Shrimps in the aquarium

1. Anatomy of shrimp

1. Rostrum
2. Carapace
3. 6 abdomenal segments
4. Antennal peduncle with 3 segments
5. Stylocerite
6. Antennule
7. Flagellum
8. Scaphocerite (antennal scale)
9. Antenna
10. Maxillipeds - the first and second pairs
11. Maxillipeds - third pair
12. Pereiopods - 5 pairs of walking legs, the first two ended dactyls, another chelae
13. Pleopods - 5 appendages used for swimming, the female holds the eggs them
14. Endopod - part of the pleopod
15. Exopod - part of the pleopod
16. Two uropods
17. Telson - covering the anus

2. Keeping freshwater shrimps

Many people think that shrimps are effective antidote with to the growth of algae and mosses in aquarium. These crustaceans feed algae and they can clean our tank but not in aquarium where is a serious problem with algal bloom. There is high concentration of ammonia, nitrites or nitrates, phosphates and large oxygen deficit in this aquarium. Accumulation of these all compounds is deadly to shrimps. So algae must always be under strict control in tanks where we keep any shrimps. The shrimps need crystalline clean and oxygen-rich water, without heavy metals (especially copper compounds) and other chemical substances. Aquarium should include lot of plants and hiding-places, a spongy filter with protected outlet, a heater and a lighting. We shouldn't keep the shrimps with fish which can hold these crustaceans in their mouth and with their natural predators in a general tank with fish. Safe tank mates will be: neon tetras, microrasboras, small corydoras and otos. Stressed shrimps often lose their colours and they can escape from aquarium. Stressed females can leave their eggs which they hold under their abdomen. The shrimps prefer to live in groups. Then they are less shy and timid. We should have minimum 20 litre of water per 5 dwarf shrimps.

3. Basic definitions - molting and metamorphosis of shrimps, the serrata shrimp group

• Molting (moulting) - each shrimp molts in order to grow i.e. it casts off its outer shell. Then the shrimps behave differently than usual. They are apathetic, without appetite, they hide among plants or other decorative elements. When the shrimp molts it vigiriusly bends at the "waist" and it almost touches the head of its tail. Next the shrimp hides until its a new shell will be hardened unless it is matured sexually female. Then she starts to reproduce. We shouldn't remove the old shells because it is valuable source of calcium for shrimps.
• Hemimetabolism and holometabolism - incomplete and complete matamorphism - these are two modes of development of crustaceans. Incomplete metamorphism (hemimetabolism) is when miniature shrimp like adult hatches from egg - it is about 1 or 2 mm long. It starts immediately feeding but its internal organs aren't fully developed - especially reproductive organs. These organs will gradually develop during next metamorphosis/molts. This shrimp doesn't need transfered to brackish water - it lives, reproduces and transforms in fresh water. Complete metamorphism (holometabolism) is when larvae (nauplius) hatches from egg. This first larvae has 3 pairs of legs and its body isn't divided into segments. It falls on the bottom or hangs under the water surface and it starts immediately feeding. Its food is very small plankton and organic matter. Larvae of shrimps which transform complete may need or not brackish water for further development - it depends on specific of species. The young will look like adults after a few larval stages and metamorphosis.
• Serrata shrimp group (group of C. serrata) - this is group of shrimps from China which have common morphological features. These features veryfied, classified and systematized Y.CAI and K.NG. They described and published these informations in Jurnal of Natural History (33, 1603-1638) in 1999s. Characteristic features of serrata shrimp group:
• long stylocerite (scale developed from the lateral base of the first segment of the antennular peduncle) which is visible longer than first segment of the antennular peduncle,
• rostral dentition - teeth on the upper part of the rostrum,
• male's endopod of the first pleopod has characteristic, well developed appendix interna,
• female lays large in size eggs,
• larval stage is shortened.
Caridina serrata, Caridina cantonensis (and its multicolour variants of Bee, Red Crystal and Tiger), Caridina sphyrapoda, Caridina ananoensis, Caridina apodosis, Caridina yulinica, Caridina wamingensis, Caridina mutata, Caridina trifasciata and other belong to the serrata shrimp group. This group still changes with regard to the lists of species because researches constantly last. But what is the value of these informations for ordinary aquarist and amateur of these crustaceans? Actually, no value. These morphological features aren't practically visible and "negative" hybrydization species from this group isn't confirmed scientifically. Wild species from this group aren't available for aquarists, only selectively bred multicolour variants are available. I think all the fuss around the serrata shrimp group is result that hybridization of Bee, Tiger, etc. shrimps causes irretrievable reversion of their colors to the wild forms. Unfortunately, here doesn't work the principle of blending colors and we don't want this. So you should remember: we can't keep Red Crystal, Bee and Tiger shrimps together.