The first occurrence of a neritopsine gastropod from a phreatic community
The first occurrence of a neritopsine gastropod from a phreatic community
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neritopsine 腹足动物首次出现在潜水群落中
DOI：
10.1093/mollus/68.3.286
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发表时间：
2002
影响因子：
1.2
通讯作者：
H. Ishikawa
中科院分区：
文献类型：
--
作者：
Takenori Sasaki;H. Ishikawa
© The Malacological Society of London 2002 neritosine 腹足动物是一个独特的分支，已辐射到广泛的环境中。它们主要出现在潮间带岩石海岸以及从热带到亚热带地区的咸水到淡水栖息地。许多类群也出现在神秘的环境中，例如海底洞穴和巨石的底部、深海中基于化学合成的群落（参见下文参考资料）和一些陆地栖息地。然而，迄今为止，尚未从与海洋环境隔离的纯淡水地下地点收集到任何奈托辛物种。在对stygobiont动物群进行调查的过程中，从日本西部爱媛县宇和岛伊吹町12 m深的井中采集了浅色neritimorph腹足动物。该地区距离最近的海岸约1.9公里，海拔约20m。该井于 1995 年 10 月钻探，通过泵将水排出并过滤以去除沉积颗粒。泵的过滤室由业主 Mitsuhisa Fukuda 定期（大约每周一次）检查，以收集各种无脊椎动物。 1996 年 3 月 21 日首次发现了 neritopsine 物种的活体标本（标本编号 1 和 2，UMUT RM 28044 和 28045，存放于东京大学大学博物馆历史地质和古生物学系），并于 1996 年 8 月 15 日再次发现（标本编号 3，UMUT RM 28046），同时还发现了几个空壳Hydrobiids，Saganoa morimotoi (Kuroda & Habe，1958)。 1997 年 10 月 20 日大雨后，当水中的沉积物被搅动时，又收集到了另外三个标本（标本编号 4-6，UMUT RM 28047-28049）。 此后，过滤器上的沉积物很少，尽管定期检查过滤室，但没有发现更多标本。该物种的壳（图1A）凹陷，顶端低平，脆弱，全白色。轮生表面偶尔有不规则的生长线，部分被薄薄的骨膜覆盖。体螺轮比壳的尖顶大得多。顶端被严重侵蚀，在任何标本中都无法清楚地观察到原壳。孔径为半月形，内唇直。即使在最大的样本中，外唇也不会增厚。内唇缘和孔的内部没有设置小齿或脊。引颈呈梯形，略凹，从内唇处广泛延伸；在低倍镜下，其表面几乎光滑，但在高倍观察下，其表面密布着鳞片状微沉积物。鳃盖以稍微缩回的位置完全关闭孔径。鳃盖的外表面是角质的，呈红棕色。核在近轴侧是偏心的，并显示出宽间隔的片状生长环（图1B）。内部仅钙化至近轴三分之一，近轴侧有突起突出；其余区域完全角质化。在2号标本中观察到齿齿。齿齿公式用n-1-0-1-n表示（n大于60，达到约80；图1C、D）。中央牙齿缺失；齿根膜在宽阔的中心区域无齿。侧齿采用三个元件的融合复合体的形式。第一个元素是三个元素中最大的；轴呈三角形，底伸，尖部不明显，无细齿。第二元件很薄，起源于第一元件和第三元件之间的凹槽，并与每侧的相邻元件结合在一起。第三个元素倾斜对齐，是三个元素中第二大的；轴沿边缘加厚，内侧有凹槽；尖头的切削刃呈锐利锯齿状，有18个三角形小齿。边缘齿拉长；最里面的牙齿的牙尖有七个针状小齿。上述外壳和齿根形态表明，该物种与最近在日本西部描述的 Neritilia mimotoi Kano, Sasaki 和 Ishikawa, 2001 关系最密切，分布于九州至四国。然而，它们在形态上并不相同：Mimotoi 猪笼草的特点是唇部宽阔，顶端有尖锐的突起，而宇和岛井中的标本即使大小相似，也没有形成如此特殊的特征。然而，由于口唇的这种差异可能代表了不同地点个体发生的种内变异，因此我们不建议将该物种分开，而是暂时将其鉴定为Neritilia sp。参见米本井。随着未来更多材料的出现，必须对这一分类判断进行审查。从地理范围来看，Neritilia属近乎泛热带-亚热带分布于加勒比海、非洲中西部、西印度洋至西太平洋的岛屿、日本和夏威夷。在已知物种中，只有日本物种 N. mimotoi 栖息在暖温带，而不是热带或亚热带地区。这里记录的地点位于游鱼属和游鱼科纬度范围的北端。从生态学角度来说，大多数奈瑞提利亚物种都是河流生长的。只有夏威夷猪笼草和米莫托猪笼草这两个物种典型地出现在安奇阿林池塘中，安奇阿林池塘被定义为仅通过地下通道与海洋相连的咸水栖息地。 Neritilia mimotoi 也发现于咸水河口栖息地。 N. sp的出现。参见井中的 mimotoi 是来自纯淡水地下栖息地的第一个记录，不仅是 Neritiliidae 科，而且是所有 neritopsine 腹足动物。已知的 Neritopsina 栖息地可大致分为以下六组：
© The Malacological Society of London 2002 The neritopsine gastropods are a distinct clade that has radiated in a wide range of environments. They occur mainly on intertidal rocky shores and in brackish to freshwater habitats, from tropical to subtropical areas. Many taxa also occur in cryptic environments, such as submarine caves and undersides of boulders, in chemosynthesis-based communities in the deep sea (see below for references) and in some terrestrial habitats. However, no neritopsine species has so far been collected from a purely freshwater underground site that is isolated from the marine environment. In the course of investigations on stygobiont fauna, pale neritimorph gastropods were collected from a well 12 m deep in Ibukicho, Uwajima, Ehime Prefecture, western Japan. The locality is about 1.9 km from the nearest seashore and about 20 m above sea level. The well was drilled in October, 1995, and the water is drained by a pump and filtered to remove sedimentary particles. The filter chamber of the pump has been inspected periodically (about once a week) by the owner, Mitsuhisa Fukuda, to collect various invertebrates. Live specimens of a neritopsine species were first discovered on March 21, 1996 (specimens nos. 1 and 2, UMUT RM 28044 and 28045, deposited in Department of Historical Geology and Paleontology, University Museum, University of Tokyo) and again on August 15, 1996 (specimen no. 3, UMUT RM 28046), together with several empty shells of hydrobiids, Saganoa morimotoi (Kuroda & Habe, 1958). Three additional specimens (specimens nos. 4–6, UMUT RM 28047–28049) were collected alive when sediments were stirred up in the water following heavy rain on October 20, 1997. Thereafter, sediment was scarce on the filter and no additional specimens were found despite periodic inspections of the filter chamber. The shell of the species (Fig. 1A) is depressed, with a low flattened apex, fragile, and entirely white. The surface of the whorls is marked with occasional irregular growth lines and is partly covered by a thin periostracum. The body whorl is much larger than the spire of the shell. The apex is heavily eroded and the protoconch is not clearly observable in any of the specimens. The aperture is semi-lunar, with a straight inner lip. The outer lip is not thickened even in the largest specimen. The inner lip and inside of the aperture are not provided with denticles or ridges. The inductura is trapezoidal, slightly concave, and widely extended from the inner lip; its surface appears almost smooth at low magnification, but densely covered with scaly micro-deposits under high-powered observation. The operculum completely closes the aperture in a slightly retracted position. The exterior surface of the operculum is corneous and reddish brown. The nucleus is eccentric on the adaxial side and shows widely spaced lamellate growth rings (Fig. 1B). The interior is calcified only to the adaxial one-third, with an apophysis projecting on the adaxial side; the remaining area is totally corneous. The radula was observed in specimen number 2. The radular formula is represented by n-1-0-1-n (n more than 60, reaching approximately 80; Fig. 1C, D). The central tooth is absent; the radular membrane is toothless in the broad central area. The lateral teeth take the form of a fused complex of three elements. The first element is the largest of the three; the shaft is triangular with extended base, and the cusp is indistinct and lacking denticles. The second element is thin, originating in a groove between the first and third elements, and united with the adjacent elements on each side. The third element is obliquely aligned and the second largest of the three; the shaft is thickened along its margin and grooved medially; the cutting edge of the cusp is sharply serrated with 18 triangular denticles. The marginal teeth are elongated; the cusp of the innermost teeth is provided with seven spicular denticles. The shell and radular morphology described above suggests that this species is most closely related to Neritilia mimotoi Kano, Sasaki and Ishikawa, 2001 that was recently described from western Japan, occurring from Kyusyu to Shikoku. However, they are not identical morphologically: N. mimotoi is characterized by a broadly reflected peristome with an acutely pointed process on the apical side, whereas the specimens from the well in Uwajima do not form such a specialized feature even at similar size. Nevertheless, because this difference in the peristome may represent ontogenetic infra-specific variation among various localities, we do not propose to separate the species, but provisionally identify it as Neritilia sp. cf. mimotoi. This taxonomic judgment must be reviewed as more material becomes available in the future. In terms of geographic range, the genus Neritilia exhibits a nearly pantropical-subtropical distribution in the Caribbean Sea, central western Africa, islands from the western Indian Ocean to the western Pacific, Japan, and Hawaii. Among known species, only the Japanese species N. mimotoi inhabits the warm temperate, rather than tropical or subtropical, zones. The locality documented here is at the northern extremity in the latitudinal range of the genus Neritilia and also of the family Neritiliidae. Ecologically, most species of Neritilia are fluvial. Only two species, N. hawaiiensis and N. mimotoi, characteristically occur in anchialine ponds, defined as brackish water habitats connected to the sea only via underground pathways. Neritilia mimotoi is also found in brackish-water estuarine habitats. The occurrence of N. sp. cf. mimotoi in the well is the first record from a purely freshwater underground habitat not only for the Neritiliidae, but also for all neritopsine gastropods. The known habitats of the Neritopsina can be broadly categorized into six groups as follows: