瘤蜷

瘤蜷（学名："Tarebia granifera"），又名斜粒粒蜷，是锥蜷科粒蜷属的一种有口盖的淡水螺物种，属于水生腹足纲软体动物。原生于东南亚，本物种在墨西哥等地泛滥，成为了入侵物种。
亚种.
本物种有两个亚种：
形态描述.
壳略厚，右旋，壳色为黄褐色到深褐色，壳上具颗粒状突起，体螺层下半部为粗肋。壳有两型：短胖型及细长型，缝合线相当明显。
有关本物种的详细解剖构造由于1952年发表，连同在生物学及方面的笔记；而Malek (1962)亦为本物种提供了一份解剖指南。
The maximum height of adult shells of this species from South Africa is from 18.5 mm to 25.1 mm, while in Puerto Rico they can reach up to 35 mm.
Two color forms of "Tarebia granifera" exist, one has a pale brown and a dark (see photo on the right) and in the other the shell is entirely dark brown to almost black (see photo on the left). Intermediate forms exist.
分布.
分布于马达加斯加、印度、马来西亚、菲律宾、社会群岛、琉球群岛、夏威夷群岛、台湾岛以及中国大陆的海南等地，常见于热带亚及热带地区的河流湖泊池塘，甚至在稻田间亦可见其踪影。
Indigenous distribution.
The indigenous distribution of this species includes the general area of these countries: , , , , southern , 社会群岛, , .
Nonidigenous distribution.
"Tarebia granifera" has become invasive on at least three continents: North and South America and Africa. Initial introductions were presumably via the aquarium trade.
Americas:
Africa:
This spread will doubtless continue into northern South Africa, Moçambique, Zimbabwe and beyond. It has not been possible to calculate the rate of dispersal.
Asia:
Ecology.
Habitat.
In the South Africa, the snail has colonized different types of habitat, from rivers, lakes and irrigation canals to concrete lined reservoirs and ornamental ponds. It reaches very high densities, up to 21 000 m², and is likely to impact on the entire indigenous 底栖生物 of the natural waterbodies of the region – more so than any other invasive freshwater invertebrate known from the South Africa. The South African indigenous thiarids "Thiara amarula", "瘤拟黑螺", and "" are considered particularly vulnerable.
Most localities in South Africa (93%) lie below an altitude of 300 m above sea level where an estimated area of 39 500 km2 has been colonized. The only known localities outside this area are the Umsinduzi River in 彼得马里茨堡 and its confluence with the which lie closer to 500 m. (1952) noted that on 关岛 Island, "Tarebia granifera" occurred in streams and rivers at 983 m altitude but that these watercourses were consistently above 24 °C indicating that temperature may be an important determinant of distribution.
"Tarebia granifera" also occurs in several estuaries along the KwaZulu-Natal coast. Prominent among these is the dense population (±6038 m2) found at a 盐度 of 9.98‰ (28.5% sea water) in Catalina Bay, Lake St Lucia, 伊西曼格利索湿地公园, KwaZulu-Natal. These records show that "Tarebia granifera" is able to colonize 汽水 (水域) and moderately saline habitats and reach high densities there. From observations in 波多黎各 it was suggested that snails could survive temporarily saline conditions for several weeks by burying themselves in the , emerging when fresh water returned.
In common with other Thiaridae, "Tarebia granifera" is primarily a 海底生物界 species and in South Africa has been collected on a variety of substrata in both natural and artificial waterbodies, e.g. sand, mud, rock, concrete bridge foundations and the concrete walls and bottoms of reservoirs, irrigation canals and ornamental ponds. Many of these habitats were vegetated and the associated vegetation included many types of 水生植物 单子叶植物 (e.g. "纸莎草", "藨草属" sp., "香蒲属" sp., "芦苇属" sp.) and 双子叶植物 (e.g. "金鱼藻", "菹草", "延药睡莲"). Where densities are high, "Tarebia granifera" may also occur on marginal, trailing vegetation and the floating Common Water Hyacinth "凤眼蓝" as well. It favours turbulent water and tolerates current speeds up to 1.2m.s−1 and possibly greater. This habitat range is similar to that recorded for "Tarebia granifera" in Puerto Rico.
The major interest in "Tarebia granifera" outside Asia today is its invasive ability and its impact on indigenous 底栖生物 in colonized waterbodies. The pollution tolerance value is 3 (on scale 0–10; 0 is the best water quality, 10 is the worst water quality).
Typically half or more of these snails were buried in the 沉积物s and were not visible from the surface. This was also noticed in 水族箱 where they actively buried themselves in sand. Exact proportion of population of "Tarebia granifera" that is buried at any time is not known. There is also not known how long can snails remain buried.
"Tarebia granifera" will die at the temperature 7 °C in aquaria, but they do not live in water temperature under 10 °C in the wild.
Dispersal.
It is probable that 扩散 (生态学) of "Tarebia granifera" from one waterbody or river catchment to another occurs passively via birds, notably 雁形目, which eat them and void them later, perhaps in another habitat. Evidence for this comes from the finding of many small "Tarebia granifera" 5–7 mm in height and still containing the soft parts in unidentified bird droppings from the bank of the Mhlali River, South Africa. Even though the shell of "Tarebia granifera" is thick, most of these juveniles had been partially crushed with only a few still intact. Both the intact and damaged specimens could have been alive when passed and perhaps survived had they been deposited in water. None was large enough to have been reproductively mature (see below) and would have needed to survive in any new habitat for several months before reproducing.
Passive dispersal may also occur via weed on boats and boat trailers and via water pumped from one waterbody to another for industrial and irrigation purposes. In the Nseleni River juvenile "Tarebia granifera" were commonly found with another invasive snail, "", on floating clumps of water hyacinth "Eichhornia crassipes" which provide a vehicle for rapid downstream dispersal.
Once established in a particular waterbody "Tarebia granifera" is likely to disperse actively, both up and downstream in the case of flowing systems, as far as environmental factors like current speed and food availability will allow. The snail's tolerance of turbulent, flowing water was demonstrated by Prentice (1983) who reported it migrating upstream on the Caribbean island of 圣卢西亚 at a rate of 100 m month−1 in streams discharging up to 50 l.s−1. In KwaZulu-Natal it has been collected in water flowing at up to 1.2 m.s−1 which is likely to exceed the current speeds of at least the lower and middle reaches of many rivers and streams in South Africa making these watercourses open to colonization.
The sole of "Tarebia granifera" is proportionally small when compared to other thiarids and smaller snails with their higher coefficients were less able to grip the substratum in the face of moving water and so not did disperse as effectively as larger ones.
Density.
In Florida Tucker Abbott (1952) recorded a 人口密度 of "Tarebia granifera" 4444 m−2 which falls within the range of with a Van Veen grab in a number of sites in northern KwaZulu-Natal, where was measured desnsities 843.6 ±320.2 m−2 to 20764.4 ±13828.1 m−2. The site with such high density was non-flowing, devoid of rooted vegetation but it was shaded by trees ("玉蕊") and by floating "凤眼蓝". This between-site variability may be positively correlated to and food availability. Despite the very high densities recorded in the Nseleni River, indigenous invertebrates were still present in the sediments including: bivalve "Chambardia wahlbergi", 摇蚊科s, 寡毛类 (tubificids) and burrowing 多毛纲 were also found but in very low numbers.
The low densities of "Tarebia granifera" reported for the Mhlatuze River, South Africa may have been influenced by nearby activities or, more likely, high flows and mobile sediments, but they nevertheless approach those recorded by Dudgeon (1980) for "Tarebia granifera" in its native 香港 (18–193 m−2).
Little is known of the long term population fluctuations of "Tarebia granifera" and findings seem to be contradictory. Studies in Cuba (Yong et al. (1987), Ferrer López et al. (1989), Fernández et al. (1992)) indicate that the snail lives for more than a year though maximum densities were recorded at different times of the year in different habitats. Using a netting technique, Yong et al. (1987) and Ferrer López et al. (1989) found highest densities in summer when temperatures reached their maximum whereas Fernández et al. (1992) found highest densities in November (late autumn) when temperatures reached their minimum. Fernández et al. (1992) also suggested that "Tarebia granifera" density was positively correlated with 2+ -->钙质 concentrations and negatively with 4 -->铵 concentrations.
Recent surveys by Vázquez et al. (2010) of 比那尔德里奥省, Cuba have reported population densities of "Tarebia granifera" of 85 individuals/m2, well above those of its endemic relatives (5 individuals/m2).
Feeding habits.
"Tarebia granifera" feeds on algae, 矽藻 and .
Life cycle.
"Tarebia granifera" is both 单性生殖 and 卵胎生, although males have been reported. These are characteristics which are undoubtedly key to its success as an invader. For example, no males have been found amongst hundreds dissected from KwaZulu-Natal, it is probable that a few are present. Males were found in most (6/7) populations examined in 波多黎各 but were generally uncommon at up to 22.7% of the population (mean 4.6%). Live sperm were present in the testes of these males but the were apparently non-functional. R. Tucker Abbott (1952) failed to find sperm in the gonads of male "Tarebia granifera" from Florida. Most "Tarebia granifera" are therefore 克隆 of the female parent.
胚胎s develop in a brood pouch. This pouch is a compartmentalized structure lying immediately above the and develops only after the snail has reached maturity. Its size expands as the number of embryos increases. "Tarebia granifera" has 1–77 embryos in its brood pouch.
Tucker Abbott (1952), Chaniotis et al. (1980) and WHO (1981) cite the same statistic that females can give birth to one juvenile every 12 hours. Young snails emerge through a birth pore on the right side of the head. The newborn shell is <1–2 mm in height with between 1.5 and 4.8 whorls. The size of juveniles at birth is 0.7–2.1 mm. According to Chen (2003) these newborns have a high survival rate in the field.
Attainment of 性成熟 in "Tarebia granifera" is generally indicated by the size of the smallest snail observed to give birth rather than a histological assessment of the development of the gonad and associated reproductive structures. Appleton & Nadasan (2002) estimated onset of maturity at 10–12 mm shell height but unpublished data suggest a height closer to 8 mm in line with other published studies. Tucker Abbott (1952) estimated sexual maturity at between 5.5 and 8.0 mm at different stations over a short stretch of river in Florida. Chaniotis et al. (1980) gave a similar estimate of 6.0–7.0 mm from a cohort of laboratory-bred snails in Puerto Rico.
Appleton et al. (2009) extrapolated data by Yong et al. (1987), Ferrer López et al. (1989) and by Fernández et al.(1992) and they resulted that sexual maturity is reached at an age of about five months. Reported variation in maturation period varies from 97–143 days (3.2–4.8 months) under the laboratory conditions to 6–12 months, also from laboratory data. It is difficult to relate shell size at the onset of maturity to age since the size structure of populations vary over time and from one locality to another.
Dissection of "Tarebia granifera" showed 囊胚 stage embryos in the brood pouches of snails as small as 8 mm shell height. Small numbers of shelled embryos, including s, were found in snails of 10–14 mm but became more plentiful in snails >14 mm and especially those >20 mm. Importantly, unshelled embryos (blastula, 原肠胚形成 and 担轮幼虫 stages) were not found in snails >16 mm and the numbers of shelled embryos themselves decreased in the largest snails, >24 mm. This suggests that differentiation of 生殖细胞 in the ovary and their subsequent arrival in the brood pouch as blastulae is not a continuous process over a breeding season but occurs as one or more 'cohorts' or 'pulses' which stop before the birth rate of young snails reaches its maximum. So it seems that while the first birth may occur in snails as small as 8 mm, these are few and most juveniles are born to snails >14 mm. The size of the shell of the parent at peak release of juveniles is 24.0 mm.
The of "Tarebia granifera" needs to be investigated in detail before its can be properly interpreted from quantitative sampling.
寄生虫.
本物种在东南亚为多个吸虫纲物种的第一中间宿主，当中有多个属于斜睾目的异形吸虫科的物种，有报告指对人类可进行机会性感染；另有一种名为（' (Nishigori, 1924)）的棘带吸虫属物种（也是异形吸虫科的成员），也是重要的鱼类鳃寄生虫。 本物种也是鸡嗜眼吸虫（"Philopthalmus gralli" Mathis & Ledger, 1910，也是斜睾目，但属于嗜眼吸虫科）的中间宿主，2005年时在非洲津巴布韦传出有农场的鸵鸟被这种吸虫感染，"Tarebia granifera" also serves as intermediate host for the philopthalmid eyefluke which has recently (2005) been reported affecting 鸵鸟科es "" on farms in Zimbabwe. The snail host implicated in this outbreak was "Melanoides tuberculata" but the rapid spread and high population densities achieved by "Tarebia granifera", which appears to be replacing "Melanoides tuberculata" in South Africa, may exacerbate the problem in the future.
长久以来，本物种一直都被认为是卫氏肺吸虫（"Paragonimus westermani" (Kerbert, 1878)，亦作卫氏并殖吸虫）的中间宿主，但1992年时Michelson的研究证明这个假设错了。
Other interspecific relationships.
"Tarebia granifera" have been associated with the disappearance of two indigenous benthic gastropod species from rivers in 波多黎各 and have displaced the vegetation-associated pulmonate ' from streams and ponds on several Caribbean islands. Although the responsible mechanism is not understood, this has led to suggestions that it could be useful as a 生物防治 agent in snail control operations within integrated 血吸虫病 control programmes. They probably also 竞争 (生物学) for space and resources (e.g. food) with indigenous infaunal and epifaunal invertebrates, especially where its densities are high. Under such conditions it is likely to alter the structure and 生物多样性 of the entire benthic communities of invaded habitats and perhaps the vegetation-associated communities as well.
Anecdotal reports and observations suggest that in 夸祖鲁-纳塔尔省 the indigenous thiarid "瘤拟黑螺" is becoming less common and pressure from the spread of "Tarebia granifera", particularly at high densities, is a possible explanation. Like "Tarebia granifera", "Melanoides tuberculata" is parthenogenetic and ovoviviparous, grows to a similar size, are similar in size at first birth and juvenile output. Data from several habitats where the species occur show however that in all such situations "Tarebia granifera" becomes numerically dominant.
"Tarebia granifera" is likely to impact on another South-African indigenous thiarid, the poorly known "Thiara amarula" in the saline St. Lucia estuary system.
Studies on the ecological impact of "Tarebia granifera" are urgently needed.
Human importance.
In addition to its role as intermediate host for several economically important trematode species, "Tarebia granifera" has colonized 水库s, dams and ponds on the premises of three large industrial plants in northern KwaZulu-Natal and been pumped out of at least one of them, blocking 管路系统s and damaging equipment. This generally happens when snail densities are high and the damage is due to individuals being crushed so that pieces of shell and soft tissue are carried into machinery. Details of the nature and extent of this damage and the costs incurred are not available. There is no doubt that "Tarebia granifera" is able to pass unharmed through 泵, probably as juveniles.