Cave Brotulas, Lucifuga are a conspicuous genus of obligate cave-dwelling Fish, currently recognised with six species distributed in Cuba and Bahamas. Another nominal species, Lucifuga inopinata, from the Galapagos Archipelago belongs to another, yet undescribed, genus. Because of the characteristics of the habitats of Lucifuga species (caves, sinkholes and crevices) and the morphological modifications that they show in the evolutionary adaptations to the environment, the genus represents an iconic part of the fish fauna in Cuba. The scientific interest in these Fish, however, has been sporadic. Since the description of the genus and the two first Cuban species by Felipe Poey in 1858, the studies dealing with the genus are very few and have mainly been dedicated to the discussions of morphological characters of taxonomic interest for the genus and species and the descriptions of new species; some aspects of feeding and reproductive system and two studies that constituted the first approximation to the evolutionary relationships of the group based on a comparison of several morphological characters of the three species known at that time.
A 2006 study found evidence for all Cuban and all Bahamian species representing two separate evolutionary lineages, but recently another study in 2011 made a phylogenetic analysis of the Cuban species using mitochondrial and nuclear genes finding several new evolutionary lineages not identified previously by morphological analyses. It was also indicated that the separation in Cuban and Bahamian species as suggested in 2006 is no longer correct, since some of the new Cuban species are more closely related to Bahamian species than to other Cuban species. These results also questioned the specific status of the species Lucifuga teresinarum, described in 1988, showing no difference to Lucifuga subterranea, one of the species described by Felipe Poey in 1858.
In a paper published in the journal ZooKeys on 6 July 2020, Damir Hernández of the Centro de Investigaciones Marinas of the Universidad de La Habana, Peter Rask Møller of the Natural History Museum of Denmark, Didier Casane of the Université Paris-Saclay and the Université Paris Diderot, and Erik García-Machado, also of the Centro de Investigaciones Marinas of the Universidad de La Habana, and the Institut de Biologie Intégrative et des Systèmes at Université Laval, describe a new species of Lucifuga from Cuba.
This taxon was first described in 1987 as Lucifuga dentatus var. holguinensis from the Holguin province in eastern Cuba. It was suggested as a valid species name by Graham Proudlove in 2019, but the name has now been decided to be infrasubspecific and unavailable according to International Commission on Zoological Nomenclature Art. 15.2, since it was introduced as a variety after 1960.
The genus Lucifuga is characterised by a body moderately elongated and compressed mainly from the abdomen to the caudal end. Snout with two nostrils: anterior nostril tube-shape and smaller, placed near to the upper lip; posterior nostril is a larger hole, placed roughly midway between snout and eyes cavity. The mouth is subterminal with the lower jaw only slightly shorter than the upper. Opercular spines absent. Seven branchiostegal rays.
The entire body is covered with small, rounded cycloid scales; fins naked except for scales on pectoral fin basis. Predorsal area and operculum scaled. Branchiostegal membranes, entire underside of the head, snout, interorbital areas and entire course of the cavernous cephalic system are naked. Origin of dorsal fin approximately above the tip of pectoral fins. Pelvic fin is subjugular with a single ray reaching roughly one third to halfway to the anus. Pectoral fin behind the operculum, peduncle short and narrow. Lateral line with two series of sensory neuromasts: upper and anterior series extends from the head to a point roughly midway between dorsal and anal fin origins; and lower and posterior series extends from a point under and slightly in advance of the end of the upper series to the mid side from the caudal base.
There are three symmetric sensory canal series on each side of the head: supraorbital series with three pores (two anterior and one posterior): the anteriormost is at the snout rim, the second open between and above the nasal openings, and the posterior single pore is at the end of the lateral canal above the operculum. The infraorbital series with six pores (three anterior and three posterior): first pore is slightly below the anterior nasal opening, the other five pores (two anterior and three posterior) are along the edge of infraorbital rim. Finally, the mandibular series with six pores (three anterior and three posterior). The first pore is in the fold of skin between the lip and canal series, the second is at the side of the jaw tip on the lower lip, the third is at the anterior end of the mandibular series, the fourth to sixth posterior pores open ventrally along the mandibular series. There is also a large preopercular pore. Teeth are present on the premaxillae, dentaries and vomer; but are present or absent in palatines.
Sexual dimorphism. The male copulatory organ is completely integrated into a fleshy genital hood which projects posteriorly beyond the anus, the lateral end of the hood could be from broad to conical. A fleshy small conical papillae project from the middle of the distal margin of the hood and is enclosed by lateral earlike lobes. Penis is placed underneath the hood.
The new species is named Lucifuga gibarensis, which refers to the village of Gibara, where te three caves inhabited by this species are located. Hernández et al. do not follow variety epithet used in 1987, since Lucifuga gibarensis better describes the narrow distribution of the species near the village Gibara instead of the entire region Holguin.
The body of Lucifuga gibarensis is moderately elevated behind the head, with a slight depression in the interorbital region. Eyes pigmented (similar to the condition present in Lucifuga spelaeotes and Lucifuga lucayana). Anterior gill arch with three elongate rakers and 14–16 low dentigerous pads. The areas between lateral canal and preopercular canal, and the occiput are scaled. Caudal fin free (not fused with dorsal and anal fins). In the lateral line series of sensory neuromasts, the upper and anterior count with 13–15, the lower and posterior with 30–35. Teeth are present on the premaxillae (5–7 rows), dentaries (6 or 7 rows) and vomer (2 or 3 rows in two separate patches). Palatines without teeth.
The species is uniformly brown or light brown, with lighter fins and naked parts on the head. Nevertheless, one juvenile specimen (ZMUC P771732) was very pale, but still with tiny dark pigment dots.
Lucifuga gibarensis shows a very restricted known distribution, in a lithographically isolate karst patch of caves at the north of Gibara municipality, Holguín province, without any overlap with other Cuban species of the genus. It is about 800 km away from the nearest Lucifuga dentata, Lucifuga subterranea and Lucifuga simile distribution areas. The distance to the Bahamian species on Little Bahama Bank (Lucifuga lucayana) and Great Bahama Bank (Lucifuga spelaeotes) is about 650 km and 240 km, respectively. The location area is composed by three caves (Aguada de Macigo, Tanque Azul and Cueva El Baga) located near to the shore about 3–15 km from each other. The Aguada de Macigo cave is the type-locality with an emergent large doline, about 22 m deep and salinity of 16 parts per thousand. The specimen designated as the holotype of Lucifuga dentatus var. holguinensis caught at 12 m depth.
Based on external appearance, Lucifuga gibarensis resembles the Cuban species Lucifuga dentatus (from which it was designated as variety) and Lucifuga simile. Nonetheless, it differs in several characters: e.g., number of caudal fin rays (10 compared to 8), diameter of the pigmented eyes (1.1–1.9 compared 0.0–0.2% of standard length), lack of palatine teeth as oposed to palatine teeth present and scaled occiput as oposed to naked or weakly scaled occiput. It also differs in dorsal and anal fin rays mean number (fewer than Lucifuga dentatus and more than Lucifuga simile).
Lucifuga gibarensis also resembles Lucifuga subterranea in the lack of palatine teeth and the scaled occiput, but it differs in the body moderately elevate behind the head compared to little elevated, number of pectoral fin rays (15–17 compared to 10–13), number of caudal fin rays (10 compared to 8), the diameter of the pigmented eyes (1.1–1.9 compared to 0.0–0.3% of standard length) and in the number of rakers on the anterior gill arch 17–19 compared to 12–17.
Finally, Lucifuga gibarensis resembles both Bahamian species in the head profile, the number of caudal fin rays (10), the occiput scales (similar to Lucifuga spelaeotes and less scaled than Lucifuga lucayana) and in the presence of relatively large pigmented eyes. With Lucifuga lucayana it also shares the lack of palatine teeth. It differs in the number of pectoral fin rays (15–17 compared to 17–18 in L. lucayana and 17–20 in Lucifuga spelaeotes); and diameter of pigmented eye is larger than in Lucifuga lucayana (1.1–1.9 compared to 0.9–1.0% of standard length).
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