Responses of the egg-tending gobiid fish Valenciennea longipinnis to the fluctuation of dissolved oxygen in the burrow

Responses of the egg-tending male Valenciennea longipinnis (Gobiidae), a species inhabiting the near-shore moat on coral reefs, to the fluctuation of dissolved oxygen (D.O.) concentration in its enclosed burrow, were studied. D.O. concentration in egg-tending burrows decreased from high tide to low tide during the daytime. D.O. concentrations in 12 egg-tending burrows at low tide ranged from 2.17-4.50 ml D.O. L−1 (43.8-91.9% D.O. saturation) on the day after spawning. In the laboratory, an egg-tending male increased the frequency and duration of fanning as D.O. concentration decreased. Below about 1.2 ml D.O. L-1 (about 25% D.O. saturation), the frequency of fanning began to decrease. The frequency and duration of fanning increased with developmental stage of the eggs, perhaps in response to an increase in oxygen consumption of eggs with developmental stage. The rapid adjustments of fanning behavior to D.O. concentration in the burrow and developmental stage of the eggs showed indirectly that the primary role of fanning is a supply of oxygenated sea water to the eggs

Responses of the egg-tending gobiid fish Valenciennea longipinnis to the fluctuation of dissolved oxygen in the burrow

Responses of the egg-tending male Valenciennea longipinnis (Gobiidae), a species inhabiting the near-shore moat on coral reefs, to the fluctuation of dissolved oxygen (D.O.) concentration in its enclosed burrow, were studied. D.O. concentration in egg-tending burrows decreased from high tide to low tide during the daytime. D.O. concentrations in 12 egg-tending burrows at low tide ranged from 2.17-4.50 ml D.O. L−1 (43.8-91.9% D.O. saturation) on the day after spawning. In the laboratory, an egg-tending male increased the frequency and duration of fanning as D.O. concentration decreased. Below about 1.2 ml D.O. L-1 (about 25% D.O. saturation), the frequency of fanning began to decrease. The frequency and duration of fanning increased with developmental stage of the eggs, perhaps in response to an increase in oxygen consumption of eggs with developmental stage. The rapid adjustments of fanning behavior to D.O. concentration in the burrow and developmental stage of the eggs showed indirectly that the primary role of fanning is a supply of oxygenated sea water to the eggs

ホンベラHalichoeres tenuispinis (Günther)の日周活動,帰巣性,行動圏について

Honbera (wrasse), Halichoeres tenuispinis (Günther), 5～11 centimeters in total length are rocky reef fish and are abundant along the coast of northern Kyushu (Fig. 1). The authors studied the diurnal activity, homing ability and home range of the fish with a help of SCUBA. Results obtained are as follows: 1) The fish were active from sunrise to sunset and they were highly active during 1～2 hours after sunrise and l～2 hours before sunset (Fig. 3). At midday the number of fish observed within 100×4 m^2 study area decreased, because the fish hid themselves among the rocks and seaweeds (Fig. 5). 2) When the fish were highly active, in the morning and toward evening, schools of the fish appeared (Fig. 4). The members of the school swam over wide ranges along the shore line (Fig. 6), accordingly they were considered to be hovering individuals. 3) Besides the hovering individuals, the existence of sedentary individuals was made clear discriminating individuals by tagging method (Figs. 2, 8, Table 2). The sedentary individuals inhabited within a limited home ranges, and they did not form schools and did not swim around widely, and when displaced they returned to its home ranges (Fig. 7, Table 1). 4) There were not statistical differences in sex ratio and body length between hovering and sedentary individuals.九州北岸(Fig.1)の主要磯魚の1つであるホンベラについて,その日周活動,帰巣性,行動圏を体長5～11cmのものを対象として潜水観察し,以下のような結果を得た. 1) ホンベラの活動は,ほぼ日の出から日没までであるが,日の出後1～2時間,日没前1～2時間の1日2回特に活発である(Fig.3). 2) ホンベラは正午前後には海藻の間や岩影にひそむ.そのために潜水観察される個体数は少なくなる(Fig,5). 3) 朝夕の活動の活発な時刻には群れ行動がみられる(Figs.4,5).この群れ行動を示す個体は,ほぼ海岸線と平行に広範囲な移動を行なうことから,移動性の個体と考えられる(Fig.6). 4) 標識放流実験により,これら移動性の個体とは別に比較的狭い範囲に定着し,朝夕にも広範囲な移動を行なわない個体が存在することが明らかになつた(Fig.8,Table2). 5) 移動性の個体は,群れ行動の際には広い行動圏を示したが,定着性の個体はその行動圏が狭く,他の場所に放流すると従来の行動圏に帰巣性を示した(Table1,Fig.7).しかし縄ばり行動は認められなかつた. 6) 移動性と定着性の個体間では性別,体長について相違が認められなかつた(Table2)

ヘビギンポの繁殖生態と雄消化管内に出現する魚卵について

The triplefin, Enneapterygius etheostomus, is as mall reef fish attaining only 5 cm in total length. The fish is usually found solitarily on the shallow rocky reefs of southern Japan. Reproductive behavior of the fish was studied using SCUBA at Tsutsumi Island, Tsuyazaki (130'29'E, 33'47'N), Munakata, Fukuoka, during the period from July, 1985 through August, 1986. During the period, 175 specimens were collected with hand net and their gonadosomatic indices were obtained to know the spawning season. Digestive tract content of these specimens were examined and it was found that many conspecific eggs occur in the male digestive tract. The ratio of males which had eaten conspecific eggs and weight ratio of conspecific eggs to the total digestive tract content were obtained. The spawning season of the fish was considered to be from June through August from the gonadosomatic index analysis, but it was also pointed out that a part of the population reproduces in May and September. During the spawing season, the male exhibiting typical nuptial body color stayed within a very small territory of 0.2 m^2 for more than two weeks Maturation of the females which had home ranges around the male territory was not synchronous, but a small proportion of the female population matured almost everyday. Male courtship behaviors included figure 8 swimming and circling. Most of the spawnings were done by pair of a male and a female, but multi-female spawnings were also observed. Collection of eggs from the male territory showed that the male is guarding two or three clutches at the same time and it also showed that the adhesive eggs which take relatively long time to hatch almost always present in the male territory. From the digestive tracts of the male specimens, many conspecific eggs were found. The ratio of males which had eaten eggs averaged 37.9% of the specimens. The weight ratio of conspecific eggs to gut content attained 19.6% in wet weight. On the contrary, among 38 female specimens, only one individual was found to have eaten eggs. The gut content analysis showed that the males collected in the spawning season had eaten less than females collected in the same season and males collected before the spawning season. It was suggested that the males of E. etheostomus are eating their own eggs as energy source for egg-guarding during the spawing season.福岡県宗像郡津屋崎町鼓島において,1985年6月から1986年8月の間,へビギンポの繁殖生態を潜水観察した.得られた結果は以下のとおりである.(1)生殖腺脂数からみたへビギンポの繁殖期は6～8月であった.さらに,雄の婚姻色の発現,雄消化管からへビギンポの卵が出現することから5月および9月にも一部の個体は繁殖していることが明らかになった.(2)繁殖期になると雄は体色に黒味が増し,明瞭な3本の白色横帯が体側に現われ,非繁殖期とは著しく異なる婚姻色を呈した.(3)繁殖期には雄は約0.2m^2の狭いなわばりを持つが,鰭切除による個体識別により,平均2週間,最大43日間同一なわばりに留まることが明らかになった.これに対し,雌は雄のなわばりの周囲に比較的広い行動圏を持っていた.(4)繁殖行動は普通雄1尾,雌1尾のペアによって行われたが,雌2尾が同じ雄のなわばりで同時に産卵するのも観察された.雄の求愛行動としてfigure8 swimming,circlingを認めた.(5)卵は雄のなわばり内の海藻に産み付けられたが,産卵が終わると雄は卵を保護した.雄は複数の雌が産んだ卵を保護しており,任意に選んだ雄のなわばりから採集した海藻では,95.5%の頻度で卵が出現した.(6)繁殖期に採集した雄の消化管から多数のへビギンポ卵が出現した.卵を食べていた雄の割合は平均37.9%で,卵が消化管内容物に占める重量割合は平均19.6%であった.(7)繁殖期に採集した雄の体重当たりの消化管内容物重量は,繁殖期の雄および繁殖期の雌の値よりも低く,繁殖期の雄は充分に摂餌していないことが示唆された.(8)以上の結果から,繁殖期の雄の消化管より出現したヘビギンポ卵は,卵を保護しでいる雄が栄養補給のため自己の卵を食べたものと推測した

Seasonal change of egg size and number in the anemone fish, Amphiproin clarkii, at two different localities in the temperate Kyushu, Japan

The anemone fish, Amphiprion clarkii, is monogamous and spawns adhesive eggs in mass nearly at the same place, repeatedly during the warm months. The egg mass is laid on a flat hard substratu, protected by the tentacles of host sea anemone in one layer. This enables to count the total number of eggs in an egg mass after taking photography. These characteristics provide a good material to study seasonal change of egg production by a single female in temperature reef fishes. In the present study, egg numbers of clutches and egg sizes were monitored at two different places, one is at the southern end of Kyushu (Bohnotsu: 10 pairs) and the other was at the western end of Kyushu (Ushibuka: 12 pairs). The average water temperatures were slightly higher at B than U. Water temperature ranged 18.9-21.7℃ at B and 20.5-23.4℃ at U and the begeninng of spawning differed by pairs. The latest spawning also differed by pairs and confirmed to be at 25.7-29.3℃ at U, by pairs. The nuber of eggs spawned at one time by females was 1,925-5,989 at B and 483-5,535 at U were larger in the early part of spawning season and eggs sizes were apt to be larger during this period than the rest of spawning season. But, at B, where spawnnig season was slightly longer than U, the egg sizes showed a tendency to become larger again at the end of the spawing season

Reproductive Ecology of the Triplefin, Enneapterygius etheostomus, with Special Reference to the Occurrence of Fish Eggs in the Digestive Tract of the Male

The triplefin, Enneapterygius etheostomus, is as mall reef fish attaining only 5 cm in total length. The fish is usually found solitarily on the shallow rocky reefs of southern Japan. Reproductive behavior of the fish was studied using SCUBA at Tsutsumi Island, Tsuyazaki (130\u2729\u27E, 33\u2747\u27N), Munakata, Fukuoka, during the period from July, 1985 through August, 1986. During the period, 175 specimens were collected with hand net and their gonadosomatic indices were obtained to know the spawning season. Digestive tract content of these specimens were examined and it was found that many conspecific eggs occur in the male digestive tract. The ratio of males which had eaten conspecific eggs and weight ratio of conspecific eggs to the total digestive tract content were obtained. The spawning season of the fish was considered to be from June through August from the gonadosomatic index analysis, but it was also pointed out that a part of the population reproduces in May and September. During the spawing season, the male exhibiting typical nuptial body color stayed within a very small territory of 0.2 m^2 for more than two weeks Maturation of the females which had home ranges around the male territory was not synchronous, but a small proportion of the female population matured almost everyday. Male courtship behaviors included figure 8 swimming and circling. Most of the spawnings were done by pair of a male and a female, but multi-female spawnings were also observed. Collection of eggs from the male territory showed that the male is guarding two or three clutches at the same time and it also showed that the adhesive eggs which take relatively long time to hatch almost always present in the male territory. From the digestive tracts of the male specimens, many conspecific eggs were found. The ratio of males which had eaten eggs averaged 37.9% of the specimens. The weight ratio of conspecific eggs to gut content attained 19.6% in wet weight. On the contrary, among 38 female specimens, only one individual was found to have eaten eggs. The gut content analysis showed that the males collected in the spawning season had eaten less than females collected in the same season and males collected before the spawning season. It was suggested that the males of E. etheostomus are eating their own eggs as energy source for egg-guarding during the spawing season.福岡県宗像郡津屋崎町鼓島において,1985年6月から1986年8月の間,へビギンポの繁殖生態を潜水観察した.得られた結果は以下のとおりである.(1)生殖腺脂数からみたへビギンポの繁殖期は6～8月であった.さらに,雄の婚姻色の発現,雄消化管からへビギンポの卵が出現することから5月および9月にも一部の個体は繁殖していることが明らかになった.(2)繁殖期になると雄は体色に黒味が増し,明瞭な3本の白色横帯が体側に現われ,非繁殖期とは著しく異なる婚姻色を呈した.(3)繁殖期には雄は約0.2m^2の狭いなわばりを持つが,鰭切除による個体識別により,平均2週間,最大43日間同一なわばりに留まることが明らかになった.これに対し,雌は雄のなわばりの周囲に比較的広い行動圏を持っていた.(4)繁殖行動は普通雄1尾,雌1尾のペアによって行われたが,雌2尾が同じ雄のなわばりで同時に産卵するのも観察された.雄の求愛行動としてfigure8 swimming,circlingを認めた.(5)卵は雄のなわばり内の海藻に産み付けられたが,産卵が終わると雄は卵を保護した.雄は複数の雌が産んだ卵を保護しており,任意に選んだ雄のなわばりから採集した海藻では,95.5%の頻度で卵が出現した.(6)繁殖期に採集した雄の消化管から多数のへビギンポ卵が出現した.卵を食べていた雄の割合は平均37.9%で,卵が消化管内容物に占める重量割合は平均19.6%であった.(7)繁殖期に採集した雄の体重当たりの消化管内容物重量は,繁殖期の雄および繁殖期の雌の値よりも低く,繁殖期の雄は充分に摂餌していないことが示唆された.(8)以上の結果から,繁殖期の雄の消化管より出現したヘビギンポ卵は,卵を保護しでいる雄が栄養補給のため自己の卵を食べたものと推測した