Unfertilized fish oocytes have the diameter – depending on the species – from 0,5 mm to few millimetres. In contact with water they become gluey and enlarge so that their diameter increases by 1,4 - 5 times. After the fertilization oocytes undergo intensive physiological processes that in relatively short time lead to significant morphological changes. (...) Oocytes of cyprinids undergo discoidal cleavage. After the fertilization the creation of the perivitelline space is observed. Simultaneously animal pole and vegetal part are being isolated. Soon after that cytoplasm is being transferred to animal pole and two first blastomers are created. After the short time the second division of blastodisc is conducted. At first blastodisc consists of numerous blastomeres (multi-cellular blastula), than a microcellular blastula is created and a gastrulation process commences. It consists of internal blastomere migration. External layer performs a protective function only. Together with the periblast it undergoes the process of epiboly, that is encompassing the embryo by the ectoderm. The gastrulation process ends with blastopore closure.
Gymnogeophagus rhabdotus and G. meridionalis and how to help them survive winter season - two unpopular species of eartheaters - Radosław Bednarczuk;
Few people know that some cichlids found in South America in order to develop properly need periodical temperature decrease. The temperature has to be much lower than 20°C. Such requirements are typical for eartheaters from Gymnogeophagus genus. (...) Gymnogeophagus meridionalis cichlid reaches the length of 12 cm. Gymnogeophagus meridionalis usually comes in brown-grey-olive colour and a round dark spot is visible on the sides of the body. It has blue stripes on its pelvic fins and blue spots on non-paired fins. Males are bigger and more colourful than the females and their body sides are also marked with blue scales in horizontal rows. (...) The species name rhabdotos (Greek) of Gymnogeophagus rhabdotus fish means „striped” and refers to horizontal stripes on its body. It is found in small creeks and rivers, lagoons with sandy floor, often with abundant vegetation. It is slightly bigger than the first species and may reach as much as 16 cm length. Aquarium fish trade offers many local variations of the species. Basic coloration of those eartheaters is olive-brown. A characteristic spot is located in the centre part of the body and a black band crosses the eye. Pectoral fins are colourless, other fins are marked with iridescent stripes and dots. The head is visibly pointed and bluish stripes on anal and dorsal fins distinguish it from the Gymnogeophagus meridionalis described above.
Pseudotropheus demasoni – Lake Malawi flagship - Marcin Soboń;
In the article being my debut in „Nasze Akwarium” I would like to present you a representative of African cichlids from Lake Malawi –- Pseudotropheus demasoni. The fish I will hereby describe belongs to abundant mbuna group. (...) The species was discovered in 1993 in Pombo Rocks in Tanzania and described in 1994 by the biologist well known among all Malawi hobbyists – Ad Konings. Pseudotropheus demasoni is native to Pombo Rocks region and Ndumbi Reef. It prefers shallow parts of Lake Malawi, usually of four metres deep as well as rocky littoral zone with numerous shelters. There is a reason to the choice of environment, in which Pseudotropheus demasoni lives. Due to its small size the fish uses the rocks as a shelter, in which it can hide from the bigger predators. Rocks provide security for incubating females as well. Because the water in such areas is shallow, it is rich in algae (mainly thread algae and diatoms) that are a predominant component of the species diet.
International Aquatic Plants Layout Contest 2009;
Comment from Takashi Amano
Thank you very much for again sending us all of your wonderful submissions to the International Aquatic Plants Layout Contest from all over the world this year. The total number of participant countries was not quite as diverse as last year's, however we received submissions from new participant countries this year. The number of participants totaled 1,170 submissions from 47 countries. Each year the quality of the submitted layouts increases and this year's submissions were no exception. Most notably submissions made by Asian aquarists from Hong Kong and Taiwan stood out in particular. This year and last year's winners were from Hong Kong exhibiting their passion and dedication to the hobby of aquatic plant layout. Just like last year, the top 112 layouts received exemplary marks from each judge. It can be seen that these high ranked layouts make skillful use of driftwood and stone in their arrangement. We can also say that the aquascapes recreating a natural aquatic scene within the layout were highly graded this year again. All of our judges are looking forward to the passionate submissions to next year's contest displaying wonderful aquascapes from all over the world. Amano gallry.
When the snake doesn’t eat. Short study of reptile anorexia.- Witold Borkowski;
Denial to feed in reptiles as well as other animals kept in terrariums is one of the most widespread problems in the hobby. The situation in which pet denies to feed are numerous and there are different reasons behind it. Terrarium hobby is not only the act of keeping the animals in a terrarium – it is also an art of observation. You always have to regard the problem as a multi-dimensional issue because, as I have already mentioned, denial to feed has many grounds. (...) Too low temperature in a terrarium is the most common external cause of feeding denial. Reptile metabolism slows down when the temperature is too low – enzymatic processes of gastric acid and peristaltic of digestive track decelerate. Even today it is believed that some terrarium animals, especially chameleons, green iguanas, monitor lizards and tortoises are docile animals. (...) The problematic snakes include: green tree python (Morelia viridis), Amazon tree boa (Corallus hortulanus) and white-lipped tree viper (Trimeresurus albolabris).
Lawson’s dragon Pogona henrylawsoni - Alicja Papiór, Szymon Najdora;
Lawson’s dragon belongs to Agamidae family and Pogona genus. It’s native to Australia, in nature it lives in the ... part of the continent. Open areas, on which grass and bushes grow as well as black earths characterized by high annual precipitation are typical for this region. P. henrylawsoni is the smallest species of Pogona genus – it reaches up to 30 cm length. It is also the second most popular species of the genus – P. vitticeps takes the first place. Other agamids of Pogona genus are rarely a subject of terrarium trade; some of them are even not kept in amateur terrariums. Despite the fact that P. henrylawsoni is the second most popular lizard it doesn’t match its bigger cousin, P. vitticeps. The central bearded dragon is one of the most popular terrarium reptiles and its numerous colour variations have been bred. P. henrylawsoni occurs in a few colour variations but generally the choice is much narrower than in P. vitticeps. Usually Lawson’s dragons are brown, yellow, brown- (or yellow-) orange (usually the legs are orange) or grey-brown.
All are gobies yet they are not the same - dr Hubert Zientek;
Seven species of gobies live in Polish waters: black goby (Gobius niger), sand goby (Pomatoschistus minutus), common goby (Pomatoschistus microps), twospotted goby (Gobiusculus flavescens), monkey goby (Neogobius fluviatilis), goad goby (Neogobius gymnotrachelus) and the most dangerous one – round goby (Neogobius melanostomus). The most popular aquarium species are gobies from Brachygobius genus and sleeper gobies (Eleotridae). The first four species of gobies I have listed are subject to species protection. On the other hand the round goby became at the beginning of 1980s a real calamity in coastal waters of Baltic Sea as well as other waters.
White cloud mountain minnow (Tanichthys albonubes) - Mateusz Tkocz;
White cloud mountain minnow is a very decorative fish recommended both for the beginners in the hobby as well as for the more experienced aquarists. It is an undemanding and docile fish. It can live with other coldwater fish in a community tank.
Sandy deserts and little monsters - JBL workshop in Philippines
84 people from about dozen countries came to Dumaguete on Negros island in June 2007 to take part in second JBL workshop. For a week JBL research team supported by scientists and experts acquainted hobbyists, shop owners and amateur ichthyologists with aquarium research. The team focused on water analysis, light and UV radiation measurement, food tests, dividing reef into zones as well as on observing the artificial reef. Tasks were performed in small groups supervised by the renown scientists – professor Ellen Thaler and professor Claus-Dieter Zander.
The visitors - African knife fish (Xenomystus nigri) - Marcin Szmel;
One of the aquarium hobby conceptions, besides researching Nature’s laws and mechanisms as well as aiming at reaching the aesthetic goals is – or at least should be – breeding the species kept. Aquarium hobbyists more and more often as well as more consciously choose to keep and breed species that they are – indeed or at least theoretically – able to breed. (...) The name of African knife fish, Xenomystus nigri (Günther, 1868) relates to the characteristic body shape of the fish that reminds knife blade. The fish is native to Africa. It lives on a quite large area ranging from Senegal to eastern boundaries of the northern part of the continent. Knife fish can be found in Niger delta, in Congo, Nile and even in Lake Chad. African knife fish belongs to the Xenomystus genus, one of the few genera covered by the Osteoglossiformes (“bony tongues”) order. (...) We will soon find out that this group includes many interesting species kept in aquaria. However, before we proceed to the issue, let’s pay attention to quite another ichthyofauna representative – the fish that is very often compared, or even confused, with African knife fish – black ghost knifefish (Apteronotus albifrons (Linnaeus, 1766)).
Troublesome cichlid – Nanochromis transvestitus - Sławomir Siudakiewicz;
This rare species is native to Lake Mai-Ndombe and southern part of Congo River. Its name relates to the fact that unlike majority of animals the females of this cichlid are more beautiful than the males. (...) Almost two and a half years ago I bought three pairs of Nanochromis transvestitus. The fish, especially females, enchanted me with their coloration. Males are less attractive despite the fact that they reach 7 cm length – their abdomen is light-grey and their back is dark-grey with stripes along the whole body. Females reach ca. 5 cm length and have blood-red abdomen. Contrast effect of this coloration in tea-coloured water is amazing. Protruding and downward mouth as well as striped fins and elongated tip of dorsal fin complete the image. For me the fish is close to perfection.
The formula for a successful aquarium club – aquarium club organisation Decalogue - Andrzej Sieniawski;
(...) During last three years many times the aquarists, not only from Poland, have asked me how to organise a well-functioning aquarium club. (...) In 1980 together with a group of aquarium hobbyists from Tarnów I have raised an organisation named Tarnowski Klub Akwarystów (aquarium club of the city of Tarnów). (...) After founding the Polska Federacja Akwarystyczno-Terrarystyczna (Polish aquarium-terrarium federation) that united the majority of independent active Polish aquarium clubs that weren’t members of Polski Związek Akwarystów (Polish aquarium hobbyists association) I became its first president. (...) Since 2002 I have actively taken part in activities aiming at creating aquarium club that could primarily deal with discus fish keeping. Founding the Polski Klub Miłośników Dyskowców (Polish discus club) was an effect of these actions.
Examples of aggressive behaviour in swordtail males - Zbigniew Strzelecki;