Moving away from the first major Cirrhilabrus clade, we explore the various species groups that differ by having larger and longer pelvic fins. The scottorum group is a small conglomeration of two confirmed species, one of which is highly polychromatic throughout its range, with the potential of harboring at least one cryptic member liable for splitting. All the group members are strictly Pacific and allopatric.
The scottorum group members are easily identified based on their large size and coloration. These are stocky and very burley Cirrhilabrus with the potential to reach lengths of up to 15cm (6 inches). Their aggressive temperament and heavy build make them suitable candidates for larger aquaria. While generally rather beautiful, their colors are some of the most challenging to maintain in captivity. Amongst the fairy wrasses, Cirrhilabrus scottorum may be the most prone to aquarium-induced color loss, though what triggers this and how to prevent it are poorly understood.
The phylogenetic grouping for the scottorum clade is rather straightforward. Like the bathyphilus group, Cirrhilabrus scottorum forms a cladistic pair with a closely allied phenotype with an isolated range. Cirrhilabrus melanomarginatus appears to be the only relative, and it is identical in meristics and shares a very similar overall appearance.
Cirrhilabrus melanomarginatus is one of the pioneering members of its genus, being the tenth member described in 1978. A decade later in 1988, Cirrhilabrus scottorum was described from Tahiti, and joined the genus as the twenty-third member. No other Cirrhilabrus are currently closely allied to these two, but should the Coral Sea variant of C. scottorum warrant splitting, the group will increase to three members instead of the current two.
The scottorum group is rather unassuming, but gets interesting as it features one member with the propensity to form hybrids, and in this article we revisit this rarely encountered phenomenon of the Cirrhilabrus genus.
The males of the scottorum group are fairly easy to diagnose. In all species, the basal coloration is fir green. Occasionally they are slated in steely blue, especially near the snout and anterior portions of the body. Their tails are broad and weakly rhomboidal, often with a single filament threading out from the central ray. Males of the scottorum group possess a vestigial blue stripe along the posterior segment of the lateral line, which can be heavily obfuscated in certain specimens. Careful observation reveals black speckling along the body, which might be homologous to that seen in members of the cyanoplerua group. Another trait that links the scottorum group with the cyanoplerua group is the possession of wavy lines along the dorsal fin, especially on the posterior soft segment. This is only evident in specimens with a thick black dorsal margin, and especially in C. melanomarginatus.
The pelvic fins of the scottorum group are moderately long and tapered, but never as long as with the teminckii clade. They are, however, decidedly longer than those of C. laboutei and the jordani clade. Together, these clades represent the four major pelvic fin shapes of the genus. Having already completed the first major generic clade with small pelvic fins, the scottorum group is the first of three to possess relatively longer pelvic fins.
The juveniles are a rich bordeaux to merlot, overlaid in a steely gunmetal blue. A series of very fine striations run horizontally, interlaced with small white spots. A single black spot is present on the caudal peduncle. Females lose the maroon shading and take on the characteristic fir green body coloration, which increases in prominence as they mature. Juveniles and females of Cirrhilabrus scottorum and C. melanomarginatus are nearly indistinguishable in the field, but are easy to separate due to their allopatric distributions. The females of Cirrhilabrus cyanopleura are vaguely similar, and again, this serves as a possible link between the two groups.
The scottorum clade
The scottorum clade houses two phenotypes, one of which (the type species) extends throughout the Pacific, while the other is restricted to the Coral Sea region. The latter is tentatively dubbed Cirrhilabrus cf. scottorum, and may potentially be separated based on consistency in its coloration as well as genetic divergence from C. scottorum. The two forms are mutually exclusive and do not overlap.
As you may have noticed by now, the Coral Sea region is rather prone to endemism, with a handful of endemic species spanning various genera. Cirrhilabrus is represented by a few endemics, namely C. lineatus and C. squirei. C. laboutei and C. bathyphilus, although found in the same area, extends to adjacent Vanuatu as well. Cirrhilabrus cf. scottorum is chiefly restricted to the Coral Sea and Australian region. There is a possibility that the Coral Sea endemics stray to New Caledonia and Vanuatu (at least, in part). The range of Cirrhilabrus bathyphilus clearly supports this. This of course, is purely hypothetical, seeing as neither Cirrhilabrus lineatus nor C. squirei have been found outside of their restricted range (yet).
Another thought provoking question is where the line of separation exists between the New Guinea and Solomon Islands endemics vs. the Coral Sea region. Cirrhilabrus beauperryi spans both regions, a rather perplexing area to overlap.
Both scottorum phenotypes can be differentiated based on a few minor differences in color, but because they are so highly variable, the most effective means of separation still rests on the provision of their geographical range. The females are rarely encountered in the trade, and are identical in appearance.
Cirrhilabrus scottorum is the dictionary definition of variable, and the males are highly polychromatic with innumerable variants. This species runs the gamut of color forms, but it can be identified with relative ease, regardless. In this veritable kaleidoscope, males are fir green basally, fading to a darker central region before lightening again posteriorly. The ventral portions are also lighter, often in pale chalk to bright yellow. The head and dorsum is often tinted in a steely blue wash, sometimes accented in cyan or turquoise. A large red blotch is present centrally, which varies in size, intensity and clarity. In some specimens, the red blotch is separated from the green basal coloration by clearly defined margins. In others, it bleeds profusely, marring the underlying color in a red suffusion. It’s also not uncommon for the red spot to be entirely absent as well.
The dorsal fin is malt yellow, to pale green, to orange, and, again, decorated in a fleetingly variable black margin. This ranges from being totally absent, to vestigial, to copiously present along the outer limits of the dorsal fin. Occasionally, individuals sport a black margin that travels horizontally midway along the length of the dorsal fin, instead of emarginating the edge. In individuals with very melanistic dorsal fins, a labyrinth of wavy squiggles can be seen in a sidelight. This is very unobtrusive or absent in specimens with lighter colored dorsal fins.
The anal fin, as with the dorsal, is colored the same and decorated in the same black margin of variable intensity and position. It is, however, more consistently present and is very rarely absent, being at most vestigial. The pelvic fins are moderately long and very slightly trailing, being characteristic to members of this clade. A blue stripe is often present along the posterior segment of the lateral line, near the caudal peduncle. This, however, is highly vestigial and in some specimens, appears to be totally absent. C. scottorum has a weakly rhomboidal caudal fin, and in very matured males, a filamentous thread may be present extending from the central ray. It is translucent yellow to red.
The nuptial coloration and display behavior of Cirrhilabrus scottorum is poorly known. Based on those of Cirrhilabrus melanomarginatus, it is possible that the fins lighten and a transverse band appears on the anterior body. Again, aquarists may find themselves in a position to help further our understanding of this species by documenting their nuptial displays in their home aquariums.
C. scottorum is widespread across the Pacific, and can be found in the American Samoa, Cook Islands, Fiji, the French Polynesia, Niue, Pitcairns, Solomon Islands, Tonga, Vanuatu and Wallis & Funuta. Its westernmost limit is the Coral Sea, where it is replaced by the very similar Cirrhilabrus cf. scottorum. Like the previously mentioned Coral Sea region, Fiji, Tonga, Samoa and Wallis & Funuta are other areas with high endemism in Cirrhilabrus, and genetic study is needed to determine if a cryptic “species” of C. scottorum exists there.
The fish is common in the trade, and can be obtained from most importers that deal with fish from any of the above locations. Ironically, despite being so colorful and variable, this fish often fades to a sullen and ominous inky green in captivity, and quickly loses the beautiful red and yellow accents that it is so famed for.
C. scottorum is also reported to be slightly more belligerent than the usual Cirrhilabrus. Despite its large size, aggressive temperament and inability to retain coloration, it remains one of the most popular Cirrhilabrus and is always in rather high demand. Specimens from the Cook Islands are most beautiful and are highly coveted.
Cirrhilabrus cf. scottorum
Cirrhilabrus cf. scottorum is superficially very similar to the preceding species and also comes in a myriad of forms. This phenotype is often less colorful than the type species. In C. cf. scottorum, the base coloration is of the usual fir green with teal accents. The ventral portion fades to a lighter shade, often yellow or orange. The body is always without a clearly defined red spot, but is occasionally marred in a red or orange haze. The median fins are much more erythric and are colored a rich cadmium orange.
The dorsal fin is edged in black, which is variable, ranging from being totally absent to highly copious. When present, however, it is usually thicker on the posterior edge, thinning out as it reaches the anterior. Superficially, the black margin forms a teardrop or comma shape on the dorsal fin. The anal fin is also thickly-coated in black and is less variable, being mostly present. The caudal fin is a nauseatingly rich vermilion and is weakly rhomboidal.
The orange pelvic fins are, as with C. scottorum, moderately long and slightly trailing. As with Cirrhilabrus scottorum, not much is known about their nuptial colorations or behavior during display.
Cirrhilabrus cf. scottorum is confined to the Australian region of the Coral Sea, specifically the Great Barrier Reef at depths as shallow as 6m (20ft). It is, of course, found deeper as well and is fond of rubble pans adjacent to reef drop offs.
Cirrhilabrus cf. scottorum is common in the trade and is rather affordable. It is less popular than its sister species but shares the same husbandry, temperament, and inability to retain its coloration. It should be interesting to know if anyone has succeeded in retaining the rich chromatic brilliance of these wrasses. It’s not uncommon for Cirrhilabrus to lose a fair bit of color in captivity without the stimulation of females, but, with C. scottorum, its transition into a more somber state is usually quick and fairly drastic.
This is one of the largest Cirrhilabrus, rivaling even Cirrhilabrus lanceolatus. In this gargantuan member, the basal coloration is fir green, darkening toward the central portion in a deeper, mossy hue. The body is unmarked sans the vestigial lateral stripe, and is without the red coloration typical of C. scottorum. Otherwise, it remains relatively plain. The anal fin is variably colored, ranging from strawberry pink, to carmine, to cinnabar. It is never edged in black like C. scottorum. The pelvic fins are rather long, tapered and green. The caudal fin is rhomboidal, slightly more so than in C. scottorum, and, in large males, it often terminates in a filamentous extension of thicker width than the preceding species.
The specific epithet “melanomarginatus” means black margin, and this is very consistently seen translated on the edges of the dorsal fin. The basal coloration is green, and a splash of red is often present on the posterior soft dorsal. The sinuous scrawling is very evident on the dorsal fin and is most strongly represented in this species.
Cirrhilabrus melanomarginatus possesses an unusual flap of skin on its nape, just before the origin of its dorsal fin. It appears to be present only in fully terminal males, and can be erected, as with the dorsal fin, during courtship displays. Cirrhilabrus scottorum occasionally has very small vestigial remnants of this eversible skin flap, but is never as obvious as with this species.
The nuptial coloration of Cirrhilabrus melanomarginatus is well documented by underwater divers. In its courtship colors, the body intensifies to a deep army green, sans the periphery. A light transverse band appears just behind the pectoral fin, and an additional set of stripes appears behind the eye and cheek. The rest of the fins remain unchanged but are held erect as the fish maneuvers around prospective females.
Cirrhilabrus melanomarginatus ranges in the Western Pacific, specifically, the South China Sea, from Japan, south to Taiwan and the Philippines, west to Vietnam. The species is sympatric with various species of Cirrhilabrus, but hybridizes with only one species, and that is Cirrhiabrus exquisitus.
C. melanomarginatus is sporadically available in the trade, but is not very popular due to its boisterous size and stodgy coloration. It is frequently collected from Vietnam and the Philippines.
Hybridiation in Cirrhilabrus is rarely documented, and, unlike their promiscuous cousins Paracheilinus, very few examples exist. Thus far we have only visited this topic once, in the lunatus group, where Cirrhilabrus cf. lunatus and Cirrhilabrus lunatus can be seen producing hybrids with the “pintail” fairy wrasse.
In the scottorum group, only Cirrhilabrus melanomarginatus has been documented to hybridize with C. exquisitus. It’s unusual that this hybrid has only been documented in Japan, considering the wide occupancy of the latter throughout much of C. melanomarginatus’ range. Cirrhilabrus exquisitus should be just as likely to create a hybrid with C. melanomarginatus, especially on the edges of the latter’s range where it is less abundant. The fascinating story of Cirrhilabrus exquisitus will be reserved for an article in its own entirety.
It is also noteworthy that Cirrhilabrus scottorum, a very close relative of C. melanomarginatus, overlaps with C. exquisitus throughout its range, but no hybrids of the two have been documented. It can be argued that the lack of evidence supporting hybridization can be attributed to the relatively unexplored regions by field photographers, but, conversely, the same region experiences rather frequent collection, way more than that in Japan where C. melanomarginatus x C. exquisitus is documented.
The hybrid above shows a fish with a fascinating mélange from both parental phenotypes. In both species, the ground coloration is green, so a rather uniform shade of the same hue is to be expected. What is immediately apparent, however, is the double-emarginated tail of C. exquisitus peeking through, coupled with the banding and spotting on the anal fin (two traits that are absent in C. melanomarginatus). The heavily blackened dorsal fin also suggests genetic input from C. melanomarginatus, and, although C. exquisitus shows regional variants with a black dorsal fin, it is never complete or so extensive.
This is some of the strongest evidence supporting the closeness of the scottorum group with Cirrhilabrus exquisitus (which, with its numerous insular variants, forms a complex on its own). We’ve also seen how the cyanopleura group ties in rather closely with the members of the scottorum group, with the similarities in female coloration and the secondary characteristics of the males.
In conclusion, the scottorum group is superficially boring, with few members, but the incredibly variable and regional polychromatism displayed by Cirrhilabrus scottorum is nonetheless fascinating and curious. The probable recognition of a cryptic member from the Coral Sea and perhaps the Melanesian region is also exciting, and the ability of C. melanomarginatus to hybridize with C. exquisitus is a rare phenomenon that very few other Cirrhilabrus get to enjoy. The scottorum group foreshadows similar traits seen in the cyanopleura and exquisitus groups and is a good opener for the discussion of the second major Cirrhilabrus clade.