Extended Breeding Season in the Marbled Goby, Pomatoschistus Marmoratus (Teleostei: Gobiidae), in the Venetian Lagoon

Life cycle and reproductive biology of the marbled goby Pomatoschistus marmoratus was studied in the Venetian Lagoon. Lifespan was determined by reading otoliths. The maximum age recorded was 17 months juveniles occurred in samples from July to November. Nests were found in two different periods: from the middle of April to the middle of July and from the middle of August to the end of September. While individuals in a wide range of body size (35–62mm total length) mated during the first spawning peak during the second one only small individuals (28–32mm total length) developed during the first peak were in reproductive activity. Histological analyses showed that most of the juveniles developed during the first spawning peak delayed sexual maturation to the following year. Ripe females appeared to be multiple spawner showing an asynchronous ovary with oocytes at different stages of development. From nesting male body sizes gonadosomatic indices and histological analyses no indication of the presence of alternative male mating tactics emerged.     

Observations of a Nassau grouper, Epinephelus striatus, Spawning Aggregation Site in Little Cayman, Cayman Islands, Including Multi-Species Spawning Information

Mass spawning aggregations of Caribbean grouper species are a conservation priority because of declines due to over-fishing. Previous studies have documented five historical aggregation sites in the Cayman Islands. Today, three of these sites are inactive or commercially extinct. In January 2002, the Reef Environmental Education Foundation led an expedition to Little Cayman Island to document a recently re-discovered spawning aggregation of Nassau grouper, Epinephelus striatus. A team of divers estimated the abundance, color phase composition, and courtship and spawning behavior of the aggregating grouper. The color phase composition of the aggregation shifted both during the course of each evening and throughout the 10-day project. Divers documented atypical coloration and courtship behavior in 10 additional fish species, of which five were seen spawning. Artisanal fishing occurred daily on the aggregation. The Cayman Islands Department of the Environment collected landings data and sampled catches to obtain length and sex ratios. The Cayman fishing fleet, while small, had a significant impact on the aggregation with a harvest of almost 2000 Nassau grouper during the 10-day project. The study site supports the largest known Nassau grouper aggregation in the Cayman Islands. The relatively large size of fish and the high proportion of males indicate that this site supports a relatively healthy aggregation compared to other Nassau grouper aggregation sites throughout the Caribbean.     

Seasonal Timing and Diel Activity of Lacustrine Brook Charr, Salvelinus Fontinalis, Spawning in a Lake Outlet

The objectives of this study were to determine (1) the seasonal timing and diel activity patterns of lacustrine brook charr when migrating to a lake outlet for spawning, and (2) the homing of reproducing individuals. In 1995, 745 individuals were captured while migrating to the spawning ground compared to 1148 in 1996. In both years, the sex ratio was not significantly different from 1:1 but females were significantly longer than males. The spawning migrations lasted about 48d and were more nocturnal (between 20:00 and 8:00h) than diurnal. The migration to the spawning ground began when water temperature decreased to 13°C and peaked when water temperature decreased from 11°C to 7°C. Peaks in migration activity were always preceded by a sudden decrease followed by an increase in temperature. The spawning migration lasted until the third week of October, when water temperature varied between 3°C and 8°C. Males, especially larger ones, arrived on the spawning ground before females in both years. The length of males migrating to the spawning ground decreased during the spawning season while the females' length showed no pattern. Only 9.7% of the 745 fin-clipped individuals from 1995 returned to the lake outlet to spawn in 1996. The results of this study indicate that lacustrine brook charr show similarities to other anadromous and lake-spawning salmonid populations when migrating to spawning grounds.     

Karyology and Oogenesis of Radopholus similis (Cobb) Thorne

Two morphologically indistinguishable races of Radopholus similis from Florida are presently identifiable only by host preference tests. One race attacks banana and other hosts, but not citrus. The other race attacks both citrus and banana, as well as other hosts. The two races normally reproduce by amphimixis. The morphology of the female reproductive systems of both races were examined and appeared to be identical. However, slight differences were observed in developmental stages of oogenesis between the two races. The two races were distinct with respect to karyotype. There were four chromosomes in the banana race and five chromosomes i n the citrus race. Karyotypic uniformity was found i n the two Florida populations of the citrus race.     

Mating system and spawning cycle in the blenny,Istiblennius enosimae,at Kagoshima,Japan

Synopsis Field observations on reproductive ecology and territoriality of the blennyIstiblennius enosimae, were made in a tidepool at Hanaze Beach, Kagoshima Prefecture, Japan during the summer of 1988. This blenny was herbivorous, and nesting males (> 73 mm SL) maintained territories around nest sites, which were located in rocky crevices of the tidepool. Males courted females wandering near their nests, and spawnings coincided with neap tides. Males guarded the eggs until the embryos hatched at following spring tides. It was suggested that this semilunar spawning cycle guarantees a maximum dispersal of newly hatched embryos away from natal tidepool. Male reproductive success was related to large body size and/or large nest size. There is a size-assortative relationship between male and female among pairs. Egg predation rates by fishes, crabs and sea urchins were not correlated with the body size of male blennies.     

Life Cycle of Polytomella caeca (Phytomonadida, Polyblepharidae)

SYNOPSIS. Polytomella caeca (Phytomonadida, Polyblepharidae) reproduce by binary fission and sexual reproduction. The sexual process increases in frequency as the population becomes denser. Normally 2 monoecious isogametes engage their anterior flagella prior to fusion, which occurs by merging of the cells from their anterior to their posterior ends. This is followed by a period of zygotic enlargement before cleavage of the zygote into 4 daughter cells. Encystment occurs throughout the flagellates' bloom until they represent 80% of the individuals at the end of the bloom. Cysts are a resistant, not reproductive stage. The observations were made over long periods of time by following individual flagellates in microcultures and by viewing living cells taken at various stages from larger cultures.     

Contributions to the Life Cycle of Peneroplis planatus (Fichtel and Moll) Montfort

Direct observations of schizonts and agamonts releasing megalospheres clarified the asexual phase of the life cycle of Peneroplis planatus and made it most probable that this species has a paratrimorphic life cycle. Specimens with maximum lengths between 837 and 3,503 μm released about 500 to 1,500 megalospheric juveniles, which possessed two chambers (proloculi and flexostyles) prior to emergence from the parental shell. The presence of gamonts was not shown and was only implied by the occurrence of the agamonts. Since agamonts and schizonts have been found from December to May and since asexual reproduction occurs in spring in Elat, sexual reproduction probably occurs at another time of year (June to December). More detailed studies of this species need to be conducted throughout the year to improve our knowledge of the life cycle of this species.     

Prey processing in Leurognathus marmoratus and the evolution of form, and function in desmognathine salamanders (Plethodontidae)

Function and biological role of morphological specialization in desmognathine salamanders are analysed in the light of studies of feeding in Leurognatthus marmoratus. Nine morphological features uniquely characterize the Desmognathinae as compared to its sister group, the Plethodontinae, and other salamanders: (1) heavily ossified and strongly articulated skull and mandible; (2) flat, wedgelike head profile; (3) stalked occipital condyles; (4) modified atlas; (5) modified anterior trunk vertebrae; (6) atlanto-mandibular ligaments; (7) enlarged dorsal spinal muscles; (8) enlarged quadrato-pectoralis muscles; and (9) hind limbs relatively larger than forelimbs. Dorsoventral head mobility is increased at the atlanto-occipital joint by the stalked occipital condyles which simultaneously increase the mechanical advantage of the hypertrophied axial muscles that cross the joint. During head depression the atlanto-mandibular ligaments are placed in tension. Force generated by the quadrato-pectoralis muscles is transmitted directly to the mandible, creating a powerful bite with the jaws in full occlusion. Desmognathines use an efficient static pressure system for subduing and/or killing prey items held in the jaws, not a kinetic-inertial mechanism, as previously suggested. Leurognathus exhibits a behaviour ('head-tucking') unique to desmognathines that is consistent with the static-pressure hypothesis. Several desmognathine features (1, 2, 5, 7, 9) are not explicable as adaptations for feeding; these function as locomotory specializations for burrowing, especially for wedging under rocks within and alongside streams. Desmognathines use head-tucking during such wedging and burrowing movements, thus locomotory specializations act in concert with the feeding specializations. We suggest that origin of the atlanto-mandibular ligaments can be considered a 'key innovation' in that it allowed the secondary invasion of stream habitats by adults of ancestral desmognathines.     

Further data on the reproduction and larval development of Knipowitschia caucasica (Gobiidae)

The courting spawning and parental care behaviours of Knipowitschia caucasica (Kawrajsky) in an aquarium are described and the earliest stages of ontogenetic development are illustrated.     

Reproduction of Snowy Sculpin Myoxocephalus brandti(Cottidae) in Peter the Great Bay, Sea of Japan

Spawning of snowy sculpin in Peter the Great Bay begins in November and takes place at a depth of about 4–7 m. Males of this sculpin species guard their laid eggs. Larvae hatch in April. Final fecundity is attained at ovary maturity stages IV–V.     

Observations of Spawning Behaviour in Salmoninae: Salmo, Oncorhynchus and Salvelinus

Long-term data from underwater video recordings in the wild and semi-natural channels are compared to the current literature to review the reproductive behaviour of fishes in the subfamily Salmoninae. Male alternative strategies and tactics are discussed. Reproductive behaviour in Salmoninae is divided into different phases related to female nest selection, construction, and completion. Still underwater video frames are used to support conclusions drawn on spawning behaviour.     

Control of Gonadal Maturation and Regression by Experimental Variation of Environmental Factors in the Mormyrid Fish, Mormyrus rume proboscirostris

We used spawning, external appearance of the females and in part histology of gonads of the African mormyrid fish Mormyrus rume proboscirostris to evaluate the reaction of the fish to experimental variation of environmental factors. Conductivity changes are sufficient to induce gonadal maturation (decrease of conductivity) and regression (increase of conductivity), respectively. Increase of water level and simulation of rain at constant conductivity values did not induce gonadal maturation and spawning. Neither males nor females of M. rume proboscirostris showed postbreeding refractoriness. Social stress apparently prevented complete gonadal maturation and successful spawning. The females laid on average 364 eggs per fractional spawning; the spawning intervals were 21 days. Hatching rate amounted to about 40% in all experiments taken together.     

Mating Behavior of Southern Stingrays, Dasyatis americana (Dasyatidae)

We document in detail the first complete sequence of mating events in the southern stingray, Dasyatis americana, based on observations of four matings (five separate copulations) at Grand Cayman, British West Indies and Bimini, Bahamas. These observations are significant because almost nothing is known about this important aspect of the life cycle of batoids, due to the rarity of encounters with mating animals in natural settings. Similar to mating behavior described in the manta ray, Manta birostris, the mating sequence of D. americana can be characterized as (1) 'close-following', (2) 'pre-copulatory biting', (3) 'insertion/copulation', (4) 'resting' and (5) 'separation'. Additional information gained from these observations includes the fact that (1) two of the females were mated very shortly (i.e. within minutes–hours) after parturition and (2) one of the mating events involved a single female that copulated (unforced) with two males in rapid succession. The latter observation suggests that polyandry and multiple paternity may be elements of the mating system of D. americana.     

The Spawning and Early Life History of the Pollan (Coregonus pollan THOMPSON) in Lough Neagh,Northern Ireland

Studies had been carried out on the local non-migratory whitefish. Spawning behaviour and light conditions on the spawning ground are recorded. After artificial spawning, embryonal development took place under controlled conditions and the larvae were reared. Detailed characteristics of swim bladder creation and differentiation of the digestive tract are given. Distribution and number of pollan larvae near the spawning area and in the open lake were examined. Data are presented concerning the growth rates of larvae and fry in captivity and under lake conditions. Ecological data related to other coregonids are discussed and compared with the present study.     

Male and Female Parental Roles in the Monogamous Cichlid, Tilapia mariae, Introduced in Florida

We documented male and female parental roles of a monogamous fish, the spotted tilapia, Tilapia mariae, in channelized rivers in southern Florida, where this species dominated the fish fauna within 10 years of their introduction. Clearly differentiated parental roles existed between males and females, with females performing nearly all tending of embryos and most tending of free embryos. After young became free-swimming and left the nest, however, males took over primary tending of the school of young while the female patrolled the perimeter of the school and performed nearly all chases directed at predators. Male and female T. mariae also traded off vigilance and feeding, and showed a high degree of intrapair coordination. Experimental removal of one or both parents had major effects on parental behavior and brood survival and integrity. Solitary females took on a parental role intermediate between that of the male and female of a pair. Untended broods were attacked by predators and scattered into aquatic vegetation, and were not observed to reform. Under dense nesting conditions we observed adoption of broods, group rearing of free-swimming young and the presence of non-breeder satellites sharing and defending a territory with breeders. This highly complex parental care may have allowed T. mariae to invade fish communities dominated by uniparental centrarchids, as well as allowing them to use disturbed habitats such as channelized rivers that are of poor quality for nesting and rearing offspring.     

Reproduction of the calanoid copepod Calanus propinquus in the southern Weddell Sea,Antarctica: observations in laboratory

Reproduction of the dominant Antarctic copepod Calanus propinquus was studied in February–April, 1989 aboard the R.V Dmitry Mendeleev during cruise N° 43 to the Weddell Sea. Single females were kept at 0 °C in the laboratory for 56 days with abundant food concentration (above 300 µg C l^–1 of Platymonas viridis). Females released clutches at night at 2–3 day intervals. Most clutches contained from 10 to 40 eggs, mean 37.3 eggs female^–1. Average carbon content of an egg was 0.37 ± 0.05 µg C. The maximum daily egg production rate of 30–50 eggs female^–1 d^–1 was observed for the first 3 days of the laboratory incubation, corresponding to 3.7–6.2% body C. The state of gonadal development of females showed the decline of the reproductive season in late February. The data suggest that egg laying in the region under study starts in December and lasts until March. The state of ovarian maturation, changes in vertical distribution and biochemical body composition of females suggest the possibility of two-year life cycle in C. propinquus in the southern Weddell Sea.     

Potential for parthenogenesis of virgin females in a bisexual population of the geographically parthenogenetic mayfly Ephoron shigae (Insecta: Ephemeroptera,Polymitarcyidae)

The burrowing polymitarcyid mayfly Ephoron shigae is a geographically parthenogenetic species. Interestingly, the distributions of the bisexual and unisexual populations overlap broadly in their respective geographic ranges. In this mayfly, obligatory diploid thelytoky appears within unisexual populations. In the present study, we examined the potential for parthenogenesis or the parthenogenetic ability of females in a bisexual population aiming to understand the emergence of unisexual populations. The results obtained revealed that females in the examined bisexual populations showed a potential for diploid thelytoky as also seen in the unisexual populations, although, in females from bisexual populations, the development success rates of their unfertilized eggs were considerably lower than those of virgin females from unisexual populations. In the three bisexual reproducing species (Ephemera japonica, Ephemera strigata, and Ephemera orientalis) in the closely‐related family Ephemeridae, diploid thelytoky (i.e. tychoparthenogenesis; < 3%) was also observed. However, in this case, the parthenogenetic development success rates of unfertilized eggs were significantly lower than those of virgin females in the bisexual (Hino‐yosui Irrigation Canal) population of E. shigae. Accordingly, we suggest that parthenogenetic ability (i.e. tychoparthenogenesis or facultative parthenogenesis) in bisexual populations of E. shigae may facilitate the evolutionary transition to unisexual populations with fully obligatory parthenogenesis. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 326–334.     

Patterns of Embryo Mortality in a Demersally Spawning Coral Reef Fish and the Role of Predatory Fishes

The biological significance of embryo mortality in demersally spawning coral reef fishes is poorly understood. Here we describe patterns of variation in embryo mortality in Pomacentrus amboinensis (Pomacentridae) at Lizard Island (Great Barrier Reef). The aim was to determine whether numbers of embryos hatched substantially differed from egg production, and if so, identify whether predatory fishes were a source of embryo mortality. Spawning success (number of eggs laid), embryo mortality (proportion of embryos that died prior to hatching) and number of embryos hatching were estimated from daily maps of clutches laid on artificial surfaces (PVC tiles) defended by nesting males. Patterns of variation in eggs laid, embryo mortality and numbers of embryos hatched were examined at three spatial scales: (1) among widely-spaced locations around the island; (2) between adjacent reef slope and patch reef habitats occupied by P. amboinensis at a single location; and (3) among different males within these two habitats. The embryo mortality was extremely high, with a mean of 25.9pm ± 6.2% (S.E.) for 4 locations examined in 1994 and a mean of 69.2pm ± 2.9% for two habitats surveyed in 1995. There were no significant differences in embryo mortality among locations or habitats in either year. This meant that spatial patterns in the number of embryos hatching reflected differences in the number of eggs laid on tiles. Embryo mortality was extremely variable on the scale of individual territories, with embryo mortality commonly ranging from 0% to 100%. Much of the mortality could be attributed to diurnal predatory fishes, especially the wrasse Thalassoma lunare. However, variation in predator densities did not explain spatial patterns in embryo mortality rates. Both solitary and group predatory behaviour was observed, with groups often causing 100% embryo mortality. The level of embryo mortality observed suggests that predation prior to hatching may have a substantial effect on the reproductive output of populations of this demersal-nesting fish.     

Life Cycle and Mating Behavior of Belonolaimus longicaudatus in Gnotobiotic Culture

The life cycle of Belonolaimus longicaudatus was observed in vitro on excised roots of Zea mays. Roots were cultured on Gamborg''s B5 medium in petri dishes with 1.5% agar adjusted to pH 5.8 and incubated at 28 °C in darkness. Second-stage juveniles (J2) fed on the roots and started the second molt (M2) to the third-stage juveniles 2 days after inoculation (DAI). The third molt (M3) to the fourth-stage juveniles occurred 7 DAI, followed by the fourth molt (M4) to males 13 DAI or to females 14 DAI. Nematode gender differences were observed by the end of the fourth molt. The first male appeared 15 DAI and the first female 17 DAI, after which mating occurred. Males were attracted to females, and mating was observed. Mating was required for reproduction. Fertilized females began to lay eggs 19 DAI and continued egg laying without the further presence of males during a 90-day observation. All of the eggs hatched. Unfertilized females rarely laid eggs, and none of the eggs were able to hatch. Feeding took place between each molt and before egg deposition occurred. The first-stage juveniles molted in the eggs 4 days after deposition, and J2 hatched from eggs 5 days after egg deposition. The life cycle from J2 to J2 was completed in 24 days.     

Maturity, oocyte dynamics and fecundity of the roundnose grenadier from the Rockall Trough

The reproductive biology of roundnose grenadier Coryphaenoides rupestris was investigated against a background of increasing commercial exploitation. Samples were taken from surveys carried out in Rockall Trough between 1993 and 1995. An eight-point maturity scale was developed based on both visual inspection of the ovaries and histological screening. The various stages of development of roundnose grenadier oocytes were described and the relative proportion of oocyte types and their respective size range in each maturity stage were investigated. The dynamic organization of the ovary indicated a determinate maturation cycle in this species. Population spawning appears to be prolonged, extending from July to at least November. However, data were insufficient to clarify individual spawning duration. The potential fecundity of 29 mature fish ranged from 11 083-55 175 (63-95 cm total length). The results were very similar to previous values from the North Atlantic. The reproductive strategy of the roundnose grenadier is discussed in the light of the current commercial exploitation of the Species.