Pair Spawning Research Articles

Bidirectional sex-change behavior and physiological aspects in the Gorgeous goby Lythrypnus pulchellus (Gobiidae).

The Gorgeous goby Lythrypnus pulchellus shows extreme sexual plasticity with the bidirectional sex-change ability socially controlled in adults. Therefore, this study describes how the hierarchical status affects hormone synthesis through newborn hormone waste products in water and tests the influence of body size and social dominance establishment in sex reversal duration and direction. The associated changes in behavior and hormone levels are described under laboratory conditions in male-male and female-female pairs of similar and different body sizes, recording the changes until spawning. The status establishment occurred in a relatively shorter time period in male and female pairs of different sizes (1-3 days) compared to those of similar size (3-5 days), but the earlier one did not significantly affect the overall time of sex change (verified by pair spawning). The changes in gonads, hormones, and papilla occurred in sex-changer individuals, but the first one was observed in behavior. Courtship started at 3-5 days in male pairs and from 2 h to 1 day in female pairs of both groups of different and similar sizes. Hormones did not gradually move in the new sexual phenotype direction during the sex-change time course. Nonetheless, estradiol regulated sex change and 11-ketotestosterone enabled bidirectional sex change and was modulated by agonistic interactions. Cortisol is associated with status and gonadal sex change. In general, similar mechanisms underlie sex change in both directions with a temporal change sequence in phases. These results shed new light on sex-change mechanisms. Further studies should be performed to determine whether these localized changes exist in the steroid hormone synthesis along the brain-pituitary gonad axis during social and bidirectional sex changes in L. pulchellus.

Effects of cadmium exposure during the breeding period on development and reproductive functions in rare minnow (Gobiocypris rarus).

Cadmium is a common reproductive toxin in aquatic systems. Cd exposure of fish species at high concentrations can severely affect the reproductive function of fish. However, the underlying toxicity of cadmium exposure at low concentrations on the reproductive function in parental fish remains unclear. To investigate the impacts of cadmium exposure on reproductive capability, eighty-one male and eighty-one female rare minnows (Gobiocypris rarus) were exposed to cadmium at 0 (control group), 5 and 10μg/L for 28days, and then transferred into clean water to pair spawn. The results showed that cadmium exposure at 5 or 10μg/L for 28days in rare minnows could reduce the success rates of pair spawning in parent rare minnows, lessen no-spawning activities, and prolong the time for first spawning. Furthermore, the mean egg production of the cadmium exposure group increased. The fertility rate of the control group was significantly higher than that of the 5μg/L cadmium exposure group. Anatomical and histological data further revealed that the intensity of atretic vitellogenic follicles significantly increased and spermatozoa vacuolated after cadmium exposure (p < 0.05), but slightly increased the condition factor (CF), and relatively stable gonadosomatic index (GSI) values were also observed in the cadmium exposure groups. These observed results indicated that cadmium exposure at 5 or 10μg/L affected the reproductive activity of paired rare minnow by accumulating Cd in the gonads, and the effect diminished over time. The reproductive risk of low-dose cadmium exposure to fish species remains a cause for concern.

Influence of the lunar cycle and spatial gradients on size-dependent male and female reproductive investment decisions of a protogynous reef fish

Coral reef fish species experience variable environments and may employ a range of reproductive strategies to help them maximize fitness. Here, we explore patterns of variation in size- and sex-dependent spawning strategies (pair spawning, group spawning, and streaking tactics) of a sex-changing, highly iteroparous fish (the sixbar wrasse Thalassoma hardwicke) across the lunar month, and in relation to proximity to the reef edge. We test the hypothesis that adults vary their investment strategies as a function of body size. We evaluated reproductive behaviour patterns at 2–3 days intervals over 5 consecutive months, and found that frequencies of pair spawning, group spawning, and streaking attempts all significantly increased around the new moon and were greatest in the most exposed territories (i.e., those located closest to the reef edge). Smaller females and IP males largely curtailed reproductive activities during the full moon and third quarter moon, while larger individuals reproduced more consistently across the lunar month. Size-dependent reproductive decisions appeared to mediate frequencies of specific reproductive tactics (e.g., prevalence of pair spawning, group spawning, and streaking strategies). We speculate that (1) optimal tactics are shaped by size- and sex-dependent trade-offs between reproduction and growth in relation to environmental conditions, and that (2) individual investment decisions determine the prevailing reproductive mode at a spawning site. Variation in female choice might thereby act as a mechanism for maintaining these two reproductive modes (pair spawning and group spawning) in a population.

The life history characteristics of Neosebastes pandus and the relationship between sexually dimorphic growth and reproductive strategy among Scorpaeniformes.

Scorpaeniformes are an important component of commercial and recreational fisheries world-wide. The Neosebastes species, found in the western Pacific and south-east Indian Ocean, have received little attention from a research perspective. Samples of the bighead gurnard perch, Neosebastes pandus, collected from the lower west and south coasts of Western Australia, were used to undertake the first comprehensive investigation of the biological characteristics of a Neosebastes species. Opaque zones in sectioned sagittal otoliths were validated as forming annually. Female N. pandus grow to a significantly larger size, on average, than males and dominate the largest size classes, while males, growing to a smaller size, accumulate in the intermediate size classes. Although males were far less numerous than females in those age classes in which both sexes were found, males and females attain similar maximum ages >25 years. Neosebastes pandus spawns over a brief period between May (austral late autumn) and July (austral mid-autumn) when water temperature and day length are declining. The mean monthly gonadosomatic indices (GSI, IGS ) values of females during the spawning period are 37-50 times higher than those of males, which mature at an earlier age and smaller length compared to females. Histological examination of the ovaries of females indicate that their structure is consistent with "general" teleost ovarian anatomy and thus differs from Scorpaena, Helicolenus and Sebastes species whose ovaries are adapted for specialized reproductive modes. The reproductive strategy of N. pandus of maximizing the reproductive output of females, by this sex attaining a larger size than males and pair spawning (i.e., large disparity in IGS values) demonstrates the close lineage between the Neosebastes and other Scorpaeniformes, such as the Scorpaena, Helicolenus and Sebastes.

Production of albino slayer through a combination of crossing in brushmouth (Hypostomus plecostomus, Linnaeus 1758) ornamental fish

The objectives of this research was to evaluate the inheritance of albino slayer phenotype in brushmouth (Hypostomus plecostomus, Linn 1758) through the crosses and reproduction performance. The crossing scheme consisted of reciprocal crosses between albino slayer and albino non slayer (SN, NS) and between albino slayer (SS), each spawning in pairs (1:1) with three replications and twice spawning. The fish used in this study were brushmouth fish (Hypostomus sp.) albino Slayer males 9.07 ± 0.5 cm, albino slayer females 8.96 ± 0.4 cm, albino non slayer males 8.87 ± 0.17 cm, and albino non slayer female 8.86 ± 0.16 cm. Slayer phenotype category was identified based on the caudal length fin with 4.43 ± 0.64 cm. Parameters determined included the phenotype distribution of albino slayer, total number of eggs, fertilization rate, hatching rate and survival rate. The results showed that all crossing schemes produced four phenotypes classes including normal slayer, normal non slayer, albino slayer and albino non slayer. The slayer phenotype of albino brushmouth was highest percentage (75%) in crossing with male albino slayer (SN, SS) and highest number of eggs, while the reciprocal crossing with female albino slayer (NS) produced albino slayer 55% and lower egg count. The ratio of tail fin length to body length in albino slayer phenotype was lower than normal phenotype of broom fish. The fertilization and hatching rates were not significantly different in all crosses; however the number of eggs decreased in the second spawning. The similar phenotype cross between albino slayer phenotypes (SS) resulted the best average of survival rate (92%).

A phylogenetic comparative analysis on the evolution of sequential hermaphroditism in seabreams (Teleostei: Sparidae)

The Sparids are an ideal group of fishes in which to study the evolution of sexual systems since they exhibit a great sexual diversity, from gonochorism (separate sexes) to protandrous (male-first) and protogynous (female-first) sequential hermaphroditism (sex change). According to the size-advantage model (SAM), selection should favour sex change when the second sex achieves greater reproductive success at a larger body size than the first sex. Using phylogenetic comparative methods and a sample of 68 sparid species, we show that protogyny and protandry evolve from gonochorism but evolutionary transitions between these two forms of sequential hermaphroditism are unlikely to happen. Using male gonadosomatic index (GSI) as a measure of investment in gametes and proxy for sperm competition, we find that, while gonochoristic and protogynous species support the predictions of SAM, protandrous species do not, as they exhibit higher GSI values than expected even after considering mating systems and spawning modes. We suggest that small males of protandrous species have to invest disproportionally more in sperm production than predicted not only when spawning in aggregations, with high levels of sperm competition, but also when spawning in pairs due to the need to fertilize highly fecund females, much larger than themselves. We propose that this compensatory mechanism, together with Bateman’s principles in sequential hermaphrodites, should be formally incorporated in the SAM.

Where are all the moms? External fertilization predicts the rise of male parental care in bony fishes.

Parental care shows remarkable variation across the animal kingdom, but while maternal and biparental care are common in terrestrial organisms, male-only care dominates in aquatic species that provide care. Using the most complete phylogenetic tree of bony fishes to date, we test whether the opportunity for external fertilization in aquatic environments can explain the more frequent evolution of male care in this group. We show that paternal care has evolved at least 30 times independently in fish and is found exclusively in externally fertilizing species. Male care is positively associated with pair spawning, suggesting that confidence in paternity is an important determinant of the evolution of care. Crucially, while female care is constrained by other forms of reproductive investment, male care occurs more frequently when females invest heavily in gamete production. Our results suggest that moving control of fertilization outside of the female reproductive tract raises male confidence in parentage and increases the potential for paternal care, highlighting that in an aquatic environment in which fertilization is external, paternal care is an effective reproductive strategy.

Reproductive behaviour and concurrent sound production of Gulf grouper Mycteroperca jordani (Epinephelidae) at a spawning aggregation site.

The reproductive and acoustic behaviours of Gulf grouper Mycteroperca jordani were studied at a spawning aggregation site in the southern Gulf of California, México. In May 2015-2017, divers located and surveyed a spawning aggregation site within Cabo Pulmo National Park. Adult M. jordani conformed to a lek mating system in which large males formed territories over sand adjacent to a rocky reef that were spatially segregated from smaller females outside of courtship and spawning periods. Females moved into male territories during evening hours to spawn. Male courtship behaviours targeted a single female, included head shakes and burst rises and preceded pair spawning prior to sunset. Males and females displayed three shared colour phases, but four phases were sex-specific. During evening hours, courtship and spawning, both sexes exhibited sexual dichromatism concurrent with reproductive behaviours. The pair-spawning mating system and observations of bimodal size distributions by sex support previous claims of protogyny in the species. Males produced sounds during territorial patrols, courtship and spawning rushes, which corroborated the importance of acoustic communication within the behavioural repertoire associated with spawning. Long-term acoustic monitoring revealed increases in total sounds detected day-1 from March through June with diel increases (e.g., evenings) that may be indicative of the spawning season. Observations of spawning on 12 consecutive evenings in May 2017 coupled with extended periods of sound production suggest that spawning does not follow a lunar rhythm. This first description of the mating system and sounds of the endangered M. jordani facilitates future development of seasonal and areal protections to restore and manage the species.

Molecular confirmation of hybridization between Dascyllus reticulatus × Dascyllus aruanus from the Great Barrier Reef

To date, more than 81 species of tropical coral reef fish have been reported to hybridize in nature, spanning multiple families, including the Chaetodontidae, Pomacanthidae, and Labridae. Hybridization, however, is seemingly rare among benthic nesting species that engage in pair spawning, such as the Pomacentridae. Here, we present evidence for the first molecularly confirmed record of hybridization within the genus Dascyllus; D. aruanus and D. reticulatus. Interestingly, although many hybridization events are attributed to peripheral range effects or areas of limited overlap among otherwise allopatric species, this hybrid individual was collected from the northern Great Barrier Reef, centrally located within the distribution ranges of both species. The hybrid exhibited coloration and meristic counts intermediate between D. aruanus and D. reticulatus. Diagnostic genetic markers and subsequent microsatellites analysis confirmed that this individual was a hybrid offspring of D. aruanus and D. reticulatus, with the latter providing the maternal contribution. The occurrence of the D. aruanus × D. reticulatus hybrid on the Great Barrier Reef represents an exception to the otherwise species-specific haplotypes. The nuclear diagnostic marker which was identified during this study could serve as a hybrid indicator and benefit future hybrid investigations for hybridization between these two species.

Alternative male mating tactics of the endemic Red Sea parrotfish Scarus ferrugineus.

The present study shows that small non-territorial terminal-phase males of the rusty parrotfish Scarus ferrugineus are reproductively active and are comparable with initial-phase males in behaviour, rates of participation during group-spawning and success in streaking into pair spawning. Large territorial terminal-phase males defend contiguous territories for several hours during the morning where they pair spawn with initial-phase females.

Hybridization between damselfishes Dascyllus aruanus and D. reticulatus on the Great Barrier Reef

[Extract] Hybridization among closely related species is relatively common in marine fishes thatspawn mid-water. Although at least 81 species of tropical coral-reef fish have been reported to hybridize in nature (primarily Chaetodontidae, Pomacanthidae and Labridae), hybridization is thought to be exceedingly rare among benthic-nesting species that engage in pair spawning, such as the Pomacentridae (Montanari et al.2016 ). The Pomacentridae include >385 species, most of which form breeding pairs and nest on the benthos. Yet only four Pomacentridae hybridshave been confirmed based on strong molecular evidence (e.g., Yaakub et al. 2006), and only from areas where one or both species are rare, such as degraded habitats and/or geographic zones of overlap.

Pair spawning and hatching rates of eggs in Gnathopogon caerulescens

Pair spawning and hatching rates of eggs in Gnathopogon caerulescens

The reproductive biology of Pinguipes brasilianus Cuvier, 1829 (Osteichthyes: Pinguipedidae) in temperate rocky reefs of Argentina

ABSTRACT Pinguipes brasilianus is a conspicuous and abundant rocky-reef fish inhabiting the Northern Patagonian gulfs of Argentina, Southwest Atlantic. This study describes its reproductive biology in this region. We made macroscopic and histological descriptions of the testis and ovary development, analyzed the evolution of the gonadosomatic index (GSI) in both sexes throughout the year, and estimated fecundity and length at 50% maturity for females. Pinguipes brasilianus is a multiple spawner with indeterminate annual fecundity and an extended reproductive season, encompassing austral spring and summer. Low GSI values in males (monthly means ranged between 0.11% and 0.75%) and low relative fecundity in female fish (between 2 and 44 oocytes/g) are consistent with a need of close proximity between male and female during oocyte fertilization, sexual courtship and with spawning in pairs and/or within reef crevices. The estimated length at 50% maturity (± SD) for females was 15.22 ± 0.43 cm total length. Although P. brasilianus shares the main reproductive features of its congeneric species Pinguipes chilensis , male GSI and female length at 50% maturity in P. brasilianus were markedly lower than those reported for P. chilensis , while relative and batch fecundity were greater in fish of the same size.

Mating behaviour and gamete release in gilthead seabream (Sparus aurata, Linnaeus 1758) held in captivity

The present study aimed to describe the reproductive behaviour of gilthead seabream (Sparus aurata) in captivity. Twenty-four mature gilthead seabream, divided in two tanks, were utilized for the present study. Reproductive behaviour was recorded using submersibles cameras. A total of 67 spawning events were analysed. The mean duration time that gilthead seabream spent spawning was 54 ± 4 min/day, during which mean number of individual spawning events was 5.6 ± 0.2. The mean volume of eggs produced by both broodstocks was 405 ± 13.4 mL with a fertilization rate of 91.6 ± 0.4%. The reproductive behaviour began with a schooling behaviour and then forming light aggregations. From an aggregation or an encounter while swimming freely a female initiated a spawning rush followed by one or more males to gametes liberation. The spawning rush was brief, 1.6 ± 0.5 sec, over an approximately 1.7 ± 0.2 m distance from the tank bottom to the water surface. Pair spawning, between a single female and male, was the most common (71.6%). Group spawning was less common and involved a single female spawning with two males (22.5%) or three males (4.9%). Spawning rushes involving more than one female were not observed. Gilthead seabream in the present study presented a tendency to pair spawn and eggs collected as a “spawn” were actually the sum of many separate spawning events over a short time period. This is the first description of gilthead seabream spawning and the findings help to understand microsatellite based observations of spawning kinetics.

Spawning aggregation behavior and reproductive ecology of the giant bumphead parrotfish, Bolbometopon muricatum, in a remote marine reserve.

The giant bumphead parrotfish (Bolbometopon muricatum) has experienced precipitous population declines throughout its range due to its importance as a highly-prized fishery target and cultural resource. Because of its diet, Bolbometopon may serve as a keystone species on Indo-Pacific coral reefs, yet comprehensive descriptions of its reproductive ecology do not exist. We used a variety of underwater visual census (UVC) methods to study an intact population of Bolbometopon at Wake Atoll, a remote and protected coral atoll in the west Pacific. Key observations include spawning activities in the morning around the full and last quarter moon, with possible spawning extending to the new moon. We observed peaks in aggregation size just prior to and following the full and last quarter moon, respectively, and observed a distinct break in spawning at the site that persisted for four days; individuals returned to the aggregation site one day prior to the last quarter moon and resumed spawning the following day. The mating system was lek-based, characterized by early male arrival at the spawning site followed by vigorous defense (including head-butting between large males) of small territories. These territories were apparently used to attract females that arrived later in large schools, causing substantial changes in the sex ratio on the aggregation site at any given time during the morning spawning period. Aggression between males and courtship of females led to pair spawning within the upper water column. Mating interference was not witnessed but we noted instances suggesting that sperm competition might occur. Densities of Bolbometopon on the aggregation site averaged 10.07(±3.24 SE) fish per hectare (ha) with maximum densities of 51.5 fish per ha. By comparing our observations to the results of biennial surveys conducted by the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Ecosystem Division (CRED), we confirmed spatial consistency of the aggregation across years as well as a temporal break in spawning activity and aggregation that occurred during the lunar phase. We estimated the area encompassed by the spawning aggregation to be 0.72 ha, suggesting that spawning site closures and temporal closures centered around the full to the new moon might form one component of a management and conservation plan for this species. Our study of the mating system and spawning aggregation behavior of Bolbometopon from the protected, relatively pristine population at Wake Atoll provides crucial baselines of population density, sex ratio composition, and productivity of a spawning aggregation site from an oceanic atoll. Such information is key for conservation efforts and provides a basic platform for the design of marine protected areas for this threatened iconic coral reef fish, as well as for species with similar ecological and life history characteristics.

Spawning behaviour and activity in seven species of ornamental dottybacks

The marine aquarium fish industry has been growing rapidly, but still heavily relies on wild-caught organisms. Dottybacks (Pseudochromidae) are among the most popular cultured marine fishes, but issues related to pair formation and filial cannibalism commonly prevent mass production. This study investigated the behavioural aspects of dottyback aquaculture, mainly the events surrounding pair formation and spawning activity. Broodstock pairs of seven species were acquired and aggression level monitored daily for each pair, as well as spawning activity and frequency. All pairs successfully bonded, but the time until bonding varied; trends were observed in aggression level for some species. Time in between bonding and spawning also presented a high variability (5.7 ± 4.2 weeks). The spawning frequency was somewhat fixed for each pair, but variable among species. Egg masses were frequently cannibalised and most pairs required many spawning events (8.7 ± 8.2) for the first egg mass to hatch. Dottybacks present no sexual dimorphism, therefore the aggression levels and variability in bonding time are probably related to sex changes. The egg mass cannibalism decreased with time and was likely related to broodstock inexperience. The results presented should aid in enhancing aquaculture protocols and hopefully stimulate worldwide dottyback aquaculture.

Male coloration signals direct benefits in the European bitterling (Rhodeus amarus)

Female mating preferences are frequently associated with exaggerated male sexual traits. In the European bitterling, Rhodeus amarus, a fish with a resource-based mating system, male coloration is not associated with indirect genetic benefits of female mate choice, and does not reliably signal spawning site quality. We tested a link between the extent of male carotenoid-based coloration and testis size and number of spermatozoa stripped from the testes. Male body size predicted spermatozoa number, but less reliably than the extent of male coloration. Male color was a highly significant predictor of spermatozoa number, with approximately 26 % of variance in the number of spermatozoa stripped from males predicted from male color after controlling for male body size. Body size, but not coloration, predicted teste size. Female bitterling often risk sperm limitation, especially during pair spawnings, and male nuptial coloration may be under direct selection through female mate choice as a signal of male fertilization efficiency.

Temporal patterns and behavioral characteristics of aggregation formation and spawning in the Bermuda chub (Kyphosus sectatrix)

Reef fish spawning aggregations are important life history events that occur at specific times and locations and represent the primary mode of reproduction for many species. This paper provides detailed descriptions of aggregation formation and mass spawning of the Bermuda chub (Kyphosus sectatrix). Spawning coloration and gamete release of K. sectatrix were observed and filmed at the Grammanik Bank, a deep spawning aggregation site used by many different species located on the southern edge of the Puerto Rican shelf 10 km south of St. Thomas, US Virgin Islands. Underwater visual surveys using technical Nitrox and closed circuit re-breathers were conducted from December 2002 to March 2013 and documented spatial and temporal patterns of movement and aggregation formation along 1.5 km of mesophotic reef. The largest aggregations of K. sectatrix (>200 fish) were observed on the Grammanik Bank January to March from 0 to 11 d after the full moon with peak abundance from 60 to 80 d after the winter solstice across all survey years. Aggregation formation of K. sectatrix coincided with the spawning season of Nassau (Epinephelus striatus) and yellowfin (Mycteroperca venenosa) groupers. These spatial and temporal patterns of aggregation formation and spawning suggest that K. sectatrix, an herbivore, may also be a transient aggregating species. On several occasions, chubs were observed both pair spawning and mass spawning. Color patterns and behaviors associated with aggregation and spawning are described and compared to spawning characteristics observed in other species, many of which are similar but others that appear unique to K. sectatrix. This represents the first report of a kyphosid species aggregating to spawn and illuminates a portion of the poorly understood life history of the Bermuda chub.

Evolution of mating systems and sexual size dimorphism in North American cyprinids

Mating systems evolve with sexual size dimorphism (SSD) in many animals. Mating systems with males larger than females occur when males compete for female access or guard territories, while mating systems with group mating tend to occur in species where females are the same size or larger than males. In addition to variation in SSD with mating system, sperm competition varies among mating systems in predictable patterns. We examined the evolution of mating systems with SSD and testes mass in 111 North American Cyprinidae fishes using phylogenetic comparative methods. Our results demonstrate that the evolution of mating systems in Cyprinidae fishes is from ancestral taxa that are group spawners with females the same size or larger than males to pair spawning systems where males tend to be larger than females. We used an additive model to predict male and female body size from testes mass and mating system. Only mating system varied predictably with SSD. Our results for analyses of hyperallometry (Rensch’s rule) were that individual species of Cyprinidae can have hyperallometry for SSD, but the pattern is not present across all taxa.

Reproductive characteristics of the ocean leatherjacket, Nelusetta ayraudi

The ocean leatherjacket (Nelusetta ayrau- di) is one of the largest members of the family Monacanthidae. Distributed throughout inshore waters around the southern half of Australia, this schooling species supports substantial commercial and recrea- tional fisheries. N. ayraudi do not conform to either of the general reproductive modes reported within the family, but exhibit characteristics of both strong social reproductive behaviour and of being promiscuous and polygynous. Sexual dimorphism, with males and females exhibiting differing colouration and body shapes, and ripe ovaries being an order of magnitude larger than ripe testes, are characteristic of social reproductive behaviour and pair spawning. In contrast, high batch fecundity (mean of 320 oocytes per gram of body weight), similar sizes and ages at sexual maturity (350 mm and 2.5 years respectively) and the forma- tion of large spawning aggregations in offshore waters are characteristic of being promiscuous and polygy- nous. Similar to many other coastal marine species off the east and west coasts of Australia, N. ayraudi are partial spawners during the austral winter months with spawning restricted to the part of their distribution that is towards the upper area of the prevailing currents. It is hypothesized that N. ayraudi off eastern Australia have evolved a life-history strategy whereby fish move northwards through time, spawning occurs in these more northern waters and the southerly flowing Eastern Australian Current facilitates dispersal of eggs and larvae southwards. The reproductive characteris- tics described provide various options to fishery managers who wish to enhance the sustainability of the fishery through increased egg production. These include spatial and temporal fishing closures to protect breeding fish during the spawning period, the protec- tion of juveniles through either inshore area closures, improving the selectivity of fishing gears and/or regulated minimum legal lengths.