The rubrimarginatus group is home to some of the most well-known (and well-loved) of the Fairy Wrasses. The group can be divided rather equally into two clades, each with their own separate diagnostic features. The males attain fairly large sizes, are robust, and many are intricately designed with fine streaks and spots on the face and median fins. This group is the first of four in the final Cirrhilabrus lineage, where members typically possess very long pelvic fins. This feature is very clearly and well presented in members of this group, and serves as a great opener to the final stretch of this long and grueling review.
The rubrimarginatus group is entirely Pacific in distribution, with the majority inhabiting mid to deep waters of the Western Pacific. The discovery of the species within this group spanned over two decades, with Cirrhilabrus lineatus kicking off the string of discoveries when it was revealed in 1982 from the Coral Sea, in the Southwestern Pacific. C. lineatus was one of three species described in the same paper by Randall and Lubbock, and quickly became the 15th species added to this then rapidly growing genus. The species was remarkable for possessing long, tapering pelvic fins as well as fine striations across its body (a feature earning its specific name). At the time of its description, the only other species that was known to have this exaggerated pelvic fin elongation was C. temminckii.
Six years later in 1988, Randall described Cirrhilabrus rhomboidalis from the Marshall and Caroline Islands. This species, aptly named rhomboidalis, was noted for its strongly lanceolate tail, which fanned out into a rhombus when expanded. During this time, only three species with this tail characteristic were known, and they were C. blatteus, C. roseafascia and C. sanguineus. Unsurprisingly, C. rhomboidalis was regarded as a close relative to them. We disagree with this comparison, and we strongly suggest in our review here that C. rhomboidalis belongs instead to the rubrimarginatus group.
Fast forward to 1992, and a third member of this group was discovered in the Ryukyu Islands, Japan. Cirrhilabrus rubrimarginatus, with its wide distribution range, has quickly become one of the more commonly encountered members of this group.
The first member of the pylei clade was only discovered much later from New Guinea in 1996. Cirrhilabrus pylei possesses a unique set of characteristics that differ from the rubrimarginatus clade, but, cladistically, it retains similar traits that put it in the same group as the latter. A second undescribed species known as Cirrhilabrus cf. pylei is known from the Philippines, but this species is phenotypically very unusual, and it appears to form a link with the third and final member, Cirrhilabrus katoi. C. katoi was described by Senou and Hirata in 2000 from specimens in Japan. This species shows an aberration from the typical form in having very unusual coloration as well as a reduction in the pelvic fin length. As usual, each species will get a more detailed description later on in the article.
Because of taxonomic uncertainties, two possible phylogenetic scenarios are presented here. In the more conservative model, the cladistic relationships are left unresolved as a polytomy. In the more highly resolved tree, we make more presumptuous relationships between the species. The rubrimarginatus group, as mentioned, features three species, with C. rubrimarginatus and C. lineatus forming a presumed cladistic pairing (the latter replacing the former in the Coral Sea). C. rubrimarginatus is widespread across the Pacific, crossing three endemic ecoregions in Japan, the Western Pacific and Melanesia (with each showing subtle differences in coloration).
C. rhomboidalis differs from its other clade members in having a rhomboidal caudal fin. Apart from that, the similarities in the three are strong and very cohesive. The rubrimarginatus clade members occupy an almost jigsaw puzzle perfect distribution, with only a tiny overlap between two of the members in Palau.
The pylei clade is rather interesting. The three species occupy disjunct distributions, but are decidedly intractable in their taxonomic relationships. This will be discussed at length later on. As such, without the help of genetic comparison amongst the species, the clade is irresolvable and the species are best displayed as a polytomy.
The entire group shares similar features such as the striations on the face, long pelvic fins, spotting on the fin as well as a shared similarity in their female stages. The individual clades, however, can be further categorized and diagnosed based on unique traits. In the rubrimarginatus clade, males possess heavy scrawling and lineated markings on the face, which often stretch to the chest and ventral regions. In C. rhomboidalis and C. lineatus, this feature is further extended to at least the anterior portion of the body, if not throughout. All median fins are also subjected to heavily scrawling and sinuous markings, which recalls those seen in the cyanoplerua group of the medium length pelvic fin lineage. It is likely that the two groups shared a common ancestor, which likely had similar scrawling to the fins. All species possess a thick margin on the dorsal fin edge.
Their pelvic fins are very long and are at least twice the total length of those seen in the short fin Cirrhilabrus lineage where the lubbocki and jordani clades are. This allows the pelvic fins to easily extend pass the anal fin origin. Their caudal fins are remarkably round in all but C. rhomboidalis, and, in C. rubrimarginatus, it is emarginated in a thick border of red.
A strong unifying characteristic for this clade is the development of a dark epaulette on the anterior dorsum and dorsal fin during nuptial display. This epaulette is paired with another corresponding marking that develops at the base of the anal fin, becoming prominently displayed during nuptial display. This clade lacks the presence of a lateral stripe, except for C. lineatus, which displays a highly truncated and vestigial stripe restricted to the caudal peduncle.
Members of the pylei clade, like those belonging to former, also possess long pelvic fins. In this clade, however, the pelvic fins are wildly exaggerated, reaching backwards to the caudal fin in the largest males. Males twitch and flick these fins during display to females and rival males by extending them out like a pair of chopsticks. C. katoi is the only member of this group that breaks this stereotype, and, despite possessing long pelvic fins, never displays any trailing filamentous extensions.
All three species possess fine facial stripes that rarely extend past the pectoral fin. A strong dorsal stripe is present in all except C. pylei, where it is only very weakly expressed. Like the rubrimarginatus clade, the lateral stripe is very poorly-developed in this group, and, with the exception of C. katoi, is always incomplete and restricted to the caudal peduncle. In Cirrhilabrus katoi, this stripe is very well-developed and complete, running all the way along its length from the lower limit of its eye to the caudal peduncle.
Their dorsal fins are rounded and centrally taller than the anterior and posterior ends, lending a gentle semicircle shape when fully erected. The dorsal fins are heavily inscribed in cryptic sinuous squiggles, and, in C. pylei and C. katoi, a rough black spot is present at the interface of the spinuous and soft dorsal rays. Their caudal fins are rounded, and a highly chatoyant and scintillating band is present at the margin. In C. cf pylei, this band is reduced submarginally, and the caudal fin is emarginated in black. This tail pattern is not seen in any other Cirrhilabrus, and it is unique to those in the pylei clade.
When looking at the females of both clades, it becomes immediately apparent that the two clearly belong in the same group. With the exception of the highly aberrant Cirrhilabrus katoi, the females of the remaining species are light pink with reticulations on the face. In very small specimens, a black peduncular spot is present. The iris of all species are yellow-orange.
While the males of C. katoi share some features of this group, the females are aberrant, with features that do not correspond well to this group. The juveniles are of much more diagnostic value than the females, and are highly similar to the related melanomarginatus and temminckii. The figure above is likely a mixture of females and immature males, however, and what would be more informative would be a comparison of small juveniles. Locating suitable photos to use are rather difficult, and these are some of the major limitations in helping us appreciate the relatedness of these taxa.
The rubrimarginatus clade
The members of this clade are allopatric sisters with ranges that fit very nicely in the grand scheme of biogeographic evolution. They display some of the best examples of allopatric speciation, with C. rubrimarginatus and C. lineatus being poster children for this model. Again, a recurring theme occurs whereby the sisters are found in the same few endemic regions (i.e Coral Sea, Micronesia etc.) that we’ve been highlighting throughout this series. C. lineatus and C. rhomboidalis are restricted within their endemic ecoregions, while C. rubrimarginatus ranges across three. As such, although shielded by a rather homogenous phenotype, it might be plausible that specimens in Japan, the Western Pacific and Melanesia may harbor some genetic drift. As it is, very minor differences can already be discerned from these regional specimens.
Parallels can be drawn with other related taxa in this genus, such as Cirrhilabrus cf. exquisitus and Cirrhilabrus temminckii. If these species are regarded as taxa with potential taxonomic uncertainty liable for splitting, then the same should be applied to C. rubrimarginatus. It is important to be consistent in classification here, and as such, we’re giving the Western Pacific and Melanesian forms a closer look in comparison to the Japanese type species.
The one caveat to this is the relative age in these taxa. A 4 million year (MY) clade may deserve to be split, while a 0.5MY may not be as fully speciated. Another potential caveat would be differences in vagility across taxa. Perhaps C. rubrimarginatus has a longer pelagic larvae which allows it to maintain a greater genetic homogeneity. These are considerations that could be taken into account in trying to make sense on why it is important to split a species, but how it might also not always be called for.
A few recurring features can be observed between the members here. Males from this clade display very prominent whitening of the dorsal and anal fins during nuptial display. This is accompanied by the prominent display of both epaulettes on the anterior dorsum and posterior ventral regions. The members in this clade lack any of the usual dorsal, anal and lateral stripes, with the exception of Cirrhilabrus lineatus. The dorsal fin is also edged in a thick margin, but only in C. rubrimarginatus is this region strongly, and reliably, contrasted in a different color.
Cirrhilabrus rubrimarginatus (Japan [Type locality] and Taiwan)
Cirrhilabrus rubrimarginatus is instantly recognizable both in the trade and in the field. The epithet “rubrimarginatus” translates to “red margin”, and this characteristic is very evident in the caudal and dorsal fins of males and matured females. In this beautiful species, males are variable in their ground coloration, ranging from light pink, to cloud grey, to olive, before darkening to a dusky, steely teal ventrally. The head is adorned with numerous fine yellow striae, which break up in spots. These spots are most numerously dotted on the chest. The body is marked in a constellation of very minute pink dots, and, in matured specimens, this feature can be very prominent. The dorsum is occasionally variegated in green, especially near the anterior region. The posterior dorsum is sometimes suffused in a fulvous orange, but this feature is mostly noticeable in large terminal males.
The dorsal fin is marked, on the outer edge, in a thick, copious ruby margin. The inner portions are translucent and scrawled with yellow markings in-between the membranes. The caudal fin is marked in essentially the same fashion, but the red margin is bordered by a thread of metallic blue. The membranes in between the rays are marked with the same yellow scrawling. The anal fin is comparatively simple, and is uniformly chalk to custard with the usual yellow striations. As is characteristic of the third and final lineage, the ventral fins are very long and trail past the anal fin. In this species, they are variably yellow to dark grey. Cirrhilabrus rubrimarginatus lacks any of the usual dorsal, anal or lateral stripes.
The rubrimarginatus clade members are noted for possessing two epaulettes on the anterior dorsum and posterior ventral region, respectively. The first is usually present on the base of the dorsal fin and/or dorsum, and the second, just above the anal fin. In C. rubrimarginatus, this feature is only weakly present, but in large terminal males, these can be observed in a darker and slightly more contrasting shade than the ground coloration.
This species, like the others in this clade, displays prominent lightening of the median fins during nuptial display. Both dorsal and anal fins glow in a bright white, except for the anterior dorsal epaulette, which darkens to an inky maroon. A lateral suffusion of fulvous orange often develops during this period of excitation, and this corresponds most closely to a medial stripe. This feature, although only temporarily displayed during nuptial flashing, is salient in our discussion of this species from other regions later on.
The epaulette during nuptial display is bi-colored, with demarcations corresponding to the dorsal fin margin. The outer margin is a dark maroon to black, and the inner portion is olive.
In extremely excited males at the height of nuptial display, the dorsal, anal and caudal fins are clamped down, and lightens dramatically to bright white. This white can be stodgy enough to obfuscate the brilliant red margin on the caudal and dorsal fins. The head and body, likewise, becomes frosted in a powdery ivory, with an almost waxen and downy quality.
This species is very widely distributed across the Pacific. It is found in Japan and Taiwan, down to the Philippines, much of Indonesia, Palau, and east to Papua. This species reaches Melanesia in its easternmost distribution, where the population differs slightly from the Western Pacific counterparts. In line with the biogeographic ecozones of the Pacific Ocean, the Japanese, Western Pacific and Melanesian populations may harbor genetic divergence despite their outwardly similar appearance.
It is replaced entirely in the Coral Sea and Micronesia by C. lineatus and C. rhomboidalis, respectively. The distribution of these three species are almost completely allopatric, except for a very small overlap in Palau where both C. rhomboidalis and C. rubrimarginatus can be found. No hybrids have been documented between the two, despite the narrow sympatry.
Cirrhilabrus cf. rubrimarginatus (Western Pacific – Indonesia and the Philippines)
Cirrhilabrus rubrimarginatus shows slight variations in Indonesia and the Philippines. This is not surprising, seeing as numerous taxa show divergence and speciation in this region. A parallel comparison can be seen in Cirrhilabrus cf. exquisitus, where Japanese and Indonesian specimens differ greatly in appearance. As mentioned previously, consistency should be applied with the taxonomic treatment of these species. If Cirrhilabrus cf. exquisitus is made liable for splitting based on the premise of biogeographic isolation and polychromatism, then the same should be expected of C. rubrimarginatus.
Specimens from this region differ in having a fulvous orange suffusion slated laterally across the body. This suffusion is delimited by an imaginary boundary that corresponds almost perfectly with a medial stripe. This feature is the closest resemblance to a lateral stripe seen in C. rubrimarginatus, but is restricted to specimens from this region only. This same stripe can be seen in nuptial display of the Japanese forms. However, there, it is temporary and only appears when the fish is excited. In Indonesia and Philippines, it retains its presence even when the fish is at rest. In large terminal males, this feature is actually very apparent and recognizable from far.
This is the commonest form of the species that an aquarist is likely to encounter in the trade. It is moderately expensive and common.
Cirrhilabrus cf. rubrimarginatus (Melanesia – Fiji, Tonga and Vanuatu)
The Melanesian population of this species is known primarily from the regions of Fiji, Tonga and Vanuatu. Phenotypically, they harbor considerable differences in coloration from the type species, especially in the posterior dorsum. Melanesian males are generally more colorful, and have the propensity to develop a striking Barbie-pink stripe on the posterior dorsum. This is very rarely present in the Western Pacific form, and even so, is usually matte orange and never quite as neon.
The ground coloration, as with the type species, ranges from cloud gray, to light pink, to salmon, although it is often much darker and ominous than the preceding phenotypes. This regional form is rarely with any fulvous suffusion in both its resting or nuptial state. The teal coloration on its ventral regions and the prominence of the yellow facial spots are much more salient in this phenotype.
In nuptial display, the dorsal and anal fins turn bright white, except for the anterior epaulette in the dorsal fin, which darkens to a dark maroon. The pectoral fin darkens to a transluscent orange. The pink streak on the posterior dorsum lightens, but otherwise no change is seen in the body. There is no development of any orange suffusion seen in the Japanese and Indo-Pacific forms.
At the peak of nuptial display, the entire body becomes frosted in a powdery white, including the red margin on the caudal fin. The median fins, instead of fanning out, are clamped down and pressed tightly against the body.
Cirrhilabrus cf. rubrimarginatus from Melanesia is uncommon and moderately expensive. The regional polychromatic variants of Cirrhilabrus rubrimarginatus may warrant further study, and DNA comparison is inevitably needed to see if any form of genetic drift has taken place. It is obvious that this taxon is only at the precipice and incipient stages of divergence, but it is important that we remain consistent in our work.
[Update] A recent survey has revealed the presence of this species in New Caledonia, where it was found together with Cirrhilabrus lineatus. Like with C. rhomboidalis, Cirrhilabrus rubrimarginatus now mixes with its Australian sister C. lineatus in this very narrow overlapping contact zone. This serves as a range extension, making New Caledonia the easternmost limit for the Melanesian phenotype. This photo was added post completion of this article.
Cirrhilabrus lineatus
This glorious species replaces C. rubrimarginatus in the Coral Sea and New Caledonian region. The magnificent C. lineatus is decorated in a cornucopia of color, starting with a variable ground coloration ranging from grey-slated lavender, to salmon, to coral, to bright yellow-orange. The specific epithet “lineatus” comes from the word “line”, and this feature is heavily represented on its face and body. A complicated series of fine cobalt striae decorates the entire head, breaking up randomly into a series of shorter streaks and spots as it travels toward the posterior.
Cirrhilabrus lineatus is the only species in this clade to possess the usual body stripes, and presents a prominent and complete dorsal stripe starting from the upper orbital limit to the caudal peduncle. A corresponding anal stripe runs along the base of the anal fin, and a lateral stripe is also present (although this is highly vestigial, broken and always incomplete).
The dorsal fin is an amalgamation of rich pumpkin and corn yellow, with a blueberry epaulette present at the base of the anterior spinous portion. This epaulette threads out along the length of the dorsal fin, forming the inner edge of the dorsal fin border. The border is not filled with any contrasting color, and it is homogenous with the rest of the fin. The dorsal fin epaulette is paired with a corresponding one placed just along the edges of the anal fin, in the same shade of blue. These markings are very obvious in Cirrhilabrus lineatus, unlike its sister Cirrhilabrus rubrimarginatus, where this feature is unobtrusively displayed.
The pectoral fins are translucent and colorless, and the caudal fin is strawberry red with numerous fine striae set in a rough, semicircular pattern. A metallic blue thread borders the edge. As in keeping with this lineage, the pelvic fins of C. lineatus are long, often trailing past the anal fin origin. The base of the fin is often suffused in dark navy, and the fins itself are yellow, edged in blue.
Like C. rubrimarginatus, this species is burly and rather unbecoming of a fairy wrasse. Although various literature states 11cm as its maximum size, this species has shown great potential in hitting lengths of up to 13cm with ease.
This species in nuptial display recalls that of C. rubrimarginatus. At the height of nuptial flashing, the body lightens to a grey-olive, while the dorsal, anal, caudal and body stripes and lines scintillate in metallic cerulean. The pectoral fin intensifies from transparent to transluscent tangerine. Both dorsal and anal fins glow in a bright white, except for the anterior dorsal epaulette, which darkens to an inky blue. This epaulette during nuptial displayed is bi-colored, with demarcations corresponding to the dorsal fin margin. The outer margin is light chartreuse yellow, and the inner portion is dark inky blue. The caudal fin accentuates to a beautiful violet-red with the blue scrawling becoming increasingly iridescent.
Cirrhilabrus lineatus is restricted within the Australian eco-region of endemism. It is found only in Northeastern Australia from the Great Barrier Reef to the Coral Sea, reaching its limit at the Loyalty Islands in New Caledonia. This species can be found in all usual depths starting at 12m (40ft), becoming increasingly common at 20-30m. It has been recorded at 105m (340ft), although this is very atypical and unusual for the species. As with all Cirrhilabrus, its habitat comprises of barren rubble pans along reef slopes adjacent, or away from coral reef proper.
This species is moderately common in the aquarium trade, but fetches a high price tag of at least a couple of hundred dollars.
Cirrhilabrus rhomboidalis
Cirrhilabrus rhomboidalis has captivated the hearts of aficionados around the world with its one of a kind, unique brilliance. This species possesses some of the most unusual and characteristic patterns in the genus, and it absolutely cannot be confused for any other species. The ground coloration ranges from ivory to chiffon gold, and the face is festooned in an indecipherable hieroglyphic network of aurelian filigree. The head is variably shaded in purple, and the facial scrawling breaks up into a fine ramifying network of sinuous, lacey streaks and spots that travel along the length of the fish.
The paired dorsal and anal epaulettes are prominently displayed in orchid purple on the anterior dorsum and posterior ventral regions, respectively. The dorsal fin is hyaline but copiously inscribed in a complicated network of gold squiggles. The anterior spinous portion of the dorsal fin is purple in line with the dorsal epauelette, and this extrapolates to form a thick border along the fin edge. This border is variable, and can be homogenous in coloration with the rest of the fin, or demarcated in a contrasting purple. The anal fin is patterned similarly but borderless. The pelvic fins are long, and trail past the anal fin in matured males.
Because of a disproportionate elongation of the central rays, the caudal fin fans into a rhombus, or in very terminal males, a tapering diamond. This has led to the colloquial naming of “Rhomboid”, or “Diamond-tailed Fairy Wrasse”. The caudal fin is decorated in the same golden scribbling, but this decreases in concentration towards the central region. Very large males sometimes possess a large purple patch on the posterior body, which, interestingly, becomes very evident post mortem.
The unusual dichromatic combination of purple and gold is not seen in any other species. Cirrhilabrus rhomboidalis is to me, one of those things that exude an intangible association with lavish regalia, and its appearance recalls that of an Egyptian sarcophagus.
In nuptial display, the entire fish turns bright yellow, and the hieroglyphic markings light up in an electrifying gold. The dorsal and anal epaulettes darken to a deep indigo, and a light medial saddle that develops during display connects these two regions. This saddle is very unusual and characteristic to this species, and is shared with no other members of the rubrimarginatus group (but it might be homologous to a similar pattern seen in other related grpups, i.e. temminckii).
The dorsal, anal and caudal fins turn light indigo, and when fully excited, are clamped down and held tightly against the body. The bright indigo coloration extends into the nape, up to the upper lip, as well as throughout the ventral region.
Cirrhilabrus rhomboidalis is restricted to Micronesia, where it is sister to C. rubrimarginatus and C. lineatus. Because of C. rhomboidalis’ unusual caudal fin shape, the species was thought to be more closely associated with the lanceolatus group in the past. In this article, we’ve discussed the similarities in features it shares with C. rubrimarginatus and C. lineatus, proving that its unusual diamond-shaped tail is nothing more than an unusual evolutionary feature from the rest.
C. rhomboidalis was long regarded as a Marshallese endemic, restricted to Kwajalein Atoll. Deepwater explorations of the surrounding regions have since revealed its range to be much larger than previously thought, and the species was later discovered in Majuro. Its current distribution includes Yap and Pohnpei to the west, as well as Palau and Saipan, where the species is at the edge of its range. In Palau, it overlaps with Cirrhilabrus rubrimarginatus, its sister species. This very slight sympatry is not uncommon at the boundaries of allopatric species. No hybrids between the two have been documented yet. Overall, this species maintains its stronghold within the Federated States of Micronesia and the Marshall Islands.
C. rhomboidalis is found in the typical rubble pan settings at depths between 35-50m. It can be found much deeper, often in excess of 60m. This species sometimes frequents Halimeda infested patches, much like those enjoyed by C. johnsoni. The species is moderately rare in the trade where it commands a high price. This species used to be one of the most sought after and revered of the Cirrhilabrus, but it has since relinquished its title to some of the newer, swankier species to hit the trade.
The pylei clade
This clade features three members that are restricted chiefly within the Western Pacific region. The species are presumably sisters, and are entirely allopatric. They are Cirrhilabrus pylei, Cirrhilabrus cf. pylei and Cirrhilabrus katoi. Cirrhilabrus cf. pylei is currently undescribed, and although it superficially greatly resembles C. pylei, it presents traits that are also in line with C. katoi. Cirrhilabrus katoi is another anomaly, with traits that appear unique and inconsistent with this group.
Uncertainties aside, the three species in this clade share certain unifying qualities. The males present with fine striae on the face, which recalls those seen in the rubrimarginatus clade. The dorsal fins are tall, rounded and heavily inscribed in sinuous scrawling – especially in the pylei sisters. The caudal fin is edged in a margin of highly iridescent scales that changes color based on the angle of incident light. With the exception of Cirrhilabrus katoi, the other members of this clade are remarkable for possessing some of the longest pelvic fins to be seen in any labrid.
Cirrhilabrus pylei
Cirrhilabrus pylei is variable in its coloration, ranging from beige, to fulvous orange, to gray-slated carnation. The face is heavily striated in fine lines, which break into spots near the operculum. Unlike the members of the rubrimarginatus clade, these lines do not spread past the head into the body. The body, however, is very finely punctuated in a series of miniscule, unobtrusive spots. A dorsal stripe is present, but this is very vestigial and nascent. A lateral stripe is also present, but it is always broken, highly vestigial and restricted to the caudal peduncle.
The dorsal fin is rounded and slightly taller in the central rays, lending a very slight semicircular appearance when fanned opened. It is transluscent rose pink and heavily inscribed in a labyrinth of blue and yellow squiggling. The anal fin is marked similarly, but with a reduction in the squiggling. The caudal fin is variably colored in a reddish-orange, and is edged on the outer margin in a highly iridescent and reflective blue border. This scintillating caudal margin is an important recurring feature seen in this clade, and changes color depending on the angle of incident light.
This species is remarkable for possessing some of the longest pelvic fins of any labrid. Unlike other Cirrhilabrus, the pelvic fins of C. pylei are very stiff and non-pliable. As such, although trailing and filamentous, they maintain integrity and form even when fully extended against moving water. Males are able to erect and retract these fins independently, flicking them during display. This pelvic fin morphology and behavioral usage is rather unique, and it is only seen in members belonging to this lineage. In this species, they are translucent yellow and edged in blue.
This species intensifies into a bronzy-yellow during nuptial display. The dorsal fin intensifies into a deep red and becomes opaque, obfuscating the underlying squiggling. The most noticeable characteristic during this heightened state of excitation is the brilliant caudal scintilla displayed on the outer margin of the tail. Depending on the angle of incident light, the margin scintillates in an iridescent blue to cyan, to seafoam or turquoise, and can be so intensely reflective that it appears white. Conversely, when no available light is reflected on this margin, it resumes a dull purple.
This species is widespread across the Pacific Ocean, ranging from Bali, to West Papua, Papua New Guinea and east to Vanuatu. It frequents deep water and is commonest at depths of 55m and below, inhabiting the usual rubble pans and slopes adjacent to reef walls. Despite its large range, this species, unlike C. rubrimarginatus, does not show any phenotypic differences throughout its distribution. Further north in the Philippines, this species is replaced by the undescribed Cirrhilabrus cf. pylei. The two have an unusual biogeography in that they split the Coral Triangle, with each occupying opposite ends.
This species is fairly uncommon in the trade, and is moderately expensive. It is more frequently encountered from Vanuatuan exports than Indonesia. Females are less frequently offered than males.
Cirrhilabrus cf. pylei
In this species, the ground coloration is a uniform peach to salmon, and the body scales are edged rather unobtrusively in lilac. The facial pattern is identical to Cirrhilabrus pylei in having numerous fine striations and streaks. A prominent dorsal stripe is present, which is only extremely weakly present in C. pylei. It possesses a lateral stripe, but this is always broken and restricted to the caudal peduncular region.
The dorsal fin is rather beautiful and intricately designed. The anterior spinous portion is riddled in a complex scrawling of violet and gold. This is very much more noticeable than those seen in Cirrhilabrus pylei. The posterior soft portion is hyaline and relatively unmarked. A large black spot is placed medially along the spinous and soft ray interface, and this is irregularly streaked in metallic blue. This dorsal fin spot is an important feature, which foreshadows a confusing relationship with the next species, Cirrhilabrus katoi.
The caudal fin is rather unusual for this species. It possesses the usual scintillating band in lilac, but this is reduced and placed submarginally against a thick black border. This black tail margin is seen in only one other species, and it is the distantly related Cirrhilabrus claire. Because the latter lacks any of the rubrimarginatus group characteristics and shows features more in line with the jordani clade, the two are likely not closely related and the similarities in caudal fin color could be nothing more than convergent evolution. The anal fin is yellow with the usual blue squiggles, and the pelvic fins are extremely long, stiff and white.
Because this species shares characteristics of both Cirrhilabrus pylei and C. katoi in morphology and coloration, it is difficult to determine which of the two it is more closely related to. Biogeographically, it sits right in between the two species, where it appears to form a link between Cirrhilabrus pylei and Cirrhilabrus katoi. In comparing C. pylei, C. cf pylei and C. katoi, a smooth transition in shared characteristics can be observed. As such, without genetic comparison, it is difficult to determine the exact cladistic relationship between these three species.
In nuptial display, the dorsal and lateral stripe glows in a scintillating light blue. This is accompanied by the flashing of the facial lines, scale markings as well as the dorsal fin blotch. No observable change in body color appears to occur. The black margin on the caual fin remains the same, but the submarginal band reflects in a highly chatoyant iridescence in the same way as with C. pylei.
Cirrhilabrus cf. pylei is restricted to Central Philippines in fairly deep waters. Dr. Luiz Rocha, together with the California Academy of Sciences, has collected a fair number of this species from Anilao, Philippines. It is with hope that it gets a proper description in the foreseeable future. This species is common in the trade and only moderately expensive.
Cirrhilabrus katoi
Long regarded as a Japanese mythos, Cirrhilabrus katoi is a lesser-known species of opulent sybaritic beauty. In this exuberant species, the ground coloration is a rich orangey red. The face is ornately decorated in the usual facial lines and striae, and a pair of prominent facial stripes are additionally present. Both stripes diverge in opposite directions past the orbital limits, with the upper stripe extending along the dorsum to form a complete dorsal stripe. The lower facial stripe runs along the cheek, before connecting loosely to a prominent lateral stripe which runs equatorially along the entire length of the fish.
This lateral stripe sharply delimits the reddish body from the eggshell-colored lower half. This lighter ventral region is heavily streaked in a horizontal series of broken lines. Cirrhlabrus katoi is the only species in this group to feature a complete set of both dorsal and lateral stripes.
The dorsal fin is a veritable kaleidoscope of reds, yellow and orange. A small blue ringed black spot is present in the first intermembranal space of the dorsal fin. This small but characteristic feature is present in C. pylei and C. cf. pylei as well. A series of metallic blue spots and squiggles adorned the dorsal fin in its entirely, but this is never as extensive or well reticulated as with the pylei sisters. A large black spot is present at the start of the soft dorsal region, and this is loosely spotted in a circumference of metallic blue.
The pelvic fins are long, but are never trailing as with the pylei sisters. Its anal fin is extremely lobular, large and colored in a brilliant ruby. This is sometimes punctuated with metallic blue spotting. The caudal fin is highly chatoyant and prismatic, and ranges in color from purple, pink, yellow, green or cyan depending on the angle of incident light. The caudal fin is edged in a blue-green margin of extremely iridescent scales, and this scintillates in accordance to the ambient light as well.
In comparing the three species, we see a smooth transition in the development of the key features, as we move northwards from Indonesia, to the Philippines, and finally to Japan. These three regions correspond to the biogeography of the three sisters, and below are some of the comparable traits.
1) Dorsal fin medial spot
Moving northwards from Indonesia, to the Philippines and then to Japan, we see the increased development of the medial spot on the dorsal fin. The southernmost C. pylei in Indonesia lacks this trait, while the intermediate C. cf. pylei in the Philippines shows an incipient development of the dorsal spot. The northern most C. katoi in Japan shows full development of this spot, and, in some specimens, may extend lengthways to invade the entire soft dorsal fin.
2) Dorsal fin squiggling
Conversely, moving northwards from Indonesia to the Philippines and then to Japan, we see a decrease in the dorsal fin squiggling. In C. pylei, this squiggling is present throughout the dorsal fin, while in C. cf. pylei, this is confined only to the anterior spinous portion. The soft rays are entirely void of this feature. In C. katoi, a further reduction of the dorsal squiggling is seen, and the fin is decorated with spots and broken streaks instead. The small spot present at the first dorsal fin spine is also increasingly prominent as one moves from the sourthern most C. pylei, to the northernmost C. katoi.
3) Dorsal and lateral stripes
The dorsal and lateral stripes are also observed to increase in prominence moving from Indonesia to Japan. In the Indonesian C. pylei, both stripes are vestigial and poorly expressed. C. cf. pylei in the Philippines presents with a complete and fully formed dorsal stripe, while the lateral stripe remains broken and restricted to the caudal peduncle. In C. katoi, both stripes are fully developed and prominently displayed.
4) Pelvic fins
While the pelvic fin lengths of the pylei sisters are equally long and well developed, the northernmost C. katoi lacks any of the filamentous extensions. The isolation of C. katoi in this region has presumably resulted in the loss of its pelvic fin extensions.
Because of these traits and the equivocal arguments that can be made in the cladistic pairings of the sisters, we are unable to confidently present a phylogenetic tree for this clade. This is where genetic analysis of their DNA will come in handy in determining the precise closeness of the sisters.
The incomparable beauty of this species in nuptial display is second to none. When flashing, this species transforms into a blazing ruby throughout. The ventral portion lightens to bright white, and the dorsal and lateral stripes light up in an iridescent seafoam green. All the spots, streaks and vestigial squiggling in the median fins likewise scintillate in the same brilliance.
The caudal fin is of particular interest. The reader may find this constant repetitive harping on the caudal scintilla to be redundant and boring, but this is where its placement in the pylei clade really shines, and in nuptial display, its prismatic qualities are heightened beyond belief. It is also noteworthy of mention that this feature is an ethereal peculiarity that cannot be digitalized on camera. The collage above is a poor attempt at showing the various opalescent qualities of the caudal fin in various light conditions during its nuptial display, but this is a severe bastardization of its true beauty. If you own this species at home, you’ll know what we mean.
[Update] The video above demonstrating the caudal scintilla was added post completion of this article.
As if the males were not aberrant enough, this species presents us with another highly unusual curveball. Its female form bears almost no resemblance to those seen in the rubrimarginatus group. Its uniformly orange body coupled with fine striations bears a closer resemblance to the females of the lunatus group instead.
While this indecipherable female leaves much to think about, it could potentially foreshadow Cirrhilabrus katoi’s role as a more ancestral species, with traits that are still retained from the origin of various groups. Again, this is something beyond our current abilities, and the unusualness of its female form is best left unexplained, for now.
Since its description in 2000, C. katoi was known only from Izu and Kashiwajima in Southern Japan. Its endemism was broken earlier this year in 2015, when numerous specimens were collected from Aparri, Cagayan, in the northern tip of the Philippines. The range extension of C. katoi into the Philippines was accompanied by Cirrhilabrus lunatus, and the two species were no longer regarded as strict Japanese endemics. This extension also coincides with the “pintail” fairy wrasse, which spills over from Japan into the northern Philippines.
The gap separating Japan and the northern Philippines are further bridged by the presence of C. lubbocki, C. melanomarginatus, C. cyanopleura, C. ryukyuensis, C. cf. exquisitus, C. rubrimarginatus and C. temminckii, suggesting that there is very little preventing the crossover between these regions. In at least three examples (C. cf. exquisitus, C. rubrimarginatus and C. temminckii), however, there appears to be phenotypic distinction and possible speciation. The other species retain homogeneity across this gap.
The loss of C. katoi, C. lunatus and the “pintail” fairy wrasse calls into question as to whether or not Japan is capable of housing any real endemics. The only Cirrhilabrus that has yet to break this rule is C. lanceolatus. However, the species occurs along the islands of Okinawa and Honshu, making extension into the Philippines unlikely.
C. katoi is found in fairly shallow to moderately deep waters in Japan (60-131ft), but in the warmer waters of Aparri, it compensates by dwelling only in excess of 100ft. Its habitat in Japan consists of rocky, rubble-strewn reefs dominated by kelp and other macro algae. In the Philippines, this species frequents the usual habitat, but the deeper waters probably inhibits much of the usual algae growth.
Since its discovery in beginning of the 20th century, C. katoi has held on tightly to its icon status as a book fish. Extremely few specimens have ever been collected, and these were sold at exorbitant prices to collectors. However, since its recent discovery in the Philippines, its status has been relinquished, and together with the “pintail” fairy wrasse, the species is no longer considered rare. It won’t be long before C. katoi becomes nauseatingly abundant in wholesalers, much like what is happening to the “pintail” fairy wrasse today.
In conclusion, the rubrimarginatus group offers a polar, heaven and earth look at the complexities and simplicities of reef fish biogeography. Both clades feature members with nearly exclusive allopatric distributions, but in the pylei clade, the similarities in all three species have proven too intractable for us to resolve phylogentically. We’ve also taken a closer look at one of the genus’ most unusual and perplexing species, Cirrhilabrus katoi. It is very likely that major amendments and changes to this group will have to be made with the revelation of genetic studies. Cirrhilabrus rubrimarginatus may warrant splitting in future as well, especially the rather distinct Melanesian forms.
We’ve also seen the range extension of C. katoi (a previous Japanese endemic) into the northern Philippines; a phenomenon accompanied by a handful of other species. This Cirrhilabrus coup d’état in Cagayan foreshadows a closer link between the two regions than was previously known, and who knows what else might be uncovered in this biogeographical overlap.
This concludes the end to the first group of the final Cirrhilabrus lineage. The end of this long and grueling series is nearly in sight, and with only one extremely tedious group left in our way (the temminckii group), the rest is relatively smooth sailing from here on.
