Phenology of the kelp <Emphasis Type="Italic">Saccharina japonica</Emphasis> and its effect on the gonad index of the sea urchin <Emphasis Type="Italic">Mesocentrotus nudus</Emphasis> across a depth gradient off the Sanriku coast,northeastern Japan

The kelp Saccharina japonica is a dominant seaweed along the Sanriku coast where fisheries for sea urchin and abalone are among the most prosperous in Japan. We investigated the phenology of the kelp at depths of 6, 9 and 12 m from March 2015 to March 2016. The sea urchin Mesocentrotus nudus, a dominant herbivore off the coast, was also monitored with respect to its gonads for fishery use. Juvenile kelp appeared in March and rapidly elongated until May. Weight of the kelp significantly increased from April to July. Sori formation commenced from September and ceased in December. Density and biomass of the kelp were higher in the shallower sites than in the deeper one throughout the year. The highest biomasses recorded between July and October were 3773, 1939 and 501 g dry weight m^?2 at depths of 6, 9 and 12 m, respectively. No regrowth of kelp blades was observed, indicating that S. japonica in this region has an annual life cycle. The gonad index of the sea urchin in the 12-m site was lower than that in the 6- and 9-m sites, indicating the close relation of the gonad index with the biomass of the kelp.     

Long-term effects of stocking density on survival,growth performance and marketable production of the sea urchin <Emphasis Type="Italic">Strongylocentrotus intermedius</Emphasis>

Sea urchins were stocked at a density of 15 (D15), 30 (D30), 45 (D45) and 60 (D60) urchins/cage (0.3 m long × 0.2 m wide × 0.4 m high) in a laboratory culture environment for 16 months. The wet body weight (BW) and test diameter growth were monitored at 2-month intervals during the experiment. At the conclusion of the experiment, the surviving sea urchins were counted and the gonad wet weight (GW) and gonad color were measured. Specific growth rate (SGR) of body weight, survival rate (SR), gonad index (GI), gonad color difference (ΔE ₀₀), coefficients of variation (CV) of BW, GW, GI and ΔE ₀₀, total biomass yield (TY) and total gonad yield (TGY) per cage were calculated. Two marketable yield variables, graded according to gonad index, i.e., marketable biomass yield (MY) and marketable gonad yield (MGY), were also calculated. Coefficient of variation of final body weight (FW) and final test diameter (FTD) of sea urchins increased as the stocking density increased, indicating the existence of adverse social interactions. These adverse social interactions detrimentally affected FW, FTD, SGR, GW and GI (P < 0.01). Although SR decreased with the increasing densities, no statistical significant difference was detected. Sea urchins at D15 had the lowest gonad color difference (ΔE ₀₀) (P < 0.05). However, statistically equal CV of ΔE ₀₀ indicates this density effect was not a result of adverse social interactions. TY and TGY increased with increased density and can be described by the following equations: TY = 84.18X ^0.64, R ² = 0.999 and TGY = 24.16X ^0.38, R ² = 0.979. However, the MY and MGY were not significantly different among stocking densities. The results of this study demonstrate that in intensive culture S. intermedius at low stocking density can achieve high growth rate, gonad index and desirable color without decreasing the marketable yield. Farmers should choose to culture S. intermedius at low stocking densities.     

Optimizing metamorphosis in <Emphasis Type="Italic">Paracentrotus lividus</Emphasis> aquaculture using alternative macroalgae species to <Emphasis Type="Italic">Corallina</Emphasis> sp.

Metamorphosis induction cues (by chemical mediation or direct contact) were tested in Paracentrotus lividus using three different macroalgae treatments: Corallina sp., Palmaria palmata, and Laminaria digitata. Higher percentages of metamorphosis were reached in Paracentrotus lividus larvae by direct contact with a Palmaria palmata substrate.     

Feeding,somatic condition and survival of sand lance <Emphasis Type="Italic">Ammodytes</Emphasis> sp. larvae in Mutsu Bay,Japan

To clarify the recruitment process of sand lance Ammodytes sp., we investigated larval condition factor, relative gut fullness (%GF), prey abundance and oceanographic structure in Mutsu Bay, Japan, during 1999–2001. Ammodytes sp. larvae, which were collected by horizontal hauls of Motoda nets and a ring net at depths of 1, 10, 20, 30 and 40 m, were mainly distributed at 10–30 m. Larvae at the first feeding time until 12 mm in body length (BL) fed predominantly on copepod nauplii, whereas large larvae with BL of 12.1–14.0 mm fed on a mixture of copepod nauplii, copepodites and appendicularians from late February to April. A path analysis showed that difference in water density between 35- and 5-m depths negatively affected naupliar abundance at 10–30-m depth (standardised path coefficient β = ?0.71, p = 0.005 for 3.3–8.0-mm BL larvae and β = ?0.78, p < 0.001 for 8.1–12.0-mm BL larvae). Naupliar abundance positively affected the %GF of Ammodytes sp. larvae (β = 0.75, p < 0.001 for 3.3–8.0-mm BL larvae and β = 0.66, p < 0.001 for 8.1–12.0-mm BL larvae), whereas it was negatively affected by water temperature (β = ?0.45, p = 0.008 for 3.3–8.0-mm BL larvae and β = ?0.56, p = 0.002 for 8.1–12.0-mm BL larvae), and the temperature effect was weak compared with that of naupliar abundance. In turn, %GF positively affected larval somatic weight (β = 0.91, p < 0.001 for 6.0-mm BL larvae and β = 0.70, p = 0.005 for 10.0-mm BL larvae). The recruitment failure in 1999 was likely caused by a reduced condition factor, which resulted from low naupliar abundance. In contrast, the abundance of nauplii and Oithona similis copepodites was high in 2000 and 2001. It is possible that the higher recruitment success in 2001 was because of the higher water temperatures in Mutsu Bay, sustaining faster growth of the larvae than in 2000 under the high-prey abundance conditions.     

Ontogenetic habitat shift in <Emphasis Type="Italic">Pugettia quadridens</Emphasis> on the coast of Sagami Bay,Japan

Population dynamics of the kelp crab Pugettia quadridens, a potential predator of juvenile abalone, were investigated on the coast of Nagai, Sagami Bay, to examine its cryptic ontogenetic habitat shift. Monthly quantitative sampling over 2 years, which was carried out in 11 different subtidal habitats (< 0.1–8 m deep), revealed that P. quadridens changes ontogenetically according to its habitat: P. quadridens occurred in shallow lower subtidal (1–4 m) small red algal turfs (mainly Grateoloupia cornea) almost all year around, when the population was dominated by juveniles and stage I (immature) individuals; on the other hand, in the shallow upper subtidal (0.1–1 m) habitat (mainly Sargassum fusiforme beds near the low tidal mark), P. quadridens occurred only during winter to early spring, when the population was dominated by individuals of senior ontogenetic stages. These finding suggest that P. quadridens inhabit subtidal small red algal turfs during their early benthic phase, and then, the majority of larger individuals of stages II and III migrate to Sargassum beds. Our results suggest that the impact of P. quadridens predation on abalone stocks is limited in the present study site, primarily because the habitat of P. quadridens is segregated from that of juvenile abalone.     

A preliminary study on the potential value of a novel integrated aquaculture system on water purification

Intensive and semi-intensive sea cucumber aquaculture produces effluents that impact the quality of the local aquatic environment and sea cucumber growth; such effluents are an important cause of coastal water eutrophication. Integrated aquaculture has been shown to efficiently reduce the release of nutrients during aquaculture and to provide economic benefits. In this study, we report our investigation of a polyculture system utilizing Styela clava (stalked sea squirt) and Stichopus japonicus (Japanese sea cucumber) under two feeding modes. To examine purification of the water in the system, nutrients in the water and the sediment, attached heterotrophic bacteria, and the survival rates and growth rates of S. clava and S. japonicus were determined. Tank cultivation trials showed that, under the same feeding modes, the concentration of nutrients in the polyculture system was approximately 50–60 % of the sum of the nutrients in the S. japonicus mixture and S. clava monoculture systems. The abundance of attached heterotrophic bacteria in the polyculture system was remarkably lower than that of the mixed culture system under the same feeding mode. S. japonicus in the polyculture system grew better than those in the mixed culture system under the same feeding mode. These results demonstrate that the S. clava–S. japonicus integrated culture system offers a means of constraining or reversing the pollutive impacts of coastal sea cucumber aquaculture.     

Food habits of fishes in a freshwater reed belt in Lake Kitaura,eastern Japan,in summer

The diets and feeding guild structure of a freshwater reed belt fish assemblage (30 species) were examined in Lake Kitaura, part of the Lake Kasumigaura system, eastern Japan, from June to September in 2009 and 2010. Ontogenetic dietary shifts were recognized in 14 species, including several species (e.g., Cyprinus carpio, Tridentiger brevispinis and Hyporhamphus intermedius) targeted by local fisheries. Juveniles of these species generally fed on zooplankton, later switching to other prey items (e.g., benthic chironomid larvae, gammaridean amphipods, shrimps, juvenile fishes, diatoms and decomposing reeds) with growth. A cluster analysis based on dietary overlaps showed that the reed belt fish assemblage comprised five feeding guilds (plant, zooplankton, benthic invertebrate, terrestrial insect and fish feeders). Of these, zooplankton feeders were the most abundantly represented in terms of species numbers, suggesting that the main food items for the fish assemblage were zooplankton (e.g., cladocerans, and calanoid and cyclopoid copepods). Fish feeders included five species, of which one was an alien species introduced from another region in Japan (Opsariichthys uncirostris) and three were from foreign countries (Micropterus salmoides, Lepomis macrochirus macrochirus and Ictalurus punctatus).     

Dietary supplementation of curcumin augments heat stress tolerance through upregulation of <Emphasis Type="Italic">nrf-2</Emphasis>-mediated antioxidative enzymes and <Emphasis Type="Italic">hsps</Emphasis> in <Emphasis Type="Italic">Puntius sophore</Emphasis>

Heat stress is one of the major environmental concerns in global warming regime and rising temperature has resulted in mass mortalities of animals including fishes. Therefore, strategies for high temperature stress tolerance and ameliorating the effects of heat stress are being looked for. In an earlier study, we reported that Nrf-2 (nuclear factor E2-related factor 2) mediated upregulation of antioxidative enzymes and heat shock proteins (Hsps) provide survivability to fish under heat stress. In this study, we have evaluated the ameliorative potential of dietary curcumin, a potential Nrf-2 inducer in heat stressed cyprinid Puntius sophore. Fishes were fed with diet supplemented with 0.5, 1.0, and 1.5% curcumin at the rate 2% of body weight daily in three separate groups (n = 40 in each group) for 60 days. Fishes fed with basal diet (without curcumin) served as the control (n = 40). Critical thermal maxima (CTmax) was determined for all the groups (n = 10, in duplicates) after the feeding trial. Significant increase in the CTmax was observed in the group fed with 1.5% curcumin- supplemented fishes whereas it remained similar in groups fed with 0.5%, and 1% curcumin-supplemented diet, as compared to control. To understand the molecular mechanism of elevated thermotolerance in the 1.5% curcumin supplemented group, fishes were given a sub-lethal heat shock treatment (36 °C) for 6 h and expression analysis of nrf-2, keap-1, sod, catalase, gpx, and hsp27, hsp60, hsp70, hsp90, and hsp110 was carried out using RT-PCR. In the gill, expression of nrf-2, sod, catalase, gpx, and hsp60, hsp70, hsp90, and hsp110 was found to be elevated in the 1.5% curcumin-fed heat-shocked group compared to control and the basal diet-fed, heat-shocked fishes. Similarly, in the liver, upregulation in expression of nrf-2, sod, catalase, and hsp70 and hsp110 was observed in 1.5% curcumin supplemented and heat shocked group. Thus, this study showed that supplementation of curcumin augments tolerance to high temperature stress in P. sophore that could be attributed to nrf-2-induced upregulation of antioxidative enzymes sod, catalase, gpx, and the hsps.     

Importance of <Emphasis Type="Italic">Gammarus</Emphasis> in aquaculture

In recent years, there have been significant increases in the production and breeding of aquaculture species; for example, the gilt-head (sea) bream and seabass in salt water and trout, carp, and tilapia in fresh water., Amphipods in the genus Gammarus are used as a rich source of protein to feed various pet animals such as aquarium fish, lizards, and turtles, as well as in aquatic ecotoxicology and water quality assessment. Gammarus meal is used as a partial replacement (10–20%) of fish meal. However, the reproduction and rearing of Gammarus in intensive or semi-intensive conditions has not yet been carried out. Gammarus products (live, dried flakes, or powdered) transported to the markets are constituted from wild caught Gammarus. Due to the high price of these products, Gammarus aquaculture potentially has great economic benefits. Therefore, there is a need to focus on the importance of Gammarus in aquaculture. In the present review, the ecology and distribution of Gammarus, its importance in aquatic ecotoxicology and water quality assessment, the chemical analysis of Gammarus and factors affecting chemical composition of it, and the importance of Gammarus in fish nutrition are discussed. In addition, the economic importance and culture methods of Gammarus are also reviewed. This review will be beneficial for scientific investigators and fish-crustacean farmers.     

Ontogenetic habitat and dietary shifts in Japanese turban snail <Emphasis Type="Italic">Turbo cornutus</Emphasis> at Nagai,Sagami Bay,Japan

A field survey and a laboratory experiment were conducted to examine ontogenetic shifts in habitat and diet of the turban snail Turbo cornutus. The main habitat of turban snail juveniles smaller than 10 mm shell height (SH) was turfs of articulated coralline algae, and that of adults larger than 50 mm SH was kelp beds of Ecklonia bicyclis and Ecklonia cava. However, the ontogenetic habitat shift during the juvenile stage of 20–50 mm SH was unclear. From the results of a long-term feeding experiment and stable isotope analysis, the gelidiacean alga Gelidium elegans was assumed to be more important as a food source for juvenile turban snail than E. cava in the field. However, the frequency of individuals inhabiting gelidiacean algal turfs was low in both juvenile and adult stages. Thus, the ontogenetic shifts in habitat and diet did not coincide and other factors, i.e., daytime refuge, are important. As the growth rate was higher in the juveniles fed on the two algal species than those fed on single algal species, co-occurrence of various algal habitats in rocky shore ecosystems as a coastal ecosystem complex may enhance growth of turban snail juveniles feeding on a combination of different algal species.     

Environmental quality and natural food performance at feeding sites in a carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) pond

Just like other domesticated animals, common carp (Cyprinus carpio) are able to learn where food can easily be obtained. As a result, carp in semi-intensive polyculture ponds could conceivably restrict their main activity centres to supplemental feeding sites, leading to lowered exploitation of natural food resources (zooplankton and macrozoobenthos) and localised degradation of environmental conditions. At two semi-intensive ponds in southern Moravia (Czech Republic), areas around feeding sites displayed significantly reduced oxygen concentration and saturation (mainly p < 0.001). Likewise, temperature, pH and transparency also decreased significantly at feeding sites (mainly p < 0.05), while turbidity increased. While there was no significant difference in zooplankton biovolume at feeding and non-feeding sites, zoobenthos density and biomass were significantly lower at feeding sites (mainly p < 0.01). The feeding behaviour of carp, therefore, led to significant changes in both abiotic and biotic conditions at supplemental feeding sites.     

Influence of different microalgal diets on gonadal development of the carpet shell clam <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> broodstock

Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning.     

Molecular endocrine changes of Gh/Igf1 axis in gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis> L.) exposed to different environmental salinities during larvae to post-larvae stages

The influence of acclimation of the euryhaline gilthead sea bream (Sparus aurata) larvae/post-larvae to brackish water on growth, energetic contents, and mRNA levels of selected hormones and growth-regulating hypothalamic neurohormones was assessed. Specimens from 49 days post-hatching were acclimated during 28 days to two different environmental salinities: 38 and 20 psu (as brackish water). Both groups were then transferred to 38 psu and acclimated for an additional week. Early juveniles were sampled after 28 days of acclimation to both salinities and one week after transfer to 38 psu. Pituitary adenylate cyclase-activating peptide (adcyap1; pacap), somatostatin-I (sst1), growth hormone (gh1), insulin-like growth factor-I (igf1), and prolactin (prl) mRNA expression were all studied by QPCR. Post-larvae acclimated to 20 psu showed better growth performance and body energetic content than post-larvae maintained at 38 psu. prl, adcyap1, and igf1 mRNA expression levels increased in 20-psu-acclimated post-larvae but decreased upon transfer to 38 psu. GH1 expression did not show significant changes under both experimental conditions. Our results suggested an enhanced general performance for post-larvae in brackish water, supported by the actions of adcyap1, igf1, and prl.     

Bait-subsidized diets and their effects on ovigerous North American lobsters (<Emphasis Type="Italic">Homarus americanus</Emphasis>)

Ovigerous American lobsters (Homarus americanus) display a protracted period of ovary maturation and maternal care when incubating their eggs, potentially influencing offspring fitness. Lobsters consume a wide range of food items; however, trap bait may comprise a larger proportion of their diet in some fished areas compared to non-fished areas, and the long-term consequences of a bait-based diet remain largely unexplored in lobsters. We tested the hypothesis that disproportionate amounts of bait in the diets of pre-ovigerous females affect the quality of their ovaries and eggs. We held pre-ovigerous lobsters (n?=?29) over a period of ~?300 days (range?=?270–378) and fed them diets of herring bait, natural prey items (crab, mussel, urchin, macroalgae), or a combination of both diet types. Nutritional status, measured as biweekly blood indices and total glucose levels, suggest differences between lobsters fed a natural or combination diet and lobsters fed a bait-based diet (ANOVA; P?<?0.05). We found that bait diets contained more protein (58.5%) and lipids (31.6%) compared to natural diets (34.5 and 13.2%, respectively) and lipid levels in ovaries and eggs significantly correlated with each other for all treatments (r?=?0.76, n?=?15, P?=?0.028). Histopathological analysis indicates that ovaries contained more variable maturation in starved lobsters or those fed with bait, with some animals showing delayed gonad maturation. Results suggest that a varied diet promotes the overall fitness of ovigerous lobsters and the associated reserves that are used for ovarian development and subsequent oocyte formation.     

Inhibitory neurotransmitter serotonin and excitatory neurotransmitter dopamine both decrease food intake in Chinese perch (<Emphasis Type="Italic">Siniperca chuatsi</Emphasis>)

Aminergic neurotransmitters play important roles in the regulation of food intake. However, their effects on feeding in fish have been less explored and still unclear. In the present study, the effects of serotonin (5-HT) and dopamine (DA) on food intake were evaluated through intraventricular (ICV) administration in Chinese perch (Siniperca chuatsi) and the mRNA expression levels of neuropeptide Y (NPY), agouti gene-related protein (AgRP), and pro-opiomelanocortin (POMC) were detected. At 1 h post-injection, 5-HT significantly decreased food intake in a dose-dependent manner. The mRNA expression of NPY and AgRP were significantly decreased (p < 0.05), whereas the mRNA expression of POMC was significantly increased (p < 0.05), suggesting the involvement of NPY, AgRP, and POMC in inhibitory action of 5-HT on food intake in Chinese perch. DA significantly decreased (p < 0.05) food intake and AgRP mRNA expression at 1 h post-injection, indicating the inhibitory effect of DA on food intake might be mediated through AgRP. This might shed new light on the regulation of food intake in Chinese perch.     

Effects of dietary microencapsulated <Emphasis Type="Italic">Cymbopogon flexuosus</Emphasis> essential oil on reproductive-related parameters in male <Emphasis Type="Italic">Rhamdia quelen</Emphasis>

In aquaculture, nutrition and supplemented diets have been shown to affect broodstock reproductive performance. In this study, we investigated the effects of dietary supplementation with Cymbopogon flexuosus essential oil (CFEO) microcapsules on reproductive-related parameters in silver catfish (Rhamdia quelen) male broodfish. Adult male broodstocks were separated into three groups according to the concentrations of supplemented CFEO (0.0?=?control; 1.0 or 3.0 mL per kg of diet). After 20 days under experimental conditions, the animals were euthanized and the gonads were harvested for gonadosomatic index, sperm analysis, oxidative stress, and histopathology; testosterone levels were measured in the plasma; gene expression of prl, smtl, pomca, and pomcb was assessed in the pituitary gland by real-time PCR. The results showed no alterations on reproductive parameters in R. quelen males treated with Cymbopogon flexuosus essential oil compared to the control-diet animals. In conclusion, CFEO microcapsules supplied for 20 days in the concentrations of 1.00 or 3.00 mL per kilogram of diet did not affect the reproduction criteria evaluated in this study in male silver catfish.     

Ontogenetic habitat shift in abalone <Emphasis Type="Italic">Haliotis discus hannai</Emphasis>: a review

Ecological literature on abalone Haliotis discus hannai populations is reviewed to identify processes and factors driving ontogenetic shifts in habitat. Abalone recruitment is related to the algal community type, with abalone shifting with growth from deeper crustose coralline algal (CCA) habitats to shallower kelp bed habitats via algal turfs. Timing of the habitat shifts is linked to ontogenetic changes in diet, from benthic diatoms to a diet dominated by macroalgae. Susceptibility to predation appears to change, concomitant with the shift from cryptic microhabitats during early-life stages to more exposed habitats during latter-life stages. Interstitial spaces between cobbles and boulders in the CCA habitat are considered to be important for reducing predation risk. The loss of CCA nursery habitat through sedimentation and macroalgal overgrowth likely negatively affects abalone recruitment. Preservation of diverse algal communities, including suitable habitats for the different abalone growth stages, is critical for successful abalone recruitment.     

Characterization and expression of <Emphasis Type="Italic">lin-28a</Emphasis> involved in <Emphasis Type="Italic">lin28/let-7</Emphasis>signal pathway during early development of <Emphasis Type="Italic">P. olivaceus</Emphasis>

Heterochronic lin-28 is a conserved RNA-binding protein that plays a key role in the timing of developmental events in organisms. As a crucial heterochronic gene, the protein controls developmental events of the second of four larval stages in Caenorhabditi elegans. Heterochronic let-7 miRNAs are often present in various species and highly conserved in sequence and biological function and are required for various biological processes. Previous studies showed that ten let-7 miRNAs were identified in the Japanese flounder (Paralichthys olivaceus) and that they were primarily expressed during metamorphosis. In this study, we clone and characterize the lin-28a gene from P. olivaceus and exhibit its dynamic expression pattern at different developmental stages and various adult tissues. The results show that the P. olivaceus lin-28a gene has high sequence similarity with other species and is highly expressed in the embryonic stage but weakly expressed in the larval stage. In addition, lin-28a overexpression causes cell proliferation and significantly promotes the levels of pre-let-7a and pre-let-7d while markedly depressing let-7a and let-7d expression in FEC (Flounder Embryonic Cell), which indicate that lin-28 possibly blocks the maturation of let-7 miRNAs. Additionally, lin-28a is identified as a target gene of let-7 miRNAs, and let-7 miRNAs directly regulate lin-28a expression by targeting its 3′ UTR. Taken together, lin-28a along with let-7 miRNA participates in a lin-28/let-7 axis pathway that regulates cell division and timing of embryonic and metamorphic events in P. olivaceus.     

Spexin in the half-smooth tongue sole (<Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis>): molecular cloning,expression profiles,and physiological effects

Spexin (SPX), a novel neuropeptide discovered by the bioinformatics approach, has been shown to exert pleiotropic functions in mammals. However, little information regarding the physiological role of SPX is available in teleosts. As a first step, we cloned the spexin gene from a flatfish, the half-smooth tongue sole. The open reading frame (ORF) of tongue sole spexin contained 363 nucleotides encoding a 120 amino acid (aa) preprohormone with a calculated molecular mass and isoelectric point of 14.06 kDa and 5.86, respectively. The tongue sole SPX precursor contained a 27 aa signal peptide and a 14 aa mature peptide flanked by two dibasic protein cleavage sites (RR and GRR). Tissue distribution analysis showed that spexin mRNA could be detected in various tissues, notably in the brain. In addition, fasting stimulated the hypothalamic expression of spexin mRNA. Intraperitoneal injection of SPX increased gnih and gnrh3 mRNA levels in the hypothalamus; however, SPX inhibited the pituitary expression of gh, fshβ, and gthα mRNAs. Overall, our results reveal the existence of a functional SPX in the tongue sole, which could represent an important factor in the neuroendocrine control of flatfish reproduction and growth, and the spexin mRNA expression is regulated by feeding status.     

Age estimation of Antarctic minke whales <Emphasis Type="Italic">Balaenoptera bonaerensis</Emphasis> based on aspartic acid racemization technique

Counting of the growth layers in the earplugs is the most accepted technique for determining chronological age of Antarctic minke whales; however, unreadable growth layers form in some individuals, especially in young animals. In this study, aspartic acid racemization (AAR) technique was developed for estimating ages in this species with the aim of complementing the age estimated using earplugs. To validate the technique and to determine the specific coefficients for age estimation, the ratio of d and l-enantiomers of aspartic acid (Asp D/L) in lens of 18 whales and 20 fetuses were analyzed and compared with earplug-based age estimates. The equation for age estimation by AAR in this species was as follows: Log_e{[1 + (Asp D/L)_act]/[1 ? (Asp D/L)_act]} = 2.30 × 10^?3 × earplug age (year) + 0.0201 (p < 0.001, r ²  = 0.918). There is a strong correlation between the age estimates by AAR and earplugs. This study was successful in developing the AAR technique for the Antarctic minke whale, and the application of this technique can complement the age estimation of this species based on earplug readings, especially for young animals with unreadable earplugs.