瘤蜷

瘤蜷（學名：Tarebia granifera），又名斜粒粒蜷，是錐蜷科粒蜷屬的一種有口蓋的淡水螺物種，屬於水生腹足綱軟體動物。原生於東南亞，本物種在墨西哥等地泛濫，成為了入侵物種。

亞種

本物種有兩個亞種：

Tarebia granifera granifera (Lamarck, 1822)
Tarebia granifera mauiensis Brot, 1877

形態描述

殼略厚，右旋，殼色為黃褐色到深褐色，殼上具顆粒狀突起，體螺層下半部為粗肋。殼有兩型：短胖型及細長型，縫合線相當明顯。

有關本物種的詳細解剖構造由於 1952 年發表，連同在生物學及方面的筆記；而 Malek (1962) 亦為本物種提供了一份解剖指南。

The maximum height of adult shells of this species from South Africa is from 18.5mm to 25.1mm, while in Puerto Rico they can reach up to 35mm.

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.

分佈

分佈於馬達加斯加、印度、馬來西亞、菲律賓、社會群島、琉球群島、夏威夷群島、臺灣島以及中國大陸的海南等地，常見於熱帶亞及熱帶地區的河流湖泊池塘，甚至在稻田間亦可見其蹤影。

3.1 Indigenous distribution

The indigenous distribution of this species includes the general area of these countries: , , , , southern , 社會群島，Taiwan, , .

3.2 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:

This species occurs in several southern states of the U.S.A.: , Florida, Texas and 愛達荷州
Many Caribbean islands:
– along with 尖膀胱螺 it is the most common freshwater snail in Cuba
The Dominican Republic
聖露西亞
since 1991
Central America: Mexico

Africa:

The Tarebia granifera was reported from South Africa (and Africa) for the first time in 1999 in northern 誇祖魯 - 納塔爾省 though it was probably introduced sometime prior to 1996. In the 10 years since its discovery it has spread rapidly, particularly northwards, into 普馬蘭加省 province, the 克留格爾國家公園 and 史瓦濟蘭.

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:

(non-indigenous)

Ecology

4.1 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 底棲生物 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, 瘤擬黑螺，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 500km2 has been colonized. The only known localities outside this area are the Umsinduzi River in 彼得馬裡茨堡 and its confluence with the which lie closer to 500 m. (1952) noted that on 關島 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 鹽度 of 9.98‰ (28.5% sea water) in Catalina Bay, Lake St Lucia, 伊西曼格利索溼地公園，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 單子葉植物 (e.g. 紙莎草，藨草屬 sp., 香蒲屬 sp., 蘆葦屬 sp.) and 雙子葉植物 (e.g. 金魚藻，菹草，延藥睡蓮). Where densities are high, Tarebia granifera may also occur on marginal, trailing vegetation and the floating Common Water Hyacinth 鳳眼藍 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 底棲生物 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 沉積物 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.

4.2 Dispersal

It is probable that 擴散 (生態學) 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 5–7mm 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 聖露西亞 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.

4.3 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 鳳眼藍. 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, 搖蚊科 s, 寡毛類 (tubificids) and burrowing 多毛綱 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 鈣質 concentrations and negatively with 銨 concentrations.

Recent surveys by Vázquez et al. (2010) of 比那爾德里奧省，Cuba have reported population densities of Tarebia granifera of 85 individuals/m2, well above those of its endemic relatives (5 individuals/m2).

4.4 Feeding habits

Tarebia granifera feeds on algae, 矽藻 and .

4.5 Life cycle

Tarebia granifera is both 單性生殖 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 14mm and especially those >20mm. Importantly, unshelled embryos (blastula, 原腸胚形成 and 擔輪幼蟲 stages) were not found in snails >16mm and the numbers of shelled embryos themselves decreased in the largest snails, >24mm. This suggests that differentiation of 生殖細胞 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 8mm, these are few and most juveniles are born to snails >14mm. The size of the shell of the parent at peak release of juveniles is 24.0mm.

The of Tarebia granifera needs to be investigated in detail before its can be properly interpreted from quantitative sampling.

4.6 寄生蟲

本物種在東南亞為多個吸蟲綱物種的第一中間宿主，當中有多個屬於斜睪目的異形吸蟲科的物種，有報告指對人類可進行機會性感染；另有一種名為（ (Nishigori, 1924)）的棘帶吸蟲屬物種（也是異形吸蟲科的成員），也是重要的魚類鰓寄生蟲。 本物種也是雞嗜眼吸蟲（Philopthalmus gralli Mathis & Ledger, 1910，也是斜睪目，但屬於嗜眼吸蟲科）的中間宿主，2005 年時在非洲津巴布韋傳出有農場的鴕鳥被這種吸蟲感染，Tarebia granifera also serves as intermediate host for the philopthalmid eyefluke which has recently (2005) been reported affecting 鴕鳥科 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.

長久以來，本物種一直都被認為是衛氏肺吸蟲（Paragonimus westermani (Kerbert, 1878)，亦作衛氏並殖吸蟲）的中間宿主，但 1992 年時 Michelson 的研究證明這個假設錯了。

4.7 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 血吸蟲病 control programmes. They probably also 競爭 (生物學) 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 生物多樣性 of the entire benthic communities of invaded habitats and perhaps the vegetation-associated communities as well.

Anecdotal reports and observations suggest that in 誇祖魯 - 納塔爾省 the indigenous thiarid 瘤擬黑螺 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 水庫 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 管路系統 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.