Official common name: (accepted by ESA)
Blue Morph shrimp
Blue Leg shrimp, Caridina ensifera ‘Blue’, Blue Poso shrimp
The species name caerulea (“blue”) is derived from Latin caeruleus, which means ‘blue’. This refers to the general colouration of the shrimp. C. caerulea is the only ancient lake species that exhibits blue body colouration under normal conditions.
The former species name ensifera (“sword-wielder”) is derived from Latin ensis and ferre, which mean ‘sword’ and ‘to carry’ respectively. This refers to the elongated rostrum of the species.
C. caerulea is a lacustrine species endemic to Lake Poso, Sulawesi, Indonesia. Although it is widely distributed in the lake, it does not occur in the connected rivers.¹
The image below show the distribution of the species within the lake.¹
C. caerulea is mostly found on hard substrate (rocks and wood).¹ However, it is also found sporadically on soft substrate, such as macrophytes (aquatic plants).¹
25 – 30 mm
C. caerulea has a distinctive elongated, slender rostrum which, like the legs, is light blue in colour. The body is transparent, but often changes hue between of a range of colours; red, pink/orange, yellow, and blue. The antennules are a strong red whilst the antennae are clear, and each endopod of the tailfan bears a strong blue streak.
Unlike most lacustrine Sulawesian species, C. caerulea is not a timid species, and will be out in full-view foraging for food during the day. It will not often retreat when the tank is approached, unless the change in light intensity is extreme (such as standing in front of a light source).
Due to the delicate nature of these shrimp, I recommend only experienced and skilled aquarists attempt to keep this species.
Despite this, I highly recommend C. caerulea to those considering trying lacustrine Sulawesian species as it is a relatively forgiving species. I have found that it will tolerate and breed within a wide range of alkaline conditions unlike most species of the Sulawesian lakes. However, it is unlikely that the delicate shrimplets will survive unless provided the optimum parameters.
In addition to the naturally occurring food sources of aquaria, such as algae and biofilms, C. caerulea can be fed on a wide range of foods. My colony accept:
- Commercial shrimp foods
- Commercial fish foods
- Boiled carrot, boiled cucumber
- Frozen bloodworm
- Freeze-dried brine shrimp
- Katappa leaves
Sexing C. caerulea is generally quite easy. The most obvious sign in adult shrimp is the egg saddle present in the female shrimp, which is usually green or bright yellow. Following their first parturial moult, female shrimp also often have a deeper and more curved abdomen around the pleopods for carrying eggs as part of their breeding dress.
The reproduction of C. caerulea takes place entirely in freshwater. The eggs take about 18-20 days to hatch. Juvenile C. caerulea immediately assume a benthic lifestyle after hatching. Rather than stimulating breeding, it is the raising of the offspring that is the challenge. In the optimum conditions, this can be achieved with very little effort. However, in less suitable conditions, the juveniles will literally vanish. I assume the juveniles have difficulty moulting, resulting in death. The juveniles are also physically fragile and will not endure currents (these shrimp are lacustrine; they are from lakes where the water is still), so refrain from using more filters with power-heads or similar.
Juveniles will graze on biofilm and algae in the aquarium. They tend to enjoy grazing on the aquarium glass where these thrive.
This species was originally known as C. ensifera var. ‘Blue Morph(e)‘. This is due to the fact Lake Poso is occupied by another similar species which has brown-red colouration on its body rather than blue. This was believed to be an example of polymorphism, and that they were in fact the same species expressing different phenotypes. However, it has since been discovered that they are distinct species. At the time, the other species was known as C. ensifera var. ‘Red Morph(e)’, and is now officially described as Caridina ensifera. Below is an image showing the morphological differences between the two species.
- von Rintelen, K. & Cai, Y., (2009). Radiation of endemic species flocks in ancient lakes: systematic revision of the freshwater shrimp Caridina H. Milne Edwards, 1837 (Crustacea: Decapoda: Atyidae) from the ancient lakes Of Sulawesi, Indonesia, with the description of eight new species. Raffles Bulletin of Zoology, 57(2).