The in depth guide to keeping as well as breeding Amarinus lacustris by Hervey Doerr-Rolley
The aim of this article is to educate and warn people of the mistakes I made and how I was successful with breeding and keeping this species. I published an article about this species several years ago so thought it was time for an updated guide for anyone wanting to keep and breed this species. All my knowledge about this species has been developed over the 4 years I've kept this species as well as the many scientific articles I've studied, I first kept this species when I was 15 and now 19, my colony is still going strongly. Currently studying a bachelor of Marine science. Firstly I'd like to point out this species does not have a larval cycle, it is a far too common misconception people have. I believe this thought is derived from their much larger cousin the Amarinus laevis and the Thai micro crab, Limnopilos naiyanetri. Amarinus lacustris have fully formed offspring, meaning their offspring are essentially miniature adults once hatched from their egg. Some points of interest about this species, there are 8 instars before their pubertal moult. Females up to two moults before their pubertal moult can copulate and store spermatozoon, once she reaches the pubertal moult she can then impregnate herself without the need of copulation. The stored spermatozoon can then be used up to 15 separate brood cycles (15 clutches of eggs). Adult females can carry up to *35 eggs (anecdotal) and take around 25-30 days at 15 degrees Celsius to hatch as fully formed offspring.
A. lacustris have a strong preference for hard water, I keep and breed mine in;
*25% water changes are done weekly*
Breeding and Husbandry
Key points for their care;
Gravel substrate - fine pea gravel is best.
Air pump sponge filters are essential as this provides cleaner water as well as a feeding ground for the offspring as well as adults.
Mulm and moss are essential.
A good rule of thumb from my experience is 500ml of aquarium space per baby-sub adult, and then 1L per adult crab, this allows for less aggression from male to male behavior. It is up to you but the less stocking density the better due to the aggression of breeding from males, keep in mind this aggression is only towards other males however females that are being copulated with may sustain serious injuries if too many males are kept together. The best ratios are two males to 8 females. When a female sheds she releases hormones into the water column just like shrimp, if any of you are familiar with breeding shrimp you can note this by the erratic and fast speeds the males zoom around the aquarium searching for the female, this is the same case with A. lacustris except the swimming, rather they crawl quickly around the aquarium in search for the female to copulate with. Once the male finds the female he will grasp the female tightly underside to underside in a 'hug' embrace, he will then fertilize the female. This embrace can last minutes or hours depending on the male. Eggs will soon become visible and as described above hatch within 25-30 days*. This species is a cold water crustacean so you must remember that, breeding will cease if the temperature goes above 22 Celsius. Keep them in a mature mulm filled aquarium with leaf litter (I use oak leaves) with plenty of hiding spots and moss, a 8pH and 15 Celsius and before you know it you will have berried females.
Surprisingly my A. lacustris do not eat commercial foods, I feed mine cultured white worms which are perfect as they grow to a max size of 3cm and survive underwater for several days. I also add snails to my aquarium as the crabs feed on their feces. Funnily enough baby crabs will eat the white worms too once they are 2 instars old, so it is not uncommon to see a 2mm baby crab hanging on to a 2cm long white worm! I feed my crabs every 3 days and small amounts of the worms to reduce water quality issues.
Common questions I am asked
As I was the first person in Australia and the world to raise fully tank raised F2 offspring i have come across many commonly asked questions. "can I get these crabs in country x?" so far you can legally only get these crabs in their native geographical regions, however once these crabs are even more commonly bred their popularity over the Thai micro crab will be clearly abundant simply due to their ease of breeding which you know, therefore I wouldn't be surprised if these hit the international market once they're being large scale bred. "Do you have any for sale?" when I have crabs for sale I have a waiting list, If you want to ask questions or be on the waiting list email me: [email protected] "can these go with fish x?" if the fish is 4cm or less they are fine generally, my opinion is keep the species only or with shrimp which leads to the next question "are the shrimp safe" and yes they are, however they are naturally scavengers so if you have dead or sick shrimp they will eat them, if your shrimp are healthy they will not predate on them. "how long do they live for?" they live for around 2-3 years+. "why are all my crabs dying" this question is addressed below;
Major issue that needs to be addressed
Since my first sales of A. lacustris I suddenly saw a spike of ads for them in Australia, unfortunately I could tell the individuals for sale were all wild caught and at best had only lived in an aquarium for a couple weeks of their life. This then would result in people encouraging the decimation and local extinction of the species in our waterways due to peoples greed of wanting to make a quick buck off this amazing native species. The crabs that I breed and sell are all aquarium raised individuals ONLY, I have put time, money and effort into the crabs I breed to ensure I do not impact the wild populations and offer aquarium suited specimens for people wanting to keep them. I have had a plethora of emails from people asking me why crabs they had sourced outside of my individuals had suddenly died off, this is simply due to the fact these crabs have not been aquarium raised and selectively bred for years like mine have. I find it horrendous that people think it is okay to collect many wild individuals to then sell knowing full well they will die within around a 3 month period just for their sake to make some 'fast' money. So please before you buy from a seller of these crabs ask as many questions as you can to find out how many generations old your crabs are and how long they've been bred for etc. If they cannot supply a high amount of detail or simply quote my articles about them do not buy from that seller. Do not support poachers for your aquarium! This applies with all species, worldwide.
Thank you for reading my article,
again if you have any questions feel free to email me as I'm always happy to help out ethical keepers and potential breeders of this species.
Author and credits: Hervey Doerr-Rolley