Reproductive biology of Bagrus docmak in the Victoria Nile,Uganda

Aspects of the reproductive biology of Bagrus docmak in the Victoria Nile were investigated between November 2005 and October 2006. Macroscopic and histological analysis of the gonads confirmed it as an asynchronous batch spawner which spawns throughout the year with bimodal spawning peaks coinciding with rainfall seasons. The first spawning peak occurred from March to May, the second from September to November. The sex ratio did not significantly deviate from 1:1. Length at sexual maturity was 33.6 cm and 31.6 cm fork length (FL) for females and males, respectively. Batch fecundity ranged from 1 000 eggs in 34 cm FL fish to 43 000 eggs in 79 cm FL fish, and correlated linearly with FL (r = 0.72) and body weight (r = 0.79). Mean relative batch fecundity was 6 eggs g^?1 (SE 2). These results could guide research into the possibility of artificially inducing the fish to spawn, and its subsequent culture.     

Two stages of juvenile hormone-mediated growth of secondary follicles in Culex pipiens

To investigate the effect of juvenile hormone deprivation on the growth of secondary follicles during the second gonotrophic cycle, female mosquitoes, Culex pipiens L., were allatectomized daily after the first blood meal. Allatectomy on days 1–3 suppressed growth of secondary follicles indicating that juvenile hormone was required for a second gonotrophic cycle. When allatectomy was performed 4 days or more after the first blood meal, secondary follicles grew, indicating the presence of juvenile hormone. However, if mosquitoes were allatectomized before oviposition, only 25% developed a second batch of eggs after a second blood meal.Allatectomies performed 1 and 24 h after oviposition indicated that additional juvenile hormone was released after deposition of the first batch of eggs, and that this second release was needed for secondary follicles to complete previtellogenic growth. Thus, in C. pipiens, secondary follicles undergo two periods of juvenile hormone-mediated growth-one before and one after oviposition.     

Adaptive increase of level of serotonin-modulated anticonsolidational protein in tissues of semimigratory and migratory fish at increase of water salinity

The article deals with studies of serotonergic system activity in different tissues of semimigratory fish—the Caspian roach (Rutilus rutilus caspicus) and the carpbream (Abramis brama orientalis)—and of migratory fish—shemaya (Chalcalburnus chalcoides) caught in fresh and brackish waters, as well as in the common carp (Cyprinus carpio L.) tissues under effect of brackish water in model experiments. Using the indirect solid-phase ELISA-test, the serotonergic system activity was evaluated by measuring in the tissues of the studied fish the serotonin-modulated anticonsolidation protein (SMAP) which is in linear relationship with the serotonin level. There was found a significant elevation of SMAP levels in brains of the Caspian roach, carpbream, shemaya, and the common carp under action of increased water salinity. A revealed increase of the SMAP content in brain of the Caspian roach, carpbream, shemaya and the common carp under action of increased water salinity reflects the corresponding elevated activity of the serotoninergic system and indicates involvement of adaptive readjustments in the animals’ body.     

Fine structure of the egg envelope and the supporting stalk in the dipliran Campodea (Apterygota : Campodeidae)

The eggs and supporting stalks of one Campodea (Apterygota : Campodeidae) species were studied by scanning and transmission electron microscopes. Each egg batch is attached to the substrate by a supporting stalk. The stalk is composed of tangled lamellae and dense annular structures. Both elements are strongly PAS-positive. The eggs are covered by one envelope only. It is built of fine granular, PAS-negative material. The surface of the envelope is smooth and possesses 2–4 ring-like structures, which are likely involved in the attachment of the eggs within a batch.     

Evidence for the reproductive isolation ofDermacentor marginatus andDermacentor reticulatus (Acari: Ixodidae) ticks based on cross-breeding, morphology and molecular studies

The species status ofDermacentor marginatus andDermacentor reticulatus was evaluated by scanning electron microscope (SEM) examination of adult ticks, cross-breeding experiments and molecular biological analysis of eggs derived from transspecific pairings. The SEM investigations including the morphometric quantification of phenotypic features, resulted in an unequivocal differentiation of adultD. marginatus andD. reticulatus ticks. The cross-breeding experiments demonstrated that irrespective of whether female ticks of both species were applied with con- or transspecific male ticks or without males to sheep, they engorged and laid eggs. The larvae, however, developed only in eggs which originated from conspecific matings. A nested polymerase chain reaction (PCR) of the second internal transcribed spacer (ITS2) using the DNA of eggs from transspecific pairings and sequencing of the PCR products revealed two different genotypes. The genotypes of eggs originating fromD. marginatus andD. reticulatus females of these pairings differed. However, the eggs deposited byD. marginatus always possessed the same two genotypes as did the eggs produced byD. reticulatus. These results argue for a strict reproductive isolation ofD. marginatus andD. reticulatus and, therefore, for a separate species status.     

Mating and fecundity of Dermatophagoides farinae

Studies of the life cycle of cultured Dermatophagoides farinae found that after an initial mating D. farinae females lived for 63.3 ± 64.6 (SD) dafter their egg production period ended .The long period after cessation of egg production for D. farinae suggested D. farinae females could mate multiple times and produce eggs continuously for a longer period. The purpose of this study was to determine if female D. farinae could mate at least two times, and subsequently increase the production of viable eggs over a longer period of time compared to a single mating. Female D. farinae were randomly selected from thriving cultures and isolated in cages. When the females had ceased to lay eggs a male was added to the cage. Fifty-seven percent of the isolated females mated again and produced a second batch of viable eggs. In natural or culture populations, females have continuous availability of males. Therefore, in another experiment, females that emerged from the tritonymphal stages were continuously exposed to fresh males and fecundity and lengths of the reproductive and post reproductive periods were determined. These females had a 11 d longer reproductive period and produced 30.7% more eggs compared to females that only mated one time after they emerged from the tritonymphal stage. However, the post reproductive period was still long (58.6 ± 11.4 [SE] d) the significance of which is not clear. In conclusion, this study revealed that D. farinae females are capable of more than one successful mating that results in increased egg production compared to that of a single mating. It is likely that females mate multiple times in natural and culture populations. It was observed that females actively attract males during the reproductive period but not afterward even though she continues to live a long time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive behavior and spawning success of female Amblyglyphidodon leucogaster (Pisces: Pomacentridae) from the Red Sea

The reproductive behavior of female whitebelly damselfish, Amblyglyphidodon leucogaster, was investigated in the Gulf of Aqaba, Red Sea over two breeding seasons. Females were promiscuous, mating with 7–10 different males throughout the season. Females lay eggs in distinct batches, defined as the total number of eggs laid in a day. Generally females deposit a batch of eggs with one male (87.2%) and are capable of laying a new batch every other day. Egg batch size averaged 4009 eggs and females laid from 2 to 22 egg batches per season. The variation in spawning success was not correlated to body size. Females preferred to deposit eggs in nests that already contained early stage eggs (0–2 days old). Within a nest, females chose to lay eggs contiguous to the youngest egg batch, regardless if the nest contained either a single batch or multiple batches of different ages. Female within-nest spawning patterns appear to be a consequence of between nest preferences for nests with young eggs. It is proposed that the strong within-nest preference is a consequence of mate selection where females may use new egg batches as a visual cue as part of a copying style. Such a style may reduce the risk of predation and increase feeding opportunities, because less time is expended in mate selection, which would provide additional resources for egg production and ultimately increase female spawning success over the breeding season. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive biology of an amphidromous goby, Sicyopterus lagocephalus, in La Réunion Island

In the Indo-Pacific region, rivers are inhabited by amphidromous gobies. They are often subjected to a heavy fishing pressure, highlighting the urgent need to acquire knowledge on their biology for management purposes. This study investigated the reproductive strategy of Sicyopterus lagocephalus, a widespread amphidromous goby, in two rivers of La Réunion Island. Histological observations of ovarian samples and oocyte-size frequency distributions revealed that females had a group-synchronous ovarian follicle development (i.e., two cohorts of oocytes were distinguished simultaneously in ovaries). Females laid an entire clutch in a unique event (from 14,304 to 232,475 eggs) and then another batch of oocytes was recruited, showing that the annual fecundity is indeterminate. Ovarian growth was isometric at all oocyte development stages showing that the gonadosomatic index (GSI) is a good proxy of reproductive condition. The main reproductive season of S. lagocephalus spanned from early February to May with a narrower range upstream and a wider one downstream. Reproduction activity is mainly restricted by water temperatures in upstream areas, whereas it is likely influenced by female body condition and competition in downstream areas. The variability of reproductive traits leads to size structure variation in stocks of spawning females throughout the year.     

SPERM MIXING IN THE COCKROACH DIPLOPTERA PUNCTATA

Females of the viviparous cockroach Diploptera punctata store sperm from their first mating, and do not remate until after giving birth to their first batch of young. The irradiated male technique was used to determine the outcome of sperm competition in the second batch of eggs of females mated sequentially to normal and irradiated males. It is estimated that the second male to mate with a female fertilizes approximately two thirds of the eggs in a female's second batch of eggs. Direct evidence for sperm mixing was obtained. Undeveloped eggs (fertilized by irradiated sperm) and developing embryos (fertilized by normal sperm) were found interspersed throughout oothecae that were extruded from females, demonstrating that normal and irradiated sperm were released from the spermathecae at oviposition and that they competed for fertilizations.     

Assessing the age of field female wheat bulb flies (Leptohylemyia coarctata)

From 1967 to 1971, wheat bulb fly females caught by sweeping from a number of localities contained mature eggs from the third week of July to the end of August. In 1971 when female wheat bulb flies were caught by sweeping, by white water traps, by suction traps as well as by light traps, the first flies containing mature eggs were caught 29 days after the first detected emergence while the first batch was laid 29–58 days after first emergence. The peak period of egg laying occurred in the fourth week of July, 24–38 days after the peak emergence. The second batch of eggs was laid when the flies were 8 weeks old, 29 days after the first; the peak for this batch was 35 days after the first. A few females laid a third batch of eggs 28 days after the first record of the laying of the second batch. A female that lives sufficiently long to lay the third batch of eggs is at least 12 weeks old. In 1970, when emergence started earlier in June, ripening and laying of eggs of the three batches was also earlier. After the harvest of cereal crops more females were caught by white water traps placed on the fallow than by other methods. The most important pathogen affecting adult wheat bulb flies was a fungus, probably Entomophthora muscae. When infection occurred early in July, fewer eggs from the first batch were laid than when infection developed later. Fewer flies were infected in 1971 than in 1970. To be effective against wheat bulb fly in the early spring, control measures-should be applied against adults before their eggs mature in early July of the preceding year.     

Divergence in reproductive ecology of the three-spined stickleback,Gasterosteus aculeatus

An anadromous population (trachurus form) and three freshwater populations (leiurus form) of the three-spined stickleback,Gasterosteus aculeatus, in central Japan were compared with one another in the reproductive traits: body length at maturity, egg size, clutch size, the swell of abdomen and the number of eggs per nest. The anadromous fish which become larger in body size at maturity spawn eggs smaller in size and greater in number than the freshwater fish. The abdomen swell of gravid females expressed by the proportion of abdomen width to body length was greater in the freshwater fish. The anadromous male fish collected a mean of 2,638 eggs with a range of 1,119 to 4,052 eggs from about 6–7 females. In the three freshwater (the Yamayoke, the Tsuya and the Jizo) populations, males must have mated with about 9–22, 7–18 and 4–7 females respectively. It seems that theleiurus form increases its reproductive success by its much more mating opportunities and the parental efforts of nesting males as well as by spawning large eggs. Furthermore, among the freshwater populations, the Jizo one inhabiting the upper stream was clearly larger in body size, in egg size and in clutch size than the Yamayoke and the Tsuya ones which inhabit stable waterbodies with springs. It is possible that the Jizo population adopted the strategy of spawning a few large eggs as an adaptation to its habitat. The causal and functional explanations in reproductive characteristics among the four populations are discussed in regard to differences in the environmental conditions.     

Development of choline acetyltransferase activity in chick cranial neural crest cells in culture

The types of mouse parthenogenones obtained in a medium modified with respect to Ca²⁺ and/or Mg²⁺ ions were investigated in “spontaneously” activating eggs after culturing cumulus masses in vitro for 5 hr. The second meiotic division was affected in eggs cultured in medium lacking Ca²⁺ and Mg²⁺ or Ca²⁺ alone, resulting in suppression of second polar body extrusion in a high proportion of cases, giving rise to two pronuclear eggs or eggs that underwent immediate cleavage. Extrusion of the second polar body occurred normally when the cumulus mass was cultured in complete medium and, in a high proportion of eggs, when Mg²⁺ alone was lacking in the medium. The results are discussed with reference to the second meiotic division. The method provides an efficient way for obtaining a large number of different types of parthenogenetic embryos.     

Laying characteristics of one- and two-year old pheasants (Phasianus colchicus, L.)

The aim ofthe study was to assess laying traits, the weight of eggs and characters ofthe laying rhythm of pheasants in the first and second years of reproduction. Pheasants (10 cockerels and 50 hens) were kept in aviaries. Daily, individual control of laying was performed beginning with the day of the first laying and ending with the last egg. The following parameters were evaluated: age at first laying, length of the laying period, number of laid eggs and the average weight of the egg in the 8th week of laying. The laying rhythm was also assessed and comprised: the number of egg clutches, the number of eggs in a clutch, the number of eggs in the longest clutch, the number of intervals, the length of intervals and the longest interval between clutches. During the first period of reproduction, in comparison with the second, pheasants laid slightly more eggs of similar average weight. The first laying period was longer than the second and was characterised by a greater number of egg clutches and greater number of intervals between clutches. The greatest number of eggs was laid in 10-egg and longer clutches, although the l-egg clutches were the most numerous. A positive correlation was found between the number of eggs and the number of clutches, the greatest number of eggs in a clutch and the number of intervals between clutches. The similar values of the reproductive characters of one- and two-year old pheasants point to the possibility of longer utilization of these birds than only for one laying period. On the other hand, the considerable variability between the experimental hens with regard to the number and the length of egg clutches, as well as the intervals between them, indicate the possibility to carry out selection taking into account traits characterising the laying rhythm.     

Distribution ofChilo partellus (Lepidoptera: Pyralidae) egg batches on maize

Distribution ofChilo partellus egg masses was studied in field, greenhouse, and laboratory experiments. The eggs were laid in batches mainly on the lower side and the lower leaves of the plant. The egg batch size ranged from 1 to 169 eggs, with a median of 33.5 eggs per batch (average, 40.5). Oviposition ofC. partellus is described at two levels. The first level, choice of oviposition plants, followed a random distribution. The second level, number of egg batches per plant, followed an aggregated distribution in the field, where more than one egg batch was deposited on the same plant by the same female, which was found on 25% of the oviposition plants. A mechanism for egg-layingC. partellus females to perceive preceding oviposition or injured plants could not be detected. Oviposition site choice seemed to be mediated by tactile stimuli.     

Estimation of population fecundity of the bitterling,Rhodeus ocellatus,and ecological significance of its spawning habit into bivalves

Fluctuations of the population abundance of the rose bitterling,Rhodeus ocellatus (Kner) in a small pond, Shimizu-ike (700 m²), Osaka Prefecture, Japan, were estimated by the Petersen method from 1973 to 1977. The number of fish fluctuated between 12,600 and 46,700 during that period. In 1974, a large reproductive peak in May contributed mainly by 2- and 3-year-old spawners and a small peak in late July contributed by 1–2-year-old fish were observed. Average number of eggs laid in a bivalve,Anodonta woodiana Lea, in each month was estimated with field experiments from March to November, 1974. In total, 93,400 eggs were laid during the first reproductive peak, and 13,100 eggs during the second reproductive peak. The mortality of eggs and larvae incubated in the bivalve was less than 30%, and approximately 70 % of the larvae that had swum out from the host died in the following six months. Thus, it is estimated that approximately 20% of the eggs laid in the bivalves can survive and grow up to reach the first maturity. The high survival rate ofR. ocellatus among cyprinid fishes might be due to the fact that the eggs and larvae are protected from predation by being embedded in a bivalve, and to the fact that the larvae at the earliest free swimming stage have a good opportunity of surviving because they are much larger in size and more developed morphologically than those of other cyprinid fishes.     

Effect of multiple mating on the reproductive performance of the rice leaffolder moth,Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

To clarify whether multiple mating of females and males affects the reproductive performance of the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we examined the effect of the number of matings (once, twice, or three times) for females (female treatment) and males (male treatment) on the incidence of moth mating, number of eggs laid, egg hatchability, and adult longevity. We also compared the effect of multiple mating imposed on males or females separately with the effect of that imposed on both sexes simultaneously (both sexes treatment). The incidence of mating of females and males that mated three times (3-mated females and males) was significantly lower than for females and males that mated twice or once (2-mated or 1-mated females and males). The incidence of mating of 1-mated moths (both sexes) was significantly higher than for 2-mated or 3-mated moths (both sexes). Two-mated or 3-mated females laid significantly more eggs with significantly higher hatchability than 1-mated females. Females that mated with 1-mated males (second male mating) or 2-mated males (third male mating) laid significantly fewer eggs than those that mated with virgin males (first male mating). Females laid significantly more eggs after the second and third matings for moths of both sexes than after the first mating for moths of both sexes. The mechanisms of improvement and decline of female reproductive performance when multiple mating was imposed on males or females are also discussed in relation to the reproductive biology of C. medinalis.     

Development of the olfactory organ in the ontogeny of carps (Cyprinidae)

Morphogenesis of the olfactory organ is followed with a light microscopy method in silver carp Hypophthalmichthys molitrix, common carp Cyprinus carpio, Eurasian minnow Phoxinus phoxinus, shemaya Alburnus chalcoides, zebra danio Danio rerio, and bitterling Rhodeus sericeus amarus. In these fishes with different reproductive ecology, the olfactory organ develops in a similar way, and it is characterized by a similar structure in the representatives of different species of the same body length. Morphological features revealed in different species are not numerous, and they are not associated with the development of main structures of the olfactory organ. However, the interspecific differences can be connected with different developmental rates of these structures. Based on developmental rate of the olfactory organ, the studied species are divided into three groups with (1) accelerated development (the litophils, Eurasian minnow and shemaya); (2) moderate development (a pelagophil, silver carp, and the phitophils, common carp and zebra danio; and (3) retarded development (an ostracophil, bitterling). The differences in the degree of development of the olfactory organ in the species from various ecological groups are particularly evident to the beginning of the juvenile period. The appearance of all main structures of the olfactory organ is completed in the litophils at the onset of the second juvenile step (XVII); that in the pelagophils and phitophils is by the end of this step, that in ostracophils is substantially later (young of the current year), and that in zebra danio is to the beginning of sexual maturation. In the studied species, olfactory organ becomes differentiated/formed at different age and at various morphological states of the progeny, but at similar body size (29–30 mm). Thus, the body length of carps can be regarded as an indicator of a level of morphological development of the olfactory organ.     

The reproductive strategy of Argonauta nouryi (Cephalopoda: Argonautidae) in the Mexican South Pacific

ABSTRACT

Aspects of the reproductive biology of Argonauta nouryi Lorois, 1852 from the coast of Oaxaca, Mexico, were analysed. A total of 54 specimens with dorsal mantle length (ML) ranging from 6.2 to 41.1?mm were obtained from the stomach contents of five species of large predatory fishes from January 2016 to June 2018. The goals of this study were to collect data on reproductive indicators in order to evaluate the reproductive strategy of A. nouryi in the southeast Mexican Pacific and to use histological analysis to characterise the different ovarian phases based on oogenesis. Immature females (19.6?mm?ML) had sperm in their oviducal glands, indicating that female A. nouryi store sperm long after hectocotyli transmission by males. Potential fecundity was estimated as 31,000–75,026 eggs, with a batch fecundity of 2,000–8,000 eggs. Six distinct developmental stages were observed in the eggs suspended in the A. nouryi shell. Our data indicate that the A. nouryi reproductive strategy includes continuous low batch spawnings, mating early in life, and sperm storage in the spermatheca.     

Reproductive allocation by the blow fly Lucilia sericata in response to protein limitation

Adult females of the anautogenous blow fly Lucilia sericata (Meigen) (Diptera: Calliphoridae) were fed standardized meals of liquidized liver, in quantities shown to range around the minimum required to initiate yolk deposition. Females from each feeding regime were dissected at daily intervals between 4 and 11 days of age; the number and stage of development of all oöcytes were recorded. Once an initial threshold quantity of protein was ingested, yolk deposition was initiated in all available oöcytes. Subsequently, one of two distinct developmental pathways was followed: arrested development in all oöcytes at an early stage of yolk deposition, or more extensive yolk deposition followed by progressive oösorbtion and the maturation of small batches of eggs. The proportion of females showing oösorbtion relative to arrested follicular development increased with increasing protein meal size, suggesting that the difference in response may be triggered by a second protein threshold, either side of which the arrested development or oösorbtion pathways are followed. The behaviour observed may reflect strategies to maximize reproductive output in this short‐lived, resource‐limited insect species. Flies that display arrested development may have sufficient protein to mature few if any complete eggs, but may subsequently be able to mature a full egg‐batch if they obtain further protein meals; this possibility is offset by the risk of death before finding such a meal. Flies that show oöcyte development and oösorbtion produce smaller egg batches more quickly and hence have a higher probability of achieving at least some reproductive output. By initiating yolk deposition in all oöcytes, female L. sericata retain the potential to adopt either developmental pathway, depending on subsequent protein intake.     

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake,China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934?±?5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560?±?137 eggs g^?1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.