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 R. Tucker Abbott 於 1952 年發表，連同在生物學及生物經濟學方面的筆記；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 18.5 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 body whorl and a dark spire (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

分布於馬達加斯加、印度、馬來西亞、菲律賓、社會群島、琉球群島、夏威夷群島、台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。

### Indigenous distribution

The indigenous distribution of this species includes the general area of these countries: India, Sri Lanka, Philippines, Hawaii, southern Japan, 社會群島， Taiwan, Hong Kong, Thailand.

### 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.: Puerto Rico, Florida, Texas and 愛達荷州
* Hawaii
* Many Caribbean islands:
  * Cuba – along with _尖膀胱螺_ it is the most common freshwater snail in Cuba
  * The Dominican Republic
  * 聖露西亞
  * Martinique since 1991
* Central America: Mexico
* El Hatillo Municipality, Miranda, Venezuela

Africa:

* South Africa The _Tarebia granifera_ was reported from South Africa (and Africa) for the first time in 1999 in northern 夸祖魯 - 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 史瓦帝尼.

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:

* Israel (non-indigenous)

## 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 _Cleopatra ferruginea_ 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 彼得馬里茨堡 and its confluence with the Umgeni River which lie closer to 500 m. R. Tucker Abbott (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, 伊西曼格利索濕地公園，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 substratum, 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.

### 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_ 5–7 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, _Pseudosuccinea columella_, 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.

### Density

In Florida Tucker Abbott (1952) recorded a 人口密度 of _Tarebia granifera_ 4444 m−2 which falls within the range of densities measured 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 habitat heterogeneity 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 sand mining 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 catch per unit effort 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).

### Feeding habits

_Tarebia granifera_ feeds on algae, 矽藻 and detritus.

### 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 genitalia 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 oesophagus 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 veligers, 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, 原腸胚形成 and 擔輪幼蟲 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 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 reproductive biology of _Tarebia granifera_ needs to be investigated in detail before its population dynamics can be properly interpreted from quantitative sampling.

### 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；另有一種名為美麗棘帶吸蟲（_Centrocestus formosanus_ (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 年時在非洲辛巴威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。

### 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 _Biomphalaria glabrata_ 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 夸祖魯 - 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 sympatrically 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.

## 參考文獻

## 延伸閱讀

* Butler J. M., Ferguson F. F., Palmer J. R. & Jobin W. R. (1980). "Displacement of a colony of _Biomphalaria glabrata_ by an invading population of _Tarebia granifera_ in a small stream in Puerto Rico". _Caribbean Journal of Science_ **16**: 73–79. PDF （頁面存檔備份，存於網際網路檔案館）.
* Chaniotis B. N., Butler J. M., Ferguson F. F. & Jobin W. R. (1980). "Thermal limits, desiccation tolerance, and humidity reactions of _Thiara_ (_Tarebia_) _granifera mauiensis_ (Gastropoda: Thiaridae) host of the asiatic lung fluke disease". _Caribbean Journal of Science_ **16**: 91–93. PDF （頁面存檔備份，存於網際網路檔案館）.
* Ferguson et al. (1958). "Potential for Biological Control of _Australorbis Glabratus_, the Intermediate Host of Puerto Rican Schistosomiasis" （頁面存檔備份，存於網際網路檔案館）. _The American Journal of Tropical Medicine and Hygiene_ **7**: 491–493.
* Miranda, N. A. F.; Perissinotto, R.; Appleton, C. C. Salinity and temperature tolerance of the invasive freshwater gastropod _Tarebia granifera_. South African Journal of Science. 2010, **106** (3/4). doi:10.4102/sajs.v106i3/4.156. .
* Miranda, N. A. F.; Perissinotto, R.; Appleton, C. C. Lalueza-Fox, Carles , 編. Population Structure of an Invasive Parthenogenetic Gastropod in Coastal Lakes and Estuaries of Northern KwaZulu-Natal, South Africa. PLoS ONE. 2011, **6** (8): e24337. Bibcode:2011PLoSO...624337M. PMC 3164166 . PMID 21904629. doi:10.1371/journal.pone.0024337. .
* Miranda N. A. F. & Perissinotto R. (2012) "Stable Isotope Evidence for Dietary Overlap between Alien and Native Gastropods in Coastal Lakes of Northern KwaZulu-Natal, South Africa". _PLoS ONE_ **7**(2): e31897. doi:10.1371/journal.pone.0031897.

## 外部連結