General Freshwater-Crustacean Practice E-Book

Sven Gehrmann

• Herausgeber: Books on Demand
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2021

Seitenzahl: 187

Beschreibung

This book has been produced with a great deal of ecological correctness and presents both: Native and imported species of crayfish and other decapods. It deals with keeping and breeding the species currently available in the zoo- and delikatessen-trade in aquaria and garden ponds, as well as the associated environmental problems. This book is aimed at nature and environmental enthusiasts, as well as aquarium and garden pond owners, who would like to take a closer look at decapod crustaceans. The book reflects the author's many years of experience with keeping and breeding various crustaceans. In addition, horseshoe crabs, as well as terrestrial and brackish water crustaceans are also presented. This also includes terrestrial hermits and the so-called cockroach-crabs of the genus Aegla.

Leseprobe

PROLOGUE

The first crayfish species I kept in a cold-water aquarium was the crayfish Orconectes limosus, introduced from North America. At that time, in the mid-1980s, this species was, as a precaution, hardly mentioned at all in aquarium literature. The only reference I found was in Hans Frey's work "Aquarienpraxis kurzgefasst". There was a short section on the care of this North American crayfish, consisting of maybe 5-6 sentences and a black and white line drawing. At that time, nothing was published about crayfish pestilence and the problems associated with it, purely as a precaution. Tropical crayfish were rarely sold in the aquarium trade at that time, and then it was mostly the Red Swamp Crayfish Procambarus clarkii, whose breeding was celebrated as a sensation in the aquarium magazines of the time! During the rest of my school years from 1985 to 1988, I was a member of a biology club that not only had many a water fight in the school's climate chamber during breaks, but also always acquired various interesting animals. During this time I procured crayfish from the edible crayfish trade for the first time, and managed to find Swamp and Signal Crayfish. During this time I also had my first experience with the crayfish pestilence, which killed all Swamp Crayfish. I had bought from "Nordsee" one by one. At about the same time I was looking for crayfish in a nearby gravel pond and found them rather by chance. Apart from the crayfish, I also caught the Freshwater Shrimp Atyaephyra desmarestii as a by-catch, which I could only identify with the help of the GDR reference book by Stresemann. A remarkable achievement, considering that at that time there was neither popular scientific literature on these animals nor the aid of the internet. This book thus contains my lifeblood, which has flowed over many years for these animals. You may forgive me for my strong language when I recommend cooking them in the chapter about the North American Crayfish, but this species is the first one I caught and kept in the aquarium myself. Since I sometimes also preserve animals and have occasionally dealt with their interior, please forgive me that I do not consider crayfish to be cuddly animals, nor do I intend to trivialise or humanise them. Rather, my intention with this work is to introduce the crustaceans of freshwater. I also want to contribute to creating a new awareness for the conservation of endemic species and their habitats. And finally, I would like to challenge the many aquarium enthusiasts in particular to deal responsibly with these versatile and interesting animals. If I were to advocate for anything, it would always be uncompromisingly for the cause of crustaceans and the conservation of their habitats. Unfortunately, it is a sad fact, that every day about 250 species disappear irretrievably from our planet due to anthropogenic influences. Also, many researchers and climate experts now assume that climate change will mean certain extinction for about 30-40% of the animal and plant species known today. What never ceases to amaze me is the indifference and ignorance of most people towards these well-known hypotheses and facts. But what can we do ourselves to slow down the decline at least a little and to preserve the (still) existing biological diversity for our children? Well, this path may seem uncomfortable, but it starts with each and every one of us. In principle, it means renunciation. Renunciation of unnecessary consumption as well as renunciation of unnecessary luxury and unnecessary transport. Let me give you an example: The overproduction of meat in Germany has become increasingly grotesque in recent decades. In the meantime, grain has to be imported from countries such as Paraguay so that we can feed our own cattle, because in Germany it is no longer possible to produce such quantities of grain... This has dramatic consequences for the poor small farmers in Paraguay, who are simply driven off their fields to increase soy production and are also poisoned with pesticides. But the consequences of this madness are also becoming visible in Germany, because where fattening farms dispose of their manure, the nitrate levels in the drinking water are rising alarmingly, in some places to 100 milligrams of nitrate and more! Although I am not a pure vegetarian either, I am of the opinion that one can reduce one's meat consumption in order to counteract such circumstances. Even refraining from consuming pork can make a big difference, as the pig industry is unfortunately one of the most destructive forms of our agricultural economy. Did you know, for example, that about one third of the pigs produced do not even reach the market, but are "disposed of" in a completely senseless way? Another example of the most serious environmental destruction is the automobile. The production of just one car consumes up to 400,000(!) litres of drinking water, not to mention the electrical energy. And this is produced with harmful brown coal... Is there anything surprising about that? If we all don't learn to do without in the foreseeable future, we will soon feel the consequences of our unholy actions. For example, in the heatwave summer of 2018, river levels dropped dramatically, making even large bodies of water like the Main and Elbe partially unnavigable. From the North Sea coast to Saxony, the inland dried up... Therefore, it is a heartfelt request to my readers to seriously think about how to find good solutions on a small scale. I am convinced that not only the crustaceans of our inland waters will thank us for this. But also our children's generation. So, let's just be the miracle ourselves! Let's give up cheap flights, unnecessary car journeys, cheap rotten meat and disposable plastic products.

Sven Gehrmann, spring 2021.

CONTENT - INTRODUCTION TO A COMPLEX TOPIC

Excerpt from the systematics of the

Arthropoda

Some remarks on the meaning and use of systematics

Keeping crayfish in aquaria

Nutrition of the crayfish

Ponds for crayfish

Pond hygienics

Keeping crustaceans in commercial facilities

Preservation of crustaceans with natural colours

Ethics and crayfish

Crayfish from Australia

Family

Parastacidae –

Crayfish from Australia

Sex differentiation in Australian crayfish

Yabby,

Cherax destructor

Koonac,

Cherax preissii

Red claw,

Cherax quadricarinatus

Lorentz's Crayfish,

Cherax lorentzi

Boesemann's Crayfish

, Cherax boesemani

Alberts' Crayfish

, Cherax albertisii

Tiger Crayfish

, Cherax peknyi

Apricot Crayfish

, Cherax holthuisi

Crayfish from Europe

Family

Astacidae -

European Crayfish

Sex differentiation in European Crayfish

Noble Crayfish,

Astacus astacus

Long Clawed Crayfish

, Astacus leptodactylus

Signal Crayfish

, Pacifastacus leniusculus

Crayfish pestilence - chronology of an epidemic

Crayfish from America

Family

Cambaridae -

Crayfish from North and Central America

Red Swamp Crayfish,

Procambarus clarkii

North American Crayfish,

Orconectes limosus

Blue Florida Crayfish,

Procambarus alleni

Marbled or Self-Cloning Crayfish,

Procambarus cf. fallax

Cuban Crayfish,

Procambarus cubensis

Dwarf Crayfish or CPO,

Cambarellus patzcuarensis

Infraorder

Caridea

– True Shrimps

Infraorder

Caridea

- True Shrimps

Amano Shrimp,

Caridina multidentata

Red Fire or Red Cherry Shrimp or “Sakura”,

Neocaridina davidi

Crystal Red Shrimp,

Caridina cf. cantonensis

Bamboo Shrimp,

Atyopsis moluccensis

Superfamily

Palaemonoidea

– Glass-Prawns

Superfamily

Palaemonoidea

– Glass-Prawns

Red Claw Shrimp,

Macrobrachium dayanum

Indopacific Glass Prawn,

Macrobrachium idea

Giant River Prawn,

Macrobrachium rosenbergii

Baltic Prawn,

Palaemon adspersus

Estuary Prawn,

Palaemon varians

Grass or Rockpool Prawn,

Palaemon elegans

Infraorder Brachyura – True Crabs

Infraorder

Brachyura

– True Crabs

Family

Gecarcinidae

- Land Crabs

Mouthless Land Crab,

Cardisoma crassum

Family

Grapsidae

– Talon, Shore or Marsh Crabs

Mitten Crab,

Eriocheir sinensis

Estuarine Mud Crab,

Rhitrhropanopeus harrisii

Superfamily

Potamoidea

- River Crabs

Siam Crab,

Thaipotamon siamense

Family

Sesarmidae

- Mangrove Crabs

Mangrove Crab,

Sesarma bidens

Tree Climbing Crab,

Episesarma mederi

Family

Portunidae

- Swimming Crabs

Pelagic or Blue Swimming Crab,

Portunus pelagicus

Green Shore Crab,

Carcinus maenas

Mediterranean Green Crab,

Carcinus aestuarii

Infraorder Anomura – Squat Lobsters, Porcelain Crabs & Hermit Crabs

Infraorder

Anomura

– Hermits & other

Family

Aeglidae

– Freshwater Squat Lobsters

De La Plata Squat Lobster,

Aegla platensis

Family

Coenobitidae

- Land Hermit Crabs

Indonesian Hermit Crab,

Coenobita brevimanus

Class Merostomata – Horseshoe Crabs (“Feeler-Less”)

Class

Merostomata

– Horseshoe Crabs (“Feeler-Less”)

Horseshoe Crab,

Limulus polyphemus

Mangrove Horseshoe Crab,

Carcinoscorpius rotundicauda

GENERAL SECTION

An aquarium for crayfish and shrimps

Construction plan of a decapod

Construction plan of a female decapod from below

Interior of a decapod

Interior and construction plan of a crab

Bibliography and sources

Thanks!

Glossary

Index of Latin nomenclature

About the author

A nerite rides around on this male Australian Red Claw....

Excerpt from the systematics of the Arthropoda

Some remarks on the meaning and use of systematics

Domain: Eukaryota (Living being with cell nucleus and cell membrane) Whittaker & Margulis, 1978 – eukaryotes.

Kingdom: Animalia (Animals) Linnaeus, 1758 - Linnaeus, 1758 – animals.

Subkingdom: Bilateria (Bilateral animals) (Hatschek, 1888) Cavalier-Smith, 1983 - (Hatschek, 1888) Cavalier-Smith, 1983 – two sided animals.

Branch: Protostomia (protostomes) Grobben, 1908 - Grobben, 1908 – protostomes.

Infrakingdom: Ecdysozoa (ecdysozoans) Aguinaldo et al., 1997 ex Cavalier-Smith, 1998 - Aguinaldo et al., 1997 ex Cavalier-Smith, 1998 – animals, which must slough.

Phylum(Tribe): Arthropoda (Arthropods) Latreille, 1829 - Latreille, 1829 – arthropods.

Subphylum(Subtribe): Crustacea (Krebstiere) Brünnich, 1772 – Crustaceans.

Class: Malacostraca (Higher Crustaceans) Latreille, 1802.

Superorder: Eucarida (Long tailed Crayfish) Calman, 1904.

Order: Decapoda (Decapods) Latreille, 1802 – Decapods.

Infraorder: Astacidea (Crayfish and Chelate Lobsters) Latreille, 1802 - Crayfish and Chelate Lobsters.

Family: Astacidae (True Crayfish).

Genus: Astacus (Crayfish) (Linnaeus, 1758).

Specific name: astacus (Noble Crayfish) Linnaeus, 1758.

Very many scientists were involved in creating this taxon-tree over many ages…

Scientific name (Genus and species): Astacus astacus, Linnaeus, 1758.

Due to international rules, the systematics of animals is mostly presented in English and Latin or Greece. Every living being on our planet can be assigned its place in this system. The best way to imagine this system is as a large shelf with many niches that have certain designations and in which the corresponding creatures can be sorted. However, Carl Linne's original system has been expanded and improved many times in the meantime, as more and more animals and plants have been discovered, that cannot be classified into simple categories, as they often move systematically between different gradations or represent transitional forms. In the example above, the scientist and year to which each stage is to be assigned was indicated behind it. This shows that the taxonomy of living organisms can still change and expand; therefore, this system must not be understood as a rigid static structure. Rather, the structure grows with the state of research, and it is conceivable that the example shown above will need twice as much space in a hundred years' time, viewed from top to bottom, because even more fine gradations have been added. I consider it particularly important to indicate the name of the first describer of a species and the corresponding date of the description after the Latin double name, because one can only assume a secure species if one has found these dates. Unfortunately, some species and/or genera are checked and revised again and again, so that one can never assume that the result of a determination will last forever. Therefore, if you want to maintain a professional collection, you should always check the topicality of the nomenclature at intervals of a few years with the help of up-to-date internet sites. For this purpose I particularly recommend the use of ZIPCODEZOO.COM. If possible, one should prefer official sites of the respective universities and always take into account that even the experts unfortunately do not agree on some things so quickly and in some cases even publish different data. In my excerpt from the Systematics of Arthropods, I myself have divided the Anomura into Anomura I and Anomura II, because I think it is likely, that a revision will still be made in this area. This is because Hermit Crabs on the one hand and porcelain and King Crabs on the other show very considerable morphological variations, so that one has to wonder here whether the classification of these animals in the same order is correct. It is my hope that molecular genetics will provide new results on this in the near future. And that taxonomists do not invent more taxa that complicate the systematics even more... Finally, it should be noted that the concept of species in biology is unfortunately not clearly defined at present. Molecular geneticists are arguing with morphologists and others; the outcome is uncertain. Is there any objective truth here at all? Probably everything is in flux at the moment! Only one thing is certain: it is not as simple as we were taught in school thirty years ago. We now know that species evolve from other species. And that in some cases even apparently different species can interbreed and produce fertile offspring. Until recently, this was considered an important criterion for species delimitation. It is possible that the importance of molecular genetic analyses is simply overestimated or even misinterpreted at the moment. Therefore, not everything that comes from this branch of research should immediately be considered objective and true. After all, the scientists of this faction could ultimately be just as addicted to profiling as their colleagues were in Carl Linnes` days. And unfortunately, it is also a deplorable shortcoming, that research work nowadays tends to be project- and goal-oriented. Because research also costs money, of course, and hardly anyone can work for free or for God`s wages. As a result, today's scientific world is not opinion-neutral or independent, which is why it often adopts the premises of its clients. This then distorts the results accordingly. So one should not be too faithful to science and better not expect value-neutral objectivity. On the other hand, you can also become a researcher yourself by writing down your observations and communicating them to others. In this way, even hobby researchers can often make a valuable contribution that is above all not unobjective due to commercial requirements. (Some hobbyists have even described new species). Become an unbiased nature researcher, too!

Keeping crayfish in aquaria

Let's be realistic: we will never succeed in recreating nature's model 100 per cent in our aquaria. All we can do is to make life in the aquarium as pleasant as possible for our animals, so that they feel completely at ease and also reproduce here. In doing so, it may be, that what is not pleasing to the eye is ideal for the animals and vice versa. On the one hand, crayfish do not like sterile aquaria that always look clean and tidy, as if a cleaning fairy had been at work only yesterday, but on the other hand, the question of water quality should not be neglected. I would therefore describe optimal crayfish tanks as being characterised on the one hand by consistently good filtration and regular water changes, but on the other hand also by a wealth of structures, cover and retreat possibilities for the animals and by well-kept detritus accumulations in certain places. My crayfish aquaria are usually set up according to the same basic idea, which I would like to briefly introduce here. But let's start with the substrate: I prefer layers of fine sand, whereby the layer height of the sand can be up to 10 centimetres or more. In this concept, the substrate is also used as a filter. With a substrate placed in this way, three layers form after a short time, which are important for water purification. The uppermost layer up to a depth of about 5 centimetres can be described as an oxic layer, in which there is still a relatively high oxygen content. - This is followed by a suboxic layer, which runs from about 5 centimetres to 8 centimetres deep and already contains considerably less oxygen. Below this is an anoxic layer, in which numerous anaerobic bacteria live, which utilise the metabolic waste products of other organisms. This layer in particular acts like a natural sewage treatment plant and breaks down nitrate. Blue-black bacterial discolouration often occurs in this layer. Especially in this lowest anaerobic zone, nitrate is split into pure nitrogen and pure oxygen by the anaerobic bacteria groups, so that an enormous nitrate decomposition takes place. Gas bubbles form in the substrate, which leave the aquarium after a while via the water surface. The older this substrate gets, the higher its biological efficiency. The main advantage over other substrate materials, such as gravel, is, that due to the fineness of the sand, it is relatively difficult for organic waste to penetrate these anoxic layers, so that no foci of putrefaction with sulphates (sulphur compounds) can form here. Another advantage of sand is, that it is a very inexpensive substrate that can be partially vacuumed out and renewed at any time. I have found commercially available bird sand, from which I rinsed out the aniseed oil before using it at home, to be a good choice. Parrot sand, on the other hand, should not be used, because it contains caustic lime, which unfortunately makes it unusable for aquarium purposes. Once you have created such a biologically functional substrate, you no longer need any elaborate filter systems, because the substrate already performs this function. Nevertheless, the strongest possible water circulation should be ensured by one or more pumps. In my crayfish tanks, the external filter of the brand "EHEIM-Liberty" has proved particularly effective, as it brings a strong, adjustable current into the water and at the same time removes considerable amounts of organic waste from the aquarium through easy-to-clean filter cartridges, so that it can be taken out of the water cycle. Another function of the sandy bottom, that should not be underestimated, is, that the crayfish can also occupy themselves sensibly here - just like in nature - by digging. I am convinced, that some animals become aggressive in the aquarium, because they do not have these opportunities to occupy themselves. Therefore, one should tolerate the redecoration of the tanks by the crayfish within certain limits. All structures in a crayfish aquarium should be built in such a way that the crayfish cannot bring them down. If larger stones are to be used, they should be placed on polystyrene or Plexiglas sheets to prevent the bottom from cracking. This is especially true when keeping larger crayfish species, which can reach final sizes of 10 centimetres and more. I think planting is rather unsuitable for most crayfish tanks, as most crayfish regard plants as food. You can help yourself with foliage and plastic plants. Foliage is a staple food of most crayfish anyway and promotes their health, as beech foliage, for example, contains substances that act like antibiotics. And many crayfish species also like waterweed very much. These natural foods contain numerous vitamins and dietary fibres that significantly increase the vitality of the animals. Conversely, the absence of these nutrients can produce pigment deficiency and moulting problems. Therefore, you should always make every effort to provide your pets with the best possible nutrition.

Plastic plants are a real alternative for crayfish tanks with herbivorous crayfish species; you might want to attach them to the bottom of the aquarium with some silicone. By the way, silicone also hardens under water and can thus be added to the aquarium afterwards.

Artificial rock backwalls are very decorative, but must be secured with Plexiglas plates at the top, otherwise the crayfish can climb behind them. Here a tank with Apricot Crayfish Cherax holthuisi and Dwarf Rainbowfish Melanotaenia praecox.

This aquarium was stocked with Dwarf Rainbowfish and Apricot Crayfish. Cryptocoryne wendtii proved to be a grateful and durable plant.

Wooden roots can be very decorative and therefore I can recommend two types of roots here: Either you use roots that have been in another aquarium for a long time and are really sure, that they do not release any harmful substances such as nitrite into the water. Or you use roots made of the non-toxic Polyrin. Another option is to find your own natural dried wood. I only use pieces of wood, that are bone dry and faded and have been lying around for several years. No algae or fungi should grow on these pieces of wood. If you water such dried wood, it usually sinks after 1-2 days. After successful watering, perching plants such as Java Moss or Java Fern