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1.
Yoshitake Takada 《Ecological Research》1996,11(3):371-379
Monodonta labio (Gastropoda: Trochidae) occurs in a wide tidal zone on a boulder-covered shore in Amakusa, Japan. To investigate sources
of variation in reproductive output within a population, the fecundity ofM. labio was estimated. Regressions of gonad egg counts on shell width were calculated from samples collected bi-weekly at three tidal
zones: high, mid and low intertidal. Seasonal fluctuations in the regression revealed that individual females spawn at least
three times a year. Variation in fecundity between the three tidal zones was not detected at any time in standard 12 mm snails.
Due to the high growth rate in the low zone during the reproductive season, annual fecundity in the low zone was larger than
that in the high and mid zones. Thus, tidal zone variation in fecundity ofM. labio was a result of growth variation between tidal zones. 相似文献
2.
Woon-Mok Sohn Jong-Yil Chai Byoung-Kuk Na Tai-Soon Yong Keeseon S. Eom Hansol Park Duk-Young Min Han-Jong Rim 《The Korean journal of parasitology》2013,51(2):191-196
The echinostome metacercariae encysted in Cipangopaludina sp. snails that were purchased from a market in Vientiane Municipality, Lao PDR, were identified as Echinostoma macrorchis (Digenea: Echinostomatidae) through recovery of adult flukes after experimental infection to rats and a cat. The metacercariae were round, 113-128 (121)×113-125 (120) µm, having a thick cyst wall, a head collar armed with collar spines, and excretory granules. The adult flukes recovered from the rats and cat at day 14 and 30 post-infection, respectively, were elongated, ventrally curved, and 3.9-6.3×0.7-1.1 mm in size. The head collar was distinct, bearing 43-45 collar spines with 5 angle spines on each side. Two testes were large (as the name implies), tandem, and slightly constricted at the middle, with irregular margins. Eggs were operculated, ovoid to elliptical, and 88-95×56-60 µm. In scanning electron microscopy, the head collar was prominent, with 43-45 collar spines. Scale-like tegumental spines were densely distributed on the ventral surface between the oral and ventral suckers. Sensory papillae were distributed mainly on the tegument around the 2 suckers. It is confirmed that E. macrorchis is distributed in Lao PDR using Cipangopaludina sp. snails as the second intermediate host. 相似文献
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4.
Ryoko Okajima Satoshi Chiba 《Evolution; international journal of organic evolution》2013,67(2):429-437
The adaptations that occur for support and protection can be studied with regard to the optimal structure that balances these objectives with any imposed constraints. The shell inclination of terrestrial gastropods is an appropriate model to address this problem. In this study, we examined how gastropods improve shell angles to well‐balanced ones from geometrically constrained shapes. Our geometric analysis and physical analysis showed that constantly coiled shells are constrained from adopting a well‐balanced angle; the shell angle of such basic shells tends to increase as the spire index (shell height/width) increases, although the optimum angle for stability is 90° for flat shells and 0° for tall shells. Furthermore, we estimated the influences of the geometric rule and the functional demands on actual shells by measuring the shell angles of both resting and active snails. We found that terrestrial gastropods have shell angles that are suited for balance. The growth lines of the shells indicated that this adaptation depends on the deflection of the last whorl: the apertures of flat shells are deflected downward, whereas those of tall shells are deflected upward. Our observations of active snails demonstrated that the animals hold their shells at better balanced angles than inactive snails. 相似文献
5.
ABSTRACTSigaloeista Shea & Griffiths, 2010 is a genus of small, litter-dwelling helicarionid snails that occurs in the rainforest and wet sclerophyll forest of northeastern New South Wales and southern Queensland. This group currently comprises three species known only from their shell morphology. We revise the taxonomy of this group using a comparison of key morphological features and mitochondrial genes COI and 16S, and describe four new species: Sigaloeista gracilis n. sp.; S. cavanbah n. sp.; S. dorrigo n. sp.; and S. ramula n. sp. Sigaloeista is unified by shared morphological characters including a small, glossy, discoidal shell of about 4.5 whorls, a body with a pronounced caudal horn and large, leaf-shaped shell lappets, and a reproductive system with a short vagina, absent epiphallic caecum, flagellum with internal cryptae and spermatophore with accessory spines.http://www.zoobank.org/urn:lsid:zoobank.org:pub:5D5D7603-06B2-4662-91BB-343E3BB5C4E8 相似文献
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7.
Jay Richard Stauffer Jr. Henry Madsen Kenneth McKaye Adrianus Konings Paul Bloch Cecilia Paola Ferreri Jeremy Likongwe Peter Makaula 《EcoHealth》2006,3(1):22-27
Prior to 1985, the open waters of Lake Malawi were free from schistosome transmission. Over the past decades, however, the
prevalence of urinary schistosomiasis has increased dramatically in the southern part of the lake. We found the prevalence
of human schistosomiasis in school-aged children to be negatively correlated with the density of molluscivorous fishes. Specifically,
the increased infection rate in southern Lake Malawi between 1978 and 1991 is coincident with the reduction in numbers of
snail-eating fishes. During 2003, we determined the relative abundance of molluscivorous fishes and snail density at 18 sites
throughout the lake and schistosome infection in school-aged children living in selected lakeshore communities of Lake Malawi.
At the 18 sites sampled in 2003, we found that snail abundance decreased with an increase in abundance of snail-eating fishes.
Furthermore, the 2003 samples showed that the abundance of snail-eating fishes increased and there was a reduction in schistosomiasis
in school-aged children in Chembe Village. We believe that we will not observe a return to the 1978 infection rates until
these fishes continue to increase and inhabit shallower waters. 相似文献
8.
The cause of mollusk decline on the Ogasawara Islands 总被引:2,自引:1,他引:1
Decline of land snails on the Ogasawara Islands was studied. In Hahajima, major alien predators such as Euglandina rosea and Platydemus manokwari are not present, but some small endemic snails, for example, Hirasea spp. and Ogasawarana spp., are already rare and more common endemic snails, for example, Mandarina spp., are also declining in the northern mountains. The decline cannot be directly explained by forest deforestation and by its subsequent regeneration. Three species of flatworms were found to eat small snails under captive conditions. The distribution of these flatworms is restricted to the northern mountains of Hahajima where Mandarina is declining and its survival is low. These predators are plausible candidates as a cause of the decline of the endemic snails. 相似文献
9.
Jing Guo Chunxia Zhang Yao Xiang Kaiming Liang 《Biocontrol Science and Technology》2017,27(9):1071-1081
The apple snail Pomacea canaliculata has been an invasive species in China for decades and causes enormous losses to agriculture. The predation capability of the leech Whitmania pigra on P. canaliculata was studied for its economic benefit and potential application. In the present study, the leech W. pigra exhibited a strong predatory capacity in controlling P. canaliculata under both laboratory and field conditions, and it showed no bias towards consuming smaller snails during the experiments. More than 80% of the 80 snails (of which half had reached maturity) were preyed upon by 20 developing leeches (2–7?g) in miniature rice fields over a 15-day period, and the number of rice seedlings damaged by P. canaliculata was decreased in the presence of W. pigra. In a separate experiment, 15 developing snails were exposed to caged leeches and conspecific snails for four weeks. The food intake and growth of P. canaliculata were inhibited under the predation risk imposed by W. pigra, but the feeding rate, food conversion efficiency and survival of P. canaliculata were not conspicuously influenced. 相似文献
10.