Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 29

All bony fish have a two‐chambered heart with four distinct anatomical regions. Blood flows through the sinus venosus into the atrium, then the ventricle, and out the bulbus arteriosus to the ventral aorta, the gills, the dorsal aorta, and the organs (Stoskopf 1993). The atrium and ventricle have partitions in the lungfish (Dipnoi) and coelacanth (Latimeria spp.). Teleosts have a pericardial sac filled with serous fluid.

Renal and hepatic portal systems are present in most fish although the proportion of blood that passes through the portal system varies by species. This may impact pharmacokinetics and toxicity if drugs that may be modified or excreted by the liver or kidneys are given in the caudal half of the body (Stoskopf 1993).

The lymphatic system is curious. In some teleosts, there is a fluid system separate from the primary circulation that is considered a lymphatic system (with leukocytes and devoid of erythrocytes). A secondary vascular system (SVS) that is not a lymphatic system has also been well‐described (Steffensen and Lomholt 1992). This SVS is larger in volume than the primary circulation and has similar constituents to plasma but lacks most cellular components. Circulation rates are lower in the SVS, sometimes by hours (Roberts and Ellis 2012). Stress, hypoxia, and exercise alter the volume and cellularity in each system, most importantly resulting in a hematocrit change of the primary system (Rummer et al. 2014). The primary and secondary systems are connected with anastomoses, in contrast to other vertebrate classes. The secondary system has a role in gas and ion exchange.

Venipuncture in bony fish usually makes use of the ventral tail vessels, via a lateral or ventral approach. However, size, anatomy, or disease may necessitate other sampling sites. Other possible sites that can be used in fish are listed below.

Figure A1.14 Air‐breathing structures: modified pharyngeal mucosa in an electric eel (Electrophorus electricus) (a), modified swim bladder of a longnose gar (Lepisosteus osseus) (b), and a true lung seen on lateral radiograph of an African lungfish (Protopterus annectens) (c).

Sources: Image (a) courtesy of Catherine Hadfield, National Aquarium. Image (b) courtesy of Carlos Rodriguez, Disney’s Animals, Science and Environment.

 Gill arch (Suedmeyer 2006)

 Peduncular notch

 Retro‐orbital sinus via oral cavity (Zang et al. 2013)

 Cardiac

 Cloaca superficial vessels (especially elasmobranchs)

 Dorsal fin sinus (elasmobranchs)

 Pectoral fin/radial vessels and mesopterygial vein (elasmobranchs)

Venipuncture is described in more detail in Chapter A6.

The gross appearance of blood varies in some groups. Blood and serum are blue‐green due to biliverdin in humphead wrasse (Cheilinus undulatus) and Japanese eels (Anguilla japonica) (Fang and Bada 1990). The blood of icefish (Channichthyidae) is clear as they lack hemoglobin (Sidell and O'Brien 2006). Pale tan to brown blood can be due to methemoglobinemia, often caused by high nitrites (Mirghaed et al. 2017).