Lipogramma idabeli, Tornabene, Luke, Robertson, D. Ross & Baldwin, Carole C., 2018

Tornabene, Luke, Robertson, D. Ross & Baldwin, Carole C., 2018, A new species of Lipogramma from deep reefs of Roatan, Honduras (Teleostei, Grammatidae), ZooKeys 809, pp. 79-95 : 82-87

Lipogramma idabeli sp. n. Figures 2, 3, 4 English: Blue-backed Basslet; Spanish: Cabrilleta de Dorso Azul

Type locality.

Roatan, Honduras, western Caribbean.

Holotype.

USNM 444940, 26.2 mm SL, tissue ROA17002, 165 m depth, station IDABEL17-01, reef slope off Halfmoon Bay, West End, Roatan, Honduras, 16.305557, -86.597669, Idabel Submersible, Luke Tornabene, D. Ross Robertson, Karl Stanley, 24 July 2017. Paratypes. Locality data same as that of holotype: UW 158090, 26.3 mm SL, tissue ROA17020, 137 m depth, station IDABEL17-05, Luke Tornabene, Rachel Manning, Karl Stanley, 29 July 2017; UW 158096, 10 mm SL, tissue ROA17026, 152 m depth, station IDABEL17-05, Luke Tornabene, Rachel Manning, Karl Stanley, 29 July 2017; MUVS-V-137, 24.0 mm SL, tissue ROA18041, 125-152 m depth, station IDABEL18-03, Luke Tornabene, Rachel Manning, Karl Stanley, 6 June 2018; UF 240986, 22.5 mm SL, tissue ROA18042, 125-152 m depth, station IDABEL18-03, Luke Tornabene, Rachel Manning, Karl Stanley, 6 June 2018.

Diagnosis.

A species of Lipogramma with pectoral-fin rays 15-16 (modally 16); gill rakers 18-20 total (10-11 elongate rakers plus 2-4 short, stout rudiments on lower limb, 3-4 elongate rakers plus 1-3 rudiments on upper limb); in life, body mostly yellow to tan with bright iridescent blue coloration on eye, dorsal portion of head, nape and dorsal portion of trunk beneath spinous-dorsal fin, oblique yellow bar from tip of snout to orbit and below eye, large, round, black blotch outlined with blue below anterior origin of dorsal fin, and dark ocellus outlined in blue with yellow or dark center at rear insertion of dorsal fin that extends onto body.

Description.

Counts and measurements of type specimens given in Table 1. Dorsal-fin rays XII, 9, last ray composite; anal-fin rays III, 7-8 (four specimens including holotype with 8, one with 7), last ray composite; pectoral-fin rays 15-16 (four specimens including holotype with 16, one with 15); pelvic-fin rays I,5; total caudal-fin rays 24 (13 upper, 12 lower), principal rays 17 (9 + 8), procurrent rays 6 (III+III), and an additional 2 unbranched rays (i+i) between principal and procurrent rays that are sometimes segmented; vertebrae 25 (10+15); pattern of supraneural bones, anterior dorsal-fin pterygiophores, and dorsal-fin spines 0/0/0+2/1+1/1/; ribs on vertebrae 3-10, epineurals visible in x-rays on vertebrae 1-13; gill rakers (counted from two specimens, UF 240986, MUVS-V-137) 18-20, upper limb with 3-4 elongate rakers plus 1-2 short rudiments, lower limb with 10-11 moderate-to-elongate rakers plus 2-4 small rudiments present only as nubs, all elongate rakers possess tooth-like secondary rakers, as in L. evides ( Baldwin et al. 2016: fig. 3); pseudobranchia 6-7, filaments stout and highly branched; branchiostegals 6.

Spinous and soft sections of dorsal fin confluent, several soft rays in posterior portion of fin forming slightly elevated lobe that extends posteriorly beyond base of caudal fin. Pelvic fin, when depressed, extending at least to origin of first soft ray of anal fin, and to origin of penultimate anal-fin ray in holotype. Dorsal profile from snout to origin of dorsal fin convex. Diameter of eye contained 2.8-3.0 times in head length. Pupil tear-shaped, with small aphakic space anteriorly. Scales extending anteriorly onto top of head, ending at a vertical just behind posterior margin of eye. Scales present on cheeks, operculum, and isthmus, absent on snout, jaws, and branchiostegals. Scales large and deciduous, missing on anterodorsal flank of several specimens. Approximately 22-25 lateral scales between shoulder and base of caudal fin (24 in holotype), 4-6 cheek rows, 11 rows across body from above anal-fin origin. Scales on nape and along dorsal midline with reduced or absent cteni, those on cheek and opercula lacking cteni. Fins naked except base of posteriormost dorsal-fin rays, which possess 1 or 2 small embedded scales. No modified lateral-line scales present on body, but faint indication of a lateral line present superficially in fresh photographs.

Margins of bones of opercular series smooth, opercle without spines. Single row of teeth on premaxilla posteriorly, broadening to 2 or 3 rows anteriorly, teeth in innermost row smallest, some teeth in outer row enlarged into small canines. Dentary similar with 3 or 4 enlarged teeth in outer row near symphysis. Vomer with chevron-shaped patch of teeth that extends posterolaterally nearly length of premaxilla, palatine with long series of small teeth.

Cephalic head pores arranged as in Fig. 2, with conspicuous pores present in infraorbital canal (2), dentary canal (2), supraorbital canal (2 pores above each eye plus one median coronal pore), preopercular canal (7), posttemporal canal (3), plus a single pore in canal above post-temporal canal in line with preopercle. Anterior naris in elongate tube above upper lip, posterior naris a wide opening with slightly raised rim immediately anterior to supraorbital canal.

Coloration in fresh specimens (Fig. 3): Head: top of snout, top of head, and nape bright blue; lower part of head yellow brown, with faint blue overtone; eye with bright blue iris, black pupil; top and bottom lips with pale blue overtone; yellow oblique bar, bordered with blue, extending from tip of snout to mid orbit and continuing below orbit towards lower corner of preopercle; opercle with lavender hue from bright red gills and blood vessels visible through gill cover. Trunk: yellowish to yellow-brown, paler and sometimes with faint bluish cast on isthmus and abdomen; large, eye-size round black blotch on upper back under the origin of dorsal fin, surrounded by thin bright blue ring; blue coloration on nape extends along the upper back to end of spinous dorsal. Spinous dorsal fin: bright blue anteriorly, fading to blue-grey posteriorly on basal half; outer edge blue-grey, with thin submarginal yellow stripe formed by series of close-set, horizontally elongate yellow spots; row of yellow spots (each on and just behind a spine), beginning at base of the first 2-3 spines, then continuing as row along other 1/3 of the fin. Soft dorsal fin: rays blue-grey anteriorly, with the last several posterior rays blue; upper margin whitish-blue, with a submarginal row of vertically elongate, inter-radial yellow spots, and 3-4 rows of vertically oval, inter-radial yellow spots, those at rear forming thin, yellow lines along the membranes between last 2 or 3 rays; pupil-sized, round, yellow-brown blotch containing darker scales ringed with bright blue at rear insertion of fin, with half of blotch covering base of last 6 or 7 rays and half on upper back. Anal fin: bluish grey, with brownish cast on scaled base of fin; 3 or 4 irregular rows of yellow spots along fin elements, central spots oval, basal and outer spots forming streaks along fin elements; outer margin of fin whitish-blue. Caudal fin: base translucent yellow; center of fin with rows of yellow spots along fin rays; outer part of fin translucent, with thin whitish-blue rear margin; vertical rows of pale blue spots on rays in center of fin. Pectoral fins: pectoral rays tinged with yellow, membranes translucent; base of fin paler than adjacent body. Pelvic fins: pale bluish grey, with elongate yellowish spots along fin rays, that yellow coloration strongest at base of fin.

Juvenile coloration: Coloration of the single small juvenile is essentially the same as in the adult, except that the posterior portion of the body is more noticeably yellow, the entire center of the anal fin, and, apparently, much of the soft dorsal and caudal fins are yellow, and the dark center of the ocellus at the lower rear corner of the dorsal fin is solid black.

Comments about live coloration: As can be seen in the video of the holotype being captured (https://doi.org/10.5281/zenodo.1334518, or https://zenodo.org/record/1334518#.W89WsSPMyFU), live fish have the upper third of the head and body bright blue, the lower 2/3 yellow, and a prominent large round black blotch on the shoulder.

Color in preservation (Fig. 4): Overall pigmentation pattern largely similar to that of fresh individuals, except iridescent blue coloration replaced by dark brown pigment; oblique bar on head below eye pale in preservation versus yellow in life; dark ocelli below spinous and soft dorsal fins less distinct, with no clearly defined ring or margin; background body coloration darkest on head and below origin of spinous dorsal fin, gradually fading from brownish-tan anteriorly to pale-yellow posteriorly.

Distribution.

Known only from specimens collected off Roatan, Honduras (Fig. 5).

Habitat.

The species was frequently observed in the mid-to-upper rariphotic zone between 122-165 m depth, in or around small rock crevices, rock piles, or caves situ ated on steep limestone walls covered with coarse sediment and fine rubble composed of dead sections of the green macroalga Halimeda (Fig. 5). A video showing the collection of the holotype is available online (https://doi.org/10.5281/zenodo.1334518, or https://zenodo.org/record/1334518#.W89WsSPMyFU).

Etymology.

The specific epithet idabeli refers to the Idabel submersible, which was used to collect the type series, and recognizes of the efforts of its owner-designer and pilot Karl Stanley and engineer Thomas Trudel, who made these and other collections of fishes possible by constructing a fish-catching system that converted Idabel from an observation-only vessel to one capable of collecting scientific specimens. The name idabeli is to be treated as a patronym (adjective) formed from the female name Idabel. The generic name Lipogramma is feminine and is formed from lipo (without) and gramma (a line of text, feminine), referring to the absence of a well-developed lateral line. The common name Cabrilleta de Dorso Azul (Blue-backed Basslet in English) refers to its distinctive coloration.

Comparisons.

Lipogramma idabeli is easily distinguished from all other species of Lipogramma by the bright blue coloration on the head and eye, and by the pair of blue-margined ocelli below the anterior origin of the dorsal fin and at the posterior insertion of the dorsal fin. There are only two other species of Lipogramma in which the head is a markedly different color than the body; L. klayi and L. anabantoides both have rose, pink, or purple heads with tan or yellow bodies. No other known species has bright blue coloration on the dorsal portion of the head, nape, and dorsal portion of the trunk. All species of Lipogramma except L. klayi , L. rosea , and L. trilineata possess an ocellus on the posterior portion of the dorsal fin, but the pattern of barring and shading on the head and body differ among all of those species (Fig. 6). In addition to the differences, none have the ocellus with a blue margin except L. idabeli . Furthermore, in L. idabeli , the ocellus varies from having a dark center as a juvenile to a yellow or dusky center as an adult, whereas in the other species, the ocellus is always black. The absence of prominent vertical barring on the body distinguishes L. idabeli from L. robinsi , L. barretorum , L. haberorum , L. evides , L. levinsoni , L. schrieri , and L. regia (Fig. 6). Lipogramma idabeli has more total gill rakers (18-20) than all other species except L. evides (19-22), L. klayi (19), and L. levinsoni (17-20); all other species have 16 or fewer. The combination of XII, 9 dorsal-fin elements and III, 8 anal-fin elements present in L. idabeli is shared among most species in the genus, except L. rosea (XI, 6 and III, 6), L. trilineata (XII, 10 and III, 7), and L. anabantoides (XIII, 8 and III, 8).

Phylogenetics and eco-evolutionary relationships.

Coloration unambiguously diagnoses L. idabeli and supports its recognition as a distinct species. Molecular data from the ten species of Lipogramma for which tissue samples were available also support this distinction. The molecular phylogenies from the Bayesian and Maximum Likelihood analyses (Fig. 7; Suppl. material 1: Figure S1), which were identical in topology to that from the BP&P coalescent species-tree analysis, show that the three specimens of L. idabeli form a monophyletic group with strong support (1.0 posterior probability; 100 bootstrap). The BP&P species delimitation analysis had overwhelming support for a 10-species model (posterior probability 0.997) versus models with fewer or more species, indicating perfect congruence between morphological and molecular delimitation approaches.

Our analyses show L. idabeli as part of a well-supported clade containing L. regia , L. levinsoni , and L. anabantoides , with the relationships within this clade being less resolved. All of these species occur from the mid-to-upper rariphotic zone and shallower (20-165 m). Similar to our observations of species of Lipogramma occurring off Curacao and other localities in the Caribbean ( Baldwin et al. 2016, 2018), species off Roatan appear to be partitioning the reef by depth and microhabitat association. The known depth range for L. idabeli off Roatan, based on collected specimens and visual observations, is 122-165 m. At Roatan, its depth range broadly overlaps with that of L. levinsoni , but the two species occupy very different microhabitats. Lipogramma levinsoni is typically found hovering around and above limestone rubble and small cobble habitats on gradual slopes, whereas L. idabeli is found around larger rocks, caves, and outcroppings on steeper slopes and vertical walls. In addition to L. idabeli and L. levinsoni , other nominal species of Lipogramma observed at Roatan include L. klayi , L. evides , and L. flavescens . Like L. idabeli , L. klayi also occurs around steep walls but at depths considerably shallower than L. idabeli (~65-120 m versus 122-165 m), where the reef wall is generally covered with more extensive growth of Halimeda , encrusting sponges, gorgonians, and other sessile habitat-forming organisms. Both L. flavescens and L. evides were observed deeper than L. idabeli at 213-250 m, with L. evides usually occurring on gradual rocky slopes with a heavy layer of cobbles (similar to the habitat of L. levinsoni ), and L. flavescens found out in the open on bottoms of coarse sand with small, low, scattered piles of rock and rubble, far from the wall.