Caecieleotris morrisi Walsh & Chakrabarty 2016

Caecieleotris morrisi is distinguished from the majority of other sleepers, and all epigean forms in the Western Atlantic, by the absence of eyes and pigmentation. This species is provisionally placed in the Gobiiformes, family Eleotridae, based on a limited number of characters that it shares with other members of the family as currently recognized, e.g., having a mode of six branchiostegals, pelvic fins separated at the base, and procurrent cartilages of the caudal fin elongated posteriorly and extended over the epurals. It differs from the cave-dwelling Bostrychus microphthalmus from Sulawesi by the absence of eyes (vs. present, minute, covered by skin), complete lack of pigmentation (vs. body pale, few melanophores on dorsum), absence of scales on operculum and side of head (vs. present), lower lateral scale count (?32 vs. ?102), fewer transverse scale rows on midside of body (?6 vs. ?31), and absence of pores associated with the cephalic lateralis system (vs. present). It can be diagnosed from the blind species of Oxyeleotris from Indonesia (O. colasi) and Papua New Guinea (O. caeca) in lacking sensory pores on the head associated with the cephalic lateralis system (vs. cephalic sensory pores present, although reduced in comparison to other gobiiform fishes). It differs from the cave species of Typhleotris from Madagascar (T. madagascariensis, T. mararybe, and T. pauliani) in having the head asquamate (vs. scales extending anteriorly onto the head), squamation absent on the venter (vs. fully scaled on the belly as well as laterally below the pectoral fin), scales embedded (especially on anterior half of body) and hard to discern (vs. in prominent rows on the surface of the body and head). Cave-dwelling species of the genus Milyeringa from western Australia have elements of the first dorsal fin reduced (spines II-IV in M. veritas) to absent (M. justitia), versus V-VI in Caecieleotris morrisi; and also have 4-5 total lepidotrichia (first unsegmented) in the pelvic fin, versus six in Caecieleotris morrisi (Ref. 109339).

Dorsal spines (total): 6 - 7; Dorsal soft rays (total): 7 - 8; Analspines: 1; Analsoft rays: 6 - 10; Vertebrae: 24 - 25

A cave inhabitant. The cave entrance at the type locality lies at about 6.1 m deep beneath a rocky bluff along the shoreline of the lake. Immediately within the cave, the depth drops to about 27.4 m before rising to a depth close to 12.2 m where it then levels off. Flowstone (sheet-like mineral deposits typically consisting of calcite) was observed in the cave (Ref. 109339).

Caecieleotris morrisi, also known as the Oaxaca cave sleeper is a species of troglobitic fish in the family Eleotridae found in a single cave system beneath Presa Miguel Alemán reservoir, northern State of Oaxaca in Mexico. This species is the only member of its genus.

It is only known from museum specimens that were collected in the 1990s. Since then the cave system has been flooded because of a dam. Recent surveys have not been able to relocate the species and it might be extinct.

The generic name is a compound of the Latin caecus meaning blind suffixed with Eleotris, the type genus of the Eleotridae and specific name honours the cave diver, speleologist and conservationist Thomas L. Morris who discovered this species and collected the type specimen.