Aquarium Notes

Neocaridina Davidi External Anatomy

Body Structure

• Shrimp bodies are segmented into two main regions, the cephalothorax and the abdomen
• The cephalothorax is a fusion of the carapace/rostrum [beak-head] and thorax; it consists of
• Carapace, upper body, heavily calcified, protection of the inner organs (brain, heart, stomach, bladder, testicular or ovarian)
• Rostrum, beak or nose, hard extension of the carapace, protection of the eyes, stabilizer when swimming backwards
• Eyes, located on short, independently movable eyestalks either side of the rostrum
  • Compound eyes give shrimp panoramic vision, good at detecting movement, important for shrimp at lower end of the food chain
  • Eyes also produce the hormones which regulate metabolism, the molting process, location of pigment in the cells, and accumulation of calcium in the body
  • Shrimp can regenerate lost limbs with every molting process, but the eyes cannot be regenerated
• Antennae, long whiskers, sensors of orientation and coordination of positioning, detect vibrations in water around the shrimp
• Antennule, short whiskers, sensors of chemical information, assess suitability of food (taste and smell)
• Maxillipeds, ("foot jaw"), specialized feet/appendages designed for eating, remain in almost constant movement as shrimp seek out and bring tiny morsels of food to mouth
• Pereiopods, 5 pairs of jointed legs with varied functions
• Chela, the first 2 pair have tiny claws/pincers (chela) that shrimp use for feeding and for fighting each other for food (because the claws are small they usually cannot harm each other)
• The rest of the pereiopods are for walking/movement and for sensing the environment
• Scaphocerit, a flattened plate located at the base of the antennae and antennule, an organ of equilibrium, containing sensitive bristles that orient the shrimp in relation to the earth's gravity
• The Abdomen is made up of 6 abdominal segments and contains most of the muscle tissue
• The first segment is just after the carapace, and the sixth segment is just before the tail
• The shell of the abdomen is significantly thinner than the carapace
• Each segment has its own, separate shell
• Pleura (pleuron), are the lateral flaps on each of the anterior five segments, serving to overlap the adjacent segment shells
• The purpose of a pleuron is protection of the junction between the abdominal segments
• Each segment also has a pair of pleopods, except the sixth one adjacent to the tail
• There are 5 pairs of pleopods, swimmerets shaped like paddles, used for swimming forward
• Females use pleopods for carrying eggs
• In males, the first pair of pleopods is modified for insemination, the petasma, male genital organ
• The shell of the abdomen is significantly thinner than the carapace
• Shrimp swim backward by contracting the abdominal muscles, powerfully flexing the abdomen for rapid darting speeds
• The Tail (composed of the telson, uropods, endopod, and exopod) is used for swimming and steering
• The telson extends from the sixth abdominal segment and is used for swimming
• The uropods are attached to the sixth abdominal segment and flank the telson from both sides, sometimes called a "tail fan" used for locomotion when swimming backward, and functioning like rudders, steering when swimming forward

Molting

• Molting, or ecdysis, is the biological process by which shrimp shed their old exoskeleton to grow
• During the molting process, shrimp are in the most vulnerable condition of their life cycle
• Shrimp molt every 3-4 weeks on average
• Younger shrimp molt more often due to their rapid growth rate
• Older shrimp molt less frequently as their growth slows
• Shrimp molt for several reasons
• Growth, shrimp cannot expand within their rigid exoskeleton, so molting allows them to grow
• Repair, any damage to their exoskeleton is restored via the molting process
• Reproduction, female shrimp often molt before mating, releasing hormones that signal readiness for reproduction
• Regeneration, lost limbs or damaged appendages regenerate during molting, promoting long-term survival, but lost or damaged eyes do not regenerate
• Stages of the Molting Process
• Pre-Molt (Proecdysis) Preparation
• Shrimp prepare for molting by absorbing calcium and softening their old shell
• Before shedding, a new, larger exoskeleton begins to form beneath the old one
• The shrimp begins extracting minerals from the old shell for later use
• The exoskeleton becomes fragile, and the shrimp start showing reclusive behavior
• During this stage, shrimp may reduce their food intake as their energy is redirected toward preparing for the upcoming molt
• Molting (Ecdysis) Shedding
• The shrimp pumps water into its body cavity to increase pressure until the old shell splits open at the weak point between its carapace and abdomen
• With a swift, forceful flick or jump, the shrimp pops out of the old exoskeleton, emerging with a soft new shell
• While the "molt" itself happens in an instant, this phase can take a few minutes, but it's a highly stressful and dangerous time for the shrimp
• Many shrimp prefer to molt in hidden areas such as plants or hardscape to protect themselves from potential threats
• Post-molt (Metecdysis) Recovery
• The new shell hardens while it absorbs minerals over a period of a couple days
• Calcium intake is crucial during this stage
• The shrimp may consume its old exoskeleton to regain some of the lost nutrients
• The shrimp usually remain hidden during this vulnerable time
• Inter-Molt (Anecdysis) Growth
• The shrimp continues to grow inside its hardened new exoskeleton until it outgrows the new shell and the next molt cycle begins
• This period varies in duration, depending on the age and health of the shrimp
• Factors that Influence the Molting Process
• Water Quality, ammonia, nitrites, nitrates must be kept low to avoid stress
• pH Levels, stable ph between 6.5 to 7.5 suypports molting health
• Temperature, optimal range 72F to 78F promotes regular molting
• Nutrition, calcium-rich shrimp foods including blanched vegetables and shrimp-specific supplemental foods are crucial
• Hiding Spots, shrimp are highly vulnerable after molting and require safe spaces to recover
• Tank Mates, aggressive fish can pose a threat to molting shrimp, peaceful tank mates are recommended
• Signs of an Impending Molt
• Reduced movement or hiding behavior
• Decreased appetite
• Increased preening or cleaning of the exoskeleton
• A visible white line along the back indicates the shell is loosening
• Caring for Shrimp During the Molting Process
• Avoid sudden water changes to prevent osmotic shock, small changes with drip speed
• Provide mineral supplements like calcium and iodine
• Do not remove molted shells, as shrimp consume them to replenish lost nutrients
• Minimize disturbances during and after molting
• Common Issues Related to the Molting Process
• Failed molts caused by poor nutrition or unstable water parameters, leading to death
• White Ring of Death, a break in the exoskeleton at the wrong point, preventing a clean molt
• Soft Shell Syndrome, due to calcium deficiency, resulting in weak exoskeleton formation
• Molting Frquency Issues, either or both too frequent or infrequent molting can signal underlying health problems
• Promoting Healthy Molting
• Maintain stable water parameters, regular testing, small weekly water changes
• Balanced Diet, offer calcium-rich foods like spinach and shrimp-specific pellets
• Provide aquatic plants and hiding places for post-molt recovery
• Monitor Behavior, observe changes that may indicate molting issues

Breeding

• The Neocaridina breeding cycle is straighforward and happens continuously in freshwater
• Female shrimp develop unfertilized eggs in their "saddles," molt, release pheremones to attract males, then mate
• They carry fertilized "berries" for 20 to 30 days before hatching minature, self-sufficient shrimplets
• The complete cycle from egg to mature adult capable of reproducing takes 4 to 6 months
• The Saddle Stage (1 to 2 weeks)
• As a female matures, she develops unfertilized eggs in her ovaries, visible as a saddle-shaped patch behind her head, on her back/topside
• The color of the saddle varies (yellow, orange, green) depending on the Neocaridina variant
• Molting and Mating
• Because a female's exoskeleton hardens after a molt, she must shed her old shell to become receptive to male insemination
• Once molted, she releases potent pheremones into the water, signaling that she is ready to mate, causing males to actively search for her
• Mating occurs within minutes and is extremely fast (taking only 5 to 15 seconds), one male will fertilize the eggs
• Egg-Carrying/Berried/Ovigerous Stage (20 to 30 days)
• Within a few hours of mating, the female passes the eggs through the deposited sperm to become fertilized (external fertilization) and attaches them to her swimming legs (pleopods) under her abdomen
• The female will hold the fertilized eggs under her abdomen for the duration of their development to shrimplets ready to hatch, about 30 days
• This phase is referred to as being "berried" because the fertilized eggs resemble a cluster of berries
• She will constantly fan fresh, oxygenated water, with her swimmerets, over the eggs in the brood pouch (formed by the pleopods) to keep them free of debris and fungus
• Occasionally, the female will drop the eggs for no apparent reason, probably stress related, conditions not right for breeding, and that brood is terminated
• Hatching and Shrimplet Stage (about 2 months)
• After 3 to 4 weeks, the eggs hatch into tiny, clear (transparent) miniature versions of adult shrimp (2 mm long)
• There is no larval stage
• The mother provides no parental care, shrimplets are on their own after hatching
• The shrimplets immediately latch onto plants or rocks to hide and graze on naturally occurring biofilm and algae
• Juveniles and Maturity (2 to 6 months)
• For the first few weeks, shrimplets are highly vulnerable and spend most of their time in hiding
• As they eat and grow, they molt frequently to expand their bodies
• By 2 months, they transition into juveniles and begin to show their adult coloration
• At 4 to 6 months they reach adulthood and can begin breeding themselves, restarting the cycle

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