CRUSTACEAN RESEARCH，NO. 35・56-- 66，2006

Comparison of social behaviors among six grapsoid (Brachyura) of different habitat conditions

Yuuka Nara，Jun Kitaura and Keiji Wada

Abstract.- Social behaviors were Klaassen，1975; Henning，1975; Lindberg， observed in the field for six grapsoid 1980; Seiple & Salmon，1982; Abele et al. ， living under different habitat 1986; Beinlich & Polivka，1989) ，compared conditions from exposed to sheltered with ocypodoid crabs.Furthermore ，inter- conditions，i. e. tridens，H. specific comparison of social behaviors was jα :ponicα，H.leαchi，Ch αsmαgnαthus only attempted by Wright (1968) addressing convexus of the family ，and taxonomic distribution of chela-using display Chiromαntes dehαα ni， and pattern ，and by Brockerhoff & McLay(2005) Perisesαrmα bidens of the family dealing with comparative analysis of mating Sesarmidae. Fighting behaviors in strategies. these six species，cheliped ・displays in Semi-terrestrial crabs that live in f1 at H. tridens，H. jα:p onicαa n d P. bidens， habitats and show diurnal activity are con- and copulatory behaviors in H. tridens， sidered to have advantage for the develop- C. dehαα ni and P. bidens were ment of visual signaling (Salmon & Atsaides， described. Elements of fighting behav- 1968). Grapsoid species living in open and ior varied among species irrespective f1 at habitats ，therefore ，are expected to have of taxonomic group. The three species developed social behavior for visual commu- that showed cheliped-displays occurred nication ，compared with grapsoid species liv- in more exposed habitats compared to ing in structured habitats. the other species，suggesting the impor- 1n this study，social behaviors such as tance of habitat conditions in the evo- aggressive behavior，ch eliped-displays and lution of such displays. Copulatory copulatory behavior are described for 6 behaviors were observed in three grapsoid species that occur in open to verti- species，but precopulatory courtship cal habitats: Helicetridens (de Haan，1835) was absent. and H. japonica K. Sakai & Yatsuzuka，1980 inhabiting open mud flat (Omori et al. ， 1997) H elice leachi Rathbun 1931 Introduction ， ， ， Chasmagnathus convexus de Haan，1833 and Brachyuran species of the superfamily Chiromantes dehaani (H.Milne Edward， Ocypodoidea and Grapsoidea mostly live in 1853) inhabiting structured habitats such as intertidal to supratidal areas，but they gener- salt marsh or mangrove (Nakasone，1977; ally differ in habitat conditions. Many ocy- Fukui & Wada，1983 )， and Perisesarma podoids occur in exposed habitats ，such as bidens (de Haan，1835) inhabiting transition- sand beaches and mud/sand f1 ats ，whereas al habitats from structured to open habitats many grapsoids occur in more structured (Nakasone，1977; Fukui & Wada，1983) . vertical habitats，such as rocky shores， 1nterspecific comparisons of the behavior beneath stones or in vegetation. Given such patterns are made to explore the relation- habitat conditions，social behaviors of grap- ships with taxonomic group and habitat con- soid crabs have been described for few ditions. species (Kramer，1962; Warner，1970; SOC凶L BEHAVIORS OF GRAPSOID CRABS 57

Table 1. List of species studied，observation sites and periods. Species Site Period Family Varunidae H elice japonica Doki Ri ver Estuary，Kagawa Pref. 24，25/ August，8- 10 /September / (34 0 18' N ，133 0 48' E) 2003; 16-18/ May，15 ，16/ June /2004; 19-21 /April ，2005 (13 days) Helice leachi Funaura，Iriomote Is. ，Okinawa Pref. 16-21 /April /2004 (6 days) (24 0 23' N ，123 0 49' E) H elice tridens Kushida Ri ver Estuary，Mie Pref. 16 ，28-29/ April ，1 5-17 /May ，12-14 ， (34 0 36' N ，136 0 35' E) 27-29/ June /2003 (13 days) Chasmagnathus convexus Kogi Ri ver Estuary，Osaka Pre f. 20-23/ June /2005 (3 days) (34 0 26' N ，135 0 21' E) Family Sesarmidae Chiromantes dehaani Kogi Ri ver Estuarγ ，Osaka Pref. 19-21/ July，14 ，1 8，19 ，August /2004; (34 0 26' N ，135 0 21' E) 19 ，22，23 /July ，21 ，22 /July /2005 (11 days) Perisesarma bidens Kogaura，Shirahama ，Wakayama Pref. 3，4/ July，3 ，4 / August ，18 ，19/ (33 0 40' N ，135 0 22' E) September /2004; 9-11 /June ，4， 5 / August /2005 (11 days)

Table 2. Elements of fighting behaviors and the number of occasions observed for each element in 6 grapsoid species. Varunidae Sesarmidae Helice tridens Helice japonica Helice leachi Chasmagnathus Chiromantes Perisesarma bidens convexus deh ωnI 1) Grasping 12 33 3 7 46 26 2) Arm-flexed pushing 27 29 5 3) Arm-extended pushing 4 4) Leg-touching 2 1 6 3 52 5) Dash 3 20 14 2 11 89 6) Striking 4 12 37 63 7) Leg-tapping 72 Total 48 58 18 27 198 235

Materials and Methods of the behaviors were as follows. Fighting Four species of the family Varunidae， behavior is an agonistic interaction between Helice tridens ，H. jαponica，H. leachi， two individuals with physical contact，and Chasmagnathus convexus，and 2species of with one individual aggressively approach- the family Sesarmidae， Chiromantes ing the other. Waving displays are rhythmi- dehaani，Perisesarma bidens were observed cal motions of chelipeds. Cheliped-display is in the field for 3-13 days at each one loca- anon-waving display，with acrab moving its tion between 2003-2005 (Table 1). chelipeds repetitively in same locus. Observations were made only during day- Copulatory behavior is copulation and asso- time low tides，aided by adigital video cam- ciated behaviors occurring preceding or fol- era (SONY DCR・TRV30). 羽Tefocused on lowing copulation. When either of these three types of social behavior; fighting，dis- social behaviors was observed，sequential plays with chelipeds including waving dis- events were noted. The crabs that per- plays，and copulatory behavior. Definitions formed the social behaviors were sexed in 58 y. NARAET A L. case when the sex could be determined Three elements of fighting behavior could from the extemal feature. be distinguished as grasping，leg-touching ， and dash. All three elements were per- formed in the same way as in H. tridens. Results Successive occurrence of the elements was Fighting behαmor observed as dash to grasping. Among the three elements，dash occurred most com- Helice tridens :A total of 48 encounters monly. were observed during 13 days (Table 2). Five elements of fighting behavior could be Chαsmagnathus convexus :A total of 27 distinguished as follows. 1) Grasping (Fig encounters were observed during 3days 1-A): one extends its chelipeds to the ぐrable 2). Four elements of fighting behav- opponent and grasps it ，or both crabs grasp ior could be distinguished as grasping，leg- each other. They grasp any part of the body， touching，dash ，and striking. Grasping 1) ， induding the carapace ，walking legs ，and leg-touching 4) and dash 5) were made in chelae. 2) Arm-f1 exed pushing (Fig 1-B): the same way as in H. tridens. 6) Striking one or bo出 crabs push against the opponent was made in the same way as in H. japonica. using the outer faces of chelae. 3) Arm- Successive occurrence of the elements was extended pushing (Fig 1-C): two crabs observed as 4) to 1) or 6) ，6) to 1) ，and 5) to stand at ac1 0se distance facing each other， 6). Among the four elements，striking with their both chelipeds extending to the occurred most commonly，compared to the side ，so that their chelae sometimes touch. other three elements. 4) Leg-touching (Fig 1-E): one of walking legs is rapidly extended to make contact Chiromantes dehaani :A total of 198 with the opponen t. 5) Dash: one crab makes encounters were observed during 11 days adash for the opponent without any physical ぐfable 2). Six elements of fighting behavior contact. Successive occurrence of the ele- could be distinguished as grasping，arm- ments was observed as 4) to 1) or 2) ，and 2) flexed pushing，leg-touching ，dash ，striking ， to 3). Among the five elements，grasping and leg-tapping. Grasping 1) ，arm- f1 exed and arm-f1 exed pushing occurred more com- pushing 2) ，leg-touching 4) and dash 5) were monly，compared to other three elements. made in the same way as in H. tridens. Striking 6) was made in the same way as in Helice japonica :A total of 58 encounters H. japonica. 7) Leg-tapping (Fig 1-F): one were observed during 13 days (Table 2). crab touches the opponent by some walking Four elements of fighting behavior could be legs and vibrates them rapidly on the oppo- distinguished as grasping，leg-touching ， nen t. Successive occu汀 ence of the elements dash，and striking. Grasping 1) ，leg-touching was observed as 1) to 7) or 6) ，2) to 1) or 6) ， 4) and dash 5) were made in the same way 4) to 1) ，2) ，6) or 7) ，5) to 1) ，6) or 7) ，6)ω as in H. tridens. 6) Striking (Fig 1-D): one 1) ，and 7) t01). Among the six elements，leg- crab raises both chelipeds，and down toward tapping occurred most commonly，compared the opponent like scratching. Successive to other five elements. occurrence of the elements was observed as 4) to 1) or 6) ，5) to 1) ，and 6) to 1). Among Perisesarma bidens A total of 235 the four elements，grasping and dash encounters were observed during 11 days occurred more commonly，compared to σ'able 2). Five elements of fighting behavior other two elements. could be distinguished as grasping，arm- f1 exed pushing，leg-touching ，dash ，and Helice le αchi :A total of 18 encounters striking. Grasping 1) ，arm-flexed pushing 2) ， were observed during 6days (Table 2). leg-touching 4) and dash 5) were made in SOCIAL BEHAVIORS OF GRAPSOID CRABS 59

B

C

E

F

Fig. 1. Fighting elements observed in six grapsoid species. A ，grasping in Helice tridens; B ，arm-flexed pushing in Helice tridens; C ，arm-extended pushing in Helice tridens; D ，striking in Perisesarma bidens; E ，leg-touching in Helice tridens; F ，leg-tapping in Chiromantes dehaωu . Arrows indicate the movement of chelae or walking leg. Drawings are traced 仕omvideotapes. 60 Y. NARAETAL

A. Non-forward vertical w avin g

2 3

osec 2.17 sec . 3.00 sec.

B. Forward verticalwaving 2 3

os ec . 1. 67 sec.

C. Side-by-side 2 3

1. 18 sec. os ec . 0.56 seι

D. Chela-quivering

Fig. 2. Cheipeds-using display observed in Helice tridens ，H. japonica ，and Perisesarma bidens. A ，no ル forward vertical waving in Helice tridens; B ，forward vertical waving in Helice japonica; C ，side-by-side in Perisesarma bidens; D ，che la-quivering in Perisesarma bidens. Arrows indicate the movement of chelae. Values below crabs indicate time in sec 仕omthe initial posture (the mean value of ten waves). SOCIAL BEHAVIORS OFGRAPSOID CRABS 61

the same way as in H. tridens. Striking 6) 2-B) ，and bo出 chelipeds raised forward and was made in the same way as in H. japonica. somewhat extended in front of the body Successive occu汀 ence of the elements was (p osture 2in Fig 2-B). Then the chelipeds observed as 4) to 1) ，2) or 6) ，5) to 1) ，and 6) were lowered back to the initial position in to 1). Among the five elements，dash the same way in which they were elevated occurred most commonly，compared to (p os加 re 3in Fig 2-B). Non-forward ve此ical other five elements. waving (N = 14) was more common than for- ward vertical waving (N = 2). Non-forward Interspecific comparison of the fighting vertical waving was performed by both elements revealed that grasping，leg-touch- males (N = 3) and females (N = 11) ，but for- ing and dash occurred commonly in all 6 ward vertical waving was only seen with species，whereas arrn-extended pushing was females. Both types of waving displays were only found in H. tridens and leg-tapping only observed in the presence of neighboring in 仁 dehaani. crabs (N = 4in non-forward vertical waving， N = 1in forward ve凶cal waving) as well as Cheliped-displays in their absence (N =10 in non-forward verti- cal waving，N = 1in forward veはical waving). Waving display Waving display was at no time observed Helice tridens :A total of 29 bouts of suc- in Helice leachi ，Chasmagnathus convexus， cessive waving displays was recognized. Chiromantes dehaani，or Perisesarma bidens This display was performed with both che- during the field observations. lipeds. Both chelipeds at the beginning remained flexed in front of the buccal region Other displays (posture 1in Fig 2-A) ，and the chelipeds Perisesarma bidens :Cheliped-displays were moved up vertically to eyestalk level other than waving could be recognized as with the tip of chelae pointing downward in side-by-side (Fig 2-C) and chela-quivering the front of body (posture 2in Fig 2-A). (Fig 2-D). In side-by-side ，both chelipeds Then the chelipeds were lowered back to were moved together across the front of the the initial position in the same way in which body. In chela-quivering，one flexed che- they were elevated (p osture 3in Fig 2-A) liped was vibrated in front of the body. (non-forward vertical waving). Waving was Side-by-side display was observed only in performed by both males (N =6) and males (N =11). Thedisplay occurred often females (N =16). The display occurred in before and after encounters with neighbor- the presence of neighboring crabs (N = 18) ing crabs，iム before fighting (N = 2) ，after as well as in their absence (N = 4). In most fighting (N =6) ，and when approaching each of the former case，waving was performed other (N = 2). before or after encounters with neighboring Chela-quivering display was observed in crabs，i.e. ，before and after fighting (N = 6) ， both males (N =45) and females (N =7). after mating behaviors (N = 3) ，and as they Thedisplay occurred often before and after withdrew after approaching each other (N = encounters with neighboring crabs，i.e. ， 6). before fighting (N =1) ，after fighting (N = 39) ，and when approaching each other (N = Helice japonicα: A total of 16 bouts of 3). successive waving displays was observed. In H. trides ，H. japonica ，H. le αchi ，仁 con- Waving in c1 uded two types of non-forward vexus ，and C. dehaani，the cheliped-display vertical waving as in H. tridens and forward other than waving was at no time observed. vertical waving. In forward vertical waving， both chelipeds initially remained flexed in front of the buccal region (p osture 1in Fig 62 Y.NARAETAL.

Copulatory behavior Chiromantesd ehaani :A total of 10 incomplete copulations were observed Helice tridens :A total of 33 copulations aboveground during daytimes pring tides ， w ere observed，all occurring aboveground around spring tide in the mid to late June in 2003. Copulating pairsw erefound both in vegetated and non-vegetat edareas. During the study period，no pairs were found in 95 burrowsex aminedby digging. No courtship display prior to copulation was observed. At fir st ，a mal eran quickly to awandering female，grasping her with his chelipeds. Then he lay on his back，keeping her motionless，and lified her to face each other. Finally they openedth eir abdomens to sta rt copulation. Copulatory position was always female-uppermost (Fig. 3). Thebod- ies of copulating pairswere always hard， indicating that they were in th eintermoul t. Copulation duration was 6minut es for one case observed from sta rt to the finish ，and 3 secondsto 32 minutes for 11 cases observed from the partway to th ee nd. After copulation，th epair separated(N = 8) ，staye dtogether at the copulating site (N =1) ，or the male guarded the female by Fig. 3. Copulating pai rin H elice tridens. overlying her (N = 2) (Fig.4). Copulatory position isfemale-upperrnost

A . B .

Fig.4. Postcopulatory guard in gof afemale by amal eH eli ce tri 冶 ns. A ，female on the surfa ce; B ，fema le partly buried in mud. SOCIAL BEHAVIORS OF GRAPSOID CRABS 63

Table 3.Fighting elements that have bee nreported in grapsoid species .Dash of non-physical co ntact is not shown because its occu 汀 ence is equivoca l. Fighting elements Source A B C D E F G Gecarcinidae Cardisoma guanhumi + + + Henning (1975)

Grapsidae Grapsus grapsus + + Kramer (1967) ，Schone (1968) Goniopsis cruentatus + + + + Schone (1968) ，Warner (1970) Pachygrapsus crassiPes + + + Schりne (1968) ，Hiatt (1948) Pachygrapsus transversus + + Abele et a l. (1986)

Varunidae Chasmagnathus convexus + + + Present study Helice crassa + + + Beer (1958) ，Sch りne (1968) Helice japonica + + + Present study Helice leachi + + Present study Helice tridens + + + + Present study Hemigrapsus oregonensis + + + Lindberg (1980)

Sesarmidae Aratus pisoni + + Warner (1970) Chiromantes dehaani + + + + + Present study Perisesarma bidens + + + + Present study Armases cinereum + + + + Seiple & Salmon (1982) Sesarma reticulatum + + + Seiple & Salmon (1982) Fighting elements : A， grasping; B ， arm-fle 況ed pushing; C ，arm-extended pushing; D ，s廿 iking; E，arm- tapping; F，leg-touching; G ，leg-tapping

from mid July to mid August in 2003 and 百le male held the female's body and tilted from late June to late July，in 2004. At first ，a back to the ground to copulate，but she fled male ran quickly to awandering female and away soon in all 4cases. Copulatorγposition grasped her without any courtship.Th en he was always female-uppermost，and the bod- leaned back，holding her carapace in aface- ies of copulating pair were always hard. to-face position. He opened his abdomen and Copulatory behaviors were at no time attempted to copulate，but she fled in all 10 observed in Helice jゆ，onica，H. leachi，or cases. Copulatory position was always Chasmαgnathus convexus during the field female-uppermost，and the bodies of copulat- observations. ing pair were always hard.

Perisesarma bidens :A total of 4incom- Discussion plete copulations were observed on the sur- Fighting behavior face during daytime spring tides in early All6 species investigated in the present August in 2004 and in 2005. At first ，a male study perform grasping. Previous studies of ran quickly to awandering female and Grapsoidea have reported grasping behavior grasped her without any previous courting. (see Table 3). Grasping is ，therefore ，regard- Themale then overlaid the female，changing ed as the most common element of fighting his body direction to aface-to-face position. behavior in grapsoids. In addition ，grasping 64 Y.NARAETAL is also well known in many other families of performed side-by-side and chela-quivering Brachyura (Schりne，1968; Vannini & Sardini ， displays. Grapsoid species that have been 1971; Crane，1975; Swartz，1976; Lindberg & previously reported to perform waving dis- Frydenborg，1980; Bergamo et al. ，1988; play are Grαρ sus graρsus (Kramer，1967) ， Kitaura & Wada，2004). Arm-flexed pushing， Goniopsis cruentata (Schone，1968) and striking and leg-touching are also common Pachygrapsus transversus (Abele et al. ，1986) elements in grapsoid behavior (Table 3). of the family Grapsidae，Hemigrapsus orego- Only Helice tridens performs arm-extended nensis (Li ndberg，1980) ，MetaPlax crenulαt α pushing and only Chiromantes dehaani per- (Beinlich & Polivka，1989) ，M. distincta forms leg-tapping，and both of these ele- (Kitaura et al. ，2002) ，M. elegans (Kitaura et ments have so far only been recorded in one al. ，2002) and M. indicus (Pretzmann，1971) species of grapsoids (Table 3). Arm-tapping of the family Varunidae，Sesarma eumolPe is known only in Armases cinereum (Table (Hartnoll，1969) and Aratus pisoni (Warner， 3). Thus，arm-extended pushing，arm-tap- 1970) of the family Sesarmidae. ping and leg-tapping are rare elements in Consequently，there appears to be no corre- grapsoids. lation between occu打 ence of waving display Thepresent study revealed that fighting and the taxonomic group. behavior of H. tridens comprises five ele- On the other hand，occurrence of che- ments，H. jaρonica four elements and H. liped-displays seems to be related with habi- leachi three elements. Fighting behavior of tat conditions. 1n 6species observed in this H. cr ω，sa is known to have at least three ele- study，H. tridens and H. japonica that occur ments (Beer，1959). Although these four in exposed habitats (Omori et al. ，1997) ，like species belong to Helice ，elements of fight- many ocypodoid crabs，used waving dis- ing behavior exc1 uding dash di 旺" e r consider- plays，but Helice leachi ，Chasmagnathus con- ably among them ぐfable 3). vexus and Chiromantes dehaani that occur in Comparison of the present observations more structured habitats like cobble stones wi出 other grapsoid species has also shown or mangrove roots (Nakasone，1977; Fukui no fighting elements unique at the family & Wada，1983) exhibited no waving. 1n addi- level (see Table 3). For instance ，leg-tapping tion ，Perisesarma bidens ，which occurs in that was found in C. dehaani but not in transitional areas from structured to unstruc- Perisesarmα bidens ， is known in tured habitats (Nakasone，1977; Fukui & Pachygrapsus transversus of the family Wada，1983) ，showed side-by-side and chela- Grapsidae (Abele et al. ，1986). Arm-extend- quivering displays. These cheliped-displays ed pushing that was found in H. tridens ，but were similar to waving，but simpler and less not in other Helice species，is known in conspicuous. 1n addition ，species of Aratus ρisoni of the family Sesarmidae MetaPlax inhabiting open mud flat like many (Warner，1970). Grapsus grapsus of the fami- ocypodoid are known to perform waving dis- ly Grapsidae has the same elements of fight- plays (pretzmann，1971; Beinlich & Polivka， ing behavior as H. le αchi of the family 1989; Kitaura et al. 2002). These findings Varunidae (Kramer，1966). Similarly，the support the hypothesis that habitat plays an same elements of fighting behavior are important role in the evolution of cheliped- observed between Helice japonicαa n d displays for visual communication. Other Chαsmagnathus convexus. Fighting behavior ecological factors ，such as diurnal activity patterns in grapsoid crabs appear to have no and feeding proximity to shelters，suggested relationship with family group. by Salmon & Atsaides (1968) ，may also have contributed to the evolution of cheliped-dis- Cheliped・display plays ，but available data on these factors are Helice tridens and H. japonica performed insu血cient to be discussed for the present 6 waving displays ，and only Perisesarma bidens specles. SOCIAL BEHAVIORS OF GRAPSOID CRABS 65

Cheliped-dispays observed in H. tridens ， thanks also go to Dr. M. Ishimura and Mr. H. jaρonica and P. bidens often occurred T. Watanabe who kindly provided construc- before and after fighting and at no time tiv eadvice for this study. Members of the before copulation.τbese displays，ther efore， Laboratory of Population and Community do not seem to function as courtship as do Ecology，Nara Women's University provided waving displays in ocypodoid species. support for our study. D r. Colin L. McLay kindly reviewed an early draft of the paper. Copulatoηbehavior This work was partly supported by a Copulatory behavior was observed in Research Fellowship of the ]apan Society for H elice tridens ，Chiromant es dehaani and the Promotion of Science for Young P erises arma bidens.These species，which Scientists to ]K differ in habitat type，did not perform courtship displays prior to copulation. Typically，in grapsoid species，a male quick- Li terature Cited ly approaches afemale without any previous Abele，L. G. ，Campanella ，P. J. ，& Salmon，M. ， courting and grasps her (Brockerhoff & 1986. Natural history and social organization McLay，2005). The only grapsoid species of the se miterrestrial grapsid crab Pachygrapsus transv ersus (Gibbes). Journal of that have been reported to exhibit courtship Experimental Marine Biology and Ecology， displays prior to copulation are G ec arcinus 104: 153-170 laterα，lis (K1aassen，1975) ，Goniops ぬcruenta- B eer ，C. G. ，1959 .Notes on the behavior of two ta (Schりne，1968) ，Grapsus grapsus (Kramer， estuarin ecrab species .Transaction of the 1962) ，and Sesarma eumolρe(Hartnoll ， Royal Society of New Zealand ，86: 197-203. 1969) ，all of which occur in structured habi- Beinlich ，V. B. & Polivka ，R.， 1989. Zur optischen und vibratorisch en ba!z von Metaplax crenula - tats ，such as rocky shore or salt mash. 百l U S， ta (Gerstaecker， 1856) (Crustacea， occurrence of precopulatory courting is not Brachyura， Grapsidae). Zoologischer related to habitat conditions. Anzeiger，223: 157-164. In all of three species for which copulato- Bergamo，P. ，Fiorito ，G. & Miralto ，A.， 1988. An ηb e h a v i o r was observed，copulatory posi- analysis of the agonistic behaviour of tion was female-uppermost and the copulat- Carcinus mediterraneus (Czerniavsky) ing female was in the intermolt. Both of (Crustacea ): fighting and ritualiza- tion. Monitore zoologico italiano (N.S.) 22: these characteristics are commonly known ， ， 315-322. in other grapsoid species udsen 1964; (Kn ， Brocker hoff，A.M. & McLay，C. L.， 2005a. Yaldwyn，1966; Nye，1977; Fukui，1994; Comparative analysis of the mating strategies Kobayashi，1999). On the contrary，the post- in grapsid crabs with special refere nces to the copulatory guarding by male observed in H. intertidal crabs Cyclograpsus lavauxi and tridens has so far been reported only in two Helice crassa (Decapoda: Grapsidae) from species in grapsoids，i. e. ，Hemigrapsus New Zealand. Journal of Biology， 25: 507-520. crenulatus (Brockerhoff & MacLay，2005a) Brockerhoff，A. M. & McLay，C. L.， 2005b. Mating and (Brockerho Mc y H. sexdentatus 宜& La ， behaviour，female rec eptivity and male-male 2005b) .Postcopulatory guarding of female， competition in the intertidal crab Hemigrapsus which has been well known in ocypodoid sexdentatus (Brachyura: Grapsidae). Marine crabs in underground mating (Christy & Ecology Progress Series ，290: 179-19 1. Salmon，1984; Murai et al. ，1987) ，appears be Christy，]. H. & Salmon，M .，1984 .Ecology and limited in grapsoid species. evolution of mating systems of fiddler crabs (genus Uca). Biological Review，59 ・483-509. Crane，J .，1975 .Fiddler Crabs of the World. Acknowledgements 736pp. ，Princeton University Press，Prin ceto n， New Jersey. Wethank Drs.Y. Yusa and M. Sato for Fukui，Y.， 1994.Mating behavior of the grapsid their valuable comments on this study. Our crab ， Gaetice depressus (De H aan) 66 Y.NARAETAL

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