Labrisomus haitiensis

Diagnosis: The modal fin-ray count of D-XXI,11 A-II,21 and P-14 indicates Labrisomus haitiensis. This fin-ray count falls within the range for Malacoctenus aurolineatus, M. triangulatus, M. boehlkei, and M. macropus. (DNA) Ecology: The reef blenny is a somewhat common small blenny found mostly on well-developed coral reefs at moderate depths. The species is found in Florida, the Bahamas, the S. Gulf of Mexico, and across the Caribbean Sea except NE Venezuela. Unfortunately, the 19, 20, and 21-spined Labrisomus are very similar morphologically and are frequently confused in guidebooks and photographs. All six species share the blunt-headed and goggle-eyed appearance, at least as juveniles, i.e. the snout length (bony orbit to jaw tip) is less than two-thirds of the orbit diameter. Adult reef blennies are recognized in the field mostly by a longer pelvic fin, reaching the anal-fin origin (when straightened) and with an inconspicuous short third ray, as well as relatively long first two dorsal-fin spines (and, on close inspection, 21 dorsal-fin spines and 14 pectoral-fin rays). Although they are often described as having an unmarked operculum, many have a prominent opercular spot, sometimes even outlined as an ocellus. Juveniles can be difficult to identify, since the distinguishing markings for each species are either not well-developed or shared by other species at this early stage (but see description below). L. haitiensis larvae are occasional in collections. Description: Pre-transitional larvae: Body long, narrow, and thin with a large eye, pointed snout, and terminal medium-sized mouth. Long continuous dorsal and anal fins with a short and narrow caudal peduncle. Pectoral fins long, reaching past the vent, and pelvic fins long and thread-like, reaching more than two-thirds the way to the anal-fin origin; notably the third pelvic-fin ray is well less than half the length of the second. The typical complement of large melanophores on the top of the head consists of a row of three on each side of the head, usually in two crescents forming a wide-U, i.e. the middle side-by-side pair are often more widely spaced than the rear pair. Sometimes there is an additional near-surface melanophore at the midline behind the mid-brain lobes, completing a wide-O (not the deep nuchal midline melanophore). Some larvae develop one or a few additional smaller melanophores and an uncommon "peppered head" variant has numerous additional small melanophores over the mid-brain lobes. All larvae have a pair of melanophores behind the tip of the upper jaw, located adjacent to the base of the ascending process of the premaxilla on each side. Some larvae develop additional small melanophores around the pair. There is a cheek melanophore on each side. Melanophores run along the base of all of the soft dorsal-fin rays and some of the dorsal-fin spines, usually including spines 8 or 9 and 10, then 13-15, and then 17 rearward, but often all spines after the 8th, and occasionally only starting at the last two spines. A vertical line of melanophores develops along the base of the caudal-fin segmented rays curving around to the base of the larger procurrent rays. Rare individuals have thin linear melanophores outlining the length of the upper three and lower three caudal-fin segmented rays. Along the ventral midline there are melanophores at the isthmus and deep behind the pelvic-fin base. There is usually extensive speckling of the peritoneum visible both through the lateral abdominal wall as well as along the ventral abdominal aspect. Along the anal fin there is a melanophore at the base of each anal-fin soft ray, followed by one, sometimes none or two, along the ventral midline of the caudal peduncle. A row of internal melanophores overlies the vertebral column along the mid- and rear body, spaced about every third vertebra, usually continuing onto the caudal peduncle. Additional internal melanophores include those at the nuchal midline, otic capsule, and overlying the abdominal organs. Transitional stage: L. haitiensis larvae develop metamorphic melanophores in a distinctive pattern of isolated loops and rings with vertical extensions. As transition progresses most of the larval melanophores on top of the head disappear and often only a few fragments are apparent. Juveniles: L. haitiensis juveniles have dark bars on the body that extend onto the fins. The last dark bar ends on the caudal-fin base outlining three light spots. There can be a dark spot, often with white edging (but not an obvious complete ocellus), on the operculum. L. haitiensis have long pelvic fins, usually reaching past the anal-fin origin, with a distinctively short and inconspicuous third pelvic-fin ray (well less than half the length of the second). Analogues: There is some overlap between the melanophore patterns of larval L. haitiensis and the 19-spined species and L. bucciferus; however, L. haitiensis larvae apparently always have the combination of the pair behind the tip of the upper jaw, many along the base of the dorsal-fin spines (usually including spine 8, 9, or 10), and a well-speckled ventral abdominal wall. These are typically all present along with a minimal head complement of the simple U or O. In those other species, one or more of the combination is typically missing, especially when the head pattern is limited to a U or O. In addition, L. haitiensis larvae tend to have a wide-U or O with the middle pair of melanophores more widely-spaced than the rear pair, vs. a narrowing-U or O in the other Labrisomus. Morphology is generally required for a definitive separation: L. haitiensis larvae consistently have long pelvic fins, more than two-thirds the distance to the vent, with a short third ray (always less than half the next ray). Separation from the 18-spined species is easier: L. nuchipinnis, L. conditus, and L. cricota larvae apparently never have the pair of spots behind the tip of the upper jaw or more than two or three abdominal speckles (usually they have none visible), and consistently have melanophores on the inner cleithrum in the gill cavity as well as outlining the lower caudal-fin segmented rays (the latter rare on L. haitiensis larvae). In addition, those three species also have a narrowing-U, or often even a V-pattern of head melanophores (not seen on L. haitiensis larvae), and a different arrangement of spinous dorsal-fin base melanophores (8,11-12,14+). L. albigenys and L. nigricinctus larvae are very lightly-marked, missing most of the melanophores characteristic of L. haitiensis. Among the Malacoctenus, only M. triangulatus can occasionally have larvae with melanophores along the base of the spinous dorsal fin and they share the long pelvic fins with a short third ray and even sometimes overlap in fin-ray counts with L. haitiensis. They can also have the basic head pattern of two crescents of three large melanophores per side but have additional melanophores over all fore- and mid-brain quadrants varying from tiny to large, usually ten per side or more. The "peppered head" variant of L. haitiensis larvae can resemble that pattern, but have most or all of the additional melanophores limited to the midbrain lobes. M. triangulatus can be distinguished further by the lack of ventral abdominal speckling and the absence of the pair of melanophores behind the tip of the premaxilla, located adjacent to the base of the ascending process, that is characteristic of some Labrisomus; note that the rare M. triangulatus variant (likely in transition) can have a cluster of small melanophores in that area and a pair on the ethmoids a very short distance away. In that case, the dorsal-fin outline (with a notably short third-to-last spine) and long cirri separate M. triangulatus. Lastly, the row of internal melanophores overlying the vertebral column is spaced at one for each vertebra in M. triangulatus vs. every third vertebra in Labrisomus. Transitional L. haitiensis larvae are distinguished by fin-ray counts, persistent larval melanophores (although these disappear rapidly in this species), and the distinct pattern of metamorphic melanophores on the body. The pair of melanophores behind the tip of the upper jaw is shared only by the 19- and 20-spined species, L. gobio, L. guppyi, L. kalisherae, and L. bucciferus, all of which develop a uniform speckling of metamorphic melanophores on the body. The transitional larvae of L. nuchipinnis, L. conditus, and L. cricota develop connected reticulated lines over the body instead of the isolated loops and rings on L. haitiensis. Transitional M. triangulatus larvae have a generally similar appearance, but their melanophore pattern is inverted triangles, widest at the base of the dorsal-fin elements. Transitional M. versicolor larvae have a very similar transitional pattern of isolated bars and shapes, but have long third pelvic-fin rays (about 3/4 the length of the longest ray), no pair of spots at the tip of the jaw, notably long cirri, and very different fin ray counts. The juveniles of the 19- and 20-spined Labrisomus are blunt-headed, compared to the 18-spined Labrisomus (other than L. albigenys), i.e. the snout length (bony orbital margin to the tip of the closed jaw) is less than two-thirds the bony orbit diameter. Small juveniles of the blunt-headed Labrisomus are difficult to identify to species, especially since some species described with opercular ocelli can have only a diffuse dark spot on the operculum when young. In addition, those species described without ocelli can often have an outlined dark spot on the operculum (but not a thin-rimmed ocellus) as juveniles. Juvenile L. haitiensis have long pelvic-fins with a short third ray that separate them from all congeners (except L. filamentosus) and also have high fin-ray counts that rarely overlap with other Labrisomus species. Juvenile L. filamentosus have not been identified, but, since juvenile L. haitiensis can also have an ocellus-like spot on the operculum, it is possible that L. filamentosus may only be separated by fin-ray counts: an extra dorsal soft-fin ray (dorsal elements of 33) and 13 pectoral-fin rays (vs. 14). The marking differences for juvenile L. haitiensis are subtle, with L. bucciferus and L. kalisherae sharing the relatively long first dorsal-fin spines (often with white-shaded membranes) and the pigment on the caudal-fin base outlining three light spots (vs. ending as a mostly straight vertical line in L. gobio and L. guppyi). In addition, L. bucciferus have fewer dark bands along the pelvic fin-rays (4 vs. 6 or 7), L. gobio differ in having the dark bars on the body not extending onto the fins, and L. guppyi rapidly develop a thin-rimmed opercular ocellus and have a much shorter first dorsal-fin spine (less than a third of the body depth at the dorsal-fin origin vs. half or more). L. albigenys differ by having a very short first dorsal-fin spine and lower fin-ray counts. The remaining Labrisomus juveniles are distinguished by their longer snouts and lower fin-ray counts i.e. L. nigricinctus and L. nuchipinnis (with well-delineated ocelli), as well as L. conditus and L. cricota.