Ascidian Tunicate, Botryllus schlosseri (Pallas, 1766) infestation on Seahorse

An unusual infection by tunicate ascidians on the trunk part of a seahorse caught by gill ne ing in the Eastern Black Sea Region of Turkey was observed. The colour, zooid diameter and width of the zooids colony of tunicate was determined. The present study is the first report of this condition on seahorses. * Corresponding author’s e-mail: [email protected] Tunicates are marine invertebrate animals that are commonly found a ached to rocks in the marine systems. Some tunicates (such as Botryllus sp.) have a preference for colonial life on coral reefs rather than as solitary organisms. They have a free-swimming larval stage, but during their adult stage most species are permanently a ached to substrates such as rocks, docks and boats. At the same time they can live as invaders on other marine organisms such as marine plants, algae (Ulva lactuca, Sargassum filipendula, Fucus spp., Zostera marina and Codium fragile tomentosoides) mussels (Perna perna) and oyster (Crassostrea gigas) in their adult stage (Carman et al., 2009; Rocha et al., 2009). Botryllus schlosseri is an invasive, colonial ascidian tunicate that grows on submerged objects, plants, and animals in marine environments. Its range has spread to a nearly worldwide extent. There are many colours in which this species can be found, ranging from orange, blue and grey (Weissman et al., 1990). Botryllus schlosseri is the most common tunicate species in the Black Sea (Usov et al., 2001). Seahorses include the fish genus Hippocampus within the family Syngnathidae. There are about 40 species of seahorse which are mainly found in shallow tropical and temperate waters throughout the world. However, seahorse populations are thought to have become endangered in recent years by over fishing, through by catch and their habitat destruction (Lourie et al., 2004). A list of bacterial, viral, parasitic and environmental diseases and their treatment in seahorses was recently compiled (Lamont and Belli, 2005). However, there are no records of tunicate invasion on seahorse. The present study describes an unusual infection of seahorses from the coast of the Eastern Black Sea by Botryllus schlosseri. Ten live seahorses were caught as a by catch by gillnet in the coast of Eastern Black Sea of Turkey (41° 09’ 53′′ N; 40°48’42′′ E) in May 2010. Bull. Eur. Ass. Fish Pathol., 31(2) 2011, 82 A tunicate invasion was observed on one seahorse. Two seahorses (one infected and one normal) were fixed in 10% formaldehyde. Identification of tunicate and seahorse species were determined using Lourie et al. (2004) and Brune i (1974) based on their morphological characteristics. Colour and width of zooids of the tunicate were recorded. The tunicate and seahorse were identified respectively as Botryllus schlosseri and Hippocampus gu ulatus. However, it should be noted that some authors consider the Black Sea form of H. gu ulatus to constitute a separate species. B. schlosseri was observed on trunk part of the seahorse (Figure 1). The colour of tunicate was red, with zooid diameter and width of zooids colony (means ± sd) were 1.5 mm and 10 ± 4.2 mm respectively (Figure 2). Few studies of diseases of either tunicates or seahorses have been conducted in different aquatic systems. These include a disease of tunicates (cup cell disease) in cultures of Botryllus schlosseri (Vincent and Cli on-Hadley, 1989), a microsporidan infection in a colony of seahorses (Hippocampus erectus) caused by Glugea heraldi (Moiseeva et al., 2004) and diseases of seahorses caused by Vibrio alginolyticus and Vibrio splendidus (Balcazar et al., 2010). However, there are Figure 1. a; Affected Hippocampus gu ulatus with Botryllus schlosseri and b; normal seahorse, Scale bar: 2 cm. Bull. Eur. Ass. Fish Pathol., 31(2) 2011, 83 no records about the seahorses diseases caused by ascidians tunicates. This phenomenon may be related to the sample methods of seahorses which may limit the chances of collecting seahorses with this condition. Despite this possibility, the present study is very important in terms of studies of aquatic invaders on fish species. Lourie et al. (1999) stated that, major threats to seahorses are habitat degradation and exploitation. But the most important threats include eutrophication and destructive fishing practices such as bo om trawling, dynamiting and poisoning on natural habitats of seahorses. Eutrophication of the environment may increase the amount of tunicates. At the same time, it is know that seahorses move slowly in the environment which may increase the probability of contact between the seahorse and infective stages of the tunicate. In addition, loss of eelgrass, a favoured habitat of tunicates, may lead to increased use of seahorses as a suitable substrate in future. In this context, can be said eel grass habitat and coral reef structure should be protected in the all aquatic systems. Although no adverse effects were noted in the infected seahorse, it is not known what impact the tunicate had on survival of the host. Further studies need to be conducted to ascertain the distribution of this phenomenon and the potential impact on seahorse biology. Acknowledgements I would like to thank fisherman Mr. Bayram Raagici for providing the seahorse’s samples and Dr. Ahmet Mutlu Gozler for the identification of the tunicate Figure 2. The colony of zooids (4X). Bull. Eur. Ass. 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