The Seam Of The Snail Pdf Free

Last month, we released a new and easy way to make the classic Snail Trail quilt block using foundation paper to master the swirling shape and intricate piecing. We were so inspired by this incredible vintage design that we designed a free quilt pattern and wanted to invite you to join in the Spotted Snail Trail Quilt Along!

On ordering you will receive an eight page snail quilt block pdf pattern which includes detailed instructions and a large, colour diagram to visually illustrate how the block comes together.

the seam of the snail pdf free

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To view the free online pattern, please continue to scroll down. You can also download the ad-free and printable version of this pattern for a small fee here. Your generous contribution will help towards the cost of materials and running this website so I can continue to publish my free online patterns for everyone to enjoy.

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When I was working on this free crochet lamb lovey pattern, I was determined to try something new that would make this lamb lovey blanket stand out of the crowd. I used a new technique to crochet the head so instead of using a bobble stitch I tried something...

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We're introducing Marti's new fabric line, Ultra Violet Catalina, with a free pattern for a quilt and matching bolster pillow. Just click on the image below to download the 4-page PDF. Scroll down for more free patterns.

Make individual patterns for each applique piece from the patterns provided. Add seam allowances for hand applique, however, DO NOT ADD SEAM ALLOWANCES for fused applique (see below for abbreviated instructions for Fused Applique method).

The freshwater snail Indoplanorbis exustus is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. Indoplanorbis is of economic importance in that it is responsible for the transmission of several species of the genus Schistosoma which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that Indoplanorbis includes only a single species. The aims of the present study were to date the radiation of Indoplanorbis across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that I. exustus might be polyphyletic.

The freshwater snail Indoplanorbis exustus (Deshayes, 1834) (Planorbidae: Bulininae) is the sole member of its genus and is widely distributed across the tropics as an important intermediate host for several trematode parasites (Trematoda: Digenea). I. exustus is best known as the intermediate host responsible for the transmision of Schistosoma nasale Rao, 1933 and Schistosoma spindale (Montgomery, 1906), as well as other trematodes such as Echinostoma spp. and some spirorchids (Digenea: Spirorchiidae)[1, 2]. A third species of Schistosoma, Schistosoma indicum (Montgomery, 1906) is also transmitted by I. exustus. Although other snails have been implicated in transmission of these three Schistosoma spp. (e.g., Lymnaea luteola, S. indicum and S. nasale and Lymnaea acuminata, S. nasale and S. spindale), I. exustus is the most important host for S. nasale and S. spindale, as well as for S. indicum in certain regions. Indeed I. exustus may be the sole natural intermediate host for these three Schistosoma species on the Indian sub-continent[3]. The three Schistosoma species are parasites of Artiodactyla, in particular of buffaloes, cows, goats pigs and sheep. Two of the species cause intestinal schistosomiasis, whilst S. nasale inhabits blood vessels of the nasal mucosa and causes "snoring disease" in cattle[4]. Surveillance for cattle schistosomiasis is generally inadequate and the literature is limited, but some idea of the problem can be gained from past small scale studies. Surveys in Sri Lanka revealed a prevalence of S. spindale of 31.2% (of 901 cattle)[5], whilst in Bangladesh a similarly high prevalence of 36% has been reported[6]. More recently, in Kerala South India, prevalences have been reported of up to 57.3% in cattle, 50% in buffalo and 4.7% in goats[3].

In addition to causing disease in cattle, I. exustus has been implicated in outbeaks of cercarial dermatitis in human populations in India[7, 8], Laos[9], Malaysia[10] and Thailand[11, 12]. Cercarial dermatitis results from the cutaneous allergic reaction in people exposed to larval schistosomes (cercariae) shed by infected snails into freshwater bodies such as lakes, ponds, and paddy fields. The cercariae cause pruritis and papular eruptions, with often severe secondary infections, as they attempt to infect a non-permissive definitive host and die in the skin[13].

Indoplanorbis exustus is a hermaphroditic invasive snail species with high fecundity. Within one year of introduction the snail is able to colonize habitats with well established populations of other pulmonate and prosobranch snails[16]. The snail requires a water temperature in excess of 15C for maturation. At the optimum temperature of 30C each snail can lay up to 800 eggs[20]. The capacity for self-fertilization and high fecundity probably underlies the invasive potential of the species. The snail is found in small ponds, pools and less commonly in rice paddy fields. The snail may also occur in semi-permanent pools formed in flooded areas of fields, where it can survive the dry season buried in mud. Consequently, dispersal may occur in clumps of mud adhered to the bodies of cattle or across water in flotsam (vegetation mats), and possibly also attached to migratory birds (although this has not been observed for I. exustus). In Northeast Thailand, where I. exustus is very common, the annual rainfall is 1541 mm. In Assam, in the region where the snails were sampled for this study, the annual rainfall is much higher at around 4200 mm (data recorded 1982-2002)[21]. The current rainfall in Arabia is 340 mm per year; however, in Plio-Pleistocene humid periods this has risen to 630 mm or more[22]. It has been recognized that it is the length and severity of the dry season that influences vegetation type (savanna, rain forest, monsoon forest, etc) rather than the annual rainfall[23]. The rainfall in the dry season of Assam is approximately 250 mm, whereas that in Northeast Thailand is only 30-40 mm[21]. These observations suggest that the Assam/Bangladesh populations are subject to different ecological conditions than those of the Southeast Asian mainland (SEAM); these observations support the need to question the monophyly of Indoplanorbis. The invasive nature and ecological tolerance of the snails adds to their importance in veterinary and medical science.

The palaeogeographic, fossil and biogeographical dispersal data described above imply a Miocene origin for the radiation of Indoplanorbis across Asia. Under such a model, colonization of India could have been followed almost immediately, by radiation across Southeast Asia through land bridges created by low eustatic sea levels during Pleistocene glacial excursions. The aim of this study was therefore to collect DNA sequence data for populations of the snails across the known range. These data could then be used to address three main questions. Firstly, the timescale for the dispersal and diversification of these snails across Asia; the time of arrival of taxa in various geographical regions is important because it sheds light on how long different host:parasite assemblages have been in contact and facilitates studies on phylogenetic tracking or co-evolution. Secondly, the work aimed to determine the historical events (climatic, tectonic or palaeogeogaphical) that may have influenced the phylogeography of these taxa. Thirdly, the taxonomic status of Indoplanorbis was considered. It seems improbable that only a single species of the genus has arisen if its radiation dates from the Miocene.

Uncorrected p distances were obtained from PAUP* and transformed to percentage sequence divergence estimates. The use of this simple (there was no correction for transitional bias) distance measure was to afford comparison with other studies on inter and intraspecific variation among freshwater pond snails. The average divergence among ingroup taxa was 3.123% (range from 0.095 to 8.385%). The largest divergence was observed between the Bangladesh population and the other ingroup populations (excluding Assam), average 7.871% (range from 7.617 to 8.385%). This was followed by the divergences between the Assam population and the other ingroup populations (excluding Bangladesh), average 6.546% (range from 6.345 to 6.724%). In contrast, the divergence between the Assam and Bangladesh populations was only 4.16%. The divergence between Biomphalaria glabrata and Radix a. rubiginosa was 16.9%.

For these estimates all 15 taxa were included but gaps were excluded (as missing data). Initial runs with a Yule tree prior and an uncorrelated log-normal (relaxed) clock model showed that the ucld.stdev was >1.0 and its confidence interval did not come close to zero (mean 2.84816 HPSD ranged from 1.80335 to 3.7994); this suggested that the data were not sufficiently clock like for analyses using a strict molecular clock. A 2 partition model (by locus) with TIM + G and HKY + G was compared with a by codon model (TrN, F81, HKY, HKY + G) the latter appeared preferable (BF 87.88). Other moves, such as TrN+I or HKY, HKY did not result in significant improvement. Consequently, TrN, F81, HKY, HKY + G was used in the main analyses. The prior on the mean rate was a normal prior with mean equal to the average of published rrn L (one rate) and cox 1 (2 rates) clock rates for freshwater snails and S.D. Set such that the 95% confidence interval spanned twice the range of these 3 values. The 3 rates were as follows (in substitutions per site per year 10-8): 1.097 for rrn L, triculine snails (Gastropda: Pomatiopsidae) over the early Pleistocene[41]; 1.83 for early Pliocene Hydrobiidae[42]; and 1.62 also for Hydrobiidae[43]. These rates were estimated following the simple point estimation method of Edwards and Beerli[44], but are useful as a prior in this study. The other initial empirical prior was one on the height of the tree; this was a 100 to 350 Ma uniform prior. A more informative normal prior of 200 Ma S.D. 30 Ma was also used, but there was no marked difference on the estimation of mean rate or other TMRCAs (Time to Most Recent Common Ancestor). The informative prior was based on a Triassic/Jurassic boundary date for the divergence of the Planorbidae and Lymnaeidae[24]. Runs were also performed using an NPRS-transformation of the ML tree from PAUP as a starting tree (scaled to a height of 250 Ma), but, as this had little effect on run performance, the final runs used random starting trees. Runs using only a prior on tree height or on mean rate (but not both) gave implausible results. Sampling from the prior only (with conditions otherwise set to those of the final runs) also resulted in implausible results and TMRCA estimates very different from those obtained after observing the data. Each run was repeated with 3 different starting random number seeds the results of each run were compared and then combined for parameter estimation from the posterior distribution. 2ff7e9595c