Morphometric and gonad maturity of the spider crab Libinia ferreirae Brito Capello, 1871 (Decapoda: Majoidea: Epialtidae) on the south-eastern Brazilian coast

Sexual maturity of the spider crab Libinia ferreirae was assessed for each sex, based on body dimensions and observations of gonad condition. A total of 346 crabs were analysed, of which 68% were females. Immature and adult individuals were recognized based on their allometric growth and gonad development. Abdomen width (AW) vs carapace width (CW) and propodus length (PL) vs CW were the relationships that best separated allometric groups of females and males, respectively. For females, gonad and allometric morphological maturity were, respectively, 38.77 and 39.43 mm of CW, which is close to the carapace size of the smallest ovigerous female (38.08 mm). For males, gonad maturity was 34.86 mm of CW and three allometric phases were observed: immature (IM♂), adolescent (AD♂) and adult morphometrically mature (MM♂). The IM♂ phase showed lower values of CW and PL than the AD♂ phase, without spermatophores inside the vas deferens; the AD♂ phase exhibited higher CW values than IM♂, but lower CW and PL values than the MM♂ phase, and the presence of spermatophores in the vas deferens; the MM♂ phase had higher values of CW and PL than the AD♂ phase and spermatophores in the vas deferens. Therefore, females showed synchronic morphometric, gonadal and functional maturity, while in males, gonadal maturity was attained before morphometric maturity, which probably could be a reproductive strategy for this species.

THE ADDITION OF Ulva reticulata AS A STIMULANT INTO ARTIFICIAL FEED ON THE GONAD CONDITION OF THE COLLECTOR SEA URCHIN (Tripneustes gratilla LINNAEUS 1758)

<p>Dried <span style="text-decoration: underline;">Ulva</span> <span style="text-decoration: underline;">reticulata</span> has been proven as a feeding stimulant for the collector sea urchins (<span style="text-decoration: underline;">Tripneustes</span> <span style="text-decoration: underline;">gratilla)</span>. The purposes of this study were to determine the optimal dose of dried <span style="text-decoration: underline;">U.</span> <span style="text-decoration: underline;">reticulata</span> as a feeding stimulant into artificial feed and its effect on the gonad condition of the collector sea urchins, <span style="text-decoration: underline;">T.</span> <span style="text-decoration: underline;">gratilla</span>. Previously, starved sea urchins (ca. 66 mm diameter, n=7) was held in 80-l aquarium volume with flow through seawater system (6.25 l/hourinlet and outlet). Sea urchins were fed with diet containing 0, 10, 20, or 30% of dried <span style="text-decoration: underline;">U.</span> <span style="text-decoration: underline;">reticulata</span> (designated control, U-10, U-20, and U-30 respectively) ad libitum for 38 days. Each treatment was given 3 replicates. Survival rate, feed consumption, and gonad conditions (gonad index, biochemical composition of the gonad, gonad histology, and egg diameter) parameters were quantified and compared to sea urchins fed with the mixture of fresh macroalgae (<span style="text-decoration: underline;">Gracilaria</span> <span style="text-decoration: underline;">lichenoides</span> and <span style="text-decoration: underline;">Padina</span>) and seagrass (<span style="text-decoration: underline;">Enhalus</span> <span style="text-decoration: underline;">ac</span><span style="text-decoration: underline;">o</span><span style="text-decoration: underline;">roides</span>). The results showed that the addition of dried <span style="text-decoration: underline;">U.</span> <span style="text-decoration: underline;">reticulata</span> into artificial feed by 10% from feed weight (U-10) was the optimal dose recommended. Sea urchins treated U - 10 diet resulted in gonad index and egg diameter (5.02 % and 82.66 µm each), were higher than other diet treatments. However, this diet treatment was not able to homogenize the reproductive phase composition of <span style="text-decoration: underline;">T.</span> <span style="text-decoration: underline;">gratilla</span>.</p> <p>Keywords: <span style="text-decoration: underline;">Ulva</span> <span style="text-decoration: underline;">reticulata</span>, Feeding Stimulant, <span style="text-decoration: underline;">Tripneustes</span> <span style="text-decoration: underline;">gratilla</span>, Gonad Condition</p>

THE ADDITION OF Ulva reticulata AS A STIMULANT INTO ARTIFICIAL FEED ON THE GONAD CONDITION OF THE COLLECTOR SEA URCHIN (Tripneustes gratilla LINNAEUS 1758)

Dried Ulva reticulata has been proven as a feeding stimulant for the collector sea urchins (Tripneustes gratilla). The purposes of this study were to determine the optimal dose of dried U. reticulata as a feeding stimulant into artificial feed and its effect on the gonad condition of the collector sea urchins, T. gratilla. Previously, starved sea urchins (ca. 66 mm diameter, n=7) was held in 80-l aquarium volume with flow through seawater system (6.25 l/hour inlet and outlet). Sea urchins were fed with diet containing 0, 10, 20, or 30% of dried U. reticulata (designated control, U-10, U-20, and U-30 respectively) ad libitum for 38 days. Each treatment was given 3 replicates. Survival rate, feed consumption, and gonad conditions (gonad index, biochemical composition of the gonad, gonad histology, and egg diameter) parameters were quantified and compared to sea urchins fed with the mixture of fresh macroalgae (Gracilaria lichenoides and Padina) and seagrass (Enhalus acoroides). The results showed that the addition of dried U. reticulata into artificial feed by 10% from feed weight (U-10) was the optimal dose recommended. Sea urchins treated U - 10 diet resulted in gonad index and egg diameter (5.02 % and 82.66 µm each), were higher than other diet treatments. However, this diet treatment was not able to homogenize the reproductive phase composition of T. gratilla. Keywords: Ulva reticulata, Feeding Stimulant, Tripneustes gratilla, Gonad Condition

Reproduction period of Mimagoniates microlepis, from an Atlantic Forest Stream in Southern Brazil

Mimagoniates microlepis was collected between January and December/2002. Three sample points were chosen at higher, medium and lower portions of Ribeirão river, located at the east of Paraná state. The reproduction period was observed by the frequency of gonad developmental stages, variation of the gonosomatic relation (RGS) and gonad condition (K). The average length at the first sexual maturity (L50) and the average length when 100% of individuals were adults (L100) were calculated. The intensity of the reproductive activity (IAR) was estimated at each sample point. The reproduction period started in the winter and ended at the end of spring. The high values of IAR encountered demonstrated that the reproductive activity occurred in the whole study area, mainly at the middle portion of the river. Apparently M. microlepis synchronize its fecundation and spawning with the rain regimes using the most suitable times for the cospecific encounters and offspring survival.

Asynchronous patterns of reproduction for the sympatric scallops Chlamys bifrons and Chlamys asperrima (Bivalvia: Pectinidae) in South Australia

Patterns of spawning activity were assessed by monitoring gonad states over 2.5 years for Chlamys asperrima and Chlamys bifrons at two sites in Gulf St Vincent, South Australia. Chlamys asperrima appeared to have a minor spawning in June, followed by a major spawning starting in late August. In contrast, the gonads of C. bifrons were regressed only during winter and it appeared that C. bifrons spawned for a long period, from late spring (September) until early autumn (March). At one site where sampling was frequent, there was evidence of three series of C. bifrons spawning events during the summer of 1994/95 and at least two series of events during 1995/96. Build-up and decrease in gonad weight was quick, but there was strong evidence of serial spawning for both species. Subsequently, we once observed C. asperrima spawning in situ at Edithburgh Jetty, at a time when gonad weights had been decreasing in previous years, but also long after the time when peak gonad weights had usually occurred. Only patches within the population were seen spawning, with scallops not spawning observed less than 100 m away from those that were. Indirect sampling of gonad condition also suggested that spawning in C. bifrons at Largs Bay was not always synchronous among patches of scallops within a population, nor always between sexes within patches.

Reproduction of the commercial scallop, Pecten fumatus, Reeve, 1852 in Bass Strait, Australia

To examine the reproduction of Pecten fumatus Reeve, 1852, samples were taken monthly from beds off King Island and in Banks Strait, from July 1986 to July 1987. For each sample the mean gonad-free tissue weight and standardized gonad weight were calculated. The percentage of the sample with each of five macroscopically determined reproductive stages was also measured. Changes in the proportion of cell types within the ovarian part of the gonad were determined by histological and stereological methods. A seasonal cycle of gonadal development occurred at each site, commencing at the time of lowest water temperatures and highest nutrient concentrations. This development progressively increased as the nutrient concentrations declined. No correlation was seen between chlorophyll a and gonad condition. A synchrony in gonad condition was present among individuals in samples; this was greatest at Banks Strait where gonads were larger, and phosphate, nitrate and silicate concentrations were significantly greater. There was no reduction in somatic tissue weight with increase in gonad tissue weight. Maximum gonad development preceded spatfall at each site by about one month.

Annual change in reproductive condition and plasma concentrations of sex steroids in black bream, Acanthopagrus butcheri (Munro) (Sparidae)

Changes in gonadosomatic index (GSI), hepatosomatic index (HSI), gonad stage and plasma concentrations of sex steroids were studied over one year in black bream (Acanthopagrus butcheri). Black bream have an annual reproductive cycle with a 3-month spawning season in spring–early summer. GSI and HSI values were highest in October and May respectively. Plasma concentrations of oestradiol-17β (E2), testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were highest in females in October. Plasma concentrations of E2 and T were highest in ovulated fish. Concentrations of 17,20βP were higher in fish undergoing final oocyte maturation (FOM) than in fish with regressed gonads. In males, plasma concentrations of T and 11-ketotestosterone (11KT) increased in September and remained elevated until January, but concentrations of 17,20βP did not change with season. However, 17,20βP concentrations in spermiated fish were higher than in non-spermiated fish. Daily changes in gonad condition indicated that females undergo daily cycles of ovarian maturation with ovulation occurring after midday. Plasma T and 17,20βP concentrations of females were elevated at midday in association with FOM, but E2 showed no diel change. In males, partially spermiated fish were dominant in the early morning and fully spermiated fish at midday. Plasma T, 11KT and 17,20βP concentrations were low at midnight and reached maximum levels at 0600 hours.

Serious mortality in populations of giant clams on reefs surrounding Lizard Island, Great Barrier Reef

A survey of giant clams (family Tridacnidae) at Lizard Island fringing reefs on the Great Barrier Reef in July 1985 indicated that over the previous 6 weeks the combined total mortality for Tridacna gigas and T. derasa was 28% at Watson's Bay (WB) and 20% at the channel between Palfrey Island and South Island (P-S). Sporadic mortalities continued at intervals through to December 1985 when combined total mortalities at WB and P-S had reached 38% and 32%, respectively. By January 1987, mortality for these two species was 54% at WB and 51% at P-S. Deaths were not restricted to a particular size class and the average size of clams that died did not change with time during the study. Mortality rates for clams which had been previously biopsied for gonad condition and/or those induced to spawn with serotonin injection were not significantly different from controls. Distribution of dead clams was random to slightly clumped with respect to alive and dead clams within WB, and random within P-S. Results of heavy-metal analyses of tissues from moribund clams were similar to previous results for normal clams. The histopathology of tissues from six of eight moribund clams revealed an unidentified unicellular organism which was not found in Tridacna spp. from previous or subsequent samples from Lizard Island reefs or from other reef areas.

A Comparative Study of the Reproductive Cycles of the Cockles Cerastoderma Edule and C. Glaucum

The reproductive cycles of the two cockles Cerastoderma edule (L.) and C.glaucum (Poiret) (= Cardium lamarcki Reeve) from a mixed population in the Crouch estuary, Essex, have been investigated. Reproductive maturity was estimated by assessment of gonad condition. A difference in maturity related to shore level was noted. The reproductive cycles of the two cockles were found to be essentially similar. Rapid gametogenesis occurred in both cockles in spring, C. edule then spawned in May, whereas C. glaucum did not spawn until July. The difference in time of spawning appears to be responsible for the maintenance of the two genotypes in a sympatric association, as hybridization experiments showed an absence of isolation at the gamete level. The relationship between C. edule and C. glaucum is discussed.