Protracted oogenesis and annual reproductive periodicity in the deep‐sea pennatulacean Halipteris finmarchica (Anthozoa,Octocorallia)

Halipteris finmarchica is one of the most common species of deep‐sea pennatulacean corals in the Northwest Atlantic; it was recently determined to act as a biogenic substrate for other species and as a nursery for fish larvae. Its reproductive cycle was investigated in colonies sampled in 2006 and 2007 along the continental slope of Newfoundland and Labrador (Canada). Halipteris finmarchica exhibits large oocytes (maximum diameter of 1000 μm), which are consistent with lecithotrophic larval development. Female potential fecundity based on mature oocytes just before spawning was ~6 oocytes · polyp^?1 (500–6300 oocytes · colony^?1); male potential fecundity was 16 spermatocysts · polyp^?1 (5500–57,400 spermatocysts · colony^?1). Based on statistical analysis of size‐probability frequency distributions, males harboured one cohort of spermatocysts that matured inside 8–11 months, whereas females harboured two distinct cohorts of oocytes; a persistent pool of small ones (≤400 μm) and a small number (~20%) of larger ones that grew from ~400 to >800 μm over a year. Despite this difference in the tempo of oogenesis and spermatogenesis, a synchronic annual spawning was detected. A latitudinal shift in the spawning period occurred from south (April in the Laurentian Channel) to north (May in Grand Banks and July–August in Labrador/Lower Arctic), following the development of the phytoplankton bloom (i.e. sinking of phytodetritus). Prolonged oogenesis with the simultaneous presence of different oocyte classes in a given polyp is likely not uncommon in deep‐sea octocorals and could hamper the detection of annual/seasonal reproduction when sample sizes are low and/or time series discontinued or brief.     

Life Cycle and Population Dynamics of the Polychaete Perinereis cultrifera from the Algerian Mediterranean Coast

Abstract. The polychaete Perinereis cultrifera ( Grube, 1840 ) (Nereididae) is common along Algerian coasts in algal‐covered hard bottoms. An intensive study was conducted from June 2000 to June 2001 to characterise the life cycle of an intertidal and upper subtidal population of P. cultrifera in Algeria near the Tunisian border (30 km). P. cultrifera has a 3‐year life span and reproduces exclusively by epitoky. The reproductive season is short, and spawning occurs in late April/early May when the sea‐water surface temperature starts rising. Female sexual differentiation starts in February in the second year of life; thus, the oocytes take 16 months to mature and their diameter at maturity is approximately 250 μm.     

Batch fecundity and spawning frequency of southern blue whiting (Micromesistius australis) in the southwest Atlantic Ocean

The reproductive biology of southern blue whiting (Micromesistius australis) inhabiting waters of the southwest Atlantic Ocean (52°‐53°S and 57°‐62°W) was studied through histological analysis of the ovaries. During 2003, the spawning peak occurred at the beginning of September south of the Malvinas Islands. Batch fecundity of this species ranged from 35 000 (41 cm total length, TL) to 245 000 (62 cm TL) oocytes and relative batch fecundity was 122 ± 43 (Mean ± SD, n = 24) oocytes per gram somatic weight. The average proportion of mature females with stage‐0 post‐ovulatory follicles was 0.25 for September 2003, which indicated a spawning frequency of 4 days during the peak of the season. Large females produced more egg batches than small spawners during the same period, but no significant relationship was found between oocyte dry weight and female size of southern blue whiting.     

Reproductive cycle and gonadial changes in the New Zealand rock oyster Crassostrea glomerata

The annual reproductive cycle and the cyclical changes in the gonad of the New Zealand rock oyster, Crassostrea glomerata (Gould, 1850), during the breeding period of 1970–71 and 1971–72 have been described. The gonad passes through an intermediate phase, after a post‐spawning period, when sex is indeterminate. Gametogenesis begins in July and August, but follicles ripen mostly during the spring months of October and November. Maximum development is seen in November, and nearly all oysters are in spawning condition in December and January. Major spawning takes place in January or February depending upon water temperature, and spawning continues until the end of March. Larvae may be found in the‐ plankton until late in the season, to the end of April or even May. Following spawning, gonadial regression sets in, with leucocyte infiltration and phagocytosis of residual gonial cells. A greater percentage of oysters more than 1 y old are females. The majority of oysters of age 1 y and below are males.     

Reproduction in Galaxias fasciatus Gray (Salmoniformes : Galaxiidae)

A study of the reproductive cycle was made on Galaxias fasciatus Gray from streams on Banks Peninsula, South Island, New Zealand. There was no spawning migration; adults remained in the usual adult habitat to breed. The course of gonad maturation showed that spawning occurred in the autumn, from the end of April to mid‐June. Most males matured at 2 years of age and most females at 4 years old. Egg numbers in the females varied from 3800 to 23 600. Males were predominant in age groups 1–4, females in the older age groups. Amongst fish of potential breeding age there was an excess of males. Circumstantial evidence suggested that eggs were laid among piles of water‐logged debris lodged in pools and backwaters. The larvae, which are briefly described, probably hatch during floods to be swept quickly downstream to the sea.     

Timing and habitat of koaro (Galaxias brevipinnis) spawning in streams draining MtTaranaki,New Zealand

A spawning site of Galaxias brevipinnis Giinther was located in a New Zealand stream for the first time. It was at the edge of a riffle and only partially submerged. The habitat used for spawning matched that described for G. brevipinnis in Australia. Spawning was estimated to have occurred between late April and early May and the eggs hatched in late May. The species of fish spawning was identified by rearing the eggs through to identifiable juveniles and by DNA sequencing of one individual.     

Spatio-temporal variations in reproductive patterns and population structure of Pasiphaea multidentata (Decapoda: Caridea) in the Blanes canyon and adjacent margin, North-western Mediterranean Sea

Pasiphaea multidentata is a deep‐water caridean shrimp fished in the Mediterranean in association with the commercially exploited red‐shrimp Aristeus antennatus. A previous study describes seasonality in the reproductive pattern of P. multidentata using external morphological parametres. This study assesses the spatio‐temporal variations in the population structure, sex ratio, ovary cycle and gametogenesis of P. multidentata from three different fishing grounds in the Blanes canyon and adjacent margin (North‐western Mediterranean) over an annual cycle. The oogenetic pattern of this species is typical of a caridean shrimp. There is a pool of previtellogenic oocytes at all times that develop from the periphery of the gonad towards the centre during maturation. Previtellogenic oocytes grow to approximately 200 μm before undergoing vitellogenesis. The vitellogenic oocytes are surrounded by a monolayer of accessory cells. The maximum size observed for a mature oocyte was 1420 μm. The oocyte‐size distribution confirmed the seasonal reproductive pattern of this species; in winter, the ovaries contained mainly previtellogenic oocytes, some of which start maturing in spring, resulting in a slightly bimodal distribution. In summer, the vitellogenic oocytes reach approximately 1000 μm and in late autumn the ovaries are fully mature and ready to spawn. There were no significant differences in the reproductive and population structure patterns of P. multidentata among the three sites, suggesting that the population’s distribution is not affected by the geomorphology of the area, in particular the presence of the canyon. The populations are dominated by females at all sites and all seasons, with the arrival of juveniles in spring. The seasonal variations in the reproduction and recruitment of P. multidentata and the lack of spatial segregation within the population are discussed in terms of the species’ known biology, the effects of canyons in energy supply to the deep‐sea floor and the relationships of this species with the red‐shrimp A. antennatus.     

Spawning and length‐weight of Barracouta (Teleostei: Gempylidae) from eastern cook strait

A sample of 244 barracouta, Thyrsites atun (Euphrasen), caught in eastern Cook Strait, New Zealand, between March 1966 and April 1967, was examined to determine the spawning season and length‐weight relationship.

Female barracouta ripened from April onwards, a month earlier than males. Females tended to attain maturity more rapidly than most males. October and November were the peak spawning months, although some barracouta (mainly females) were mature until January. The smallest spawning barracouta was 55 cm L.C.F. Disappearance of barracouta preceding the spawning months suggested a spawning migration.

A mathematical analysis of the length‐weight data was used to predict one value from the other, and to obtain an index of the relationship (i.e., a condition factor). There was no significant difference between the slope of the regression line n for males and females, the equations being W = 0.03867. L^2.5209 and W = 0.07391 .L^2.3687 respectively. The equation for the regression line for all barracouta, W = 0.05893 . L^2.4222, had an exponent value n lower than expected for a length‐weight relationship of unmutilated fish. The condition factor of barraoouta, measured at monthly intervals, gave a good indication of the spawning cycle.     

Reproductive biology of Ilisha elongata (Teleostei: Pristigasteridae) in Ariake Sound,Japan: Implications for estuarine fish conservation in Asia

Elongate ilisha (Ilisha enlongata) is a commercially important species that contributes to clupeoid fisheries in Asian countries. In the present study, the reproductive biology of I. elongata in Ariake Sound, Japan is determined for the first time. Six maturity stages were described using ovarian and testicular histology throughout the annual cycle. The spawning season in Ariake Sound lasts from May to July, with peak spawning activity in May and June. Age at first maturity was estimated to be 2 years, with a few exceptions of 1 year in well-developed males. Ovaries that contained both tertiary yolk oocytes and postovulatory follicles occurred from late May to late July, indicating that I. elongata is a multiple spawner. The size–frequency distribution of oocytes provided evidence for its multiple spawning and accuracy of the fecundity estimates. The batch fecundity of this species was estimated at between 22,200 and 270,900 eggs per individual, increasing with age between two and six years. The present findings on the reproductive strategy of I. elongata in Ariake Sound are generally consistent with those in temperate or subtropical populations, but quite different from those of tropical population where first maturation occurs around 200 days and life spans are shorter, with a maximum age less than 3 years. The conservation implications of this reproductive strategy in a harsh, variable environment in Asian countries are also discussed.     

Biology and Population Dynamics of Donax trunculus L. (Bivalvia: Donacidae) in the South Adriatic Coast (Italy)

Biology and population dynamics of the suspension-feeding wedge clam Donax trunculus (Linnaeus, 1758) were studied for 13 months (November 1994–April 1996) along the Italian Southern Adriatic coast near the Lagoon of Lesina. Specimens were found at depths between 0 and 2 m, mainly in fine grain bottoms. The spatial coastal distribution showed an intraspecific segregation between young and adult wedge clams. A unimodal recruitment (length >4 mm) occurred in winter (December–February). Length frequency distributions were used to determine age and growth rate. Three year classes were regularly observed and their growth pattern defined. The population showed a maximum length of 37 mm and a longevity of 4 years. Analysis of seasonal variations in the reproductive cycle showed that gametogenesis occurred in spring in females. After the spawning season (March–July) females of D. trunculus remained in a resting stage from August to January.     

Seasonal variation in the reproductive activity and biochemical composition of the Pacific oyster (Crassostrea gigas) from the Marlborough Sounds,New Zealand

Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 μm) occurred during spring (September‐November). The developmental rate and the diameter of mature oocytes (37 μm) was similar for the 1998 and 1999 seasons. For a standard 110‐mm‐length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter‐annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world.     

Studies on the population ecology of Upogebia deltaura (Leach) (Crustacea, Thalassinidea)

Upogebia deltaura was collected quantitatively and qualitatively between June 1980 and August 1982 from a level, sandy bottom at a 12 m depth in the archipelago of Lysekil (on Gullmarsfjorden) about 70 km north of Göteborg, in western Sweden. A total of 347 individuals were obtained. The deepest burrows reached a depth of more than 65 cm into the substrate. During the cold season, U. deltaura was situated much deeper in the substrate than it was during the summer, probably as a result of ‘hibernation’. The average density was 5·0 individuals 0·1 m⁻², and the maximum of 10 specimens was found in one 0·1 m² sample. Out of the 341 individuals identifiable as to sex, 186 (54·6%) were females and 155 (45·4%) were males. Berried females were found between May and August, and the average number of eggs carried was 4757. Ecdysis took place between May and August; most females moulted in the middle of June and most males about one month later, in mid July. The chelipeds of large males were proportionally bigger than were those of large females. Maximum total body length of the females was 65·7 mm, and that of the males was 65·3 mm.     

Population biology of the fiddler crab Uca annulipes (Brachyura: Ocypodidae) in a tropical East African mangrove (Mozambique)

The community structure of the tropical fiddler crab Uca annulipes (H. Milne Edwards) has been studied in Mozambique for the first time. Ten 0.25 m² squares were randomly sampled on a monthly basis during low tide periods from January to December 2002 at Costa do Sol Mangrove, Maputo Bay, southern Mozambique. A total of 981 crabs were captured, of which 494 were males (50.36%), 231 non-ovigerous females (23.85%) and 253 ovigerous females (25.79%). The overall size frequency distribution was unimodal, with males being larger than both ovigerous and non-ovigerous females. Females were more abundant in the smallest size classes while males outnumbered females in the largest ones. The overall sex ratio (1:0.99) did not differ from the expected 1:1 proportion, but significant deviations were observed in January, April, August and November. Results indicate that the size frequency distributions of this species can also be determined through direct analysis of burrow openings. Breeding took place year-round with two peaks of spawning in summer (January and December). Recruits were present throughout the year, with high abundance in summer probably due to the high reproductive activity observed in this season. The present results may allow us to suggest that U. annulipes follows a rapid breeding cycle accompanied by a rapid larval development and settlement in the study area.     

The Reproductive Cycle of Ophioderma brevispinum (Echinodermata: Ophiuroidea)

Abstract. .The reproductive cycle of the brittlestar Ophioderma brevispinum is described using histological and organ index data for a population in Massachusetts, U.S.A. The cycle consists of a one month mid-summer spawning phase followed by gametogenesis and gradual gonadal growth during the winter, and greatly accelerated gonadal growth from May to June. At the end of the spawning season, oogonia proliferate near the base of the ovary, and a continuous layer of spermatogonia lines the testis. As oocytes grow to a maximum diameter of 350 um, yolk granules accumulate and the cytoplasm becomes less basophilic. Prior to spawning, the testis becomes branched and sulcate, and a whorl of spermatozoa produced by columns of spermatids accumulates in the lumen. Comparisons between the reproductive cycles of different populations of O. brevispinum and its congeners support the hypothesis that temperature may be a critical exogenous factor, but definitely not the only factor, in the initiation and duration of the growth and spawning phases of the ophiuroid reproductive cycle.     

Reproductive traits of sandbird octopus, <Emphasis Type="Italic">Amphioctopus aegina</Emphasis> (Gray, 1849) from Mandapam coastal waters (Palk Bay), Southeast Coast of India

The sandbird octopus Amphioctopus aegina (Gray, 1849) is one of the important octopod species in trawl catches in Mandapam waters (Palk Bay). The reproductive biology of this species from these waters was studied from October 2001 to September 2002. In the majority of months(Jan–June), the sex ratio was biased towards males. The ratios of males to females increased consistently with respect to weight Total weight at first maturity were 78.78g for females and 40.8 g for males. Four maturity stags were recognized for females and two for males. Maturation and spawning occur all year round, with a peak during October and another peak during January–February. In males, no definite seasonal changes were observed in gonadosomatic index (GSI) values. In females there were two peaks in GSI values during October and January–February. For individuals of a DML range of 67–85 mm fecundity varied between 2,962–8,820 oocytes. The average relative fecundity was estimated at 68 to 83 and the average number oocytes per gram of ovary were 488 to 539.     

Reproductive resilience of ice‐dependent Antarctic silverfish in a rapidly changing system along the Western Antarctic Peninsula

The Western Antarctic Peninsula (wAP) is globally one of the systems most heavily impacted by climate change, notably steep declines in sea ice extent. In forage species, reproductive resilience to change is particularly important because population fluctuations are rapidly communicated through the system via trophic interactions. The reproductive traits of the ice‐dependent forage species Antarctic silverfish (Pleuragramma antarctica) from different areas along the wAP and at the tip of the Antarctic Peninsula were investigated through macroscopic and histological analyses of gonads, with the aim to assess its reproductive potential and to test for spatial differences in fecundity and spawning season. Fish samples were collected in late summer off Charcot Island, in Marguerite Bay and off Joinville Island; no fish were caught in the central wAP. Samples from Charcot Island and Marguerite Bay consisted of adults in developing gonad stage, whereas those from Joinville consisted almost exclusively of juveniles. Mean GSI was relatively low (2–3%) and similar in both sexes, as specimens were still far from being actively reproducing. Developing females exhibited two discrete, though partially overlapping modes of oocytes of different size, with vitellogenic oocytes measuring 0.5–1.0 mm. Absolute and relative fecundity ranged between 3000 and 12,000 eggs per female and between 80 and 190 eggs·g^?1, with a strong relationship between absolute fecundity and body size. These results were consistent with a single population at Charcot Island and Marguerite Bay and indicated substantial reproductive potential, which may mitigate population isolation and reductions in habitat availability but cannot ultimately offset catastrophic loss of spawning habitat linked to sea‐ice retreat.     

Reproductive biology of Parazoanthus axinellae (Schmidt, 1862) and Savalia savaglia (Bertoloni, 1819) (Cnidaria,Zoantharia) from the NW Mediterranean coast

Despite the wide distribution of zoanthids, little is known about their pattern of reproduction. Here we investigate the reproductive biology of two Mediterranean species, the common Parazoanthus axinellae (Schmidt) and the rare Savalia savaglia (Bertoloni). For both species, samples were collected during an annual cycle, from January to December 2005, in the Western Mediterranean (Ligurian Sea, Italy). Both species are gonochoric. In P. axinellae the sex‐ratio (n colonies = 30) showed a slight predominance of male colonies (M/F = 1.35), whereas in the population of S. savaglia (n colonies = 15) a predominance of females was found (M/F = 0.3). In P. axinellae the first gametocytes were visible in March, whereas in S. savaglia they became visible in May. Both species reproduce at the end of autumn when seawater temperature begins to decrease. Parazoanthus axinellae (10 m depth) spawns eggs and sperms in November, whereas S. savaglia (67 m depth) spawns in December. In P. axinellae sexes were segregated on a rocky wall, with males occurring deeper, whereas male and female colonies of S. savaglia were irregularly dispersed in the population. The maximum number of oocytes differed between the species, being higher in P. axinellae than in S. savaglia.     

Ecological characteristics of Walleye pollock eggs and larvae in the southeastern Bering Sea during the late 1970s

Walleye pollock (Theragra chalcogramma) is an ecologically and economically important groundfish in the eastern Bering Sea. Its population size fluctuates widely, driving and being driven by changes in other components of the ecosystem. It is becoming apparent that dramatic shifts in climate occur on a decadal scale, and these “regime shifts” strongly affect the biota. This paper examines quantitative collections of planktonic eggs and larvae of pollock from the southeastern Bering Sea during 1976–1979. Mortality, advection, and growth rates were estimated, and compared among the years encompassing the 1970s’ regime shift. These data indicate that pollock spawning starts in late February over the basin north of Bogoslof Island. Over the shelf, most spawning occurs north of Unimak Island near the 100 m isobath in early or mid April. Pollock eggs are advected to the northwest from the main spawning area at 5–10 cm/sec. Larvae are found over the basin north of Bogoslof Island in April, and over the shelf between Unimak Island and the Priblof Islands in May. Compared to 1977, the spawning period appeared to be later in 1976 (a cold year) and earlier in 1978 (a warm year) in the study area. At the lower temperatures in 1976, egg duration would be longer and thus egg mortality would operate over a longer period than in the other years. Mean larval growth appeared to be lower in 1976 than in 1977 and 1979. Estimated egg mortality rate in 1977 was 0.6 in April and 0.3 in early May.     

曼氏无针乌贼(Sepiella japonica)繁殖期行为谱特征的研究

自然海域中曼氏无针乌贼产卵亲体性成熟提前和小型化现象明显，这可能是一种适应性进化，人工干预背景下曼氏无针乌贼繁殖期行为的动态变化值得关注。2020年4-6月室内采用聚焦个体扫描法和定点连续记录法分别观察和记录了曼氏无针乌贼繁殖期的行为活动，并按其生活习性和行为的生物学功能等进行系统化分类，构建了繁殖期行为谱。结果表明，曼氏无针乌贼繁殖期行为谱主要包括三大类12种行为：（1）游泳行为主要分为前进和后退，繁殖期的雌性多处于静潜水底或静浮水中的状态；（2）捕食行为主要分为发现、定位、捕捉和咀嚼等系列动作，曼氏无针乌贼能够快速感知周围17.0-36.0 cm范围内的饵料，捕捉的有效距离为8.0-22.0 cm，能在2.0-10.0 s内完成对饵料的高效捕获；（3）繁殖行为复杂，主要分为求偶、伴游、交配、产卵等，其中求偶行为体现在雄性对雌性的自我展示、追逐配对和争斗护卫等过程，雄性在争斗护卫和伴游过程中的护雌行为尤为激烈。曼氏无针乌贼交配时采用"头对头"的方式，平均交配持续时间42.9 s。曼氏无针乌贼对产卵附着基有选择性且偏好于最初的附卵物，卵群对雌性产卵行为有诱导和刺激作用，每次产卵到附卵过程平均用时108.6 s。曼氏无针乌贼繁殖期行为谱特征的研究可为后续曼氏无针乌贼行为机制和基于全生活史的资源保护等方面提供理论依据。