Mating amongst the Clownfish and Gender Changes - Research Paper Example

Topic: Lecturer: Presentation: Introduction The Clownfish belongs to the family Pomacentridae, with many species, many belonging to the genus Amphiprion while one belongs to the Premnas genus (Godwin 1994 p 556). The fish has many colors which depend on the species. A symbiotic relationship exists between the fish and the sea anemone that offers protection to the fish due to its stinging nature. On the other hand, the fish protects the sea anemone from harm that could be caused by hard undigested particles through feeding on them. The fish spawn on the sea anemone. A fully grown dominant female may grow to a total length of 11/2 feet, while the small adult Clownfish may be as small as 4 inches. The fish thrive in the warm waters of the tropics (Maddern 1990 p 36). They are mainly found in the salty waters of the Indian Ocean and the Pacific. The excretion from the fish is a major source of nourishment for the sea anemone that absorbs the nutrients emanating from fecal matter. More over, the movements of the Clownfish in the water surrounding the sea anemone, especially when fanning the eggs are significant for water circulation, which is significant for the distribution of nutrients for the nourishment of the sea anemone (Drury 2008 p 63). The Clownfish is covered by a mucus coating around its body which as Wittenrich et al. (2007 p 93) observed are derived from sugars, which is one of the factors that prevents the stinging reaction of the sea anemone as the nematocysts are triggered by the presence of protein based substances in the surrounding. The fish dwell in one sea anemone as a group, which means that several sea anemones will host different groups of fish (Godwin 1994 p 561). In other words one sea anemone is the territory of one small group of fish. Clownfish is one of the aquatic organisms whose sex remains a subject of controversy. It is generally known that the fish is capable of switching its sex. This essay is a critique of the Clownfish mating process and gender changes that occur, as well as an exploration of the different species. Gender Changes The ability to switch sex is one of the aspects that make the fish unique especially the fact that this can happen to any adult fish. Kuwamora & Nakashima (1998 p 126) observe that during hatching, the fish are usually one sex, i. e, all males. The dominant male that becomes larger than all the rest during adult stage develops in to a female. None other develops in to a female so long as the dominant female is alive. The fish that follows in terms of size becomes the dominant male, while the rest remain small inactive males (Godwin 1994 p 558). These phenomena lead to the questions as to why only one of them develops in to a female and assumes the normal role female fish. Questions also arise as to why the second largest male does not undergo the same process. However, these changes point at dominance as the major determinant of the sex change. The males that remain are usually inactive and remain at the bottom of the hierarchy that is headed by the dominant female followed by the dominant male. Another interesting phenomenon is in case the dominant female dies. The dominant male undergoes a sex reversal and assumes the role of the dominant female, which starts reproducing. The death of the dominant female leads to a rearrangement of the hierarchy since the largest male in the juvenile group develops in to the dominant male and begins mating. Godwin (1994 p 558) observe that the need to fill the gap left by the reproducing female triggers the degeneration of the male organs and the development of the ovaries from the female ovary cells that remain dormant when the fish is male. This is an indication that even if the Clownfish are hatched with the male sex, there are certain dormant ovarian cells that remain standby until when need arises. There seems to be an interconnection between the physiology of the fish and the social aspects of the group. The social gap created by the death of the female is filled by the mating male; leaving another gap whereby there lacks a dominant male, which on the other hand has to be filled by a male from a lower group of males in the hierarchy. Each group of Clownfish inhabiting a particular sea anemone has got its own hierarchy, and they do not mix. This is an indication of the social bond that exists within the groups whose stability is maintained by all members (Kuwamora & Nakashima 1998 p 128). It means that if the reproducing female is alive and functional, no other male regardless of the size can develop in to a female. On the other hand, no fish in the lower group can change sex to become the dominant male while one already exists. In a way, one may infer that it is due to loyalty of the lower groups to the dominant male and female that they do not change their sex or grow to a large size to outdo the fish in the upper level of the hierarchy. This is because they have the capacity to become larger and change their sex, but they do not. Maddern (1990 p 36) notes that each fish has to ensure that its body mass remain lower by a quarter of the average weight of the dominant fish, or else it may be ejected out of the group. This has enabled the fish to avoid any impending conflicts that may arise between the dominant group and the lower group. However, the initial vigor of development from the larvae stage determines whether the larvae will develop in to one of the dominant fish in the group. The ones that develop at a high rate have a high chance of becoming dominant. The behavior of the fish generates interest to research on the reasons behind the unique behavior. One wonders why the social aspect of the group is largely connected to their physiology. More over, how the fish regulate their size to maintain a lower body mass than the dominant fish is an important issue that needs further research. It is important to understand how they are able to determine the amount of feeds and aggressiveness that helps in the maintenance of a small size, which can only be changed when there arises a vacant position created by the death of one of the dominant fish. In order for the fish to qualify for change of sex, they have to be mature, which Tullock (1998 p 54) argues should be more than one year of age and the environment needs to be favorable for the change of sex. The environment that determines the success of the fish in changing sex is that within the social group. A favorable environment means that there has to be an opportunity for the fish to join the dominant group. Without the absence of the female, no change of sex can occur. On the other hand, there can be a dominant female but the group may lack a dominant male, necessitating the movement of one of the fish in the lower groups to the dominant group. Maddern (1990 p 33) further notes that even if two male clownfish were put together under controlled conditions, one of them that is more dominant than the other has to become the female, while the other becomes the mating male. On the other hand, Tullock (1998 p 67) further observes that a lone crown fish will develop in to a female if allowed to develop to a full grown fish. One can therefore infer that development in to a female is dependent of other larger and fast growing fish that are likely do dominate the group. However, this applies for the smaller fish since if one small fish is allowed to grow on its own in the absence of other fish; it develops in to a female. This means that all the Clownfish are bound to become females if there are no other fish to compete with for dominance (Kuwamora & Nakashima 1998 p 128). Mating amongst the Clownfish Mating in the Clownfish is usually ceremonial, which leads to spawning of eggs and fertilization. The fish engage in courtship prior to spawning. The behavior of the males changes to aggressiveness, which rises as the male approaches the actual mating. Wittenrich et al. (2007 p 95) observes that the male usually turns its aggressiveness towards the substrate beneath the water. On the other hand, the female joins in there after, leaving both sexes charging towards the substrate. This is the period that is regarded as courtship (Wilkerson 2003 p 66). This aggressive behavior continues until the final days prior to mating when it becomes more intense. They even become aggressive towards other fish that come close to the mating area. The courtship, as Godwin (1994 p 551) observe is usually brief and involves certain pretentious behavior of the female to attract the male and vise versa. The sea anemone plays a significant role during mating and spawning of eggs. Both fish take part in the clearance of debris and any other solid particles that may interfere with the eggs. The female later lays the eggs on the selected side of the sea anemone. They usually find the softest substrate that is favorable for the delicate eggs. The fish usually pinch one of the tentacles of the sea anemone, which makes it retract as a reaction to the nip. The tentacle settles at the selected spawning area by the female. Before laying the eggs, the female makes certain that it is the most appropriate area to spawn by making some trials that are simi1ar to laying eggs but not real. The actual laying of eggs usually comes later after ensuring that the environment is favorable. Maddern (1990 p 39) observed that the eggs are usually sticky in nature, and that they can not float on water. They stick on the substrate and the male swims closely behind as the female lays the eggs. After completing spawning of eggs for a period of 2 hours, the male is usually ready to shed the sperms to fertilize them. The fertilized eggs remain stuck on the soft substrate, where both fish offer protection against intruders who might cause harm. With the exhaustion from spawning, the female gets to feeding while the male is left to shield the eggs from attack. Hoff (1996 p 86) observes that the male is usually highly aggressive in defending the nest. More over, the male is also involved in aerating the eggs through flapping its fins. It also selects and eats the infected eggs that may not have a chance to survive. Any matter that falls on the eggs is removed by the male. In other words, the male is usually very active through out mating and after the eggs have been laid to the time that the larvae will be hatched. The female can shed up to more than 2000 eggs in one spawning season. However, the number of eggs usually depends on the size of the reproducing female. The larger the female the more the eggs it can produce (Tullock 1998 p 63). This could also be another reason as to why the large males are the ones that change in to dominant females. The mating area is also a determinant of the survival of the eggs and the strength of the fry. Wilkerson (2003 p 68) observes that it is important for the aquaculture of Clown fish to be practiced carefully to avoid mixing the species in one area whereby they are likely to stress each other. Different species are unlikely to survive together since they will constantly fight injuring each other, which is likely to make them unable to lay eggs. In controlled conditions, the presence of a sea anemone makes the environment more like the natural environment, which facilitates spawning. The fish under go the normal process of mating, laying eggs and taking care of them as they would do in the wild. However, this would require an extra task of raising the sea anemone and maintaining it while on the other hand maintaining the fish. It may be a costly venture to undertake in aquaculture. However, it is not mandatory to have the sea anemone for the Clownfish to mate and spawn in controlled conditions. The fish can also spawn in rocks whose ruggedness offers hiding places. However, the same characteristic as in the wild whereby the fish cleans the substrate on the surfaces where the eggs are laid occurs during mating under controlled conditions. Hoff (1996 p 89) observes that the mature and ready to mate Clownfish usually tend to scrub rocks with the mouth as well as fins, in a similar way as the way they clean the substrate to have a clean ground for laying eggs. The eggs get stuck to the eggs where they get fertilized by the male that swims after the female. The fish that are satisfied with the artificial environment, i. e. that which is almost similar to the natural environment are likely to lay more healthy eggs (Wilkerson 2003 p 66). Species of Clownfish There are many fish species of Clownfish which differ mainly in color as well as in many other aspects such as the structure of the fins. For example, the Amphiprion percula is one of the species of Clownfish that has a characteristic extended level band at the central point of its body. The fish is also referred to as the anemone fish, which has a distinct orange color. It also possesses some black marks as well as white strips on the fins. The structure of the dorsal fin is one of the distinguishable characteristics as it possesses 10 spines (Maddern 1990 p 61). The species is known to reproduce through out the year since it inhabits the warmer regions that are favorab3le for breeding. The fish live in groups of 6, including the dormant males. The hierarchy of the group is that of the typical Clownfish, and it exhibits all the other characteristics of the Clownfish such as change of sex. The Amphiprion clarkii is also one of the hardy Clown fishes that are highly resistant to diseases. They come in diverse colors such as yellow, white, grey and brown. These colors are also diverse on the fins and the tail, while it is missing in others. The fish are recommended for aquariums due to their hardiness as they do not need specialized care. Amphiprion ocellaris is also one of the species with distinct characteristics such as black stripes on the fins as well as an elongated dorsal fin (Tullock 1998 p 65). Premnas biaculeatus has a reddish color on their body which tends to be more inclined towards brown in some fish within the species. They have white strips along their spine. These colors are distinct from most of the other fish species. Amphiprion frenatus is a species in which juveniles tend to be dark red and black as they develop in to adults. Amphiprion sandarcinos, Amphiprion perideraion, Amphiprion frenatus and Amphiprion melanopus are also among the many species of Clownfish that can be differentiated especially through the color of their bodies (Wittenrich et al 2007 p 95). Conclusion Clownfish is one of the hardy fish species that inhabit the warm areas of sea, such as the Indian Ocean as well as the Pacific Ocean. They belong to the genus Amphiprion, and are greatly colored, which makes them good for ornamental aquaculture. In the wild, the fish usually live in groups that demonstrate a hierarchical association. The highest in the hierarchy is usually the reproducing female, which are the dominant and the largest fish in a group. The fish have a rare behavior of changing sex depending on need. The larvae are usually male, but they are capable of developing in to females. Only the dominant and largest male develops in to a female, while the second largest male in the group develops in to the mating males. The only time that there can be a change in the hierarchical structure is when the female is eliminated from the group through death, leading the mating male to become the female and the larger male in the lower level of the hierarchy to become the mating male (Drury 2008 p 63). The mating of the Clownfish takes place without complications. The sea anemone is highly supportive to the existence of the Clownfish. It offers protection through its poisonous stings to the predators. The Clownfish is not taken as a predator by the sea anemone because of the mucus covering on its body that comprises of sugars. The relationship between the sea anemone and the Clownfish is usually symbiotic, whereby each derives some advantage from the other. There are many species of Clown fish that can be distinguished through their body color as well as the body structure. However, they exhibit a similar behavior (Maddern 1990 p 41). References 1. Drury F. Marine Symbiosis: Clownfish & Anemones: The Mutual Symbiosis between Clownfish and Their Host Sea Anemones, PSA Journal, Vol. 74, (2008): 63. 2. Godwin J. Behavioral aspects of protandrous sex change in the anemonefish, Amphiprion melanopus, and endocrine correlates. Anim Behav, Vol. 48, (1994): 551-67 3. Hoff F. H. Conditioning, Spawning and Rearing of Fish with Emphasis on Marine Clownfish, Florida Aqua Farms Inc, 1996 4. Kuwamora, T., & Nakashima, Y. "New aspects of gender change among reef fishes: recent studies in Japan”. Environmental Biology of Fishes. Vol. 52, (1998): 125-135 5. Maddern E. Curious Clownfish, Little Brown & Co, 1990 6. Tullock J. Clownfish and Sea Anemones: Barrons Complete Pet Owners Manuals, Barrons Educational Series, 1998 7. Wilkerson J. Clown Fish Guide: A Guide to their Captive Care, Breeding and Natural History, T.F.H. Publications, 2003 8. Wittenrich M. L., Nilsen A. J., Michael S. W. & Moe Martin A. The Complete Illustrated Breeders Guide to Marine Aquarium Fishes, TFH Publications, 2007 Read More