The Allardi Group

by | Jul 29, 2020 | 0 comments

Like the clarkii and chrysopterus groups, the allardi group can be recognized by its robust size, the presence of multiple vertical bars, and a generalist attitude towards anemones, willing to make use of whatever host happens to be available. Together, these clownfishes were formerly thought to comprise a single wide-ranging Indo-Pacific lineage, with members spanning from the Red Sea to Polynesia, but genetic data argues that this is not so, with those from the Western Indian Ocean forming their own distantly related clade. This should come as little surprise, as this region is now well-known for the endemism of its marine fauna, representing a major hotspot for speciation during the Miocene, associated with the breakup of the ancient Tethys Sea. This same distribution can be seen with the Purple and Gem Tangs (Zebrasoma xanthurum & Z. gemmatum)… the Red Sea, Mauritian, and Madagascar Flasherwrasses (Paracheilinus octotaenia, P. piscilineatus & P. hemitaeniatus)… and the little-known, hyperdiverse Chlidichthys dottybacks, which have a remarkable 13 allopatric species scattered across this region! And these are but a few of the examples that could be mentioned, to speak nothing of the many corals found only in these ancient reef systems.

Beginning along the African coastline, Amphiprion allardi can be found from Kenya to South Africa, showing little indication of any phenotypic diversity across this large longitudinal distance. This is despite the fact that the currents in this region diverge strongly in the heart of this species’ distribution, splitting into northerly and southerly flows roughly around Northern Mozambique. Why hasn’t this caused speciation… or has it? Mature specimens are identifiable by their weakly emarginate white caudal fin and the chrysopterus-like color and pattern to the body. In fact, were this fish to be dropped into Micronesia or New Caledonia, it would be difficult to separate these distantly related fishes. The diagnostic trait to look for is in the lower portion of the caudal peduncle, which has an angular yellow section in A. allardi.

On nearby Madagascar, as well as the Comoros Islands and Mayotte, we find the Wideband Clownfish A. latifasciatus, which differs most notably in having a yellow caudal fin and a slightly wider medial bar. This is, more accurately, a complex of three distinct populations separated by some major biogeographical barriers. The true A. latifasciatus resides in the northwest corner of this region, along with the neighboring islands of Mayotte and the Comoros, and is recognized by the solidly yellow caudal fin of large males and females. Further south, in the remnants of what was formerly a major barrier reef, occurs an undescribed species with yellow restricted to the margins of the caudal fin. And the third, the so-called Whitemargin Anemonefish, occupies the limited reefs on the northeastern coastline of Madagascar, readily identified by its namesake white-margined caudal fin. This is likely one of the rarest Amphiprion species and is almost certainly in need of conservation attention, potentially being one of the few marine species that aquarium collecting could realistically imperil.

In the Red Sea and through the Gulf of Aden to nearby Socotra, we find another similar fish in the form of A. bicinctus. It’s coloration is roughly the same as in A. latifasciatus, particularly with regards to the yellow caudal fin, but it varies in usually being a lighter shade of yellow-brown (versus black) along the sides, as well as possessing somewhat thinner bars. Interestingly, this is the only species of clownfish found in the Red Sea, where it’s known to occupy Entacmaea quadricolor, Heteractis magnifica and H. crispa. Many sources cite this species as being present in the Chagos Archipelago, but this is strongly argued against by the vast biogeographical distances involved. There is no precedent for a species otherwise endemic to the Red Sea also being found at Chagos. Instead, this is merely a case of mixed identity with the previously discussed Chagos clarkii population.

The southern coastline of the Arabian Peninsula is home to the aptly named Omani Clownfish A. omanensis, known primarily from the sparse, scattered reefs of the country’s southern shoreline. Specimens have thin bars, as in A. bicinctus, but A. omanensis can be readily identified from its dark brown hue and nearly black ventral fins, as well as the white, rather than yellow, caudal fin. This is also likely to be one of the least abundant clownfishes in the world, as Oman has relatively little coral reef habitat, though within its narrow slice of the ocean this species can be quite abundant. Nearby reefs in the Persian Gulf are unlikely to harbor any additional populations either, with the currents running counterclockwise through the region, limiting northeasterly dispersal and competition from A. clarkii further excluding dispersal. On the other hand, specimens have recently turned up in low abundance at Socotra and Yemen, where the species has been documented to form a hybrid with A. bicinctus.

The final members to discuss occur along the southeastern edge of this ecoregion and stand out for having a dark caudal fin. The species in question are the Seychelles Clownfish (A. fuscocaudatus) and the Mauritian Clownfish (A. chrysogaster), both of which are very rarely encountered in the aquarium trade. In the former, the anal fin is yellow, and the black of the caudal fin is present in its basal portion and extends along the rays. It ranges throughout the Seychelles and nearby Aldabra. In A. chrysogaster, both of these fins are entirely black, but otherwise the two species are mostly identical. This species occurs along the Mascarene Plateau, at Mauritius and Réunion, though whether it occurs beyond this region, in the largely submerged reef systems and seagrass beds to the north, remains unverified. It is important to note that places like the Saya de Malha Bank and the Cargados Carajos Shoals are vast and little-studied marine habitats that were intimately connected during the lowered sea levels of the Pleistocene. No doubt, Amphiprion still occur here.


Submit a Comment

Your email address will not be published. Required fields are marked *

Benepets – 125


Upcoming Events

Reef Nutrition – 125
Reefbreeders – 125
Aquarium Specialty – 125 – 125
Reefs Internal Advertising – 125
Fauna – 125
Unique Corals – 125
Polyplab – 125

Follow Us!