Seasonal cycle of gonadal development and serum levels of vitellogenin of the red porgy, Pagrus pagrus (Teleostei: Sparidae)

Histological examination of gonads of female and male red porgy, Pagrus pagrus, reared in captivity, was carried out in order to describe the main gonadal changes related to gametogenesis and the seasonal changes of environmental factors. The gonadosomatic index (GSI) and the concentration of serum vitellogenin (VTG) were also determined. The frequency distribution of gonad development stages and the GSI and vitellogenin concentration during the annual cycle indicated the separation of the female and male reproductive cycles into three main periods. The autumn period when gametogenesis begins (October-November), the period of exogenous vitellogenesis (December-March) or spermiation (December-March), and the spawning season (March-May). The spawning period coincided with an increase in temperature (15-19°C) and daylength. Serum levels of vitellogenin rose significantly in January, reached a peak at the beginning of the spawning period (March, 405.5 µg ml^-1) and remained high until the end of the spawning period (May).     

Changes in dopamine,norepinephrine and serotonin levels in the pituitary,telencephalon and hypothalamus during gonadal development of male <Emphasis Type="Italic">Lutjanus argentiventris</Emphasis> (Teleostei)

Biogenic amines are important in the regulation of certain aspects of teleost reproduction, but relatively little is known about variations in their levels in the nervous system during the reproductive cycle. The aim of this study was to investigate changes in the levels of dopamine (DA), norepinephrine (NE), serotonin (5-HT), the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) and the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the pituitary and brain (hypothalamus and telencephalon) of the adult male of the tropical marine yellow snapper Lutjanus argentiventris during the reproductive cycle (quiescent, prespawning and spawning periods). Gonad weight, gonad/body weight ratio and plasma-testosterone levels increased steadily throughout gonadal development, but 17#-estradiol levels did not vary significantly. Pituitary DA and DOPAC levels and the DOPAC/DA ratio declined with gonadal development, whereas hypothalamic DOPAC level and DOPAC/DA ratio increased. In the telencephalon, DA and DOPAC levels and DOPAC/DA ratio all peaked in the prespawning period; however, DA level was lowest in the spawning period, whereas DOPAC level and DOPAC/DA ratio were both lowest in the quiescent period. Telencephalic NE, 5-HT and 5-HIAA levels likewise all peaked in the prespawning period, and were lowest in the spawning period. Telencephalic 5-HIAA/5-HT ratio peaked in the quiescent period and was lowest in the spawning period. No significant variation was observed either in pituitary NE level or in hypothalamic NE, 5-HT and 5-HIAA levels. The present results indicate that males of L. argentiventris show a decline in pituitary DA activity during gonadal development. We discuss the possible involvement of biogenic amines in the regulation of GTH II secretion, through direct action on the pituitary or indirect modulation of gonadotrophin-releasing hormone neuron activity.     

Reproduction of the commercial sea cucumber Holothuria scabra (Echinodermata: Holothuroidea) in the Solomon Islands

Over a 3-year period (1996-1998), reproduction of the commercial sea cucumber Holothuria scabra (Jaeger, 1833) was investigated in the Solomon Islands to determine the spawning pattern and whether gametogenesis is continuous or seasonal. The gonad consisted of a single cohort of tubules that developed uniformly. Macroscopic examination of the gonads revealed that mature gametes were present throughout the year. Individuals with gonads at different stages of maturity were present in most samples. Partly spawned gonads were prevalent in females, whereas mature gonads were prevalent in males. The time at which the peak gonad index was recorded differed among years. Although gametogenesis was continuous, with a potential for prolonged gamete release, a period of enhanced spawning occurred during the dry season, from September to December. Maximum gonad indices were reached prior to and during this period of enhanced spawning. Histology revealed that gametogenesis reinitiated in partly spawned gonads, resulting in the presence of gametes at different stages of development in the gonad. The uniform growth of gonad tubules indicated that H. scabra does not conform to the progressive tubule recruitment model described for holothurian oogenesis. Continuous reproduction in H. scabra and prolonged availability of mature gametes would facilitate use of this species for aquaculture.     

Reproductive cycle of two commercial species of sea cucumber (Echinodermata: Holothuroidea) from Caribbean Panama

The reproductive status of the holothuroid species Isostichopus badionotus (Selenka, 1867) and Holothuria mexicana (Ludwig, 1875) was studied over 16 months in Bocas del Toro (Panama), from November 1999 to February 2001. Sexual reproduction was evaluated by the gonad index method, and by histology of gonad development. In addition, population structure was assessed based on sex ratio, minimum reproductive size, and length and weight distributions of males and females. The sex ratio in both species was 1:1, with a unimodal population distribution composed mainly of mature individuals. The minimum reproductive length and weight were 13-20 cm and 150 g, respectively, for both species, although reproductive individuals 10 cm in length were also found. A consistently higher gonad index was observed in H. mexicana, due to a high proportion of mature females and males and high gonad indices in most monthly samples. Gametogenesis and spawning patterns seemed to occur throughout the year, with periods of enhanced activity. Two periods of maximum reproductive activity were tentatively identified: July-November for I. badionotus and February-July for H. mexicana, but neither species had a single, sharply defined annual spawning event. Further work on these exploited holothuroids should examine the relationships between reproduction and environmental factors and between reproductive status and recruitment.     

Sexual and asexual reproduction of <Emphasis Type="Italic">Coscinasterias</Emphasis><Emphasis Type="Italic">tenuispina</Emphasis> (Echinodermata: Asteroidea) from Rio de Janeiro,Brazil

An intertidal population of the fissiparous sea star Coscinasterias tenuispina (Lamarck, 1816) was sampled over a 1 year period at Ponta de Itaipu, Niterói, Rio de Janeiro. Gonadal indices revealed an annual reproductive cycle. Spawning occurred in the late winter and early spring between August and November. Pyloric caecal indices did not show a clear annual cycle or a reciprocal relationship with gonadal indices. The population appears to be sustained only by fission, as only males were found. Fission occurred throughout the year, but was most frequent in the winter (July, August and September). Incidence of fission was correlated with the occurrence of the extremely low tides during daytime that exposes many specimens to air. Austral winter tides are low by day and high by night, while the austral summer tides are low by night and high by day. The most extreme annual deviation in seawater temperature is about 5°C. Larval recruitment seems to be negligible, since very small individuals were not found.     

Oculina patagonica: a non-lessepsian scleractinian coral invading the Mediterranean Sea

The scleractinian coral Oculina patagonica De Angelis is a new immigrant from the Southwest Atlantic to the Mediterranean Sea, having established itself only recently along the Israeli coast. This species is the only scleractinian coral reported to have invaded a new region. In order to understand the swift establishment of this species along the Israeli coast, from 1994 to 1999 we studied its distribution, abundance, reproduction, recruitment, survival, and the effect of bleaching events on its population abundance. In addition, population studies of O. patagonica were performed at several localities along the eastern and western Mediterranean coasts. Highest abundance was recorded along the Spanish coast, reaching 30lj colonies per 10 m line transect in shallow water. Second in abundance was the Israeli coast, with a maximum of 10DŽ colonies per transect. O. patagonica was rare along the coast of Italy, and absent along the Mediterranean coast of France. During the study, both mortality and recruitment along the Israeli coast were very low. In contrast, recruitment along the Spanish coast was very high. Reproduction of the species was studied using gonadal histology. O. patagonica is gonochoric. Female gonads were first observed in May and male gonads in July, both reaching maturity in late August and early September. Naturally occurring azooxanthellate colonies of O. patagonica inhabiting small dark caves developed gonads and spawned in parallel to zooxanthellate colonies exposed to light. No gonads were found in zooxanthellate colonies that underwent bleaching during the reproduction season. The high incidence of bleaching events along the Israeli coast observed throughout the years of this study may explain the low recruitment of new colonies during the same period. In view of its current recruitment patterns, we expect further expansion of O. patagonica in range and abundance in the western Mediterranean, but very small expansion of the population in the eastern Mediterranean, due to repetitive annual bleaching events.     

Patterns of larval and early juvenile growth in a semiterrestrial crab, Armases angustipes (Decapoda: Sesarmidae): comparison with a congener with abbreviated development

In a semiterrestrial and estuarine tropical crab, Armases angustipes Dana (Grapsoidea: Sesarmidae), changes in biomass (measured as dry mass, W; carbon, C; nitrogen, N; and hydrogen, H; per individual) and relative elemental composition (C, N, H, in percent of W; C:N mass ratio) were studied during development from an early egg stage through hatching, the complete larval phase, metamorphosis and the first juvenile crab stage (CI). In the megalopa and CI, growth was measured also within the moulting cycle, and biomass and elemental composition were determined in cast exuviae. From an early egg stage to the freshly hatched larva, A. angustipes lost about 20% of W, 29% of C, 5% of N and 32% of H. Proportionally higher losses in C than in N were reflected also in a significantly decreasing C:N mass ratio (from 5.02 to 3.74). These results indicate that lipids mobilised from yolk reserves represented the principal metabolic substrate for embryonic energy production, while proteins were catabolised at a much lower rate. The present data of growth and exuviation are compared with previously published data from a congener, A. miersii Rathbun, which has an abbreviated and facultatively lecithotrophic mode of larval development (with three instead of four zoeal stages; stages I and II in principle independent of food). When growth is measured as an increase in the final (premoult) biomass of successive developmental stages, both species show an exponential pattern. Within the moulting cycles of the megalopa and the first juvenile, both species show parabola-shaped growth curves, with a rapid biomass increase in postmoult and intermoult stages, and losses in the premoult phase. Thus, the two Armases species show, in general, similar patterns of larval and early juvenile growth. However, the initial size of eggs and larvae is about four times larger in A. miersii, and its biomass remains higher throughout the period of larval and early juvenile development. A. angustipes is able to partially make up for this difference, as it has an additional zoeal stage, and its megalopa and CI stages show higher relative biomass increments (in percent of initial values). Due to this compensatory growth pattern, A. angustipes reaches in its CI stage about half the biomass of a juvenile A. miersii. When exuvial losses of megalopae and juveniles are compared between these two species, A. miersii shows higher biomass losses per individual (corresponding with its larger size), but lower relative losses (C, N, H, in percent of late premoult body mass or in percent of previously achieved growth increments). Differences in larval and early juvenile growth and in the exuvial losses of megalopae and juveniles of these two congeners are discussed in relation to their differential ecology, life history and reproductive strategy.     

Reproductive cycles of three dominant Calanus species in Disko Bay, West Greenland

This study describes the annual reproductive cycles of the three dominant Calanus species, C. finmarchicus, C. glacialis and C. hyperboreus, in Disko Bay (West Greenland) in relation to seasonal phytoplankton development. Relative abundance of females, copepodite stage V (CV) and males, and the developmental stage of the female gonad were examined from plankton samples collected at weekly to monthly intervals from May 1996 to June 1997 with a WP2 net or a pump. During spring and summer, egg production rates were determined. Females of all three species were present year round. Maximum relative abundance was reached by C. hyperboreus females at the beginning of February, by C. glacialis in mid-February, and by C. finmarchicus in April. All three species reproduced successfully in Disko Bay. Their reproductive cycles were considerably different with respect to the timing of final gonad maturation and spawning, and hence in their relation to seasonal phytoplankton development. In all three species, early gonad development took place during winter, before living food became plentiful, suggesting that these processes were largely food independent. Final gonad maturation and spawning in C. finmarchicus was related to the phytoplankton concentration, reflecting that final gonad maturation processes are food dependent in this species. C. glacialis females matured and spawned prior to the spring bloom. Our results indicate that first internal lipid stores and later ice alga grazing supplied final gonad maturation and egg production. Maximum egg production rates of C. glacialis were found in spring and summer, when the chlorophyll a concentration was high. Mature female C. hyperboreus were found from February until mid-April, when the chlorophyll a concentration was still low. In this species, reproductive activity was decoupled from phytoplankton development, and final maturation processes and spawning were solely fuelled by internal energy stores.     

Biological patterns and near-bottom population characteristics of two pasiphaeid decapod crustacean species, Pasiphaea sivado and P. multidentata, in the north-western Mediterranean Sea

Biological aspects of the only two epi-/mesopelagic pasiphaeid species distributed along the continental marginof the north-western Mediterranean Sea were studied over the period 1991-1994. The annual reproductive cycle, reproductive output, sex and size distributions by depth (near-bottom distribution), and growth were analysed using 4156 specimens of Pasiphaea sivado (Risso, 1816) and 5491 specimens of P. multidentata Esmark, 1866. The reproductive cycle in the shallower-dwelling species, P. sivado, was nearly continuous, in contrast to the reproductive cycle in P. multidentata, which was markedly seasonal in nature. Both species exhibited similar size and population structure patterns with depth, with individual size increasing along the bottom depth gradient. The shallower-dwelling species had a significantly higher reproductive output level, in terms of the relative number of eggs, than the deeper-dwelling species. Biological trends for each of the species have been compared. The comparative results for these two congeneric species revealed that the biological parameters analysed were closely linked to their population structure. The slight differences in the depth range inhabited by each species have been considered the main environmental factor affecting the life histories of these two species. The data presented supported the hypothesis that depth exerted an important influence on the biological patterns of deep-water species, with the seasonality of reproductive processes increasing in deeper-dwelling species.     

Gonadal development in the coral reef damselfish<Emphasis Type="Italic"> Dascyllus flavicaudus</Emphasis> from Moorea,French Polynesia

The present study investigated the sexual pattern of the yellow-tailed dascyllus, Dascyllus flavicaudus (Randall and Allen), through histological examination of the process of gonadal differentiation and maturation and through male-removal experiments in the laboratory. The study was conducted in Moorea, French Polynesia (17°32S; 149°50W), from 31 December 1994 to 11 March 1995. For gonadal histology, two populations were sampled, one consisting of large aggregations (n=54) and the other consisting of small- to medium-sized groups around isolated corals (n=55). An additional small sample (n=21) was also collected from a population that consisted of small groups around isolated corals. After an initially undifferentiated state, gonads of D. flavicaudus developed an ovarian lumen, followed by oocytes in the primary growth stage. From this ovarian state or from more developed ovaries with cortical-alveolus stage oocytes, some gonads developed into testes through degeneration of oocytes and development of spermatogenic tissue. In all three populations, spermatogenic tissue developed only in gonads that contained pre-vitellogenic oocytes (termed as mixed stage 1–2 gonads). The two main populations did not differ in their expression of sex change despite differences in their social organization. In both populations, size of individuals with mixed stage 1–2 gonads overlapped mainly with the size range of immature females, which suggests that functional female-to-male sex change was rare. The hypothesis that D. flavicaudus is primarily gonochoristic is further supported by removal experiments in laboratory groups, in which removal of a dominant male(s) failed to induce sex change in any of the high-ranking females. Yet, in all three field populations, some fish with mixed stage 1–2 gonads were found within the size ranges of mature females, which indicates possible occurrences of functional sex change. These conflicting results indicate that it may be premature to draw any definitive conclusions about the sexual pattern of D. flavicaudus.Communicated by T. Ikeda, Hakodate     

Reproductive investment reduces recuperation from exhaustive escape activity in the tropical scallop Euvola zizac

In scallops, mobilization of reserves from the adductor muscle to support maintenance and reproductive activity may impinge upon a major role of the adductor muscle, the movement of the valves during swimming and escape responses. The tropical scallop Euvola ziczac (Linnaeus 1758) invests energy reserves to different degrees during its two periods of reproduction each year. We evaluated the impact of reproductive investment on the escape responses (clapping capacity and recovery after exhaustive exercise) of E. ziczac sampled at different reproductive stages (immature, mature, spawned) during the two reproductive periods in 1997. We compared the escape response capacities with the levels of muscle energetic reserves (glycogen, proteins, and arginine phosphate) and muscle metabolic capacities [activity of the glycolytic enzymes: glycogen phosphorylase (GP), pyruvate kinase (PK), phosphofructokinase (PFK), octopine dehydrogenase (ODH), arginine kinase (AK), and the mitochondrial enzyme, citrate synthase (CS)]. Gonad size, gamete volume fraction, and levels of gonadal protein and lipid were greater for mature scallops during the first than during the second reproduction. Numbers of claps during escape responses (49–57) and levels of muscle arginine phosphate remained similar throughout the different reproductive stages in both reproductive periods. In contrast, recovery was slowed during gonadal maturation in both reproductive periods and during spawning in the first reproduction. Scallops generally took more time to regain their initial clapping capacity during the first (25–40 min) than during the second reproduction (20–30 min). Muscle glycogen decreased markedly during both gonadal maturation and spawning in both reproductions; whereas, muscle proteins decreased only in the first reproduction. The levels of most enzymes decreased during gonadal maturation in both reproductions, and also after spawning, particularly during the first reproduction. We concluded that gonadal maturation and spawning did not decrease clapping capacity of E. ziczac, but decreased its capacity to recover from exhaustive exercise most likely due to decreased levels of energetic reserves and a reduced metabolic capacity of the adductor muscle. Moreover, these effects were probably stronger during the first cycle because of the greater reproductive investment coincident with decreased food availability. Received: 28 April 2000 / Accepted: 21 September 2000     

Reproductive biology of the edible jellyfish Catostylus mosaicus (Rhizostomeae)

 The reproductive biology of the jellyfish Catostylus mosaicus (Quoy and Gaimard 1824) (Scyphozoa: Rhizostomeae) was investigated in New South Wales, Australia. Medusae were gonochoristic. There was a 1:1 ratio of male and female medusae and there was no evidence of sexual dimorphism. Oocytes arose from the gastrodermis and maintained contact with the gastrodermis, via trophocytes, throughout gametogenesis. Spermatogenesis occurred within follicles that arose from invagination of the gastrodermis. Detailed sampling of gonads over a period of 3.25 yr in Botany Bay, and over 2.5 yr in Lake Illawarra, indicated that gametogenesis occurred almost continuously during the year. Oocytes were smaller, or were absent from the ovaries during 3 of the 4 winters sampled at Botany Bay and during all 3 winter periods sampled at Lake Illawarra. Comparisons were made with other locations, although these were sampled less frequently. When medusae were present at a location, similar trends were observed. The size at which medusae matured varied, but during non-winter periods and at two locations, all medusae exceeding 130 mm diam were considered mature. Received: 6 January 2000 / Accepted: 3 July 2000     

Interactions among endocrinology,seasonal reproductive cycles and the nesting biology of the female green sea turtle

We collected data on plasma levels of testosterone+5a-dihydrotestosterone (T+DHT) and corticosterone (CORT) from adult female green sea turtles (Chelonia mydas) from southern Queensland during distinct stages of their reproductive cycle. Those females capable of breeding in a given year had elevated plasma steroid levels (T+DHT 0.91ǂ.08; CORT 1.05ǂ.29 ng/ml), associated with follicular development, until courtship began in October. At the beginning of the nesting season in November plasma levels of CORT were related to when the female first nested (r²=0.06; F=10.45; P=0.01). However, they were not correlated with the number of clutches a female laid in that season (F=3.65; P=0.08). We repeatedly sampled 23 turtles over the nesting season and profiled changes in steroids immediately following oviposition of each clutch. Levels of T+DHT (range 0.41-0.58 ng/ml) and CORT (range 2.13-2.81 ng/ml) were similar through the early stages of the nesting season and inter-nesting period, and declined to near basal levels (T+DHT 0.37ǂ.03 and CORT 1.85-ng/ml) following the last clutch for the season. Steroid hormone levels were also low (T+DHT 0.38ǂ.16; CORT 0.46ǂ.21 ng/ml) in four independent post-breeding (atretic) females; samples for these females were taken at a time when body condition was presumably at the lowest for the season. Subtle changes in the nesting environment, such as variation in nesting habitat or the time of night that nesting occurred, were associated with a small and slow CORT increase. We suggest CORT is increased in nesting females to assist in lipid transfer to prepare the ovarian follicles and/or the reproductive organs for ovulation.     

Factors regulating the reproductive cycles of two northeast pacific chitons,Tonicella lineata and T. insignis

The reproductive cycles of Tonicella lineata Wood and T. insignis Reeve are examined in relation to changes in physical and biotic conditions in different locations in British Columbia, Canada, over a 3 to 4 year period. A clearly annual reproductive cycle is displayed by both species, and in any one location and year reproductive events in the two species are similar. There is a progressive increase in the size of the gonads starting in the summer and continuing to mid-winter. Although no one environmental factor is likely to be correlated with this prolonged period of gonadal development, various phases of the annual temperature and photoperiod cycles do appear to coincide with particular phases of gametogenesis (such as gonial proliferation, vitellogenesis and gonadal maturation), and thus could act as external cues. There isa synchronous drop in gonadal size in T. lineata and T. insignis in the spring, as a result of spawning. The exact timing and abruptness of this event in different years can not be accounted for on the basis of temperature. However, new correlative data are presented to add further support to the hypothesis previously presented that the spring phytoplankton is the cue for natural spawning (Himmelman, 1975). Temperature may inhibit spawning in T. lineata if conditions are unseasonably cold.     

Field-testing the protandry-based mating system for the lizard, Anolis carolinesis: does the model organism have the right model?

Using the lizard Anolis carolinensis as its subject, an early and enduring model of psychobiology was presented in which neuroendocrines and social behavior interact to coordinate reproduction between the sexes. The adaptive context for the model was protandry, here defined as a "male-first" emergence pattern from winter dormancy to the onset of breeding. In the protandry scenario, males emerge, become reproductive, and contest for territories. Then, pre-reproductive females emerge to settle on male territories, whereby ovarian recrudescence is facilitated by the behavior of courting males. A collateral inference of the protandry sequence is that females are choosing their future mates from among local males and their territories (i.e., intersexual selection). The model and its assumptions, though never validated by field data, have served as the paradigm for many laboratory experiments on A. carolinensis. Recently, however, field studies described an intrasexually selected mating system for A. carolinensis, without evidence of direct female choice. Differences between the selective inferences from the two perspectives led us to test in the field a number of protandry-based characteristics previously ascribed to A. carolinensis. We monitored free-ranging adults across the winter-to-breeding period using data on sex ratios, social behavior, gut contents, sex steroids, and gonadal condition. We found no evidence of protandry, and little support for any of the associated assumptions. Instead, the sexes broadly overlapped in their temporal transition from winter retreats to an active status in the habitat, with average male reproductive development about 1-2 weeks in advance of females. We replace the traditional protandry-based A. carolinensis paradigm with a realistic onset sequence into the breeding season and a new model for the species' mating system. Our study underscores the need for field validation when laboratory-generated data are fitted to adaptive paradigms.     

Life-history traits of Plesionika martia (Decapoda: Caridea) from the eastern-central Mediterranean Sea

Life-history traits of Plesionika martia (Milne Edwards, 1883) were studied through data collected during six seasonal trawl surveys carried out in the Ionian Sea (eastern-central Mediterranean) between July 1997 and September 1998. P. martia was found at between 304 and 676 m depth, with the highest density in the 400-600 m range. Intraspecific, size-related depth segregation was shown. Recruitment occurred in summer at the shallowest depths. Juveniles moved to the deepest grounds as they grew. The largest female and male were 26 and 25 mm carapace length, respectively. The sex ratio was slightly in favour of females at depths >400 m. Although a seasonal spawning peak was shown, the reproduction appears to be rather prolonged throughout the year. Females with ripe gonads were found from spring to autumn. Ovigerous females with eggs in late maturity stage were found year round. Large females could spawn more than one time within their annual reproductive cycle. The size at first maturity (50% of the ovigerous females) was 15.5 mm CL. Average brood size of eggs with a well-developed embryo was 2,966ǃ,521. Iteroparity, low fecundity and large egg size patterns were observed. Brood size increased according to the carapace length. Two main annual groups were found in the field population of the Ionian Sea. Estimates of the Von Bertalanffy growth parameters are: L_X=30.5 mm, k=0.44 year^-1 in females; L_X=28.0 mm, k=0.50 year^-1 in males. A negative allometry was detected mostly in the ovigerous females. The life cycle of P. martia is discussed in the light of life-history adaptations shown in other deep-water shrimp species.     

Reproductive biology and population structure of the sea cucumber <Emphasis Type="Italic">Isostichopus fuscus</Emphasis> (Ludwig, 1875) (Holothuroidea) in Caamaño,Galápagos Islands,Ecuador

Pre-spawning reproductive biology and population structure of the sea cucumber Isostichopus fuscus were analysed at the Caamaño Island, Galápagos Islands, Ecuador on a monthly basis between January 1995 and June 1996. An average of 25 individuals of all sizes were collected each month. Using microscopic characteristics of the gonads three gonadal stages were described: (1) immature; (2) mature, and (3) spent. Mature individuals showed statistically different morphometric characteristics. I. fuscus was continuously sexually mature throughout the year independent of changes in sea water temperature. Mean oocyte diameter indicated planktotrophic larval development. Mean fecundity for this species was 567,884 (±95,528 SE) eggs per gonad. Size at first maturity was between 161.0 and 170.9 g drained weight and the smallest individual found with mature gonads had a drained weight between 121.0 and 130.9 g. The population sampled ranged between 13 and 31 cm (81.0–400.0 g) with less than 10% of the population of individuals ≥25 cm (≥300.0 g). No juveniles were recorded.     

Genetic population structure of the seagrass Thalassodendron ciliatum in sandy and rocky habitats in southern Mozambique

The genetic diversity of the dioecious seagrass Thalassodendron ciliatum in six populations in southern Mozambique was studied by means of random amplified polymorphic DNA (RAPD). Samples were taken from sandy and rocky habitats over a span of 880 km. Analysis of molecular variance (AMOVA) showed that most of the genetic variability (71.6% of total genetic variation) was observed within populations. There were also significant genetic differences among populations within each habitat (sandy and rocky). We did not find any significant overall genetic difference between sandy versus rocky populations, indicating that the morphological differences between plants from these two habitats are not maintained by reproductive isolation. There was no significant correlation between geographical and genetic distance, which is discussed in the light of current patterns along the coast. All sampled populations consisted of several genetically distinct individuals, indicating that sexual reproduction is widespread.     

Egg production in the arrow squid Nototodarus gouldi (Cephalopoda: Ommastrephidae), fast and furious or slow and steady?

The process of reproductive maturation and egg release was examined in the temperate shelf squid Nototodarus gouldi. The energy allocation between somatic and reproductive growth from juvenile to mature adult was investigated throughout the life span to determine the underlying energetic strategy adopted by individuals. The relative weight of the mantle, fin and digestive gland remained unchanged during ovarian development, with no significant correlations found between the mantle length (ML)-gonad residuals and the ML-mantle (r=0.01, P>0.05), ML-fin (r=0.07, P>0.05) and ML-digestive gland (r=0.07, P>0.05) residuals. This suggested that energy was not being diverted away from somatic growth during sexual development, and consequently neither muscle nor digestive gland was being utilised as an energy store. Since squid in all maturity stages contained some food in their stomachs (e.g. 66.7% of mature animals), it is likely that the cost of maturation in this species is largely being met by food intake. The energy investment in reproductive tissues was relatively low (mean gonado-somatic index for mature individuals was 9.29% - 0.40%), indicating that only small amounts of energy were being allocated to reproduction at anyone point in time, which is characteristic of a multiple-spawning strategy. Furthermore, oviduct weight was not correlated with body size (r=0.256, P>0.05), suggesting that eggs are not stored for a single release. In all except one individual, ovary weight was consistently heavier than oviduct weight, suggesting that the ovary is not being depleted of oocytes as mature ova move into the oviducts. Additionally, the ovaries of mature females contained a range of oocyte sizes with discrete peaks, indicating a continued production and development of oocyte cohorts. The presence of some individuals with stretched empty oviducts is further evidence that the reproductive strategy of N. gouldi is slow and steady, with eggs possibly being released in discrete batches over a period of time.     

Effect of chronic exposure to drilling fluid XP-07 on gonad histology in Tilapia guineensis

Changes in Tilapia guineensis gonads exposed for 12 weeks to XP-07 at a concentration of 2.5, 1.25, 0.63, or 0.32% were investigated using a static renewal method. The histological changes noted in the gonads of the exposed fish were inhibition of maturation in oocytes or spermatogenesis. In contrast, the four stages of sperm or ova development were present in the control fish and spawning occurred. The increasing degeneration (artesia) of maturing egg resulted in complete absence of matured eggs in the female gonads of fish exposed to highest concentration (2.5%) of drilling fluid. The gonadal somatic index (GSI) values were recorded in a decreasing order towards the higher tested concentrations. The GSI values ranged from 3.11 to 1.47% in females and from 0.42 to 0.16% in males, whereas in control, it was 3.18% for females and 0.52% for males. Data showed that XP-07 exerted adverse effects on reproductive processes, which led to impairment in the reproductive success of T. guineensis.