Commercial Importance and Adaptability of the Giant Freshwater Prawn

Macrobrachium rosenbergii, commonly referred to as the giant freshwater prawn, holds immense commercial significance due to its adaptability, large size, and high market value. Native to the Indo-Pacific region, it thrives in tropical and subtropical regions stretching from India to Southeast Asia and Northern Australia. While it is native to these areas, its cultivation has spread globally, particularly in regions with aquaculture industries, making it a staple in both local and international markets.

One of the reasons for its commercial appeal is its size. Males can reach an impressive length of up to 32 cm (12.6 inches), while females typically grow to around 25 cm (9.8 inches). Their coloration is primarily brownish, though younger or smaller individuals may appear greenish with faint vertical stripes, making them visually distinct. The prawn's rostrum, a spiked projection from its head, is an essential feature, with 11 to 14 dorsal teeth and 8 to 11 ventral teeth, which serve as both a protective mechanism and a distinguishing characteristic.

The species is also sexually dimorphic, meaning males and females exhibit distinct physical differences. Males have significantly larger second pereiopods, or walking legs, compared to females. These legs are covered in dense bristles, creating a velvety texture, which adds to the prawn's unique appearance. This characteristic, along with their ability to thrive in varying environments, adds to their appeal for aquaculture. Notably, their larvae require brackish water for development, while juveniles and adults can live in freshwater, enhancing their farming versatility.

In addition to being adaptable and visually striking, M. rosenbergii provides numerous nutritional benefits. Rich in protein, essential amino acids, and healthy fats, it supports human nutrition while bolstering aquaculture's role in global food security and economic development. These qualities make the species a valuable resource in addressing the growing demand for sustainable seafood.
Commercial Importance and Adaptability of the Giant Freshwater Prawn

Sea Star Characteristics

Sea stars, also referred to as starfish, belong to the class Asteroidea, which is a star-shaped phylum of echinoderms. They are part of the larger group of echinoderms that includes sea urchins (Echinoidea), sea cucumbers (Holothuroidea), and various other living and extinct creatures.

There are approximately 2,000 species of sea stars that can be found in both tropical and cold oceans.

Echinoderms, which are marine invertebrates without a backbone, have a skeleton made up of hard calcite plates. Most sea stars exhibit pentameral symmetry, meaning they have five rays or arms.

While sea stars live in water, their similarities to fish end there. They lack gills, scales, and fins and are exclusively found in saltwater habitats. Interestingly, sea stars do not rely on lungs or gills for breathing; instead, they absorb oxygen directly from the surrounding water through a process called osmosis.

Sea stars utilize small tube feet located on the undersides of their bodies to move. Adult sunflower sea stars can achieve an impressive speed of one meter per minute by using their 15,000 tube feet.

Sea stars have a bony and calcified skin, which can feel rough or leathery. However, this outer layer serves as protection against predators. Additionally, their vibrant colors often serve to intimidate potential threats or help them blend into their surroundings. Despite these adaptations, sea stars are slow movers, making them vulnerable to a wide range of marine animals, including marine birds, crabs, fish, sharks, and even humans.
Sea Star Characteristics

Fish spoilage

Fish is highly perishable due to high moisture content, availability of the nutrients for the growth of microorganisms and ambient temperature. Fish spoilage results from three basic mechanisms:
*Enzymatic autolysis (reactions caused by the activities of the fish’s own enzymes)
*Oxidation (oxidation of unsaturated lipids)
*Microbial growth (metabolic activities of microorganisms)

One-fourth of the world's fish supply and 30% of landed fish are lost through microbial activity alone.

Fresh fish spoilage can be very rapid after it is caught. The spoilage process (Rigor mortis) will start within 12 h of their catch in the high ambient temperatures of the tropics.

Spoilage of fish can be considered as any change that render the product unacceptable for human consumption. When fish dies, the biochemical changes responsible for anabolism stop. As an inevitable consequence of this process of cessation of anabolism, catabolism starts bringing spoilage to fish flesh. The digestive enzymes still being active, instead of acting on the food present inside the gut, begin to digest tissue components such as lipids, carbohydrates and proteins. This process is called “autolysis”.

One important action determining the onset of spoilage in freshly caught fish is rigor mortis, the stiffening of the body. Usually, this develops within 1-7 hours after death. Rigor mortis sets in and passes quickly in very active fish but slowly in inert fish.

Characteristics of spoiled fish
*The flesh is soft to touch. When the flesh is pressed it leaves a permanent indentation.
*The skin looks dull and has slime on the surface.
*The gills look brownish.
*It gives a bad smell.

With the ever-growing world population and the need to store and transport the food from one place to another where it is needed, food preservation becomes necessary in order to increase its shelf life and maintain its nutritional value, texture and flavor.
Fish spoilage

Seahorses

Seahorses are grouped with pipefishes, pipehorses and seadragons as members of the family Syngnathidae. They are of the same order (Gasterosteiformes) as cornetfishes, pegasids (seamoths), snipefishes, sticklebacks and trumpetfishes. Seahorses are thought to have evolved at least 40 million years ago.

They are generally characterized by a sparse distribution, low mobility, small home ranges, low fecundity, lengthy parental care and mate fidelity. In addition, the male seahorse, rather than the female, becomes pregnant.

Seahorses occupy both temperate and tropical coastal waters, with a distribution from about 50 degrees north to 50 degrees south. They may usually be found among corals, macro algae, mangrove roots and seagrasses, but some live on open sandy or muddy bottoms.

In a marine environment, depending on their species, seahorses feed on amphipods, copepods, shrimp, and larval fish. When juvenile seahorses leave the male’s pouch they are very similar to the adult seahorse, but smaller in size. Immediately after birth, seahorses are able to feed on live prey.

The body armor of seahorses is composed of plates that overlay to allow ventral bending. The armor is flexible and fracture resistant due to the complex plate and segments designed to slide and slip when compressed. Seahorses have no teeth and no stomach. Food passes through their digestive systems so quickly that they must eat almost constantly to stay alive.
Seahorses