Fish Reproduction

The evaluation of the growth patterns and reproductive strategies of fish species are vitally important for the understanding of their biology and the management of stocks. The present study focused on the Amazonian electric eel (Electrophorus electricus), which is capable of producing an electrical discharge of up to 800 V. Specimens were collected on a monthly schedule from a floodplain in the eastern Amazon basin. The gonads of these specimens were examined, and the sex ratio, growth parameters, population structure, body size at first gonadal maturation, and the gonadosomatic index were determined. A balanced sex ratio was found. Males were larger than females, and both sexes presented isometric growth, which is unusual in species with an elongated anatomy. This isometry may be related to the reduction of the coelomic cavity, and its position near the head. The spawning period coincided with the start of the rainy season, and continued until high water, with the variation in gonadal development following the fluctuations in precipitation and river water levels. The asymptotic body length in both sexes was relatively large, and was inversely related to the growth coefficient (k), with a slower growth rate being recorded in the males. Mortality rates were relatively low in comparison with most species of tropical fish. The larger size of the male may be related to their role in parental care, and sexual selection on the part of the females. These findings may be important for the management of wild stocks, as well as captive rearing.

Presented July 8, 2017 at the National Museum of Marine Science & Technology to guests and attendees of the 20th World Guppy Contest, Keelung City, Taiwan

I.  The Cellular Expression and Genetics of an Established Polymorphism in Poecilia reticulata; “Purple Body, (Pb)” is an Autosomal Dominant Gene

II.  The Cellular Expression and Genetics of Purple Body (Pb) in Poecilia reticulata, and its Interactions with Asian Blau (Ab) and Blond (bb) under Reflected and Transmitted Light

III.  The Cellular Expression and Genetics of Purple Body (Pb) in the Ocular Media of the Guppy Poecilia reticulata

IV.  The Phenotypic Expression of Purple Body (Pb) in Domestic Guppy Strains of Poecilia reticulata

The Purple Body color pigment modification is a distinct polymorphism in wild P. reticulata populations.  Modification of wild-type carotenoid orange and pteridine red coloration and spotting of male ornaments in both wild populations of  Poecilia reticulata (Guppies) and modern Domestic Guppy  strains by the Purple Body (Pb) gene has long been overlooked in research articles and little understood in breeder publications. This modification is commonly found in wild-type Poecilia reticulata  populations from numerous collection sites and has been photographed but not recognized in these collections. It is non-existent or near absent in collections taken from variant populations of Poecilia reticulata wingei.

Tilapia rendalli juveniles (±9.5 g) were cultured in concrete tanks to determine the effect of four dietary protein levels (30, 35, 40 and 45% crude protein (CP) in feed on ammonia concentration and growth performance of the fish, stocked at 15 fish per tank. Fish were monitored for a period of 90 days. Fish that were fed on 40% CP diet had significantly (P<0.05) higher weight gain, growth, and low feed conversion ratio (FCR). Ammonia concentration was significantly higher (P<0.05) in tanks where the 45% CP diet was administered, and where also poor growth and survival rate was observed. Poor growth performance of the fish at inadequate (below 30% CP) and oversupply (above 40% CP) protein diet is evidence of the importance of taking precautions on the levels of protein inclusion in diet in tank culture. Higher dietary protein diet precipitates ammonia accumulation, thus compromising growth performance. Based on findings in this study, optimal protein level of 40% CP is recommended for tank culture.

The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning and yet, the research conducted at these extreme and logistically challenging environments still continues to reveal unique biological processes. Here, we report for the first time, a unique behavior where the deep-sea skate, Bathyraja spinosissima, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally " incubate " developing egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development time given that deep-sea skates have some of the longest egg incubation times reported for the animal kingdom. Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment. Despite being the largest biome, the deep sea remains the least explored ecosystem on earth 1,2. In 1977, the discovery of the first deep-sea ecosystems supported by hydrothermal vent fluid emissions at the Galapagos Rift, challenged our views of ecosystem functioning and fueled new hypotheses about how life on earth could have originated around these chemically reactive environments 3–5. Forty years later, we now know that hydrothermal vent ecosystems exist in every ocean basin, supporting rich communities and unique biological processes 6–9. Initially considered isolated patches of life within a barren deep-sea floor, we are beginning to appreciate that these ecosystems interact with the surrounding environment and influence global geochemical cycles 7,8. Most hydrothermal vent sites remain unexplored, and our understanding of the ecology of these ecosystems in most parts of the world remains limited. Furthermore, some of these chemosynthesis based ecosystems are now under threat from human activities and are targeted for exploitation of their mineral resources 10,11. Here, we report for the first time a unique behavior where the Pacific white skate Bathyraja spinosissima, one of the deepest living of all known skate species 12 , uses active hydrothermal vent fields as a natural incubator for their external egg-capsules. To the best of our knowledge and understanding, this is the first time this incubating behavior at an active hydrothermal vent field has been recorded for a species within the marine environment. The Galapagos Platform in the eastern tropical Pacific consists of 13 major volcanic islands and numerous seamounts that straddle the equator 13. To the north of the archipelago and parallel to the equator, the Galapagos Spreading Center (GSC) extends for over 1000 km west to east, crossing the Galapagos Marine Reserve north of Darwin Island (Fig. 1). Previous exploration of the area revealed the presence of active hydrothermal vents,