Amphiprion Thiellei

''Amphiprion thiellei'' (Thielle's anemonefish) is thought to be a naturally occurring hybrid anemonefish found in the vicinity of Cebu, Philippines. Like all anemonefishes it forms a symbiotic mutualism with sea anemones and is unaffected by the stinging tentacles of the host anemone. It is a sequential hermaphrodite with a strict dominance hierarchy.

Description

''A. thielli'' has reddish orange body, with a single white head bar that may be connected at the top with a bonnet and two saddles on the dorsal fin and tail base. They have 10-11 dorsal spines, 2 anal spines, 16 dorsal soft rays and 14 anal soft rays. They reach a maximum length of . The species was described from two aquarium dealer specimens.

Hybridisation

In 1992 Fautin & Allen stated that until more specimens are studied, its status as a valid species was provisional and postulated that it might represent a rare variant of another species or a hybrid. More than 30 years after ''A. thielli'' was originally described, its scientific status does not appear to have been clarified, although the scientific consensus appears to be that it likely to be a naturally occurring hybrid. One theory is that it is a cross between ''A. chrysopterus'' and ''A. sandaracinos''. A second theory is that it is a cross between ''A. ocellaris'' and ''A. sandaracinos''. Some support for the latter theory comes from the observations that two thiellei have never been seen as a pair in the wild, and it often pairs with ''A. ocellaris'' in the wild.

In any group of anemonefish, there is a strict sized based dominance hierarchy: the female is largest, the breeding male is second largest, and the male non-breeders get progressively smaller as the hierarchy descends. They exhibit protandry, meaning the breeding male will change to female if the sole breeding female dies, with the largest non-breeder becomes the breeding male.

This strict sized based dominance hierarchy makes the relative size of the parent species critical in shaping the outcome of hybridization In this regard ''A. chrysopterus'' is one of the largest anemonefish, growing to 17 cm in length. while ''A. sandaracinos'' is significantly smaller growing up to 11 cm as a female and just 3 to 6.5 cm as a male. ''A.. ocellaris'' is similarly small.

Constraints upon hybridization are overlap in distribution, depth and host anemone. Each of the three proposed parents have a common host anemone in ''Stichodactyla mertensii''. There is some doubt as to the distribution of ''A. chrysopterus'' with Fautin & Allen including the Philippines and Gainsford et al. excluding the Philippines. The distribution of ''A. sandaracinos'' and ''A. ocellaris'' largely overlap from northern Australia through the central Malay Archipelago to the Philippines. If they are the parents, is ''A. thiellei'' to be found throughout the overlapping distribution, and if not, why not?

Possible parent species

Image:Amphiprion chrysopterus, Vava'eu.jpg, ''A. chrysopterus''
Image:Amphiprion sandaracinos.jpg, ''A. sandaracinos''
Image:Amphiprion ocellaris (Clown anemonefish) Nemo.jpg, ''A. ocellaris''

Color variations

If ''A. thiellei'' is a hybrid, it may show a variety of intermediate colors and patterns similar to ''A. leucokranosis''. Some species of anemonefish, such as ''A. clarkii'' show melanism when hosted by ''S. mertensii'' however the small number of observations of ''A. thiellei'' make no reference to any such melanism.

Similar species

''A. perideraion'' has a pinkish body and a continuous white stripe along the base of the dorsal fin, rather than broken into a bonnet and two saddles. ''A. nigripes'' is distinguished by its black belly, pelvic fins and anal fin and the absence of the saddles on the dorsal fin and tail base.

Image:Amphiprion perideraion 2.jpg, ''A. perideraion'' (pink skunk clownfish) showing the distinctive pink body & continuous stripe
Image:Amphiprion nigripes Maldives.jpg, ''A. nigripes'' (Maldives anemonefish) showing the distinctive black pelvic & anal fins.

Distribution and Habitat

''A. thielli'' is believed to have originated in the vicinity of Cebu, Philippines.. Field records are lacking for ''A. thiellei'' however the most probable hosts are thought to be:

*'' Heteractis crispa'' Sebae anemone
*''Stichodactyla mertensii'' Mertens' carpet sea anemone

References

External links

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{{Taxonbar, from=Q1572652

Pomacentridae
thiellei
Fish described in 1981