Osteological development in the Japanese sardine,Sardinops melanostictus

The development of all osteological elements, except scales, of the Japanese sardine,Sardinops melanostictus, is described from newly-hatched larvae to adult fishes. Newly-hatched larvae lacked osteological elements. Part of the head skeleton began to develop in 53 hour old larvae (4.2 mm in notochord length [NL]). Larvae at the first-feeding stage (77 hours, 5.5 mm NL) possessed several elements of the head skeleton and pectoral fin supports. In a 10.5 mm NL specimen, part of the caudal and dorsal fin supports were apparent. The centra appeared in specimens 18–22.7 mm in standard length (SL). Gill rakers were first observed in the lower branchial arches at 13 mm NL and spine-like processes with spiny nodules from about 25 mm SL. The distance between the predorsal and first dorsal proximal radial relative to SL rapidly decreased with forward translocation of the dorsal fin and became constant beyond approximately 34 mm SL. At this stage, most basic osteological elements were established. Completion of the osteological structure was characterized by the disappearance of the dentary teeth at 60–70 mm SL. Based on the osteological development, ontogenetic intervals consisting of four periods and eight phases were recognized.     

Large mating aggregations and daily long-distance spawning migrations in the bluehead wrasse,Thalassoma bifasciatum

Synopsis The mating system of the labrid fishThalassoma bifasciatum has been extensively described in the literature, and the species has formed the basis for much work in ecology and behavior. However, most work in the past on this species has concentrated in small patch reef habitats. Here I describe a different mating pattern in bluehead wrasses occurring on a large, linear barrier reef in St. Croix, U.S. Virgin Islands. On this reef, very large group-mating aggregations (> 10000 fish) form daily at a single area on the forepart of the reef. Tagging studies showed that fishes are faithful to particular feeding schools arrayed along the forereef, and that they migrate to the spawning grounds along a specific path from distances more than 1.5 km away. No mating appears to occur in other upcurrent areas of the forereef. One-way migration times averaged 52 min from the farthest site studied, and feeding does not occur en route. Despite large differences in time spent in migration, no significant differences existed in fecundity or frequency of spawning among females living at different distances from the mating aggregation. The only apparent differences was a significantlyhigher growth rate in the fishes residing farthest from the aggregation. This higher growth rate corresponded to a higher overall feeding rate in the distant location, suggesting that food intake can more than compensate for the increased costs of migration.     

Two spawning seasons and mating system of the bastard halibut, Tarphops oligolepis

We investigated the breeding habits of the bastard halibut, Tarphops oligolepis, in the southwest of Kyushu Island, Japan. This fish was found to have two spawning seasons in a year (around July and November); individual fish spawned over the two spawning seasons. During the spawning seasons, males established territories. Home ranges of females overlapped with those of other females and with territories of plural males. The courtship partner changed during a day, and multiple matings among both sexes were observed during a spawning season, suggesting that T. oligolepis bred promiscuously. This is the first report of the mating system among Paralichthyidae. Received: October 18, 2000 / Revised: May 7, 2001 / Accepted: July 9, 2001     

Size-dependent precopulatory behavior as mate-securing tactic in the Japanese stag beetle, Prosopocoilus inclinatus (Coleoptera; Lucanidae)

Males of the Japanese stag beetle Prosopocoilus inclinatus show dimorphism in body size. Since females frequently resist male courtship behavior, males often fail to mate after encounters with females. The males of two morphs showed different precopulatory behavior. During encounters with females, small males acted more persistently against females resistance than large males by grasping the female more solidly and as a result, succeeded in copulation more frequently. This persistent precopulatory behavior could be regarded as an alternative mating tactic of small males that are inferior to large males in direct physical competition.     

Aspects of the spawning of labrid and scarid fishes (Pisces: Labroidei) at Enewetak Atoll,Marshall Islands with notes on other families

Synopsis Spawning of 32 species of Labridae and 13 species of Scaridae was seen at Enewetak Atoll, Marshall Islands. Most spawned on a reef bisecting the main ocean-lagoon passage which had strong tidal currents. Others spawned on lagoon reefs and in Halimeda beds. Polygynous haremic, lek-like and promiscuous mating systems were found which were species specific. Data on reproductive patterns, sexual dichromatism, sexual dimorphism, seasonality and spawning behavior were determined. Many spawned during the day in a time-phase dependent pattern from near sunrise to sunset. Scarid spawning began at slack high water or after when currents were starting to move out of the lagoon. Labrid spawning usually started about 30 min later with some continuing up to 2 h after high tide. With high tide before sunrise, scarid spawning began 30–50 min after sunrise as the current started flowing over the reef. With high tide near sunset, spawning occurred with an incoming current. Most labroids spawned on all phases of the moon. Acanthuridae (6 spp), Caesionidae (1 sp.) and Zanclidae (1 sp.) spawned after high tide at the same time as labroids. Pomacanthidae (5 spp.) spawned only shortly before sunset without reference to tidal currents. Fishes producing pelagic eggs at the lagoon-ocean channel spawned (1) at or slightly after high tide (44spp.), (2) in late afternoon without reference to tide (6 spp.) or (3) after slack low water (1 sp. ). Spawning style can vary within a single species in different environments. Despite the presence of many piscivores, no successful predation on spawning adults was seen. Predation on newly released eggs was uncommon. Labrichthys unilineata and Anampses twistii attempted to defend their eggs for a few sec after release. Attacks by piscivores on spawning adults on tropical reefs occur once per 100–1000 spawnings. Most are wary when preparing to spawn and prespawning behavior is easily interrupted. The risk from piscivores goes down and spawning ascent speed decreases with increasing size of spawners. Egg predation by zooplanktivores is less for pair spawners than group spawners possibly due to less conspicuous gamete clouds and times of spawning. Increasing height of egg release, speed and length of the spawning ascent, and trajectory alteration of ascending adults are believed to make it more difficult for zooplanktivores to locate eggs after release. For labrids, permanent full sexual dichromatism was found among haremic, lek-like and promiscuous mating systems. Species with temporary full dichromatism, permanent and temporary partial dichromatism and monochromatism were haremic. Smaller scarids were believed to have lek-like, and larger species haremic, mating systems. Smaller scarids had male looping behavior and post spawning displays, plus faster spawning ascents and different locations for egg release than larger ones. Eggs of 21 labrids were spherical or nearly spherical, ranging from 0.55–0.80 mm in diameter, and most had one oil globule. Among 7 is scarids, 6 had spindle-shaped eggs ranging from 1.25 ×0.50 mm 2.14× 0.48 mm while one had a nearly spherical egg. One scarid egg lacked an oil globule.     

Effects of mating system in Japanese quail

Summary A 17-generation selection experiment was conducted to study direct and correlated responses to mass selection under a mating system with alternating generations of full-sib inbreeding and wide outbreeding (population I) as compared with a mass selected, randomly mated population (population II). The selection criterion was an index of total egg mass to 78 days divided by adult female body weight. Estimates of heritabilities and genetic correlations are reported. Estimated heritabilities for the index were 0.38±0.04 and 0.29±0.05 in population I and II, respectively. Realized heritabilites were 0.10±0.05 and 0.12±0.03. For most traits studied the mean phenotypic values in the cyclic mated population decreased for inbred generations. Increased inbreeding levels also caused outbred generation means of population I to decrease through the first six or seven generations. After this period of adaptation to inbreeding selection response was positive for the index and positively correlated traits. Total response to selection under the cyclic inbred-outbred mating system did not exceed selection response made under random mating. However, the rate of response in the cyclically mated population exceeded that in the randomly mated population in later generations when the cyclically mated population had apparently adapted to inbreeding.Published with approval of the Director of the Montana Agricultural Experiment Station, Journal Series No. 1221     

Interannual fluctuations in recruitment and growth of the sardine,Sardinops melanostictus,in the sea of Japan and adjacent waters

Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine.     

Changes in ovarian development and plasma levels of sex steroid hormones in the wild female Japanese sardine (Sardinops melanostictus) during the spawning period

In order to clarify the spawning pattern of Japaneses sardine ( Sardinops melanostictus ) during the spawning period, changes in ovarian histology, frequency distributions of oocyte diameter and plasma levels of oestradiol-17β (E₂) and 17 a ,20β-dihydroxy-4-pregnen-3-one (17 a ,20β-diOH-P) were examined in female fish captured in the region off Kyushu and Shikoku in Japan. With the development of the ovary, the gonadosomatic index (GSI) increased gradually and the size of oocytes became larger. When the GSI exceeded 13, the translucent hydrated eggs began to dominate and ovulation subsequently occurred. After ovulation, GSI decreased to less than 3. Post-ovulatory follicles were found only in the lower GSI ranges and atretic oocytes were always observed in the ovary. Plasma E₂ levels increased along with ovarian development but decreased after completion of yolk accumulation. On the other hand, 17 a ,20β-diOH-P showed the highest level just before and after ovulation. Ovarian histology and hormonal profiles suggest that the sardine spawns repeatedly during the spawning period. Based on the concentration of 17a,20β-diOH-P, the female Japanese sardine was estimated to ovulate before the middle of the night.     

Reproductive behavior of free-ranging Lemur catta at Beza Mahafaly Special Reserve,Madagascar

Observations of reproductive behavior in free-ranging Lemur catta were carried out during one annual cycle. Variability in the behavior of female ringtailed lemurs during parturition appears to be mainly a function of the female's parity and thus her experience. Females within a troop show estrous asynchrony and characteristically mate with more than one male. Females also exhibit proceptive behavior toward and mate with some males from other troops and with transferring males. The potential for a male to monopolize mating opportunities during a female's short estrous period is therefore limited. Male mating strategies in ringtailed lemurs can be seen as adaptations to female mate choice during a highly restricted breeding season. In this species the dominance hierarchy does not break down with regard to the order of mating. The highest ranking male (central male) mates first and shows precopulatory guarding and longer postejaculatory guarding, which may increase his chances of siring the offspring. Subsequent mating partners have developed various counterstrategies to mitigate mating order effects.     

Intrasexual copulation and mate discrimination in a population of Nodilittorina radiata (Gastropoda: Littorinidae)

Intrasexual copulation and mate discrimination by Nodilittorina radiata (Gastropoda: Littorinidae) were studied on a concrete breakwater at Hakodate Bay, southern Hokkaido, Japan. Intrasexual (male–male) copulations were observed in 4.7–21.1% of copulating pairs on the shore. As females were relatively larger than males and males copulated with females larger than themselves, we hypothesized that males choose potential mates larger than themselves. However, two male mates showed no significant size preference in intrasexual copulations, suggesting that males do not choose relatively larger individuals as mates. In a laboratory mate-choice experiment, male N. radiata preferred to mate with females, indicating precopulatory sex identification. They copulated with males, however, at the frequency of 37%, perhaps because of sex misidentification.     

Observations of spawning in the Leather Bass, <Emphasis Type="Italic">Dermatolepis dermatolepis</Emphasis> (Teleostei: Epinephelidae), at Cocos Island,Costa Rica

Courtship and spawning behavior is described for the Leather Bass, Dermatolepis dermatolepis, from observations made from a manned submersible at Cocos Island, Costa Rica on 19 days between November 2006 and February 2007. Spawning occurred in the evening (16:00–18:30 h) in subgroups of 10–32 individuals that formed within aggregations of 50–70 individuals. The mating sequence was characterized by subgroup formation and crowding behavior followed by a brief vertical spawning rush, gamete release, and the rapid separation of participants. The aggregation was present on all dives, and spawning was not restricted to specific lunar phases.     

Mating behavior of ring-tailed lemurs (Lemur catta) at Berenty,Madagascar

The mating behavior of ring-tailed lemurs at Berenty, Madagascar, was observed in April 1982. Although Troop A included five adult females, only two were observed to mate. The mating period covered two consecutive days, April 24 and 25. Each female was receptive for about 4 hr. Data from 47 copulations, of which 38 were with ejaculation, suggest that to be the first mating partner is of importance for male ring-tailed lemurs. Previously it has been suggested that male dominance is of little significance in determining mating partners. In this investigation it was observed that the second most dominant male MK was always the first mating partner. Only after several ejaculations and resultant fatigue did he lose possession of the female to lower ranking males, and the first ranking male was not seen to copulate with either female at any time. These results suggest that a male's mating success is partly, but not completely correlated with his dominance rank, and that other factors, including his length of residence in the group and female choice, also determine patterns of mating.     

Copulatory behaviors and body condition predict post-mating female hormone concentrations, fertilization success, and primary sex ratios in Japanese quail

Environmental cues and social interactions are known to influence reproductive physiology and behavior in vertebrates. In female birds, male courtship displays can result in the growth of ovarian follicles, the production of reproductive hormones, and stimulation of oviduct development, all of which have the potential to influence maternal investment. Male Japanese quail follow a typical sequence of copulatory behaviors during a mating interaction and often force copulations with unreceptive females. We hypothesized that female Japanese quail could adjust maternal investment in response to male copulatory behaviors during a single mating interaction. We investigated the relationships between 1) male copulatory behaviors and post-mating concentrations of steroids in the female, 2) female steroid concentrations and fertilization success of inseminations and 3) female steroid concentrations and the offspring sex ratio. We found that male condition and copulatory behaviors predicted female steroid concentrations and maternal investment in eggs laid after a mating trial. The body condition of one or both mates was a significant predictor of the changes in female corticosterone and testosterone concentrations after mating, whereas specific male copulatory behaviors significantly predicted changes in female progesterone concentrations. Male and female body condition, male neck grabs and post-mating concentrations of female corticosterone, progesterone, and testosterone were all significant predictors of egg fertilization rates. Female body condition, male copulation efficiency, and female testosterone concentrations were significant predictors of offspring sex ratios. Our results show that phenotypic and behavioral characteristics of male Japanese quail modulate female steroid concentrations and result in changes in maternal investment.     

Stereotyped sequence of mating behavior in the Far Eastern catfish, Silurus asotus, from Lake Biwa

 Mating behavior of the Far Eastern catfish, Silurus asotus (Siluriformes: Siluridae), was observed in a ricefield system facing the shore of Lake Biwa in mid-May to early June in 1990–1997. A set behavioral sequence similar to those of two other silurid fishes, S. biwaensis and S. lithophilus, both endemic to the Lake Biwa system, was observed: “chasing,”“clinging,”“enfolding” while “squeezing” by the male, and “circling” by the spawning pair. This form of mating behavior is quite different from that of S. asotus reported from the Ooi River system in Kyoto Prefecture, which mainly spawns in running water in ditches. Received: April 10, 2001 / Revised: November 5, 2001 / Accetped: November 20, 2001     

Observations of mating behavior of the manta ray,manta birostris, at the ogasawara islands, japan

On 11 July 1997, the mating behavior of wild manta rays,Manta birostris, was observed while skin diving off Chichijima. Ogasawara Islands, Japan, and recorded with 49 underwater photographs and about 20 minutes of video tape. The female manta ray involved was estimated as being approximately 5 m in dise width (DW) and the two males involved, approximately 4 m DW. Copulatory behavior of the two males appeared to be almost the same, copulation itself being of the abdomen-to-abdomen type. Initially, the males chased the female for 20–30 minutes, all animals swimming at approximately 10 km/h. Each copulation event occurred within one meter of the surface, during which time the participating male grasped the tip of the female's left pectoral fin with his mouth. The clasper was inserted for 90 seconds (Male No. 1) and 60 seconds (Male No. 2), respectively. The mating behavior sequence of the manta rays involved following five steps. 1.: Male chases behind the tail of the female, attempting (several times) to grasp the latter's pectoral fin (chasing behavior). 2.: Male bites the tip of the female's pectoral fin, before positioning itself against the latter's underside (biting behavior). 3.: Male inserts a clasper into the cloaca of the female (copulating behavior). 4.: Male removes the clasper from the cloaca of the female, but continues biting the latter's pectoral fin (post-copulating behavior). 5.: Male releases the pectoral fin of the female, setting her free (separating behavior).     

Reproductive behavior of the halfmoon grouper, <Emphasis Type="Italic">Epinephelus rivulatus</Emphasis>, at Ningaloo Reef,Western Australia

Behaviors associated with spawning by the halfmoon grouper, Epinephelus rivulatus, at Ningaloo Reef, Western Australia, are described from in situ observations made each evening throughout most of a lunar cycle. Spawning occurred after sunset on six consecutive evenings during the full moon period. During this time males were particularly aggressive toward one another and maintained high levels of activity among the gravid females that rested within each of their territories. Spawning occurred when a male swam alongside a responsive female and the pair rose in a tight spiral 1–1.5 m into the water column before releasing gametes and returning to the seabed. Spawning activity was followed by a longer nonspawning period (ca. 20 days), when fewer intraspecific interactions were observed and gamete reserves were replenished. Histological and behavioral evidence suggests that this cycle of spawning and replenishment may occur on a monthly basis. Although individual fish, particularly females, moved into certain areas to spawn, E. rivulatus did not form spawning aggregations as do larger species of grouper.     

Impact of photoperiod manipulation on day/night changes in melatonin, sex steroids and vitellogenin plasma levels and spawning rhythms in Senegal sole, Solea senegalensis

Photoperiod and temperature are known as the main synchronizers of seasonal reproduction in fish. This paper studied the role of photoperiod on the synchronization of F1 Senegal sole reproduction rhythms. Fish were maintained under constant short-photoperiod (9L:15D) from the winter solstice onwards (experimental group) or under naturally-changing photoperiod (control group), and water temperature naturally oscillated in both groups. Blood samples were collected during the reproduction season at pre-spawning (March), spawning (April) and post-spawning (May) to determine the endocrine status. Spawning events and egg quality parameters were also monitored. The results revealed a significant increase in nocturnal melatonin concentration from March to May in the control group, while in the experimental group such seasonal change did not occur. As to plasma levels of vitellogenin, testosterone, estradiol and 11keto-testosterone, differences between groups were found mostly in March, while in April and May levels were often similar. Spawning was observed in both groups, although the experimental group started slightly earlier and also finished earlier than the control group, perhaps as a result of the increase in sex steroids and VTG observed at pre-spawning. Briefly, reproduction rhythms persisted in the absence of the natural lengthening of photoperiod, although photoperiod manipulation altered the seasonal modulation of melatonin, increased sex steroids and vitellogenin at pre-spawning, and slightly advanced the timing of spawning.     

Spawning Periodicity, Spawning Migration, and Size at Maturity of Green Sturgeon, Acipenser medirostris, in the Rogue River, Oregon

The Rogue River, Oregon represents one of three important spawning systems for green sturgeon, Acipenser medirostris, in North America. In this paper we describe the spawning migration, spawning periodicity, and size at maturity for green sturgeon caught in the Rogue River during 2000–2004. Green sturgeon were caught by gill net or angling; 103 individuals were tagged with radio or sonic transmitters (externally or internally). Green sturgeon caught by gill net and angling ranged from 145 cm to 225 cm total length. Histological and visual examinations of gonad tissues indicated that most green sturgeon were spawning or post-spawning adults that entered the Rogue River to spawn. Ripe individuals were caught when water temperature was 10–18°C. Specimens carrying transmitters migrated 17–105 km up river; reaches consisting of likely spawning sites were identified based on sturgeon migratory behavior. Most green sturgeon remained in the Rogue River until late fall or early winter when flows increased, after which they returned to the ocean. Eight green sturgeon (males and females) returned to the Rogue River 2–4 years after leaving, entering the river during March, April, and May when water temperatures ranged from 9°C to 16°C. None of the 103-tagged individuals entered the Rogue River during successive years. There appear to be few known natural threats to adult green sturgeon in the Rogue River. However, our data suggest that a high percentage of adults that spawn in the Rogue River (particularly males) were susceptible to harvest by commercial, Tribal, and sport fisheries after leaving the system because they were not adequately protected by maximum size limits during the period of this study. The implications of maximum size limits (or lack of size limits) to green sturgeon are discussed, and recent actions taken by Oregon and Washington Fish and Wildlife Commissions to manage green sturgeon more conservatively are presented.     

A four-year study of the association between male dominance rank, residency status, and reproductive activity in rhesus macaques (Macaca mulatta)

Considerable controversy exists on the nature of the relationship between male dominance rank and reproductive activity. The nature of this relationship has important implications for understanding the manner in which males compete for access to limited resources. Behavioral data on mating patterns were collected over a four-year period from one social group of rhesus macaques on Cayo Santiago. Correlations between dominance rank and reproductive activity were not stable over a four-year period, but changed yearly. Positive, significant correlations were present in the first two years of the study while non-significant correlations were found in the second two years. The variation found in the correlations between rank and mating activity could be accounted for by changes in the mating frequencies of different classes of males. The long-term resident males had declines in ejaculation frequencies over the duration of the study. Males who immigrated into the group had yearly increases in reproductive behavior over three consecutive years. Maturing natal males also increased their levels of reproductive activity from year-to-year. Combining these mating patterns over time resulted in shifting the proportions of matings away from the long-term residents and in favor of the new males. High-ranking males had an advantage in reproductive activity over the first two years of the study, as measured by both the total number of ejaculations and the mean number of ejaculation per male. New males, comprised of recent immigrants and maturing natal males, had a greater level of reproductive activity over the last two years. These results suggest that the effect of rank on reproductive activity is variable and that males utilize alternative tactics to attain access to limited resources. Simple one-factor models explaining the relationship between rank and reproductive activity must be replaced with models explaining how alternate strategies affect male competition and reproductive success in primates.