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.

Ecophenotypic plasticity in shell growth direction of asari clam Ruditapes philippinarum

2021 ◽  
pp. 1-6
Author(s):  
Takeshi Tomiyama
Keyword(s):  
Growth Rate ◽  
Shell Growth ◽  
Shell Height ◽  
Growth Direction ◽  
Ruditapes Philippinarum ◽  
Shell Morphology ◽  
Individual Growth ◽  
Shell Size ◽  
Internal Factors ◽  
Suitable Habitats

Abstract Asari clam (or Manila clam) Ruditapes philippinarum is an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

The effects of salinity on the density, shell size and survival of a mangrove gastropod: laboratory and field evidence

2015 ◽  
Vol 96 (6) ◽  
pp. 1191-1199
Author(s):  
Rafaela Camargo Maia ◽  
Ricardo Coutinho
Keyword(s):  
Population Density ◽  
Temporal Distribution ◽  
Shell Morphology ◽  
Eastern Coast ◽  
Ecological Indicator ◽  
Mangrove Forests ◽  
Shell Size ◽  
The North ◽  
Field Evidence ◽  
Melampus Coffeus

The macro-detritivore gastropod Melampus coffeus plays an important role in energy transfer in neotropical mangroves and, because it consumes tree leaves, it may be a potential ecological indicator of degraded mangrove areas. The objective of this study was to analyse the spatial-temporal distribution and population dynamics parameters of M. coffeus in mangroves and correlate environmental variables with population density, shell morphology and survival. Samples were collected monthly in two mangrove forests with different salinities, located on the north-eastern coast of Brazil. Height, width and aperture height of the animals’ shell were measured. The effects of salinity on population density and size distribution in M. coffeus were evaluated in field and laboratory experiments. The results showed that populations of M. coffeus present low density and are composed of large individuals during the dry season in both mangrove forests. These populations are denser and show predominance of small individuals during the rainy season when salinity decreases. The results obtained in the experiments confirm the observations in the field. Animals at extreme sizes (small and large) subjected to different salinity treatments over a moderate period showed higher mortality rates than individuals of intermediate size.

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.

Limits to optimization: fluid dynamics, adhesive strength and the evolution of shape in limpet shells

2000 ◽  
Vol 203 (17) ◽  
pp. 2603-2622 ◽  
Author(s):  
M.W. Denny
Keyword(s):  
Fluid Dynamics ◽  
Shell Height ◽  
Adhesive System ◽  
Hydrodynamic Forces ◽  
Optimal Shape ◽  
Shell Morphology ◽  
Rocky Shores ◽  
Adhesion System ◽  
Selection For ◽  
Lift And Drag

Limpets are commonly found on wave-swept rocky shores, where they may be subjected to water velocities in excess of 20 m s(−1). These extreme flows can impose large forces (lift and drag), challenging the animal's ability to adhere to the substratum. It is commonly thought that the conical shape of limpet shells has evolved in part to reduce these hydrodynamic forces while providing a large aperture for adhesion. This study documents how lift and drag actually vary with the shape of limpet-like models and uses these data to explore the potential of hydrodynamic forces to serve as a selective factor in the evolution of limpet shell morphology. At a low ratio of shell height to shell radius, lift is the dominant force, while at high ratios of height to radius drag is dominant. The risk of dislodgment is minimized when the ratio of height to radius is 1.06 and the apex is in the center of the shell. Real limpets are seldom optimally shaped, however, with a typical height-to-radius ratio of 0.68 and an apex well anterior of the shell's center. The disparity between the actual and the hydrodynamically optimal shape of shells may be due to the high tenacity of limpets' adhesive system. Most limpets adhere to the substratum so strongly that they are unlikely to be dislodged by lift or drag regardless of the shape of their shell. The evolution of a tenacious adhesion system (perhaps in response to predation) has thus preempted selection for a hydrodynamically optimal shell, allowing the shell to respond to alternative selective factors.

scholarly journals A fixed axis coiling model for the living planktonic foraminifer Globigerinella siphonifera

1992 ◽  
Vol 6 ◽  
pp. 29-29
Author(s):  
Jelle Bijma ◽  
Brian T. Huber ◽  
Christoph Hemleben
Keyword(s):  
Volume Ratio ◽  
Shell Morphology ◽  
Type I ◽  
Type Ii ◽  
Shell Size ◽  
Translation Rate ◽  
Ecological Requirements ◽  
Primary Rule ◽  
Fixed Axis ◽  
Chamber Size

Two morphotypes of Globigerinella siphonifera (Types I and II) can be clearly distinguished in their natural environment based on differences in symbiont distribution, which is dependent on the structure of the pseudopodial network. Laboratory experiments have demonstrated that the life cycle and ecological requirements of Types I and II differ considerably as well. However, qualitative observation of the empty shells reveals no significant differences between these two morphotypes. Therefore, a “fixed-axis” coiling model has been developed to simulate foraminiferal shell morphology with a computer. The model is based on the assumption that isometry is the primary rule implemented in planktonic foraminiferal development. Four parameters (rate of radius increase, number of chambers per whorl, translation rate, and relative distance from the center of any chamber to the coiling axis) and two scaling factors (initial chamber size and number of chambers) suffice to generate geometric models of the shells of these planispirally coiled organisms.Values for the four parameters extracted from digitized SEM microphotographs of dissected specimens of G. siphonifera demonstrate significant differences between the Types I and II. These are primarily due to a different rate of radius increase and a different number of chambers per whorl. Type I has a higher rate, which in combination with its lower number of chambers per whorl results in a more lobate test and a 22% smaller adult shell size than Type II. We suggest that the smaller surface area-to-volume ratio in the Type I population can be explained by increased respiration due to higher oxygen production during symbiotic photosynthesis; TEM has demonstrated that Type II contains twice as many symbionts than Type I and each symbiont contains a higher concentration of chloroplasts.The fixed axis model was also used to describe the ontogeny of G. siphonifera. The model shows that early chambers in log-spirally coiled structures must deviate from a strict isometric arrangement. To maintain exponential growth, the juvenile stage of Types I and II is more planispiral, more umbilicated, and contains more chambers per whorl than the adult stage. Future investigations will focus on the transformation of the shape parameters during later ontogenetic development and during cladogenesis.

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.

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.

Ontogenetic change and intra-specific variation of shell morphology in the Cretaceous nautiloid (Cephalopoda, Mollusca) Eutrephoceras clementinum (d'Orbigny, 1840) from the Ariyalur area, southern India

2009 ◽  
Vol 83 (3) ◽  
pp. 365-378 ◽  
Author(s):  
Ryoji Wani ◽  
Krishnan Ayyasami
Keyword(s):  
Shell Morphology ◽  
Southern India ◽  
Shell Shape ◽  
Morphometric Study ◽  
Central Position ◽  
Ontogenetic Change ◽  
Allometric Relationship ◽  
Shell Diameter ◽  
Mode Of Life ◽  
Specific Variation

Morphometric analyses of shell morphology in the Cretaceous nautiloid Eutrephoceras clementinum (d'Orbigny, 1840) (Cephalopoda, Mollusca) from the Ariyalur area, southern India, reveal ontogenetic change from hatching to maturity as well as intra-specific variation in shell morphology. the shell breadth has a negative allometric relationship with shell diameter and with whorl height, and the umbilicus diameter has a positive allometric relationship with shell diameter. This shows that shell shape became relatively thinner with less variation, and the umbilicus diameter became relatively broader with growth. the siphuncle position moves from a dorso-central to ventro-central position with growth. A constriction was recognized on the early whorl at 20 mm in shell diameter, and the interval angles of succeeding septa were changed at the 8th septum, indicating that they hatched at this stage. the bending of umbilical walls of apertures toward the center of coiling suggests that E. clementinum attained maturity at about 115 mm in shell diameter. the comparison of the shell morphology of E. clementinum with that of E. bouchardianum (d'Orbigny, 1840) reported in the literature clarifies their difference in whorl shape and umbilical size, especially in the adult stage. This kind of morphometric study of nautiloids is essential for elucidating their adaptive designs for environment and mode of life, functional shell morphology, taxonomy, phylogeny, and evolution.

scholarly journals Spatial distribution and morphometry of the succineid snail Succinea baconi (Pfeiffer, 1854) in India

2021 ◽  
Author(s):  
Himangshu Barman ◽  
Soujita Pramanik ◽  
Gargi Nandy ◽  
Sampa Banerjee ◽  
Gautam Aditya
Keyword(s):  
Spatial Distribution ◽  
Vertical Distribution ◽  
Shell Length ◽  
Land Snail ◽  
Shell Morphology ◽  
Shell Shape ◽  
Regression Equations ◽  
Growth Strategies ◽  
Shell Weight ◽  
Significant Difference

The spatial distribution and morphological features of the land snail Succinea baconi (Pfeiffer, 1854) (Gastropoda: Succineidae) from India were evaluated. The survey performed in gardens and bushes in Coochbehar, West Bengal, India, has made it possible to assess the abundance of the snail S. baconi on the randomly selected lemon plants (n = 18). Logistic regressions were employed to judge differences in vertical distribution, resource association and size class variation in the snails under study. Variation in shell morphology was assessed by performing the regression analysis of the sampled shells of live snails (n = 258) and vacant shells of the deceased individuals (n = 100). An overall significant difference (p < 0.05) in the vertical distribution of snails in lemon plants was observed. As to their association with resources available, snails were found to be more abundant in detritus than on living parts of the plants. The performed logistic regression revealed that the relative abundance of different S. baconi size classes was significantly different (p < 0.001). Significant correlations (p < 0.001) were found among different body size variables, with the shell length (x)-body weight (y) relationship being: y = 0.232x2.524 (for live snails) and the shell length (x)-shell weight (y) relationship being: y = 0.358x2.537 (for shells of dead snails). Various parameters of the snail shell shape could be represented through regression equations. Although reproduction and growth strategies of snails need to be explored further, the presented observations improve our understanding of the ecology of S. baconi, which may prove useful for future conservation efforts.

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