The atyid shrimp Neocaridina davidi, generally known as “Red Cherry shrimp” or “RCS”. They are extremely popular and widespread across the world in the aquarium industry (since the first introduction in 2003). Their bright red color really adds beauty to the aquarium. Red cherry shrimp are easy to breed and keep especially because they are very hardy. These shrimp can live in conditions that would be considered too extreme for other types of the shrimp. Aquarists love them because they are outstanding maintenance crews and will stand out in the aquarium especially against plants and darker substrates. However, despite its popularity, basic information on the biology of this species is still scarce in the literature.
In this article, you will know that fertilized eggs have an oval shape with color varies from greenish to yellowish. The eggs size are comparatively large, with an average diameter of 1.19 mm. Depending on the temperature the embryonic development of the eggs can last from 25 to 35 days. Newly hatched shrimplets look like a tiny version of the adult shrimp with an average total length of 2.3 mm. There are 16 stages of post-hatching development of the baby cherry shrimp. That shrimp female can usually produce about 21-51 shrimplets per hatching. Larger females produce more shrimplets. It takes around 60 days for the cherry shrimplets to reach the juvenile stage. Until then it is not possible to differentiate males from females with the naked eye. Juveniles become adults 15 days later. Females are obvious with the presence of orange-colored ovary at the cephalothorax region. Within 1 to 3 days, these males and females are ready to spawn.
There are not many types of research and reports about this particular species breeding and life cycle. In order to fill this gap I decided to write an article based on conducted experiments:
- Breeding and Life Cycle of Neocaridina denticulata sinensis. Asian Journal of Animal and Veterinary Advances 8 (1): 108-115, 2013). I have tried to collect everything I could about the breeding activities and life cycle of the shrimplets until adulthood.
- Post-hatching development of the ornamental “Red Cherry Shrimp” Neocaridina davidi (Crustacea, Caridea, Atyidae) under laboratorial conditions. Article in Aquaculture Research. October 2015.
The article is rather big and full of scientific terminology. For those who are too lazy to read the whole article I have summarized it above in a simple way. However, if you want to read everything in details, get comfortable and let’s start.
Experiment conditions (Tank preparation, feeding, water quality)
During the experiment, females, ovigerous females, males, shrimplets had different aquariums with aerated tap water. Once a week the researchers did a water change around 50% and feed them 2 times a day with 40% protein. Only healthy specimen participated in all stages of the experiments.
- Temperature 27-28
- pH 6,5-7,5
- Ammonia (mg L-1) <0.1
- Nitrite (mg L_1) <0.1
Note: there is a popular rumor in shrimp breeding community that too much protein (more than 40%) can be bad for the shrimp. Allegedly, it may disrupt a metabolic process in their digestion. Shrimp will get sick and can die, eventually. Frankly saying, I have not found any proof for that. Moreover, I have read several different kinds of research about shrimps and almost all the time researchers give them a lot of protein (40%). I have not seen any reports that it caused the death of the shrimp. Anyway, I prefer to play on the safe side if I am not certain about something.
At thirst, the researchers placed shrimplets (one week old) in the tank. They observed it until all the shrimplets reached the first maturity. After that researchers measured Neocaridina shrimp from rostral tip to posteromedian margin of the telson (the last segment in the abdomen), excluding posterior setae.
The difference of Neocaridina and Caridina Shrimp
Neocaridina shrimp is an indigenous species of Japan, Korea, China, Vietnam, and Taiwan. Previously Neocaridina shrimp was incorrectly identified as Caridina weberi. A little bit later scientists reclassified Neocaridina shrimp. From that moment they based new classification on the morphological difference in the male that is the presence of endopod on the first pleopod.
In short, the shape and size of the reproductive appendage are different. On Neocaridina the end of the appendage is round and flat. While the end of the Caridina species appendage is longer but slender than that of the Neocaridina shrimp. That is the reason why these two species cannot interbreed. Their organs just do not fit together.
Maturity and Mating of Neocaridina shrimp
Red cherry shrimp usually reached maturity at around 75 days old with the length about 2.3±0.2 cm. When they reach maturity, we can see:
- An orange colored ovaries through the cephalothorax region of the females ( 1).
- That the males have an appendix masculina on the second pleopod ( 2).
Mature female picks up eggs in the ovary, which is located at the junction of the cephalothorax (carapax) with the tail (abdomen). For a characteristic location and a special form, aquarists call the ovaries a “saddle”. The mating process usually takes place in 1-3 day(s) after the introduction of male and female into the same tank.
Mating of the Red cherry shrimp
When the eggs “ripen”, the female start molting. They always molt before mating because at that time new female cuticle is soft and flexible, which makes fertilization possible. The molting process happens very fast and takes no more than 10-15 seconds.
After that, female releases certain chemical substance (pheromone) into the surrounding water. It is the signal for the males that she is ready to mate. The “smell” attract the males and allows them to find the female in the water column.
If you notice that some shrimp rush feverishly around the aquarium from corner to corner, this means that one of the females has just molted. That is him responding to the hormones and he will try to find that female and mate with her.
The mating occurs rapidly as well – about 10 seconds or less. In order to start mating, male and female should face each other. The male leaves sperm into the genital opening of female Neocaridina shrimp using its appendix masculine.
After that, the female starts moving the eggs from the “saddle” to the brood pouch and at that moment the eggs go through the sperm and become fertilized. Therefore, it is certain that any shrimp carrying eggs has mated. A female carrying eggs under her abdomen is said to be “berried”.
Fertilized eggs of Neocaridina shrimp
It is very hard to see the process of moving eggs from the saddle to the abdomen because females hide all the time at this stage. Nonetheless, there are some reports that to do so the female lies on her side and bends the abdomen. As a result, the eggs start falling into this area.
The pouch itself is formed by pleopods and overhanging of pleura of the female. The female holds the eggs in the brood pouch until hatching day. This kind of parental care will result in the higher survival rate of the shrimplets .
Fertilized eggs have an oval shape and vary from greenish to yellowish in color. The egg size is rather large, with an average length of 1.19 mm. Thin ribbon-like filament binds the eggs in grape-like bunches and attached it to the female’s pleopod. It is almost impossible to distinguish the membrane since it is very thin and transparent.
Eggs development of the Red cherry shrimp
There are three stages of eggs development as follows:
- Stage I
Developing: thin, pale orange, filling one-third of the cephalothorax volume;
- Stage II
Mature: orange, filling two-thirds of the cephalothorax volume;
- Stage III
Ripe or almost ripe: deep orange, filling almost all of the cephalothorax.
In the process of embryogenesis, the shrimplets pass through 9-12 stages. At this time, changes are taking place in their structure: at the beginning of the mandible, and a little later, the cephalothorax.
Cherry shrimp will keep fanning its eggs with its hind pleopods and washing them with water until the eggs are ready to hatch. Depending on the temperature, the egg incubation can last from 25 to 35 days. The shortest incubation period 15 days takes place at 27°C. The eggs start to have lighter in color and translucent just before hatching. Closer to the hatching day it is possible to notice black dots on the eggs (eyes on the young shrimp).
The early development of the Red cherry shrimp
|Carapace||Carapace: spineless; rostrum slightly exceeding the eye stalks. Several round balls of yolk are visible in the median region of the carapace through the transparent exoskeleton.
Rostrum with 3–4 small teeth dorsally, and 1 tooth, 1 simple seta and 1 plumose seta ventrally.
Abdomen: six-segmented, with the sixth separated from the telson.
|Carapace: similar to the previous stage
Rostrum has seven teeth on dorsal margin, one tooth, one simple seta and one plumose seta on ventral margin.
Abdomen: some small simple setae present on fifth and sixth segment.
|Carapace: similar to previous Stage.
Rostrum has eight dorsal teeth; one plumose seta and one tooth on ventral margin.
Abdomen: similar to previous stage, except for third somite, which is larger than others.
|Telson: oval in shape, bearing eight plumose setae on each side of the posterior lateral margin, dorsal surface smooth. The first seta on lateral margin has setules only on the inferior border. The buds of uropods can be seen through the transparent cuticle.
|Telson: longer than wide bearing
three serrated setae, five plumose setae and two fine simple setae on its postero-lateral margin. Surface smooth.
| Telson: longer than wide with 5 + 5
plumose setae on posterior margin. Three serrated setae on each side of postero-lateral margin.
|Antennule: 3-segmented peduncle, proximal segment with very small and spiny stylocerite bearing three simple setae on latero-distal margin and a small knob-like apical spine.
Four small plumose setae in angle located between stylocerite and basal segment. There is a simple seta on the median margin at the opposite side of the stylocerite. One, 3 and 3 plumose setae on ventromedian margin of basal, second and third segments of peduncle respectively. Dorsal margin of
the peduncle with two small simple setae, two serrated setae and four plumose setae on basal segment,
three serrated setae and two small simple setae on second segment, and one simple seta on the third segment. Ventral flagellum with six segments of similar size with 0, 2, 3, 0, 4 and 3 simple setae respectively. Dorsal flagellum with six
segments, but the total length is shorter than the ventral flagellum. This flagellum has zero, two simple setae, three aestethascs, zero, three simplesetae and four simple setae respectively.
|Antennule: Peduncle 3-segmented, proximal segment with a stylocerite bearing three simple setae on laterodistal margin; and four small plumose setae in angle between stylocerite and basal segment. Proximal segment also has subterminal plumose setae, 10 terminal plumose setae and one serrated seta. Second segment with two lateral plumose setae, four terminal plumose setae and third serrated setae. Third segment with four terminal plumose setae and four (2 + 2) simple setae. Ventral flagellum six-segmented with 0, 3, 0, 3, 1 and 3 simple setae. Dorsal flagellum sixsegmented with 0, 1, 0, 0 3 and 3 simple setae respectively. Three aestethascs present on ventral margin of third segment.
||Antennule: Peduncle similar to previous
stage. Proximal segment has one lateral and subterminal, and one lateral and terminal plumose setae; 11 terminal plumose setae and two serrated setae. Second segment with three lateral
plumose setae and one simple seta; two terminal plumose setae and one simple seta and four terminal serrated setae. Third segment with four terminal setae (two short) and five simple setae.
Ventral flagellum nine-segmented with 4, 0, 4, 4, 0, 2, 0, 4 and 3 simple setae. Dorsal flagellum sixsegmented with 1, 1, 0, 0, 4 and 4 simple setae respectively. Three short aestethascs present on
ventral margin of third segment.
|Antenna: long, with the flagellum curved and reaching over back of the carapace Peduncle bearing three simple setae and one plumose seta. Flagellum with 42 segments, approximately, bearing sparse simple setae on it.
Scaphocerite (exopod) with a large apical spine and three small simple setae on dorsal margin;
ventral margin with 21 plumose setae.
|Antenna: Peduncle bearing one plumose
seta and two simple setae. Flagellum with approximately 49 segments, bearing one plumose and two simple setae on first segment, sparse simple
setae on other segments. Scaphocerite with a large apical spine and three small simple setae on dorsal margin; ventral margin with 22 plumose setae.
|Antenna: Peduncle smooth. Flagellum
with 56–59 segments bearing three simple setae on first segment, and other segments with sparse simple setae. Scaphocerite with a large apical spine
and three small simple setae on dorsal margin; ventral margin with one simple seta and 22–24 plumose setae.
|Mandible: incisor process with three small teeth, median portion with three rows of fine simple setae (4 + 5 + 3), and molar process rounded and smooth. No palp.
||Mandible: incisor process with three teeth, median portion with three rows of setae bearing three plumose setae, seven simple setae and four simple setae; molar process rounded and smooth. No palp.
||Mandible: incisor process with four teeth, median portion with two rows of setae bearing three plumose and five simple setae; molar process rounded with 25–27 serrated setae. No palp.
|Maxillule: rudimentary. Unsegmented endopod with one very small spine distally. Basial endite with 10–11 short serrate setae. Coxal endite with three small spines.
||Maxillule: unsegmented endopod with one small spine and one simple seta, distally.
Basial endite with two plumose setae distally, 13–15 short serrated setae, two to three plumose and two to three serrated setae marginally;
coxal endite with two small plumose setae, 18–20 median plumose setae marginally and six to seven serrated setae, eight spines on its surface.
|Maxillule: similar to previous stage.
|Maxilla: Scaphognathite with four plumose setae on proximal portion, four serrulate setae apically and 30–31 plumose setae from median to distal portion. Endopod reduced. Basial endite
with 14 min serrated setae on proximal lobe, and 6 min serrated setae on distal lobe. Coxal endite unilobed with 21 simple setae.
|Maxilla: Scaphognathite with two plumose setae proximally, four serrulate setae apically, and 27–29 plumose setae along median to distal. Endopod reduced. Basial endite with approximately 28 simple setae on proximal lobe; approximately nine simple setae and three plumose setae on distal lobe. Coxal endite unilobed with approximately
30 simple setae.
|Maxilla: Scaphognathite with six plumose setae proximally, seven serrulate setae apically, and 34–35 plumose setae from median to distal. Endopod reduced with one simple seta.
Basial endite with approximately 40 simple setae on proximal lobe; and approximately 10–12 simple setae, four plumose setae and one sparsely plumose
seta on distal lobe. Coxal endite unilobed
with 40–43 simple setae.
|First maxilliped: biramous. Endopod reduced with one small plumose seta. Basial endite with approximately 18 serrated setae. Coxal endite with five simple setae. Exopod unsegmented, enlarged from proximal to one-third before the distal part; 17–18 plumose setae on enlarged part and one plumose and one small sparsely plumose
setae on distal part. Epipod reduced and smooth.
|First maxilliped: biramous. Endopod
reduced with two small plumose setae. Basial endite with microtrichia on dorsal margin, third plumose setae on terminal end and five sparsely plumose setae on median margin; several small spoon-tipped setae on median margin. Coxal endite with 11 plumose setae. Exopod similar to previous stage with 16 plumose setae on enlarged part, three sparsely plumose and one plumose seta on distal part. Epipod very reduced.
|First Maxilliped: Endopod reduced
with 1–2 small plumose setae. Basial endite with microtrichia on dorsal margin, three plumose setae
on terminal end; approximately two rows of 16–18 plumose setae each on median margin; approximately 70 spoon-tipped setae distributed in 4 rows. Coxal endite with 11 plumose setae. Exopod unsegmented, similar to previous stage with 19–20 plumose setae on enlarged part and three to five sparsely plumose setae on distal part. Epipod very reduced.
|Second maxilliped: biramous. Endopod fur-segmented, shorter than exopod, bearing 0, 0, 5, 11 small serrated setae. Exopod long with four long terminal plumose setae. Epipod reduced and smooth.
||Second maxilliped: biramous. Protopod with one simple seta and four plumose setae. Endopod four-segmented bearing zero, one plumose seta, four plumose setae and two simple setae, and three plumose and 16–20 plumose brush-like setae respectively. Exopod long with four long terminal plumose and one simple seta.
Epipod reduced and smooth.
|Second Maxilliped: Protopod with
sixto seven plumose setae. Endopod four-segmented bearing one plumose seta on first segment; no seta on second segment; three plumose and three simple setae on third segment; threeplumose setae and two rows of 11–13 plumose brush-like setae each and one row of five to six plumose setae. Exopod long with four long terminal plumose and one simple seta. Epipod reduced and smooth.
|Third maxilliped: biramous. Endopod four-segmented, first and second segment with six and eight simple setae, respectively; third segment with 2 simple setae, 1 plumose setae and 14 (3 + 5 + 3 + 3) cuspidate setae; and fourth segment with three fine simple setae and three short and enlarge serrated setae. Exopod shorter than endopod, bearing four long terminal plumose and one small simple seta. Epipod as a small bud.
||Third maxilliped: biramous. Protopod with five simple and six plumose setae. Endopod 4-segmented with 5, 8, 3 and 2 simple setae and 4 serrated setae. Third segment has 16 (5 + 5 + 3 + 3) cuspidate setae. Exopod shorter than endopod, bearing four long terminal plumose and one simple seta. Epipod as a small bud.
||Third Maxilliped: Protopod with eight simple setae and six plumose setae. Endopod foursegmented.
First segment with two plumose, six simple and two serrated setae; second segment with 11 simple setae; third segment with three simple and four rows of 5–6, 5–6, 4 and 3-4 cuspidate setae; fourth segment with four simple and five serrated setae. Exopod with four long terminal plumose and one simple seta. Epipod represented by a bud.
|Pereiopods: 1st and 2nd chelate, 5-segmented, former shorter than later. Both chelipeds bear very small simple setae on the tip of the dactylus and propodus, and some sparse simple setae on all segments. A slender serrulated seta present on the dorsal margin of the basis, which is common for all pereiopods except for the fifth. The dactylus of the third, fourth and fifth pereiopods is provided with a terminal claw and 2, 2 and 6 small and strong serrated setae respectively. Third, fourth and fifth pereiopods with some serrated setae on ventral margin of merus, carpus and propodus.
|Pereiopods: both chelipeds similar as in previous stages, except for the presence of several serrated and pappose brush-like setae on tips of dactylus and propodus. Some sparse simple setae present on all segments. Dactylus of third, fourth and fifth pereiopods with a claw and 2, 1 and 5 small and strong serrated setae. Third and fourth pereiopods with one plumose seta on dorsal margin of merus; fifth pereiopod with one plumose seta on dorsal margin of ischium and merus.
Third, fourth and fifth pereopods with some serrated setae on ventral margin of merus, carpus and propodus.
|Pereiopods: similar to previous stage. Dactylus of last three pereiopods with a claw and 2, 2 and 7 small and strong serrated setae. Fifth pereiopod has no plumose setae on ischium. Third, fourth and fifth pereopods with some serrated setae on ventral margin of merus, carpus and propodus.
|Pleopods: all five biramous and bearing a simple setae on protopod. Exopods with 10, 11, 10, 10 and 10 plumose setae. The second and the fifth pairs also have one simple seta on the distal margin of the exopod. Endopods with 3, 6, 7, 7 and 6 plumose setae on terminal margin. The fifth pleopod also has one plumose seta on its proximal margin. All the endopods of pleopods, except for the first, have a fully developed appendix interna with four cincinnuli each.
||Pleopods: very similar to previous stage.
|Pleopods: similar to previous stages, but the seta number can vary. All five pleopods have one simple seta on protopod. Last four pleopods with appendix interna and four cincinnulli.
First pleopod with four and 11 plumose setae on endopod and exopod respectively. Second pleopod with eight plumose setae and one simple seta on endopod, and 11 plumose setae and one simple seta on exopod. Third pleopod with 7 and 12 plumose setae on endopod and exopod respectively.
Fourth pleopod with 8 and 10 plumose setae on endopod and exopod respectively; one plumose seta on proximal portion of endopod. Fifth pleopod with 7 and 10 plumose setae on endopod and exopod respectively; one plumose seta on proximal region of endopod.
|Uropods: biramous. Exopod with five simple setae on its dorsal margin; and one terminal spine, three simple setae, 16–20 plumose setae and one small seta distributed along postero-ventral margin. Endopod with 14–17 plumose setae and one simple seta along postero-ventral margin.
||Uropods: Exopod with five simple and one plumose setae on dorsal margin; one spine and two serrated setae terminally; rounded by 22–24 plumose setae. Some small setae hair-like and plumose setae present between terminal spines and the set of plumose setae. Endopod with 20–23 plumose setae.
Classification of the early development of the shrimp
The early development of the atyid shrimp is very diverse with species showing common, abbreviated and completely suppressed type. Some authors have emphasized the importance of the egg’s size and the shrimplets morphology to classify the early development of shrimps. Following such arguments, we have three categories:
- the common type of early development has from 9 to 12 planktonic stages, and the pleopods of the first stage are not yet developed;
- the abbreviated type has fewer (from 4 to 7) planktonic stages, and the pleopods of the first stage are still only rudiments and
- the complete suppressed type has no planktonic stage, and the pleopods are well developed.
Red cherry shrimp development follows the third type. When pereiopods and pleopods completely developed. Nevertheless, some variation could occur in species showing intermediate development. Newly “born” cherry shrimp look like the miniature version of the adult with an average length of 2.3±0.5 mm and an average height less than 1mm.
Right after hatching baby shrimps will hide for 3-4 days. They are small, transparent and remain consistently near the bottom, walls, leaves and in the Java moss for better protection. They molt after 1st day. Actually, shrimplets grow very quickly and often molts.
The sex of the shrimp is not clear during the early stages. From Stage 7 onwards, the sex could be determined despite its inconspicuous characteristic by using special tools.
Food and baby cherry shrimps
Young shrimp does not search for food until Stage 3. At the initial stage of development, shrimplets feed on stocks of egg yolk. Moreover, shrimplets at this (protozoan) stage cannot efficiently seek food as the swimming appendages do not work properly yet.
In the later stages, the shrimplets are able to feed on zooplankton. That is why it is vital to feed them in sufficient quantity with powder food in your aquarium. Each day baby shrimps consume approximately 2% of the average weight of their body.
Morphological descriptions of post-hatching stages of Red cherry shrimp
From the third post-hatching stage on, there are slight alterations in shape and setation. Most of these changes are related to the size and number of setae.
The number of eggs
The number of eggs depends on the weight and size of the female. The bigger is the female the more eggs she can carry. It ranged from 21-51 shrimplets per hatching, increased linearly (R2 = 0.9587) with the size of the female.
In nature, most of the hatched shrimplets die due to adverse conditions or because of predators. As a rule, maturity reaches only 5-10% of brood. Another important factor affecting the reproduction of the shrimp is overpopulation. In this case, shrimp spend all their energy on keeping their living space. Thus it prevents them from multiplying. So if you have a lot of shrimps in the aquarium, it should not surprise you that at one point they will stop breeding. In addition, that kind of closeness increases the risk of the rapid spread of diseases.
Note #2: If you are impatient and want to see the shrimplets after hatching there is a way to do it. You need to turn off the light in the room. The aquarium lamp should be directed straight down from above so that the light will penetrate through the water column towards the bottom. Therefore, the floating shrimplets will have shadows and you can see them. Some people confuse baby shrimps with parasites and drain the allegedly “dirty” water. As a result, they remain without baby shrimps.
After 60 days, shrimplets reach the juvenile stage. At this stage, it is not possible to distinguish male and female with the naked eye yet. Juvenile stage lasts around 15 days. At this time sex difference start to show itself clearly. After that, juvenile shrimp reach adulthood and first maturity. Thus completing the life cycle of the Red Cherry shrimp.
Info: During the study period, it was found that shrimplets and adult shrimp cultured in freshwater were susceptible to clitellate annelids, (Holtodrilus sp.) resulted in high mortality. Holtodrilus sp. spread all over the body surface of Neocaridina shrimp with a higher concentration around the appendages. Culture of this species in slight saline condition between 5-10 ppt can effectively treat this parasite-worm.
- As we can see, Neocaridina shrimp can successfully breed even in laboratory conditions using a simple experimental setup.
- Neocaridina shrimp lack the planktonic larval stage, therefore, it is a completely suppressed type based on the type.
- Numbers of egg produced per female of the cherry shrimp is depending on the size of the female. Smaller females produced fewer eggs compared to larger females.
- We found out that it takes shrimp at least 75 days to reach the first maturity.
- It reproduces throughout the year in the aquarium.
- It is better to keep newly hatched shrimplets in slight saline water (5-10 ppt). This will help to avoid infestation and mortality due to clitellate annelid because this parasite cannot tolerate saline water.
The findings of this study can be used as a guideline for culturist interested in the mass production of this ornamental shrimp for the aquarium industry.