Faculty Profiles - KOGA Tsunenori

Published Papers - KOGA Tsunenori

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Parasite and Species Richness : Association of Scopimera globosa (Crustacea: Decapoda: Ocypodidae), Batillaria cumingi (Mollusca: Gastropoda: Potamididae) and Gynaecotyla squatarolae (Trematoda: Digenea: Microphallidae)

KOGA Tsunenori

Japanese journal of benthology ( 日本ベントス学会誌編集委員会 ) 57 67 - 70 2002 [Refereed]

DOI

Functional Assessment for Restoration of Intertidal Sandy and Muddy Flat Ecosystems(<SPECIAL ISSUE> Restoration of Ecosystems)

YABE Tohru, NOHARA Seiichi, UTAGAWA Hirokatsu, SATAKE Kiyoshi, HIROKI Mikiya, UENO Ryuhei, KAWACHI Masanobu, WATANABE Makoto, KOGA Tsunenori

Landscape Research Japan Online ( The Japanese Institute of Landscape Architecture ) 65 ( 4 ) 286 - 289 2002 [Refereed]

The restoration of the wetland ecosystems is an essential problem in the world, however, the evaluation technique for the functions of ecosystems, especially in the intertidal wetlands, has not been established still in spite of the ecosystems adjoining with the human life. The Functions of a wetland tend to roughly correspond with characteristics of both the water and sediments of the wetland. In this study, the 13 intertidal sandy and muddy flat wetlands were selected from Hokkaido to Okinawa, and the indicators for water and sediments were investigated as a first step of the functional ecosystem assessment in Japan. The classification for traditional landform subclass, i.e. fore-beach, estuary and lagoon, was unclearly changeable, and it often did not agree with the functional classification. In the intertidal sandy and muddy flat wetlands in Japan, the subclass for HGM Approach should be set corresponding to the characteristics of influent water and sediments, and it was considered that the ecosystem evaluation should be carried out in each Hydrogeomorphic Unit classified at smaller-scale than the original HGM Approach in U.S..

DOI

Male-biased predation of a fiddler crab

T Koga, PRY Backwell, JH Christy, M Murai, E Kasuya

ANIMAL BEHAVIOUR ( ACADEMIC PRESS LTD ) 62 ( 2 ) 201 - 207 2001.08 [Refereed]

Great-tailed grackles, Quiscalus mexicanus, prey on fiddler crabs, Uca beebei, either by running straight at them or by running past them then angling sharply back to strike. Grackles that used angled runs caught only males and were twice as successful as birds that used straight runs and caught equal numbers of males and females. Why do grackles that use angled runs catch only males? Males were not differentially available, nor did grackles prefer them to females in choice tests. Fewer crabs entered their burrows when we moved a model predator past them than when we moved it directly towards them and crabs allowed the model to get closer when it passed then returned to strike. Although crabs may take more risks when birds use angled runs, the sexes did not differ in their escape responses. Hence, differential risk taking cannot explain male-biased predation by birds using angled runs. We suggest that males, with their large claws and lighter colours, are more conspicuous than cryptic females. When a bird runs past then turns to dash back at a crab it may be able to keep track of a male much better than a female. Indeed, grackles missed all females they struck at using angled runs. Hence, males may be conspicuous and preferred prey to birds using angled runs. Males' enlarged claws, bright colours and other sexually selected traits may increase male predation rate in this context. (C) 2001 The Association for the Study of Animal Behaviour.

DOI

千葉県の東京湾沿岸部と和歌山県和歌川河口干潟で得られたコメツギガニに寄生するMicrophallidae（扁形動物門：吸虫綱）の被嚢幼虫について。（共著）

木船悌嗣, 古賀庸憲

長崎県生物学会誌 ( 長崎県生物学会 ) 53, 50-53 ( 53 ) 50 - 53 2001

On the metacercariae of three species of the genus Maritrema (Trematoda: Microphallidae) found in Scopimera globosa inhabiting on three main islands of the Ryukyus

Transactions of the Nagasaki Biological Society (53): 12-16 2001

Burrow defense behaviors in a sand-bubbler crab: Scopimera globosa, in relation to body size and prior, residence

M Takahashi, N Suzuki, T Koga

JOURNAL OF ETHOLOGY ( JAPAN ETHOL SOC ) 19 ( 2 ) 93 - 96 2001 [Refereed]

The burrow defense behaviors in a sand-bubbler crab, Scopimera globosa, living on a tidal flat, were experimentally examined. Body size and prior residence influenced the results of struggles for the burrows, and large individuals or the burrow owners won in most cases when the intruders were not significantly larger than the owners. Most large owners defended their burrows by directly fighting their opponents. On the other hand, small owners defended their burrows in three different ways. (1) Owners fought directly against same-sized or smaller intruders. For larger intruders, (2) most owners returned to their burrows when the owner was nearer to the burrow than the intruder (returning behavior), and (3) owners sat motionless when the intruder was nearer to the burrow than the owner (sitting behavior). Success ratios of the three types of burrow defense were 38.2%, 88.5%, and 100%, respectively, It was considered that sitting behavior of the cryptically colored S. globosa has evolved because intruders cannot see motionless owners and consequently cannot detect the owner's burrow.

DOI

南西諸島のコメツキガニに寄生するMaritrema属（吸虫綱：Microphallidae）の嚢幼虫３種について。（共著）

木船悌嗣, 古賀庸憲

長崎県生物学会誌 ( 長崎県生物学会 ) 53, 12-16 ( 53 ) 12 - 16 2001

Underground mating in the fiddler crab Uca tetragonon: the association between female life history traits and male mating tactics

T Koga, M Murai, S Goshima, S Poovachiranon

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY ( ELSEVIER SCIENCE BV ) 248 ( 1 ) 35 - 52 2000.05

Brood size and other life-history traits of females affect male investment in mating. Female Uca tetragonon, producing relatively small broods, were attracted to the burrows of males for underground mating (UM) while carrying eggs, Most UM females released larvae and ovulated new broods during the pairing, averaging 3.9 days. While a female was incubating one brood, another brood was developing within the ovaries because the females were feeding adequately during incubation. These findings suggest that in U. tetragonon, a small-brood species, females increase the total number of broods produced by breeding continually. In contrast, in large-brood species, feeding by ovigerous females is relatively brief and not enough to prepare the next brood during incubation, inducing temporal separation between incubation and brood production. Unlike females in other ocypodids where females with large broods remain in thr breeding burrows of males, most female U. tetragonon left the male after UM. Wandering in female U. tetragonon after the pairs separate may occur because their small broods are adequately protected by an abdominal flap. Relative brood size probably determines the vulnerability of the incubated broods to the females' surface behavior. Hence, male reproductive success in large-brood species may decrease greatly if males expel their mates after ovulation, although this is not necessarily so in small-brood species. Whether the male drives away the female or not may depend on which behavior within tither small- or large-brood species yields the greater male reproductive success. In U. tetragonon some females extruded eggs in their own burrows after surface mating as well as in males' burrows after UM. It was unclear whether females chose a male with a larger burrow as an UR I mate unlike several large-brood species. Burrows of both UM males and ovigerous females in U. tetragonon were relatively smaller than those in some large-brood species, indicating that incubation of small broods does not require large burrows. Rather than benefits of UM by female choice, wandering resulting from intersexual conflict, and sperm competition may explain why some females mate in males' burrows in this small-brood species. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI

Male-male competition and intersexual interactions in underground mating of the fiddler crab Uca paradussumieri

T Koga, M Murai, HS Yong

BEHAVIOUR ( BRILL ACADEMIC PUBLISHERS ) 136 651 - 667 1999.06

We investigated inter-male competition for female mates and intersexual interactions in underground mating (UM) of the fiddler crab Uca paradussumieri. Males search for and then enter the burrows of females that are ready to ovulate ('pre-ovigerous'). In order to ensure their paternity, these males guard the female until she ovulates the following day. Thereafter the male leaves. Intruding male conspecifics attempt to reach the female. Guarding males either fight with them (N = 27), or use the flat-claw defence (N = 96) in which the male stands in the burrow shaft and blocks the entrance with his enlarged claw. The flat-claw was a very successful defence tactic (93% success), even when the intruder was larger than the guarding male. Pre-ovigerous females accepted the first male to enter her burrow, suggesting that female mate choice does not occur. Though males that succeeded to enter the burrow of pre-ovigerous female were larger than males that failed to do so, males that succeeded UM were not larger than males that failed UM. Males that succeeded UM by a take-over were not larger than either the males that were defeated or the males that succeeded in UM after their first entering. Early localization of pre-ovigerous females was important in male mating success, as was a male's ability to defend the female before she ovulated. However, some females that were not pre-ovigerous were guarded forcibly for 2 days by males that had failed to pair with a pre-ovigerous female that day. Prolonged guarding was less successful for males than guarding for one day, probably because the males had to fight with more intruders. Ln addition, prolonged guarding may not be adaptive for females because they lose feeding time and mate with males that lack competitive abilities.

Metacercaria of Microphalloides japonicus (Digenea : Microphallidae) found in Ilyoplax pusilla (Decapoda : Ocypodidae) on the seashore of the eastern part of Fukuoka City, Kyushu, Japan(共著)

Transactions of the Nagasaki Biological Society 50 5 - 8 1999

「福岡市東部沿岸産チゴガニに寄生するMicrophalloides japonicusの被嚢幼虫(吸虫網:Microphallidae)」(共著)

木船悌嗣, 古賀庸憲

「長崎県生物学会誌」 ( 長崎県生物学会 ) 50 ( 50 ) 5 - 8 1999

Reproductive success and two modes of mating in the sand-bubbler crab Scopimera globosa

T Koga

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY ( ELSEVIER SCIENCE BV ) 229 ( 2 ) 197 - 207 1998.11

Reproductive success of male (number of eggs fertilized by sperm of the male) and female (number of eggs extruded by the female) sand-bubbler crab, Scopimera globosa, was investigated in a field enclosure. The number of eggs extruded by females was positively correlated with their body size. Small males significantly tended to mate on the surface (surface mating, SM), while large males did so inside male burrows (underground mating, UM). The success ratio (matings per courtship) of UM (32%) was significantly lower than that for SM (69%). However, UM was more likely to be followed by oviposition (61%) than was SM (17%). These findings concur with previous studies suggesting that most females performing UM were ready for ovulation but those performing SM were not. During the study, 79% of eggs were fertilized by UM males, 10% by SM males and 11% were extruded without the female mating (presumably using stored sperm). Both burrowless and burrow-holding females engaged in SM, but only burrowless females engaged in UM. Discrete response of females to male mating attempts depending on females' occupancy of burrows is therefore an important factor in the maintenance of alternative mating tactics in male S. globosa. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

DOI

Elevated predation risk changes mating behaviour and courtship in a fiddler crab

T Koga, PRY Backwell, MD Jennions, JH Christy

PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES ( ROYAL SOC ) 265 ( 1404 ) 1385 - 1390 1998.08

The fiddler crab, Uca beebei, lives in individually defended burrows, in mixed-sex colonies on intertidal mud flats. Avian predation is common, especially of crabs unable to escape into burrows. Mating pairs form in two ways. Females either mate on the surface at their burrow entrance ('surface mating') or leave their own burrow and sequentially enter and leave ('sample') courting males' burrows, before staying in one to mate underground ('burrow mating'). We tested whether perceived predation risk affects the relative frequency of these mating modes. We first observed mating under natural levels of predation during one biweekly, semi-lunar cycle. We then experimentally increased the perceived predation risk by attracting grackles (Quiscalus mexicanus) to each half of the study site in two successive biweekly cycles. In each experimental cycle, crabs were significantly less likely to mate on the side with more birds. Moreover, on the side with elevated predation risk, the number of females leaving burrows to sample was greatly reduced relative to the number of females that surface-mated. Males waved less and built fewer mud pillars, which attract females, when birds were present. We discuss several plausible proximate explanations for these results and the effect of changes in predation regime on sexual selection.

Size-dependent mating behaviours of male sand-bubbler crab, Scopimera globosa: Alternative tactics in the life history

T Koga, M Murai

ETHOLOGY ( BLACKWELL WISSENSCHAFTS-VERLAG GMBH ) 103 ( 7 ) 578 - 587 1997.07

Factors leading to the separation of mating behaviours were investigated in the sand-bubbler crab, Scopimera globosa. The crabs mated on the surface (surface copulation, SC) and underground (UC). UC males mere large (old) whilst SC males were small (young). Burrowless females bred in the UC males' burrows. These females accepted UC in exchange for access to a burrow. UC occurred much more frequently than SC in the burrow area in which females oviposited. Most SC occurred in the water-saturated area affording a rich diet. SC was accepted by most large and small females in both areas and most UC by small females in the burrow area. SC was an alternative to UC for males in that there was a size dependence between types of copulation. These two mating behaviours involved different degrees of interaction with neighbouring males. Males attempting to carry a female to their burrows for UC were more often disturbed by other males than were males attempting SC. In the interaction for both UC and SC, larger males were likely to resist the disturbances. UC males needed their own burrows, bur these burrows were not enlarged before mating. UC males have a higher paternity of eggs than SC males, because SC males' sperm is often displaced by other males. Thus, UC was a behaviour with relatively higher costs and benefits for male crabs than SC behaviour, Alternative mating behaviours in male S. globosa are conditional, and explained by intrasexual interactions and a male life history strategy with a trade-off between growth and reproduction. It is nor likely that the size dependence of male mating behaviour is caused by mate preference of females for UC males in the burrow area.

Mate acceptance and guarding by male fiddler crabs Uca tetragonon (Herbst)

S Goshima, T Koga, M Murai

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY ( ELSEVIER SCIENCE BV ) 196 ( 1-2 ) 131 - 143 1996.03

The fiddler crab, Uca tetragonon (Herbst) mates both on the surface near female-defended burrows and underground in male-defended burrows. In underground mating, which requires relatively high male investment, males attract both non-ovigerous and ovigerous females into their burrows by claw waving. Males aggressively expel some females soon after they enter their burrows and others after pair formation, but before females spawn. Finally males guard some females in their burrows until they spawn, which presumably ensures paternity. Males do not select mates of a particular body size, but they do differentially accept females with late-stage eggs, those about to release larvae and spawn another clutch. Except at the beginning of the reproductive season, few ripe non-ovigerous females are available because females spawn successively and only in moderate synchrony. By differentially accepting late stage ovigerous females, males may increase their fertilization rates because they minimize the time they spend guarding each of their mates to ensure their paternity. A male-biased operational sex ratio and a high last male advantage in sperm competition are two conditions that may have favored male choice based on female guarding time in this species.

DOI

Metacercaria of Gynaecotyla squatarolae (Digenea : Microphallidae) found in Scopimera globosa (Decapoda : Ocypodidae) on the seashore of the eastern part of Fukuoka City, Kyushu(共著)

KIFUNE T

Transactions of the Nagasaki Biological Society 47 51 - 54 1996

「福岡市東部沿岸産コメツキガニに寄生する微小二生吸虫Gynaecotyla squataroaeの被嚢幼虫」(共著)

木船悌嗣

「長崎県生物学会誌」 47 51 - 54 1996

Predation and cannibalism by the male fiddler crab Uca tetragonon

T Koga, S Goshima, M Murai, S Poovachiranon

JOURNAL OF ETHOLOGY ( SPRINGER JAPAN KK ) 13 ( 2 ) 181 - 183 1995.12

COURTSHIP AND THE EVOLUTION OF UNDERGROUND MATING IN UCA TETRAGONON (DECAPODA, OCYPODIDAE)

M MURAI, T KOGA, S GOSHIMA, S POOVACHIRANON

JOURNAL OF CRUSTACEAN BIOLOGY ( CRUSTACEAN SOC ) 15 ( 4 ) 655 - 658 1995.11

Uca tetragonon is an Indo-West Pacific species of fiddler crab in the narrow-front (NF) species group. Male Uca tetragonon used display by claw-waving to attract females into burrows of males for mating. Pairing attempts by male Uca tetragonon attracting conspecific females into their burrows occurred in 2 different ways. In type 1, males entered their burrows after their mates did, and, in type 2, males entered their burrows first and their mates followed. Both types occurred with similar frequencies. Rate of pair formation and spawning rate of paired females were not significantly different between the 2 types. Nine of 20 females spawned in the pooled data from both types.
In Indo-West Pacific fiddlers, type 1 pair formation (female first) has been found in the 5 subgenera (NF and the broad-front species (BF) group) and type 2 (male first) previously only in the BF group, but now also in Uca tetragonon. Type 1 is common to all subgenera of Uca in the Indo-West Pacific, a criterion typical of ancestral characters. Since NF and BF groups are distinctly different in phylogenesis as well as in their ecology, type 2 pair formation is supposed to be a derived behavioral character in NF fiddlers, having evolved independently from the BF group.

MOVEMENTS BETWEEN MICROHABITATS DEPENDING ON REPRODUCTION AND LIFE-HISTORY IN THE SAND-BUBBLER CRAB SCOPIMERA-GLOBOSA

T KOGA

MARINE ECOLOGY PROGRESS SERIES ( INTER-RESEARCH ) 117 ( 1-3 ) 65 - 74 1995.02

Sand-bubbler crabs Scopimera globosa inhabit burrows in the upper tidal sand flat and form droves in the water-saturated area of the lower tidal flat. To elucidate the function of the movements between the microhabitats in this species, I investigated the change in population density, crab body size and reproductive conditions of both sexes within each microhabitat. Ovigerous females were found in the burrow area while spent females (releasing zoea recently) were concentrated in the water-saturated area. Gonad weights of nonovigerous females in the burrow area were higher than those in the water-saturated area. Both male and female crabs in the water-saturated area, where diet quality (organic nitrogen content of the surface substratum) exceeded that in the burrow area, spent more time foraging and suffered less from interactions with neighbours than crabs in the burrow area. In contrast, although both gonad and hepatopancreas weights of males decreased with time in the early to mid reproductive season, there was no difference in male body condition between microhabitats. Few crabs moved between the microhabitats in the mid to late reproductive season, indicating that most crabs active in the water-saturated area during low tides did not return to the burrow area during high tides, differing from the movements of other ocypodid species. S. globosa have alternative mating behaviours, underground copulation (UC) and surface copulation (SC). UC, followed by oviposition, was dominant in the burrow area, though both UC and SC were conducted there. In contrast, SC, not always followed by oviposition, was dominant in the water-saturated area. Females maximized their use of the microhabitats, i.e. the burrow area for mating, oviposition and incubation and the water-saturated area for foraging and partly for mating. The operational sex ratio was biased towards males in the burrow area and towards females in the water-saturated area, due to the fact that the last male to mate fertilizes most of the eggs extruded by a female. A high proportion of large (i.e. older) crabs of both sexes stayed in the burrow area during the reproductive season, whereas small (young) crabs spent most of their time in the water-saturated area for growth. Thus, the crabs made suitable use of their time in different microhabitats under a Life history strategy.

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Published Papers - KOGA Tsunenori