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VENUS Jour. Malac.)n# (Jup, - VoL 57, No. 2C]99R): 115 120

Distribution of Two Intertidal Gastropods, Batielaria 7n2LltofoTmis and B. c2emingi (Batillariidae) at a Co-oceurring Area

Naoko ADAcHI and Keiji WADA (Department of Biological Science, fucutty of Science. IVitra Plk)men's University. Kitauaya-nishimachi, IVbra 630-8506, Jtapan)

Abstract: Distributions of two intertidal gastropods, Batillaria multijbrmis (Lischke) and B. cumingi (Crosse), were studied in relation to intertidal height and vegetation on a tidal flat where they co-occuTred. B. multijbrmis occurred abundantly in the intertidal higher level, while B, cumingi did in the lower tevel around low tide shore line. In areas with with regard to halophilous plants, the two species tended to segregate to each other plant in water to species. Laboratery experiment indicated that B. cumingi preferred to stay in interti- more extent than B. muttijbrmis, corresponding with the distributional difference dal height between the two species.

Keywords: Distributien, Batillaria multijbrmis, BatiUaria cumingi, tidal flat

Introduction

family Batil- Batiltaria multijbrmis and B. cumingi are intertidal snails belonging to the lariidae. Their shel! morphology and anatomica! features are similar to each other, which has caused taxonomical confusion (Kurozumi, 1995). But phyletic analysis using mitochon- drial DNA has confirmed that they are distinct species (Ozawa, 1996). The form of egg capsule and the developmental mede has been also known to differ between them (Furota, personal communication). Whilst the two species occur in intertidal zone of various substrata such as rock, boulder and sand or mud in wave-protected bays and estuaries (Abe, 1934; Wells 1983; Adachi & Wada, 1997>, there has been no published work analyzing the distributional difference quantitatively between the two species. This study was under- taken to elucidate distributional diffeTence between B. muttijbrmis and B, cumingi at a

co-occurring area. In addition, laboratory experiment was made to compare the preference for air-exposed/submerged condition between thern.

Materials and Methods

Field study was conducted at a tidal flat (1750 m2) in Yukashigata (33e36'N, 135055'E), located on O.5 km up the mouth of Yukawa Bay in Wakayama Prefecture, middle Japan, half of the during the daytime low tide of spring on 8 and 9 April, 1997. More than flat area had halophilous plants such as Zqysia sinica, Limonium tetragonum, Artemisia the surface water jukudo, and Phragmites communis (Fig. 1). Salinity and temperature of Toa measured at 3 points around the study area by portable salinometer (CM-14P:

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Electronics Ltd.) at low tide of the study period, ranged from 11.6 to 29.0CVbo and from 16.0 to 34.90C, respectively. Distributions of B. multijbrmis and B. eumingi were investigat- ed by establishing 7 transects crossing the flat. Along each transeet, sampling points were selected at intervals of 2m. Additional 4 sampling points were established under water (1-32cm depth) below the lowest level of low tide. Total number of sampling points was 99 (-40 cm to +58.5 cm relative to mean tide level). At each point, snails were collected by hands to the depth of 2cm, using two 25 x 25 cm quadrats. For quadrats where vegetation occurred, the plant species were recorded. Substratum of all the quadrats was muddy sand with pebbles. The following diagnostic characters were used to identify BatiUaria snails, based on their shell morphology, except for the small snails (<10 mm in shell length) lacking charac- teristic features of respective species. B. multijbrmis; 1) varix turned to siphonal canal well developed, 2) projecting outer lip and shell shape smoothly curved from shell apex to siphonal canal, 3) callus between outer lip and inner lip white and well developed, B. cumingi; 1) no varix turned to siphonal canal, 2) no projecting outer lip, and shell shape not smoothly curved from shell apex to siphonal canal, 3) callus between outer lip and inner lip translucent and not developed. Snail species was identified in case when the speci- men had all the three or the two characters of each species, When the specimen showed beth characters of B. muUijbrmis and B. cumingi or intermediate character between B. muttijbrmis and B. cumingi, its species was not determined. Among 2362 BatiUaria snails collected through the survey, specimens identified as B. multijbrmis accounted for 18.80glb and those as B. cumingi for 64.44{7b. Data of species-undetermined specimens were omitted from analysis. Laboratory experiment was carried out to compare preference for air-exposed!submerged condition between B. muttijbrmis and B. cumingi, using two plastic tanks (19 x 12 x 12 cm high) under constant temperature (250C). Each tank, with seawater (2 cm deep), was tilted in order to make one fourth area of the bottom exposed to air and the remaining area

submerged. Ten snails of each species, after being kept under seawater for 12 hours, were

placed at the center of each tank, where submerged. The numbers of snails staying under water and those above water were counted at 10 minute intervals during an hour. The experiment was carried out sirnultaneousty between the two tanks (two species) and triplicat-

ed, using different individuals.

Results

Densities of Batillaria multijbrmis and B. cttmingi at sampling points are shown in Fig. 1. B. muttijbrmis was found above low-tide shore-line of the southern half of the study area, whereas B. c"mingi occurred in high density around low-tide shore-line of the

northern half of the study area. B. multijbrmis occurred from -16.5 cm to +48.5 cm relative to mean tide level (MTL), while B. cumingi did widely from - 40 cm to + 51.5 cm relative to MTL. The mean (± SD) density per O,125 m2 were 4.67 ± 13.03 in B. mutti- formis and 15.25 ± 26.02 in B. cumingi. The highest density was recorded at 39.5 cm above MTL (73 snails per O,125 m2) in B. miltijbrmis and at 25.5 cm below MTL (133 snails per O.125 m2) in B. cumingi.

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Adach1 ＆ Wada Distnbution of Bati〃arla ll7

Seaward B ．cumln I

● 一 ● 、 ● ’／ 紅 孝 数 ’一一，，一● P ● 、 、 ● ， ■ ； ● 、 ノμ 響 、 ’， ■ ， 」 鮮 ● 、、 ， ● 、 ’ 緊 、、一 ！” o 雲 修 二 ● 、、、 ● 嫡 穿 丶 ’／ ● 丶 ● 窺 莚 圭 ・ ： 、 （、 喝4 霊 靠 、、噛眇噛 6 ≒ ； ． ｝ 9 、 ● ・ 1 ’ で 豊 ： ＼ ＿一 ・ ノ 。 、、■ ： 《 o ’ 、 、 一 ’ 丶 ・ 0＜ ＜ 20 丶ご ！ 、臓 二 毒 ● ！ 、、 ノ r 、 書 ’ ● 20 ≦ ＜ 50 、、 ● ， 一 ， ＼ ● 50 ≦ 丶 ↓ 一．．− r （denslty per O 125m2 ） ：

F 且91Densttie 、 of Bantlana mutttformls and B cutntngt at each sampling pomt Sohd hne， broken】lne dnd 、hddcd area lndlcaIe nverbank （at low tide｝， low

t置de shore lme of tidal fldt dnd 、 dlt marsh arca respectively 各採集 地 声 て の ウ ミ ニ ナ と ホ ソ ウ ミ ニ ナ の 密 度 実線 は 川 岸 （十 潮 時 〕 を ， uH 線 及 ひ そ の 内 側 は 人 潮 低 潮線 と i 出域 を，灰 色 の 部 分 は 植 生 σ）範 囲 を 示 す

Table l shows the denslty of the two specles ln re 且anon to vegetatlon In areas wlthout

vegetatlon the mean of multtformts was at the mld −nde whlle ， denslty B hlghest level，

of β cu 〃 llngl was at the −tlde areas wlth vegetatlon that hlghest low level In ， the hlghest

denslty of both specles was observed ln hlgh−tlde level η 〃 ， and the denslty of B ． 7〃 妙 br lts

was hlgher ln sampllng domlnated by Zoysla slnlca and Limonium ごetragonum whlle polnts ，

the denslty of 、B cumlngl was hlgher m sampllng polnts domlnated by Phragmites communIS − Laboratory experlment showed that the number of snalls found above water was slgnlfl

cantly ln muttOformls larger B than ln 8 cumln81 ln one of trlpllcates，and the mean va 匡ue was hlgher ln B 〃 zulhfor 〃 lls than ln B ．α 〃 ltngl ln an the trlpllcates（Table 2）

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ll8 VENUS ： Vol ．57 ， No ．2 （1998 ）

Tabie 1Mean and range of densities（per O ．0625 m2 ）of βα ∫1〃aria mutt ヴformis（1eft values ）and B ． − cumingi （right values ）at sampling points with vegctutkon und without vegetation （bare）， sepa

− and rately for three tide leve且s of high（35−60 cm above MTL ）。 mid （0 35 cm above MTL ） low （40−O cm below MTI ．）， 植 生 の あ る 調 査 点 と 植 生 の な い 調 査 点 に お け る ウ ミ ニ ナ （左 側 の 値 ） と ホ ソ ウ ミ ニ ナ （右 ・ 側 の 値） の ，密 度 の 乎均 値 と 最 大 最 小 値 ．調 査 点 を 潮 位 に よ り，高潮 位 （平均 海 水 面 に − − 対 す る 高 さ ： 35−60cm ），中 潮 位 （O 35 cm ），低 潮位 ← 40 O・cm ＞ に 分 け て 示 し た ．

Vegetation dominated by Level Bare ZoysiasinicaLimonium ノ 4厂 ’emis ’c〜 厂σ 8〃1’1θ∫ 1・’〃lonium tet厂agonu 〃 1 fukudoPh comm 初 n ’5 ＆ 14 厂ごe 〃 2 ’∫’α

HighMeanRangeN 0／0 ．80 3．5／30 9 ．2／1．5 0 ．3／00 0／18 0．4／0．5 ／O−711 −46 ／0 −42 0−42 ／0− 10 −1／0 0〆14−22 0−3／0−4 39 12 4 2 8

MidMeanRangeN 4 ．9／10．3 0 ．5f1 ．50 1／00 0／0 ．50 − 0−34／0 −56 − 1／0−3 ＿2／0 ／O 1 68 2 2 2

LowMeanRangcN 0 ．5／12レ9 0−8／0− 104

48

Tab 且e 2 The number of snails recorded as staying above water at 6 counts during l hour in each of replicate ： 10 and itsstatistical comparison three replicates （number of snails used in each ） between Batillaria muttiformis and B ． cumingi ， n ．s ．： not significant ． ウ ミ ニ ナ と ホ ソ ウ ミ ニ ナ の 水 に 対 す る 選 好性 の 室 内実 験 の 結果 ．水 槽 内 に お い て ，水 中 に 放 逐 後 ，水 の な い 場 所 に い た 個体 数 を ，10分 お き に 1 時 間 ま で 記録 し，そ の 平均 値 と 標 準 偏 差 お よ び そ れ の 2 種 間 で の 違 い の 検 定 結 果 を 示 し た ．

Replicate B ． mutttformis B ． cumingi Wilcoxon signed −ranks test No ． Mean ± SDRange Mean ± SDRange

1 1．50 ± 1．12 0 −30 0 00 n ．s ． （p ＝0．0679 ） 自う 1．33 ± 1．ll −31 00 n ，s ． （p ＝0．0679 ） 3 l．33 ± 0 ．75 −3 ，17 ± 0．37 〇一1 p く 0．05 （p ＝0 ．043D

Discussion

The present study has revealed that distribution patterns of B ． multtfor 〃 1is and B ． cumingi differ to each other with regard to intertidal height and vegetation ． The dens 瓧y

of 且 cu 〃 lingi was of 8 ．〃 iult ヴfor〃 1is was higher at the upper 互eve1 ， while the density higher at the lower leveL Ohshima and Furota （1980）qualitative且y described zonation of these

two species in a salt marsh area ； B ． mult びformis occurred in more upper zone than B ．

cumingi ． In other batillariid snails living in mangrove swamp or sand flat， the interspecific i e ． difference in distribution pattern with regard to intertidal heigh亡 has been reported ， ．

T ． su ’cata Wens 1980 and among B ． mult br〃 lis B ． between Terebra〃a palustris and （ ， ） （ノ ，

cingulata ． ‘ ” ens ’s C ． rhiZophorarum and T． sulcata Wells ， zona ’is， Cerithidea ，C dja 加 ， （

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Adachi ＆ Wada ： Distribution of BatiUaria 119

1983）． Results of laboratory experiment suggest that β ． cumingi prefers to stay in water

− to more extent than β ，mu 〃ヴbrm ’∫， assuming that amount of activity or aggregative tenden

− cy was not differentbetween the two species in the experiment ．Thus ， distributionaldiffer

ence in intertida里 height between the two species is congruent with interspecific difference − in preference for air exposed ／submerged condition ．

σ 〃 躍 厂〃 in with halophilous in β 〃 laria ”ヶb 1is occurred abundantly areas plants， contrast

to B ． cu 〃 lingi which showed higher densities in areas without vegetation as well as in areas − with vegetation ． In areas with vegetation at the high tide leve1， B ．〃 2uttlfor 〃 1is occurred

in Limonium tetragonum and Z Jsia s ’n た a while β ． abundantly places dominated by の ， − cumingi did in places dominated by Phragmites eommunis ． These findings suggest dif ference in preference for halophilous plants between the two species ， which should be verified in the future study ．

Ackno ｝vledgments ： − We are thankful to Drs ． H ． Uchida and K ． Nomura and other members of

Kushimoto Marine Park for facilitating our field study ， and to Prof ． M ． Nagoshi ， Dr ． M ． Urabe ， and the students of the laboratory of Nara Women s University for their helpful advices during the

course of study ． We are also indebted to two anonymous referees for reviewing the manuscript and

Dr ． K ． Seto for species identification of halophilous plants．

ウ ミ ニ ナ と ホ ソ ウ ミ ニ ナ の 混 生 域 に お け る 分 布

． 足 立 尚 子 ・和 田 恵 次

（奈 良女 チ 大 学 理 学 部 生 物 科 学 科 ）

要 約

和 歌 山 県 那 智 勝 浦 ゆ か し 潟 の 潮 問 帯 砂 泥 地 に 同 的 に 生 息 す る ウ ミ ニ ナ と ホ ソ ウ ミ ニ ナ に つ い て 所 ， 潮 と 生 に る ミ ニ い 位 植 対 す 分 布 を調 査 した。 ウ ナ は ， 高潮 位 に お て 高密 度 で 出 現 し た の に 対 し ， ホ ソ ウ ミ

ニ い て で の い ナ は ，低 潮 線 付 近 に お 高密 度 出 現 し た 。 塩 生植 物 出 現 す る 場所 に お て ， 2 種 が 多 く出 現 し

の っ て い ソ ミ ニ ニ の た 植 物 種 は 異 な た 。 室 内実 験 で は ，ホ ウ ナ は ， ウ ミ ナ よ りも水 あ る 場所 を 好 む 傾 向 一 を示 し た 。 こ れ は ，野外 で の 2 種 の 潮 位 に 関 す る 分布 の 違 い の 結 果 と 致 し た 。

References

Abe ， N ，1934 ． Eco 且ogical observations on Batillar’α 〃 2 〃 ’の 厂〃 2な （Lischke ）． Sci． Rep ． Tohoku 1〃lp ． Tni − し ソ．， S θ厂 ． 4 ， 8 （4）： 383 398 ． Adachi ， N ，＆ K ． Wada ，1997 ． Distribution of Bat ’〃ar ’α c 躍 痂 g” （Gastropoda， Potamididae ）in Tanabc − Bay ， middle Japan ． ハtankiseibutu，39（1）： 33 38 （ln Japanese）．

Kurozumi ， T ．1995 ． 14． Ba 〃 ’aria 切 〃 曜b 厂mis ． In ： Report on 厂are a 《7uatic organ ’sms ’n ／Opan μ0 ， pp ．73 − 78 ． Nihon −suisanshigen −hogo −ky6kai （In Japanese ）． Ohshima ， T ．＆ T ． Furota，1980． Distribution of benthic fauna in the Obitsu River Estuary． In：

Laboratory of Marine Biology， Faculty of Science， Toho Universityand The Chiba Biological

θ Ecologica ’ in the R ’yer EstuarF Kisara てu Ch ’わ ．45 − 63 In Society （ds．）， studies ． Obitsu （ ． ¢ ノ， pp （ Japanese ）．

Ozawa T ．1996 ． A new species of Batitlaria Gastropoda ： Batillariidae from Jaban ． レ劭 μ 5 ノ ． ， （ ） （Op − Jour ． Mata ‘ ．）， 55 （3）： 且89 197 ．

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120 VENUS: Vol. 57, No.2(1998)

Wells, F. E, 1980, A comparative study of distributions of the mudwhelks 7lerebratia suicata and

r palustris in a mangrove swamp in northwestern Australia. MatacoL Rev., 13: 1-5. Wells, F. E. 1983. The Potamididae (Mollusca: Gastropoda) of Hong Kong, with an examination of habitat segregation in a small mangrove system. In: Morton, B. & D, Dudgeon (eds.), Preceedings of the Second internationat Workshop on the Malacofauna of Hong lkbng and Southern China, Hong Kong, 1983, pp. 139-154. Hong Kong University Press, Hong Kong.

[Received: January 12, 1998; Accepted: March 10, 1998]

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