do birds have a gallbladder

Although the gallbladder is one of the characteristic component of the vertebrate body, it has been independently lost in several lineages of mammals and birds. Gallbladder loss is a widely reported phenomenon; however, there have been few descriptive comparisons of entire hepatobiliary structures between birds with and without a gallbladder. Here, we discuss the evolution of avian hepatobiliary morphology by describing the gross anatomy of the hepatobiliary system in the quail and pigeon. Quails have two major extrahepatic bile ducts: the right cystic-enteric duct, which has a gallbladder, and the left hepatic-enteric duct, which does not. Together with two pancreatic ducts, they share one opening to the ascending part of duodenum. Pigeons lack a gallbladder, but also have two extrahepatic ducts similar to those of quails. However, the hepatic-enteric duct opens solely to the descending part of the duodenum close to the stomach. The pancreatic duct opens to the very posterior part of the duodenum independent from the biliary tracts, giving rise to three separate openings in the duodenum. The hepatobiliary anatomy of the pigeon represents a highly derived condition not only because of gallbladder loss. Avian gallbladder loss may be related to remodeling of the entire hepatobiliary system, and may have occurred via a different mechanism from that of mammals, which can be explained simply by the disappearance of the gallbladder primordium.

Comparison of the quail and pigeon

There are numerous anatomical distinctions between the quail and pigeon’s hepatobiliary systems. The pancreatic and two bile ducts opened to the duodenum at the same level in the quail, but each duct opened to the duodenum at a different level in the pigeon. Thus, in addition to gallbladder status (i. e. , present vs. absent), the entire morphology of the biliary system differed. Nonetheless, it is unclear if variations in the biliary tract are connected to gallbladder loss. In some ways, the morphology of the biliary tract is one of the vertebrate body’s most malleable components. For instance, rats that have gallbladders have a wide variety of ductal variations. Branching of the biliary tract is observed in certain instances (e g. , chinchillas [29]), but in some, the pancreatic and biliary ducts’ duodenal openings are completely distinct from one another, despite the fact that many rodents (e.g., g. , prairie dogs and guinea pigs [10]). It is believed that there is no connection between this variation in connectivity and dietary and life history factors. Despite these difficulties, comparing our findings with those of other research should help elucidate the evolutionary patterns of the avian biliary system and determine which system is more ancestral—the quail or the pigeon system.

According to the current study, the quail’s hepatobiliary system’s topography is very similar to that of the chicken, which is a close relative [32, 33]. Although blood vessel information is lacking, the biliary tract’s branching pattern, as seen in modern quails, is also conserved in a number of duck species [23]. The chicken (Gallus gallus; “Gallus domesticus”), pigeon (Columba livia; “Columba intermedia”), tree sparrow (Passer montanus), Japanese bush warbler (Horornis diphone?; “Horeihus cantous”), brambling (Fringilla montifringilla), Japanese quail (Coturnix japonica), duck (Anas platyrhynchos; “Anas domestica”), and little egret (Egretta garzetta; “Herodias garjetta”) were all studied in comparison by Yamagishi [41]. These species exhibit two biliary ducts. Almost all branches of the duodenum originate from the ascending portion, despite minor variations in the locations of the pancreatic ductal and bile trunks. This indicates that both the gallbladder loss and the biliary tract’s branching pattern are highly derived from the system seen in pigeons. (18).

The ostrich is another animal without a gallbladder, and its hepatobiliary morphology seems to be a more extreme variation of that of pigeons. As in the case of the pigeon, the ostrich biliary tract consists solely of the hepatic-enteric duct, which opens to the anterior-most level of the descending part of the duodenum [1, 24]. Separate from the biliary duct, the pancreatic duct opens to the ascending portion of the duodenum [1]. Therefore, the hepatobiliary system of the ostrich is similar to that of the pigeon, except for the cystic-enteric duct, even though the blood-vessel pattern is still unknown.

The aforementioned parallels imply that alterations in the biliary tract’s connectivity may be connected to the loss of the gallbladder in birds. However, more research is needed to support this theory because of how flexible the biliary tract is in rodents. Morphological information from columbiform taxa—such as Ptilinopus, Ducula, and Gymnophaps—that have not lost their gallbladder is required in order to assess gallbladder loss in birds in greater detail [7, 11].

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What animal lacks a gallbladder?

Several species of mammals (including horses, deer, rats, and laminoids), several species of birds (such as pigeons and some psittacine species), lampreys and all invertebrates do not have a gallbladder.

Do any animals have a gallbladder?

Horses don’t have a gall bladder. In many other animal species including humans, dogs, cows, sheep, and goats for starters, the gall bladder is responsible for storing bile. This bile is produced by the liver and used in the digestion of fats in the intestines. The gall bladder releases the bile as needed.

Why don’t pigeons have a gallbladder?

When “eating” they are in fact collecting food into their oesophagus. They will then digest this food at a later time. Doves and Pigeons have no gall bladder. Although the reason behind this anomaly in unknown, interestingly, these birds still produce bile (it’s simply secreted directly into the gut).

Do chickens have a gallbladder?

In the chicken, there are two bile ducts, one draining the left lobe of the liver directly into the duodenum and the other draining the right lobe via the gall bladder.