Ozobranchus ist der Name einer Gattung von kleinen Blutegeln in der Ordnung der Rüsselegel, die im Meer und im Süßwasser leben und an Schildkröten, bei einer Art an Krokodilen parasitieren. Sie umfasst 7 Arten innerhalb der 8 Arten zählenden Familie Ozobranchidae und ist in den Tropen weltweit verbreitet.
Die Egel Gattung Ozobranchus haben einen deutlich in eine vordere Region aus Kopf und Hals sowie einen Hinterleib (Abdomen) gegliederten Körper. Am vorderen Abschnitt des Hinterleibs ab dem 13. Segment trägt jedes der folgenden, je nach Art 5 bis 20 Segmente je ein Paar Kiemen, während die hintersten Segmente kiemenlos sind. Kennzeichnend für die Gattung Ozobranchus innerhalb der Familie Ozobranchidae sind die baumartig verzweigten Kiemen im Gegensatz zu den nur einfachen, unverzweigten Kiemen der Gattung Bogabdella.
Die sieben Arten der Gattung Ozobranchus sind je nach Lebensraum der parasitierten Reptilienart Meeres- oder Süßwasserbewohner der Tropen. Als dauerhafte Ektoparasiten saugen sie Blut – Ozobranchus quatrefagesi in Westafrika an Krokodilen und Pelikanen, alle übrigen Arten dagegen ausschließlich an Wasserschildkröten. Ozobranchus branchiatus als artspezifischer Parasit an Chelonia mydas und Ozobranchus margoi an Caretta caretta sind in tropischen Meeren weltweit verbreitet, während die übrigen Arten, davon als am weitesten verbreitete Art Ozobranchus jantseanus, an verschiedenen Schildkröten in Binnengewässern Asiens saugen.
Jean Louis Armand de Quatrefages de Bréau wählte 1852 bei der Beschreibung der Gattung den Namen Ozobranchus ‚Zweig-Kiemer‘ (altgriechisch ὄζος ózos, deutsch ‚Zweig‘, βράγχιον bránchion, deutsch ‚Kieme‘) auf Grund der auffälligen verzweigten Kiemen dieser Egel.
Die Gattung Ozobranchus bildet zusammen mit der Gattung Bogabdella die Familie Ozobranchidae.
Zur Gattung Ozobranchus zählen folgende 7 Arten:
Ozobranchus ist der Name einer Gattung von kleinen Blutegeln in der Ordnung der Rüsselegel, die im Meer und im Süßwasser leben und an Schildkröten, bei einer Art an Krokodilen parasitieren. Sie umfasst 7 Arten innerhalb der 8 Arten zählenden Familie Ozobranchidae und ist in den Tropen weltweit verbreitet.
Turtle leeches are a genus, Ozobranchus, of leeches (Hirudinea) that feed exclusively on the blood of turtles.[2] Only two species – Ozobranchus margoi and Ozobranchus branchiatus – are found in the Atlantic coast of the United States and the Gulf of Mexico. Little is known about these leeches due to difficulties in studying their sea turtle hosts.[3]
Species of Ozobranchus spp. can be very small (down to a few millimeters in length),[3] making them morphologically difficult to distinguish. Ozobranchus margoi and Ozobranchus branchiatus are the most anatomically documented. According to researchers from the University of Wales and the Gulf Coast Research Lab in Mississippi, the two species are very similar externally with their main difference being the number of pairs of finger-shaped gills; Ozobranchus margoi has 5 pairs while Ozobranchus branchiatus has 7.[4] Both possess a light or slightly pink coloration and sometimes dark spots form from ingested blood visible through the epidermis.[5] Ozobranchus branchiatus range generally from 3.5–10 mm, while Ozobranchus margoi generally range from 4–22 mm. The body is composed primarily of two unequal annuli.[4] Both species have large suckers on each end of their bodies. The sucker on the anterior is not distinguishable from the neck. The anterior end also has two light-sensitive eye spots.[5] The finger-like gills tend to get smaller as they progress towards the posterior end. Another of the species, Ozobranchus jantseanus, was studied by Japanese researchers who found it could adapt to extreme cold, surviving for 24 hours at -196 °C (-321 °F) and for nine months at -90 °C (-130 °F).[6][7]
Like other leeches, Ozobranchus spp. are hermaphrodites with separate male and female reproductive systems.[2] As hermaphrodites, they have both testes and ovaries. Unlike some hermaphrodites, however, leeches cannot self-fertilize. They have four pairs of testes connected to various ducts and to an external gonopore with an eversible penis controlled by a muscular bulb. The gonopore also functions as a receptacle for sperm with a connection to the ovaries.[5] Ozobranchus spp. lay eggs like leeches. Ozobranchus branchiatus are known to lay eggs directly on their host and cementing their cocoons on the host species.[4]
Due to the difficulties in studying sea turtles, relatively little is known about the life cycle of Ozobranchus spp. It is not fully understood if these leeches are capable of surviving independently of a turtle host for any extensive period of time. It is also unknown if they can feed off of organisms other than turtles,[3] although the possibility was indicated by the discovery of a single Ozobranchus margoi specimen on a longbeaked dolphin. Ozobranchus branchiatus are known to complete their entire life cycle on host turtles, which is an unusual trait shared only by a few other species of leeches. This is accomplished by laying eggs on the turtle and attaching them with a cementing substance. The eggs will hatch and attach to the host turtle.[4] Ozobranchus margoi has also been observed to lay eggs directly on heavily infested turtles in the event of an epizootic.[8]
Ozobranchus branchiatus are historically known to only host on green turtles (Chelonia mydas), while Ozobranchus margoi targets multiple sea turtle species but are found mostly on loggerhead turtles (Caretta caretta) and, in one special case, on the long-beaked common dolphin.[4] The leeches attach themselves on the mouth, neck, cloaca, and the undersides of the flippers of turtles.[3] Once there, they use the same technique for blood extraction as other sanguivorous leeches: opening of a small wound, usage of an anticoagulant to prevent blood clotting, and ingestion of the blood.[2]
Occasionally, as a scientific journal reported in 1974, overwhelming infestations of leeches called "epizootics" occur. Frank J Schwartz of the University of North Carolina’s Institute of Marine Sciences described it thusly:
- [T]he largest females were so devastated that their eyes had been eaten away to reveal the internal bone and skull. Leeches filled every possible crevice, nostrils, mouth, flippers, cloaca, etc. Large masses of leeches clung over all the body including the carapace. Three of the four females [. . .] and a 36-kg male succumbed between 24 July and 2 August. All turtles stopped feeding during the height of the epizootic.[8]
Apart from the direct damage they inflict on the turtles, Ozobranchus spp. are suspected by scientists to transfer diseases to turtles. Fibropapillomatosis, a neoplastic sea turtle disease associated with a turtle herpesvirus (FPTHV), is suspected to be transferred between turtles by a vector organism: specifically, Ozobranchus spp. In a study conducted by several members of Cornell University's Department of Microbiology and Immunology and United States Government employees, high viral loads of FPTHV were found in Ozobranchus spp. specimens, implicating it as a possible mechanical vector for transmission of the disease.[9]
The difficulties in applying common taxonomic techniques to identify leeches, especially to mature specimens, have led to the application of DNA barcoding using the cytochrome c oxidase I gene (COI) for identification purposes. A team of scientists from Wright State University, the University of Central Florida, and the Inwater Research Group collected and analyzed several Ozobranchus margoi and Ozobranchus branchiatus leeches. The specimens were first morphologically identified based upon the number of gills. Afterwards, genomic DNA was extracted from leech tissue far from the digestive tract in order to avoid contamination from turtle host’s blood. The COI gene was sequenced from the extracted genomic DNA using polymerase chain reaction. These sequences were added to GenBank, which prior to the study did not have any genetic data on Ozobranchus branchiatus.[3]
Turtle leeches are a genus, Ozobranchus, of leeches (Hirudinea) that feed exclusively on the blood of turtles. Only two species – Ozobranchus margoi and Ozobranchus branchiatus – are found in the Atlantic coast of the United States and the Gulf of Mexico. Little is known about these leeches due to difficulties in studying their sea turtle hosts.
Ozobranchus is een geslacht van ringwormen uit de familie van de Ozobranchidae. De wetenschappelijke naam is voor het eerst geldig gepubliceerd in 1852 door Armand de Quatrefages.
Archibald Menzies had in 1791 een "nieuw soort bloedzuiger" gevonden op een schildpad in de tropische Stille Oceaan. Dat was tijdens de expeditie van HMS Discovery. Hij noemde die bloedzuiger Hirudo branchiata. Latere auteurs, waaronder de Quatrefages, meenden evenwel dat dit geen gepaste naam was. In 1852 deelde de Quatrefages Hirudo branchiata daarom in bij een nieuw geslacht, dat hij Ozobranchus noemde.[1] Nochtans had de Quatrefages het specimen nooit gezien, en hij gaf ook geen beschrijving van het geslacht.[2]
Het zijn kleine bloedzuigers met van 5 tot 21 paar kieuwen (branchiae). Het zijn ectoparasieten op zowel zoetwater- als zeeschildpadden.
Ozobranchus is een geslacht van ringwormen uit de familie van de Ozobranchidae. De wetenschappelijke naam is voor het eerst geldig gepubliceerd in 1852 door Armand de Quatrefages.
Archibald Menzies had in 1791 een "nieuw soort bloedzuiger" gevonden op een schildpad in de tropische Stille Oceaan. Dat was tijdens de expeditie van HMS Discovery. Hij noemde die bloedzuiger Hirudo branchiata. Latere auteurs, waaronder de Quatrefages, meenden evenwel dat dit geen gepaste naam was. In 1852 deelde de Quatrefages Hirudo branchiata daarom in bij een nieuw geslacht, dat hij Ozobranchus noemde. Nochtans had de Quatrefages het specimen nooit gezien, en hij gaf ook geen beschrijving van het geslacht.
Het zijn kleine bloedzuigers met van 5 tot 21 paar kieuwen (branchiae). Het zijn ectoparasieten op zowel zoetwater- als zeeschildpadden.
Загальна довжина представників цього роду коливається від 3,5 до 22 мм. Поєднують примітивні та розвинені ознаки: мають 5-7 пар палецеподних зябр (зменьшуються за розміром до задньої частини тіла), спереду є 2 світлочутливих очей. Тіло складається в основному з 2-кільцевих сомітів. Кільця не є однаковими за розміром. Є великі присоски на кожному кінці тіла. Передня присоска не відділена від тулуба. Мають 4 пари яєчок, що з'єднані з різними протоками, до зовнішнього гонопору з еверсифікованим членом, контрольованим м'язовою цибулиною. Гонопор також функціонує як ємність для сперматозоїдів з приєднанням до яєчників.
Забарвлення білувате або рожеве з темними плямами.
Морські види. Деякі здатни переносити низькі температури. Паразитують переважно на черепах (ектопаразити). Звідси походить їх назва. Зустрічаючись у значних кількостях на черепах насамперед родини морські черепахи, завдаючи їм суттєвої шкоди, а також є носіями вірусу хвороби фібропапіломатоз. Відмічено окремі випадки на капському дельфіні. Висловлюється гіпотеза, що ці п'явки ніколи не залишають свого господаря, але це остаточно не доведено.
Є гермафродитами. Відкладають яйця в коконах на «господаря».
Мешкають у північній частині Атлантичного океану.
