Diversity of Freshwater Gastropoda Snails Found in District Swat, Khyber Pakhtunkhwa, Pakistan

The study was conducted in District Swat, Pakistan (Fig. 1). It is situated in the North of Pakistan (34.30o-35.05oN, 71.45o-72.50oE). Geographical studies revealed the possession of altitudinal variation like plain areas to a high peaks ranging from 600m-6000m above sea level form hilly as well as mountainous extremities. From these high peaks a single drainage basin (River Swat) originates which is a major source of freshwater (Ahmad et al., 2015). The region possesses an unusual weather profile i.e. the average recorded temperature revealed a significant fluctuation monthly wise which is 32.71oC in June falls to 0oC or below in December and January. The high precipitation in July (143.00mm) unlike the month of November and December (only 20mm). Humidity is high in August (82.58%) (Ahmad et al., 2015). Due to their unusual environmental condition the valley also possesses a rich flora and fauna and can be estimated from the presence forests (natural and artificial) and the agroforestry which provide a favorable condition for animal life such as terrestrial and freshwater to the life of birds (resident and migratory) (Ahmad et al., 2015).

Specimen collected from all the seven tehsils except Bahrain due to low water temperature Ghalegay, Guligram, Kabal, Charbagh, Khwaza Khela, Matta and Bahrain. Specimen were collected from different freshwater sources like spring water, river Swat and rice fields through a mesh as well as by handpicking (Qureshi et al. 2015). All the live snail specimen were brought to zoological Laboratory in ¾ filled plastic boxes (Qureshi et al. 2015) with constant aeration. The collection and rearing of the live specimen during transect as well as in the Laboratory was done by following the standard protocols provided by the guide entitled Guidelines and Procedures for the Malacology Collection of the Tom Ridge Environment Centre at Presque Isle Gastropoda-Snails Bivalvia-mussels (integrated taxonomic information system) with some modifications.

Using the keys provided by (Neubert, 1998; Brown, 2002; Kakar et al., 2017) snails were identified up to species taxon. The identification was based on conchology i.e. shell height and width, no. of whorls, shell coiling (sinistral or dextral). Aperture shape and size, presence or absence of operculum, shape and texture of operculum, spire position, texture of periostracum, presence/absence of aperture lip and umbilical features (open or closed). The shell morphometry was done by Analogue Vernier caliper. Shannon-Wiener and Simpson’s diversity indices were also calculated using MS Excel sheet 2013.

From 1135 collected snail specimens from various localities (Table I), three freshwater snail species were identified belonging to three gastropods’ families i.e. Physidae, Viviparidae and Planorbidae. The species are Physa acuta, Draparnaud, 1805, Indoplanorbis exustus, Deshayes, 1834 and Bellamya bengalensis, Lamarck, 1882. The species’ abundance calculated during the study were 615(54.18%), 300(26.43%) and 220(19.38%) for P. acuta, I. exustus and B. bengalensis, respectively (Fig. 2) indicating P. acuta as the dominant species.

The environmental factors such as water pH and temperature were also recorded and the average values found were 7.00 and 26.18ºC, respectively.

Family Physidae

Genus Physa Haldeman, 1843

Physa acuta, Draparnaud, 1805

(Fig. 2a, b, c)

Measurable features of the shell that is shell height and width are 13.31mm and 7.07mm, respectively. The species has wide distribution throughout the district. It is familiar with the name “fruit fly” of the malacology because of their very fast maturation and higher reproduction rate (Kakar et al., 2017).

Family Planorbidae

Genus Indoplanorbis, Annandale and Prashad, 1921

Indoplanorbis exustus, Deshayes, 1834

(Fig. 2d, e)

Shell’s height and width are 4.01mm and 10.11mm, respectively. This is a native species of Asia and is known for their role as an intermediate host for the transmission of trematode’s infections, especially Asiatic schistosomiasis (Kakar et al., 2017).

Family Viviparidae

Genus Bellamya, Jousseaume, 1886

Bellamya bengalensis, Lamark, 1882

(Fig. 2f, g, h)

Shell’s height and width are 32.40mm and 22.47mm, respectively. The presence of color bands (striation) is one of their main diagnostic character among the other members of the same genus. In many countries throughout the world it is used as a food. It is a well-known vector for parasitic nematode of human and other animals like fishes (Farahnak and Ghobadi, 2006).

Using Shannon-Wiener and Simpson’s diversity indices the diversity of gastropods were calculated for the region, which are 1.001 and 0.599, respectively (Table II) showing the significance value for diversity of gastropods in the study area. These values are less than the calculated indices found in the study of Shahrbabak et al. (2021), but provided a baseline for the future studies regarding the biodiversity of gastropods in the region.

Among the identified species, the P. acuta Draparnaud, 1805 is the more prevalent and abundant species (54.18%) collected from all the sampling sites strongly supports the idea presented by Kakar et al. (2017) that is the P. acuta has high reproductive and maturation rate as compare to other gastropod species. The abundance of I. exustus recorded was 26.43% nearly similar to the result of Qureshi et al. (2015) which is 23.4%. Looking to the species richness, tehsil Babozai and Barikot are richer because all the three gastropod species were found here might be due to a little bit high water temperature (27.5oC) than the other sampling sites which is in line of the work of McCreesh and Booth (2014) i.e. snails survive well in between the range of 15oC-31oC.

The height to width ratio of the shells has calculated, they were 1.8, 1.44 and 0.39 for P. acuta, B. bengalensis and I. exustus respectively and have confirmed their shell shapes i.e. conical for P. acuta and B. bengalensis and plane shape for I. exustus. Mostly the samples were collected from the agricultural lands as compared to other water bodies supporting the idea that agro-ecosystem is rich in species than the other water bodies (Altaf et al., 2016).

The authors have declared no conflict of interest.