Triplefins have demersal brooded eggs and hatch as well-developed larvae around 3-4 mm in length. The early-stage post-flexion larvae can be recognized by a moderately long and narrow body with a small pointed head, medium mouth, prominent jaw angle, large rounded eye, no head spines, snout-to-vent length slightly less than half of body length, long fin bases, and early-forming posterior dorsal and anal-fin elements. Pigmentation is distinctive, with a single midline surface melanophore over the rear braincase and a short row of two or three melanophores along the dorsal and ventral midlines of the caudal peduncle. In addition, there is a row of three ventral midline melanophores along the base of the rear portion of the developing anal fin. There are internal melanophores at the sacculus, over the swim bladder, and around the gut near the vent.
The two more conspicuous labrisomid genera, Malacoctenus and Labrisomus, are frequently observed by divers on Caribbean reefs. The Malacoctenus species are relatively small, usually an inch or two, and ubiquitous on reefs, while Labrisomus species are larger and bulkier (some can reach six inches) and not as common. The two genera are best distinguished (in collections) from their tiny relatives, Starksia and Paraclinus, by fin-ray counts: Starksia have fewer dorsal-fin soft rays and pectoral-fin rays (with a few exceptions) and Paraclinus have all or all-but-one dorsal-fin elements spinous. Despite the obvious differences among adult labrisomids in size and shape, their larvae can appear quite similar and can be a problem to identify, even to genus.
The larvae of Malacoctenus and Labrisomus are difficult to separate since many of their features, including fin-ray counts, can overlap. In addition, there is little diversity in larval markings within these genera and many species have fundamentally similar melanophore patterns. Adding to the problem, most species show some variation in the diagnostic patterns of melanophores, especially the cranial melanophores. Many individuals show less than the full complement characteristic of the species and, occasionally, a variant specimen will have a set of additional markings, notably overlapping the patterns characteristic of other species. I have confirmed this with DNA sequencing, although it is uncommon. DNA sequencing is probably necessary for a firm species identification in some groups and certainly in many earlier stages.
Markings: Most of the variation in appearance among the larvae of Malacoctenus and Labrisomus is in the pattern of melanophores on the head and the presence or absence of melanophores along the fin bases. Otherwise, much of the larval morphology and most of the marking patterns are shared among the many members of these two large genera and diagnostic differences can be quite subtle. Fortunately, this problem is mitigated to some degree by the persistence of larval melanophores through transition, and often well into the juvenile stage, providing useful links to establish species identification.
In addition to the basic set of labrisomid melanophores discussed above, some species, or sets of species, have distinctive patterns of larval melanophores that are indispensable for identifications. A very few melanophore locations are unique to larvae of one species, but combinations are often diagnostic for species. An interesting observation is that melanophores that are characteristic of one species may occasionally (or rarely) be found on other related species to a lesser degree or at a later point in transition. Because of these overlaps, not every larva can be easily assigned to species on the basis of a diagnostic larval melanophore pattern; several characters sometimes need to be weighed in the decision (note that metamorphic melanophore patterns are very specific and diagnostic). No single marking identifies all Malacoctenus or Labrisomus, but some are found only in one genus (but not in all of the species), such as the pair of melanophores behind the tip of the upper jaw on some Labrisomus.
Morphology: Most of the adult characters that separate Malacoctenus and Labrisomus do not apply to larvae. Adults are typically separated by the shape of the snout: pointed in Malacoctenus and blunted in most Labrisomus (except for very pointed in L. nigricinctus). This feature does not apply to the larval stages (or even small juveniles) which have pointed snouts in both genera. Most Labrisomus species develop characteristically thick bulky heads as juveniles and adults, but this too does not apply to the larval stages. Another basic difference in adult fishes is that the rear edge of the maxilla is sheathed in Malacoctenus and exposed in Labrisomus, but this is difficult to assess on larvae.The mouth is typically small in both juvenile and adult Malacoctenus (and L. nigricinctus) and the maxilla extends back only to the level of the anterior orbit vs. large and extending back past the level of the pupil in most Labrisomus. This mouth-size character is the best character for distinguishing juveniles but does not generally apply in larvae, and, when it does, can be quite subtle, although sometimes useful. For example, in the photograph below, the maxilla is distinctly longer in the 15 mm Labrisomus guppyi larva on the left vs. the same-sized Malacoctenus triangulatus on the right (note eye diameters are identical).
The dorsal-fin profile typically differs between genera (and often species). A loose but useful rule for juveniles and adults is that most Malacoctenus have very short penultimate and third-to-last dorsal-fin spines, less than a third the length the longest dorsal-fin soft ray, while many Labrisomus have the shortest dorsal-fin spine about half or more the length of the longest dorsal-fin soft ray. There are certainly exceptions: L. nigricinctus, L. albigenys, and, to a degree, the 19-spined Labrisomus species have short posterior dorsal-fin spines, and M. macropus and M. boehlkei have relatively long posterior spines. The dorsal-fin profiles of larvae do not always match those of juveniles or adults, but they can be helpful, especially for late larvae approaching transition. In general, most Labrisomus larvae have relatively low soft dorsal fins while many Malacoctenus larvae have high soft dorsal fins and short posterior dorsal-fin spines (see transitional larvae below: Labrisomus haitiensis top vs. Malacoctenus versicolor bottom).
Transition: Larvae undergo a rapid and profound transition during the night of settlement as they prepare for life on the reef after living as transparent pelagic larvae in the open ocean. The changes include a new set of markings, longer fins, cirri on the head, and changes in body shape. The genus-level larval differences in mouth size and dorsal-fin profile become more developed. Malacoctenus larvae (right and below) develop distinctly longer cirri early in transition, with the orbital and nuchal cirri often more than a lens diameter in length, while Labrisomus larvae have short and stubby cirri through the transition, although later, as juveniles, their cirri become long and prominent.
In contrast to the similarity in larval markings, the patterns of fine surface melanophores that develop at metamorphosis are often complex and distinctive and thus transitional larvae and recruits can be assigned to species relatively easily. These metamorphic melanophores are usually easy to differentiate from larval melanophores by their much smaller size, their lighter appearance (often appearing brown vs. black), and their occurrence in dense patches or in a dense uniform speckling (occasionally in long strands or lines). Technically, they can be defined as tiny melanophores (about 10-25 microns in diameter, or about 30 into the lens diameter) with multiple similar-sized melanophores within two diameters of each spot. The M. triangulatus larvae illustrated (upper left) has both arrays. Occasionally, some transitional larvae can develop a few additional melanophores that look just like small larval melanophores, i.e. darker and 2 or 3 times the size of metamorphic melanophores (shown on M. macropus at lower left). I refer to these troublesome melanophores as "pseudo-larval" melanophores. In some species, they occur in clusters around fading large larval melanophores, resembling a "fragmentation" of the larval melanophores. An interesting pattern often observed is the tendency of metamorphic melanophores to leave a clear halo around larval (and pseudo-larval) melanophores.
Another general, although less reliable, difference between the two genera is the hunched-over appearance that develops in many transitional Labrisomus larvae (e.g. L. bucciferus at right and L. haitiensis full-body photo above), where the head is generally lower than the body: i.e. the tip of the jaw (and often the center of the orbit) is below the lateral midline of the body. There is also an overall size difference between late larvae, with Malacoctenus generally settling between 10 and 15 mm SL and most Labrisomus settling between 15 and 20 mm SL. There is, however, some overlap between the larger-settling Malacoctenus (e.g. M. triangulatus and M. versicolor) and the Labrisomus species.
The morphology of the two genera diverges rapidly after transition and juveniles can be easily distinguished. Most juvenile Labrisomus have thick bulky heads and large mouths with the maxilla extending past the midline of the orbit and juvenile Malacoctenus are slim and have a small mouth. In addition, Labrisomus juveniles have dark or mottled camouflage and are usually well-hidden in their habitats while Malacoctenus are usually out in the open and have distinctive colors and patterns.
Fin-ray counts: Although there is extensive overlap, fin-ray counts are very useful in this family since the modes within species are relatively strong, often two-thirds or more of the specimens, and the ranges of counts are well-documented. Note, however, that recent evidence indicates that local cryptic species or populations can have slightly variant modes. The species are listed here in order of increasing fin-ray counts (the range, with the known combinations in parentheses).
Counts are mostly from Springer's classic monograph: Springer, V. G.: Systematics and zoogeography of the clinid fishes of the subtribe Labrisomini Hubbs. Pubs. Inst. Mar. Sci. Univ. Texas 5:417492 (1959), often cited as (1958).
M. versicolor: mode D-XVIII,12 and A-II,18-19 P-14 (rarely 11 dorsal-fin soft rays; P-13-14)
M. delalandii: mode D-XX,10 and A-II,19 P-14 (dorsal 19/9-11, 20/9-11, 21/9; A-II,17-20; P-13-15)
M. gilli: mode D-XX,10 and A-II,19 P-14 (dorsal 18/10, 19/10-11, 20/9-11, 21/9-10; A-II,17-21; P-13-16)
M. aurolineatus: mode D-XIX-XX,11 and A-II,19-20 P-14 (dorsal 18/10-11, 19/10-12, 20/10-12, 21/10-11; A-II,17-21; P-13-15)
M. triangulatus: mode D-XX,12 and A-II,21 P-14 (dorsal 19/12-13, 20/11-13, 21/11; A-II,20-22; P-13-15)
M. erdmani: D-XXI,9 and A-II,18-19 P-16 (dorsal 20/9-10, 21/8-10, 22/8-9; A-II,17-20; P-15-17)
M. macropus: D-XXI,9-11 or XXII,8-10 or XXIII,9-10 and A-II,20-21 (range 18-22) P-15 (range 14-16)
M. boehlkei: D-XX,13 or XXI,11-12 or XXII,11 and A-II,22 (range 20-23) P-15
note: Some Starksia species can barely overlap the lower range of fin-ray counts for those few Malacoctenus species that can have 8 or 9 dorsal-fin soft rays and 14 or fewer pectoral-fin rays.
L. albigenys: mode D-XVIII,11 A-II,18 P-13 (holotype recorded as D-XVIII,10 A-II,18, not repeated)
L. nigricinctus: mode D-XVIII,11 A-II,18 P-13 (dorsal 17/11, 18/10-12, 19/11; A-II,17-20)
L. nuchipinnis: mode D-XVIII,12 A-II,18-19 P-14 (dorsal 17/12-13, 18/10-13, 19/11-12, 20/12; A-II,17-19; P-13-15)
L. conditus: mode D-XVIII,12 A-II,18-19 P-14 (dorsal 18/12; A-II,18-19; P-14) Sazima, Carvalho-Filho, Gasparini & Sazima (2009)
L. cricota: mode D-XVIII,12 A-II,18 P-14 (dorsal 18/11-12; A-II,17-19; P-13-14) Sazima, Gasparini & Leao de Moura (2002)
L. gobio: mode D-XIX,11 A-II,19 P-13 (dorsal 18/12, 19/10-12, 20/10-11; A-II,18-20; P-12-13)
L. guppyi: mode D-XIX,11 A-II,19 P-13 (dorsal 18/11-12, 19/10-12; A-II,18-20; P-12-14)
L. kalisherae: mode D-XIX,11 A-II,19 P-13 (dorsal 18/11-12, 19/10-12, 20/10-11; A-II,18-20; P-13-14)
L. bucciferus: mode D-XX,11 A-II,20 P-13 (dorsal 19/11-12, 20/10-12, 21/10; A-II,19-21; P-12-14)
L. haitiensis: mode D-XX-XXI,10-11 A-II,20-21 P-14 (dorsal 20/10-12, 21/10-11, 22/10-11; A-II,18-22; P-13-15)
L. filamentosus: mode D-XXI,12 A-II,21 P-13
note: some chaenopsid blennies overlap the fin-ray counts of many of the labrisomids listed above: i.e. the genus Emblemariopsis and Coralliozetus cardonae (D-XVIII,12 A-II-20 (dorsal 17-19/10-13; A-II,18-24; pectoral 11-13) and (rarely) Emblemaria vitta (D-XVIII-IXX,13-14 and A-II,19-20).
The labrisomids, or scaled blennies, are mostly small and inconspicuous fishes commonly found on and around Caribbean reefs. They comprise one of the largest families of New World reef fishes, with more than 50 regional species and many more cryptic species (distinct genetic lineages with subtle morphological differences) waiting to be described. Labrisomid genera tend to be speciose and species-level identifications are generally difficult. Fortunately, almost all the Atlantic labrisomids belong to just four genera. The larger and more conspicuous members belong to Labrisomus, presently with eleven Caribbean species (including two recently described species from Brazil but found widely in the Caribbean), and Malacoctenus, presently with eight Caribbean species. The two other genera, Starksia and Paraclinus, contain numerous species and are tiny and elusive, typically well-hidden and rarely encountered or photographed by divers. The remaining regional labrisomids are two obscure deep-water genera with a single species each: Nemaclinus atelestos, found on deep reef walls, and Haptoclinus apectolophus, an enigmatic species found only on the Arrowsmith Banks off the Yucatan at 1,000 feet deep. Labrisomid larvae are very common in collections around Caribbean reefs and are present in more than 90% of my daily larval collections from Panama. They can be recognized by their long narrow body, large round eyes, and short pointed snout, with a long continuous dorsal fin with numerous slender spines, a long anal fin with just two slender spines, a very short and narrow caudal peduncle, pelvic fins thoracic (in front of the pectoral fins) with only 2 or 3 long strand-like rays (not markedly curled-up over the body), no obvious head spines, no silvery peritoneal lining, and light markings. The markings vary little within the family and typically comprise a row of melanophores along the anal-fin base (sometimes also the dorsal-fin base) and a pattern of spots on top of the head. These larval characters are shared with the larvae of the closely-related hole-dwelling blennies of the family Chaenopsidae, which are similar in appearance to larval labrisomids but much less frequent in larval collections. The chaenopsid blennies are distinguished mainly by having more dorsal-fin elements (although there is a small overlap): most chaenopsids have more than 31 dorsal-fin elements, often with 13 or more soft rays, while regional labrisomids have 12 or fewer dorsal-fin soft rays (with a rare 13) and rarely have more than 32 total dorsal-fin elements. The Caribbean chaenopsids that can overlap the low dorsal-fin counts of labrisomids are Coralliozetus cardonae and the Emblemariopsis species, along with the rare Emblemaria vitta. The larvae of these chaenopsids can be distinguished from similar labrisomid larvae by their smaller size at stage, fewer markings, and their mostly differing modes and combinations of fin-ray counts, as well as fewer procurrent caudal-fin rays. The taxonomic features generally separating the two families, i.e. scales on labrisomids and scales absent on chaenopsids and a set of osteological characters, are useless for larval stages. The unusual genus Stathmonotus is still considered chaenopsid even though their dorsal fin is made up of all spines and they can have scales. Some labrisomids of Paraclinus also have a dorsal fin made up of all spines; fortunately the larvae of the two genera are easily distinguished by morphology. Labrisomid larvae generally resemble those of the other blennioid families of reef fishes- they can be distinguished easily from larvae of the combtooth blennies (family Blenniidae), which have fewer dorsal-fin spines than soft rays and blunt snouts at all stages (labrisomids have twice as many dorsal-fin spines as rays (or more) and pointed snouts as larvae). Larvae of the blennioid triplefins (family Tripterygiidae) have three separate dorsal fins and distinctive markings and the stargazers (family Dactyloscopidae) have relatively foreshortened anterior bodies and curled-up pelvic fins. Larval labrisomids are superficially similar to the larvae of gobies and scarids, which also often have a similar anal-fin row of melanophores and are very common in collections and are about the same size as labrisomid larvae. However, those larvae notably have many fewer dorsal-fin spines, short and/or fused pelvic fins, and narrowed or oddly-shaped eyes, while later-stage labrisomids have long thread-like pelvic fins and large round eyes. Larval gerreids (mojarras) are also common and can be mistaken for labrisomid larvae, however they have silvery abdominal linings. Larval grunts (Haemulidae) often have an anal-fin row of melanophores and can resemble earlier-stage labrisomids, but they develop a notably short anal fin and characteristic tail spots.
Labrisomid larvae share, to varying degrees, a basic set of melanophores that develop progressively after hatching and are very useful for identifying larvae at least to genus and often to species. The timing of the development of each marking can be somewhat variable within a species, resulting in a variety of patterns on earlier-stage larvae that preclude a simple key to species identification. Late and pre-transitional larvae typically have their full complement of larval melanophores, making identifications at these larger sizes somewhat easier. During transition, however, larval melanophores begin to disappear and metamorphic melanophore patterns develop. Metamorphic melanophores consist primarily of intricate patterns of small surface melanophores, usually starting on the head and spreading over the body to form the juvenile markings. This transitional sequence is also variably timed, promoting a proliferation of intermediate melanophore complements that can easily lead to the impression of a greater number of species than are actually present. The basic melanophore complement on most labrisomid larvae comprise the following list, from head to tail: note: a number of other melanophores are present at specific, and often diagnostic, locations on the larvae of particular species (or groups of species) and are discussed under the genus or species descriptions in the next sections.
Cranial: These dorsal melanophores shield the brain and are near the surface, usually on the meningeal membrane or over the skull. They can best be labeled by the quadrant of the brain they overlie, i.e. the forebrain, the smaller lobes forming a triangle between the eyes, and the large midbrain (optic) lobes, behind the eyes (forebrain or midbrain cranial melanophores). They are present in differing patterns on many of the larger labrisomid species and are usefully classified as midline or paired (side-by-side) and uniformly large or a range of sizes. (left: M. macropus with paired midbrain cranial melanophores) fc mc
Deep Nuchal: This large midline melanophore develops in the early stages at or just after hatching in most labrisomid genera (deep nuchal melanophore). It lines the musculature behind the braincase, overlying the brainstem and the exit of the spinal cord. In early stages it is near the surface but becomes deeper and progressively more obscured in larger well-developed larvae (but still diagnostically important). It is rarely absent on larvae in those genera after the very early stages. (left: M. macropus, with nuchal muscle removed) dn
Cheek: The cheek melanophore lies just under the upper edge of the preopercle on each side and is characteristic of some labrisomid genera. The cheek melanophores develop on later larvae and can be variably absent on mid-stage larval samples. On well-marked later-stage larvae of those genera, the cheek melanophores are virtually always present. ch
Otic: Larvae of most labrisomid genera have one or two melanophores on the capsule that surrounds the otoliths, likely protecting the hair cells of this sensory organ critical to balance and hearing. These deep internal melanophores are placed on each side of the lower braincase, just above the gill cavity, and are visible on early-stage and more translucent larvae. They are often obscured on well-developed larvae (otic melanophore). ot
Isthmus: The ventral midline forward of the pelvic fins, the isthmus, can be divided into an anterior portion running from the cleithral symphysis forward to the hyoids and a posterior half from the cleithral symphysis back to the insertion of the pelvic fins (this segment overlaps the pelvic fin musculature, a triangle with the apex near the cleithral symphysis). Melanophores can be located anywhere along the isthmus, but are usually at the mid-isthmus (around the cleithral symphysis) or the posterior isthmus, which merges into the pelvic fin musculature. If the melanophore extends along the symphysis between the fin insertions, it can be considered a pelvic-fin melanophore (anterior, mid-, and posterior isthmus melanophores). (left: Starksia robertsoni with pinpoint mid-isthmus melanophore) ai, mi, pi
Pelvic-fin Base (including Transverse Septum): Melanophores can be at several locations around the pelvic-fin base. There is commonly a deep midline melanophore beneath the pelvic-fin insertion (deep pelvic melanophore). On early-stage larvae, this melanophore can be seen covering the transverse septum, the membrane separating the pericardial (thorax) and peritoneal (abdominal) cavities (the pericardioperitoneal membrane), and it may function to shield the thoracic organs from sunlight. The deep pelvic melanophore can extend to the surface at or forward of the pelvic-fin insertion, or there can be a separate surface melanophore, often linear, along the pelvic symphysis near the base of the rays (surface pelvic melanophore). Less commonly, there can be a melanophore tucked behind the base of the rays, technically on the abdomen and sometimes connecting with the transverse septum (post-pelvic melanophore). As larvae develop, the deep melanophore can become obscured, but is still an important diagnostic character. (left: Paraclinus fasciatus above with mid-isthmus and deep pelvic melanophores; below Starksia occidentalis with additional abdominal) dp, sp, pp
Dorsal and Posterior Peritoneum: Two or three large melanophores overlie the abdomen and are usually expanded to shield the viscera, i.e. along the dorsal aspect of the swim bladder and extending along the rear wall of the abdomen to surround the hindgut; both locations are technically retroperitoneal, just outside the peritoneal cavity. They are present as a rule on all labrisomid larvae at all stages, but are not visible on well-developed larvae (retroperitoneal melanophores). rp
Anal-fin Base Row: A row of melanophores along the posterior ventral midline is present on all labrisomid larvae, typically one at the base of each anal-fin soft ray and sometimes at the base of the spines as well. On earlier-stage larvae, only some of the anal-fin rays have an associated melanophore and the sequence of development of the row can be a useful character. Some melanophores in the anal row can be irregular, either larger or deeper (often both), and then are an important diagnostic character. .(anal row melanophores). (left; Starksia occidentalis with larger deeper last one) The total posterior ventral-midline melanophore count is a useful screening tool for larvae, counting both anal row and ventral caudal peduncle melanophores. pvm
Ventral Caudal Peduncle: The anal-fin row of melanophores extends past the fin onto the caudal peduncle in many species, ending at or before the start of the procurrent caudal-fin rays (non-segmented rays). These melanophores are often variable in number and placement. Technically, the melanophore just after the base of the last ray should be considered part of the anal row if still touching the ray or pterygiophore (ventral caudal-peduncle melanophores). vcp
Metamorphic Melanophores: During the settlement transition, larvae rapidly develop patterns of tiny surface melanophores that are usually easily distinguished from the larger and darker larval melanophores. Larval melanophores, typically isolated and discrete, extend below the surface and are often dendritic, while metamorphic melanophores form intricate patterns, usually species-specific. The two sets of melanophores can coexist for some period after settlement, providing a useful link between larvae and clearly identifiable juveniles. (left: transitional larva of Malacoctenus triangulatus with metamorphic melanophores and persistent cheek and midbrain cranial larval melanophores)
Labrisomids have demersal brooded eggs and hatch several days after fertilization as well-developed larvae around 3 mm in length. The early-stage post-flexion larvae can be recognized by a long, narrow, tapering body with a small pointed head, medium terminal mouth, relatively large, mostly rounded eye, a few small preopercular spines (or none), snout-to-vent length slightly less than half of body length, a short caudal peduncle with long dorsal and anal-fin bases with early-forming posterior elements on the dorsal fin and inconspicuous slender spines and rays. Pigmentation follows the genus-level identification patterns, primarily various head and ventral midline melanophores. Before larvae develop their full complement of fin rays and melanophore patterns, species-level identifications would often require DNA sequencing. The pigment pattern on the common Malacoctenus macropus larvae comprises a deep nuchal melanophore, usually one or two midbrain cranial melanophores, a cheek melanophore, and the anal row extending onto the ventral midline of the caudal peduncle. There are internal otic and retroperitoneal melanophores.
There is sufficient divergence in appearance among labrisomid larvae in the region to identify most later-stage larvae to species and all to the genus level. The exceptions are those species recently shown by DNA sequencing to be made up of sets of closely-related species that can be hard to distinguish, even as adults (i.e. cryptic species). Some labrisomids, unlike most other reef fishes, have benthic eggs and short larval lives which promote reproductive isolation and genetic divergence within the region. As a result, there can be a proliferation of cryptic species and lineages and quite complex phylogeography. The larvae and juveniles of cryptic species would be expected to be almost identical and are thus pooled into a type for that species complex in the descriptions below.
Larval identifications are possible in the labrisomids using a combination of marking patterns, fin-ray counts, and morphology. Basic body shape is often useful as a preliminary screen, typically a gestalt rather than a conscious calculation of proportions, usually narrowing down the identification to genus. Melanophore patterns are easily observed and most useful for separations, but they are rarely species-specific and show a troublesome propensity to vary. Nevertheless, in combination with other features, marking patterns can quickly identify most larvae. Fin-ray counts are also rarely diagnostic on their own, but can be required for the identification. Counts can be laborious but sometimes necessary, especially on ambiguous-appearing larvae. Specific morphological characters, especially the relative lengths of fin elements, occasionally are the deciding factor.
The Diagnosis paragraph under each species listed in the following sections describes the criteria that confirm the species designation for a larval type, usually the fin-ray counts, narrowing the possibilities to one or a few species and sometimes a morphological feature to distinguish among the remainder. Of course, a DNA-sequence match is the ultimate confirmation. A sequence match has been used for many of the taxa described below, indicated by the notation (DNA). The Analogues section briefly describes how to distinguish larvae at particular stages from other similar-appearing species, highlighting which of the characters- fin-ray counts, melanophore patterns, morphology, or various combinations thereof- are most useful for each comparison. In most cases, especially for late-stage larvae, these features can rapidly narrow down an ID to the species level.
Some diagnostic characters are more easily visible on larvae than on larger fishes. One of the more obscure characters that is useful for distinguishing among the numerous blennioid families and genera is the number of procurrent rays in the caudal fin. These accessory rays are defined as the non-segmented rays anterior to the large segmented caudal-fin rays. The transparency of fish larvae allows for an easy assessment of the number of procurrent caudal-fin rays. Adjustment of the transmitted-light angle highlights bony tissues well. Fortunately, the caudal-fin rays are usually preserved in otherwise-damaged larvae and they can provide diagnostic information for identifications when little else is available.
There is a quite consistent count of 13 caudal-fin segmented rays in the blennioids, 7 dorsal and 6 ventral, with a variable number of procurrent rays. Procurrent-ray counts usually vary within species by one, and usually there is one additional procurrent ray in the dorsal series than in the ventral series. Among the labrisomids, Paraclinus have the fewest, with only 4 or 5, while Starksia typically have 5 or 6, and Malacoctenus and Labrisomus have 6 to 10. Although the numerical differences can be slight, the procurrent rays look distinctly more crowded in the latter genera. Other blennioid families can also be distinguished: chaenopsids have few, from 3 to 5, while the tripterygiid Enneanectes have 6 to 8.
Labrisomids are small blennioids (blennies), percomorph marine fish belonging to the family Labrisomidae. Found mostly in the tropical Atlantic and Pacific Ocean, the family contains about 110 species in 15 genera.[1]
Stockier than the average blenny, labrisomids are elongated nonetheless; their dorsal fin spines outnumber soft rays (which may be absent altogether), and their pelvic fins are long and slender. Like many other blennies, labrisomids have whisker-like structures called cirri on their heads and napes. Scales may be cycloid or absent in labrisomids; many species are brightly coloured. Labrisomus philippii is the largest species at 35 cm in length; most are far smaller.[1]
Generally staying within shallow coastal regions to depths around 10 m, labrisomids are benthic fish spending most of their time on or near the bottom. Both sandy and rocky substrates are frequented, sometimes at reefs or amongst beds of seagrass. Labrisomids are shy fish and will retreat into crevices if threatened. Crustaceans, gastropods, brittle stars, and sea urchins make up much of the labrisomid diet.[1]
Two genera of labrisomid are noted for their ovoviviparity; Xenomedea and Starksia both retain eggs within their oviducts, where they develop in safety. However, only Starksia species possess gonopodia (modified anal fins used as a copulatory organ).[2]
Some workers have found that the Labrisomidae is paraphyletic.[3]
The following genera are currently included in this family:[1][4]
Labrisomids are small blennioids (blennies), percomorph marine fish belonging to the family Labrisomidae. Found mostly in the tropical Atlantic and Pacific Ocean, the family contains about 110 species in 15 genera.
Stockier than the average blenny, labrisomids are elongated nonetheless; their dorsal fin spines outnumber soft rays (which may be absent altogether), and their pelvic fins are long and slender. Like many other blennies, labrisomids have whisker-like structures called cirri on their heads and napes. Scales may be cycloid or absent in labrisomids; many species are brightly coloured. Labrisomus philippii is the largest species at 35 cm in length; most are far smaller.
Generally staying within shallow coastal regions to depths around 10 m, labrisomids are benthic fish spending most of their time on or near the bottom. Both sandy and rocky substrates are frequented, sometimes at reefs or amongst beds of seagrass. Labrisomids are shy fish and will retreat into crevices if threatened. Crustaceans, gastropods, brittle stars, and sea urchins make up much of the labrisomid diet.
Two genera of labrisomid are noted for their ovoviviparity; Xenomedea and Starksia both retain eggs within their oviducts, where they develop in safety. However, only Starksia species possess gonopodia (modified anal fins used as a copulatory organ).
Some workers have found that the Labrisomidae is paraphyletic.
