plants and/or higher limestone contribution than today. Intrashell δ13C values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth. Shell δ18O values were − 1.1 ± 0.7‰, − 0.9 ± 0.8‰ and − 0.1 ± 0.7‰ for modern, Holocene and late-glacial specimens, respectively. A snail flux-balance model suggests that during ~ 12.1 − 10.9 cal ka BP conditions were drier and became wetter at ~ 8.4 − 6.3 cal ka BP and today. Intrashell δ18O profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells, despite possible larger hibernation periods. Shell size correlated positively with δ18O values, suggesting that growth rates and ultimate adult size of C. nemoralis may respond to climate fluctuation in northern Spain.

scholarly journals Intra-Specific Variability in Whorl Growth-Rate among Land Gastropods with Conispirally-Coiled Shells

2021 ◽  
pp. 59-69
Author(s):  
Jean Béguinot
Keyword(s):  
Growth Rate ◽  
Statistical Significance ◽  
Repeated Measurements ◽  
Species Level ◽  
Shell Shape ◽  
Snail Species ◽  
Strong Positive Correlation ◽  
Shell Size ◽  
Strong Negative Correlation ◽  
Species Specific

For most conispirally-coiled Gastropods with determinate growth, the geometry of spirally-winding whorls is usually constrained by a strong negative correlation between whorl growth rate and the number of whorls reached at adulthood, as originally reported by the late S.J. Gould. Yet, beyond the tight control of shell-shape at the species level – resulting from this constraint – what about the amplitude of the intra-specific variability of whorl growth-rate, partly contributing to the variability of the overall shell-size at the species level? I address the issue by designing and implementing a new, indirect method for routinely evaluating whorl growth-rate, thereby aiming at considerably saving measurement time, and making it possible to easily achieve repeated measurements across samples large enough to reach statistical significance. This approach was applied to a series of eight common land snail species. The amplitude of intra-specific variability in whorl growth, evaluated this way, proves: (i) being markedly different among the eight investigated species (by a factor that can exceed 2x); (ii) being, yet, high enough, in all cases, to require compensating variations in the adult number of whorls, so as to limit the resulting consequences on the amplitude of the intra-specific variability of adult shell-size. Despite those marked differences in the amplitudes of intra-specific variability of whorl growth-rate among species, no significant relationship was observed between intraspecific variability of whorl growth rate and species-specific shell-shape types (discoidal/globular/elongate) and only weak positive relationship was observed with species-specific typical shell sizes. However, a rather strong positive correlation was found, as expected, between the degree of intra-specific variability of the whorl growth-rate and the degree of intra-specific variability of the number of whorls reached at adulthood (with the yet unexplained exception of one among the eight investigated species).

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