Sexual dimorphism is a common phenomenon in the animal kingdom. To test the consistency of sexual dimorphism patterns among sympatric species of the same genus, ten morphometric characteristics of mud crabs Scylla olivacea, S. tranquebarica and S. paramamosain were measured and compared using Discriminant Function Analysis (DFA). The descriptive analysis revealed that in all three species, body size dimensions and cheliped dimensions were significantly larger in males whereas the abdomen width was female-biased. Also, we described a morphological variation (carapace width, CW ≤ CW at spine 8, 8CW) that is unique to S. olivacea. Discriminant function analysis revealed that all nine morphometric characteristics were sexually dimorphic in S. olivacea, S. tranquebarica (except right cheliped's merus length, ML) and S. paramamosain (except 8CW). The obtained discriminant functions based on the morphometric ratios (with CW as divisor) correctly classified 100% of adults of known sex of all three species. Further, based on the selected body traits, DFA was able to almost completely distinguish males (94%), but not females (74%), among the three Scylla species. This study highlights that congeneric species of portunids (e.g., Scylla spp.) show similar sexually dimorphic characteristics (body size and secondary sexual characteristics).
There are four species of mud crabs within the genus Scylla, and most of them live sympatrically in the equatorial region. Apart from a report in Japan about the finding of a natural Scylla hybrid more than a decade ago after the division of genus Scylla into four species by Keenan, Davie & Mann (1998), no subsequent sighting was found. Thus, this study investigates the possible natural occurrence of potential hybridization among Scylla species in the wild. A total of 76,211 individuals from mud crab landing sites around the Malacca Straits, South China Sea and Sulu Sea were screened. In addition to the four-purebred species, four groups (SH 1, n = 2, 627; SH 2, n = 136; SH 3, n = 1; SH 4, n = 2) with intermediate characteristics were found, mostly at Sulu Sea. Discriminant Function Analysis revealed that all Scylla species, including SH 1 - 4, are distinguishable via their morphometric ratios. The most powerful discriminant ratios for each character and the top five discriminant ratios of males and females were suggested. The carapace width of SH 1 males and females were significantly smaller than pure species. Based on the discriminant ratios and the description of morphological characters, we hypothesize that the additional four groups of Scylla with intermediate characteristics could be presumed hybrids. Future work at the molecular level is urgently needed to validate this postulate.
Owing to their availability, cost effectiveness and environmental-friendly nature, plant extracts are promising additives for fish farming. This study aims to determine the optimal dosage of fermented herbal extract (FHE)-composed of Morus alba (33.3%), Curcuma xanthorrhiza (33.3%), and Boesenbergia rotunda (33.3%)-for growth enhancement and feed utilisation efficiency of Oreochromis niloticus fingerlings. Fermentation was conducted using probiotics Lactobacillus casei (Yakult®, Tokyo, Japan) and Saccharomyces cereviceae (commercial baker's yeast). The FHE was high in flavonoid and alkaloid, vitamin C, potassium, natrium, lipase and protease. Four doses of FHE treatments, namely treatment A (0 mg/kg of feed); treatment B (100 mg/kg of feed); treatment C (300 mg/kg of feed); treatment D (500 mg/kg of feed) were compared. After subjected to 35 days of culture, tilapias subjected to FHE-coated feed exhibited better weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) compared to control. The best dosage that gave the highest growth and feed efficiency was treatment C (300 mg/kg of feed). Furthermore, the feed efficiencies of FHE-incorporated treatments were positively influenced by the increased in length and density of intestinal villi, number of goblet cells, lymphocytes, as well as nutrient retention to support growth. The results of this study indicate that FHE is a promising functional feed additive to stimulate growth and improve feed efficiency in tilapia farming.
Sea cucumbers have high economic value, and in most forms of trade, their body wall is typically the only part that is harvested and sold. The organs of the sea cucumber, collectively known as the viscera, are frequently discarded, contributing to land and water pollution. However, discarded sea cucumber viscera contain various nutrients that can be used in many applications. Therefore, this review highlights the biological and economic aspects of sea cucumbers, followed by a critical discussion of the nutritional value of their internal organs and possible applications, including as functional feed additives in the aquaculture industry, sources of natural testosterone for application in sex reversal and production of monosex population, of neuroprotective agents against central nervous system disorders and of cosmetic ingredients, especially for skin whitening and anti-ageing products. The review further highlights the valorisation potential of viscera to maximize their economic potential, thus providing an enormous prospect for reusing sea cucumber waste, thereby reducing the negative impact of the sea cucumber fishery sector on the environment.