Caecieleotris morrisi, Stephen J. Walsh & Prosanta Chakrabarty, 2016

Stephen J. Walsh & Prosanta Chakrabarty, 2016, A New Genus and Species of Blind Sleeper (Teleostei: Eleotridae) from Oaxaca, Mexico: First Obligate Cave Gobiiform in the Western Hemisphere, Copeia 104 (2), pp. 506-517 : 508-514

Caecieleotris morrisi , new species

urn:lsid:zoobank.org:act:193B8DF5-31BD-4BE6-AAD5- 34A6DF872681

Oaxaca Cave Sleeper, Guavina Cueva de Oaxaca Figures 1, 2, 3; Table 2

Holotype.— CNPE-IBUNAM 19073 (ex. UF 101173), 34.1 mm SL, Mexico, Oaxaca State, submerged cave at the bottom of Presa Miguel Alema'n reservoir , approximately 18811"22.58"" N, 96836"56.02"" W, 16 April 1995, T. L. Morris.

Paratypes.— LSUMZ 17726 (ex UF 101173), 1, 28.0 mm SL; UF 101173, 9, 11.6–31.6 mm SL (1 CS, 28.2 mm SL); UMMZ 231174, 2, 19.3–29.9 mm SL. Same locality and date as the holotype.

Diagnosis.— Species diagnosis is that of the monotypic genus, with character states of Caecieleotris as stated above.

Description.— Selected proportional measurements presented in Table 2 . A diminutive, anophthalmic, unpigmented eleotrid. Size range of type specimens 11.6–34.1 mm SL. Body slender, relatively elongate, laterally compressed, body depth at pelvic-fin origin 14.2–18.6% SL ( Fig. 1 A). Body width at pectoral-fin origin 11.6–17.4% SL. Head broad and moderately depressed, shovel-shaped, head width 54.1– 68.2% HL. Snout prominently upturned. Dorsal profile of head straight to weakly concave. Ventral profile of head weakly convex. Dorsal and ventral profiles of body posterior to pectoral fins gradually tapered, nearly symmetrical except for position of median fins, body depth only slightly reduced from pectoral-fin insertion to anal-fin origin. Caudal peduncle relatively shallow (depth 7.4–8.4% SL) and narrow (width 2.9–5.4% SL). Deep fleshy groove on ventral side of body from pectoral-fin insertion to anal-fin origin, with a keel-like midventral flap of skin, possibly representing artifact of shrinkage following preservation or presence of little or no food in the gut of individuals when preserved.

Meristic characters exclude data for the two smallest, presumably juvenile, paratypes (UF 101173; 11.6–11.9 mm SL) and include only partial data for two other paratypes (UMMZ 231174). Values for holotype indicated by asterisk, number of specimens parenthetically as follows. First dorsalfin elements modally VI: V (5), VI* (6); spines thin, flexible. Second dorsal-fin elements modally I,7: I,7* (6), I,8 (5). Analfin ray elements modally I,8: I,6 (1), I,7 (2), I,8* (6), I,9 (1), I,10 (1). Pelvic-fin elements I,5* (11). Spines in second dorsal, anal, and pelvic fins feeble, thin, flexible. Pectoral-fin rays modally 14: 13 (4), 14 (6), 15* (1). Upper principal (segmented) caudal-fin rays modally 6: 5 (1), 6* (7), 7 (3). Lower principal caudal-fin rays modally 6: 5* (4), 6 (5), 7 (2). Upper procurrent caudal-fin rays modally 8: 5 (1), 6 (3), 7 (2), 8* (5). Branchiostegals modally 6: 4 (1), 5 (1), 6* (9). Scales in lateral series modally 27: 25 (2), 26 (1), 27 (3), 28* (1), 31 (2), 32 (1). Scales on body cycloid, large (5–6 transverse scales on midside of body), imbricate, thin, tightly appressed to body. Circumferential caudal peduncle scales modally 10: 10* (6),

11 (4). Total vertebrae modally 24: 24* (6), 25 (3). Rib pairs modally 6: 6 (4), 8* (2).

Head large, its length 29.2–42.5% SL. Dorsum of snout at midline forming a small raised bump, extending posteriorly a short distance along midline as a weakly ossified ridge. Snout broadly crescentic in dorsal view ( Fig. 1 B). Mouth large, superior, length of both jaws about one-third HL; mouth distinctly upturned, midline of lower jaw projecting anterior to midline of upper jaw. Posterior edges of jaws curved gently inward in ventral view ( Fig. 1 C). Lips relatively thin, prominent groove between upper lip and anterodorsal part of head, frenum present at midline. Basihyal reaching to approximately midway between tip of snout and rear margin of jaw. Teeth in upper and lower jaw conical, slender, sharp, uniform in size, slightly recurved inward, in 1–3 irregular rows. Gill rakers short, blunt, denticulate at terminal end; gill filaments also short, about 3–4 times length of rakers. Nares large and prominent, anterior naris a broad tube extending above upper lip and angled forward about 458 from sagittal plane of head, with thin fleshy flap surrounding oval opening. Posterior naris a large, oval to circular, dorsaloriented opening lacking marginal flap. Nasal rosette and broad tubular connection between anterior and posterior nares readily visible through unpigmented skin. Brain visible beneath skin on top of head, detailed structure not readily visible eternally, but olfactory lobes, cerebellum, and hindbrain evident; optic lobes presumed reduced. Olfactory nerve well developed. Narrow posterior process of mesethmoid and lateral ethmoid articulating with long, closely apposed frontals, together forming a narrow median keel-like ossification connecting the upper jaw bones with the rear of the skull ( Fig. 2 A), much thinner than in Eleotris ( Fig. 2 B). Large oval foramen on dorsum of head in anophthalmic orbital region ( Fig. 2 A), on each side of longitudinal midline, formed in unossified area surrounded by jaw apparatus anteriorly, frontals medially, suspensorium posteriorly and ventrolaterally, overlain by thin opaque yellow musculature and integument. No eyes visible externally in most specimens, but some individuals with a minute spherical black lens located on either side dorsally just below the epidermis, slightly medial to point midway between side of head and center of frontal, at a longitudinal distance of about onethird from tip of the snout to posterior margin of opercle. Opercular openings large, thin opercular membranes nearly separate, only narrowly joined anteroventrally to isthmus. Posteriorly, opercular membrane attached to body anterodorsal to pectoral-fin origin. Branchiostegals acicular, flexible; anterior 1–2 shortest, posterior-most 3–4 longer, gently curved dorsolaterally.

Lateral line and cephalic pores absent. Head and body with profuse distribution of sensory papillae in discrete vertical, transverse, horizontal, and oblique rows. The head papillae pattern is essentially the transverse type following the nomenclature of Hoese (1983), but it is unknown if individual lines of papillae are homologous with numbered series as described for many other gobiiforms. The following description is based on a specimen illustrated in Figure 3 and the holotype ( Fig. 1 ). Sensory papillae system forming marked relief on dorsolateral aspect of snout and anterior portion of head, with rows of papillae developed on prominent fleshy ridges; 3–5 ridges in preorbital region with papillae elevated on each ridge in a semicircular pattern from the dorsolateral edge of the head extending around to the ventrolateral aspect of the chin ( Fig. 3 A), with an additional dorso-ventral oriented ridge of papillae in an approximately sagittal plane nearly equal to or just behind the posterior margin of the brain ( Fig. 3 B). Top of snout with a short longitudinal series of papillae on each side extending from a plane just in front of the anterior naris to a plane approaching the rear margin of the posterior naris, and another short row of papillae distributed laterally and obliquely from each longitudinal series toward the posterior naris. A parallel, oblique row of papillae posterior to the latter, extending from the mid-dorsal to lateral preorbital region of the head. Three irregular horizontal series of papillae on the ventrolateral side of the head, the top two broken, the lower continuous from the posterior margin of the jaw to above the origin of the preopercle and posteriormost branchiostegals; the uppermost of these may correspond to the upper horizontal line (LTU) and the lower to the lower horizontal line (LTB) as described by Hoese (1983). Five vertical rows of papillae on the ventrolateral side of the head distributed from posterior edge of the jaw to anterior edge of the opercle, apparently corresponding to vertical transverse lines (VT) of Hoese (1983). Lateral margin of opercle with a semicircular pattern of papillae in a continuous dorsolateral, vertical, and ventrolateral row. Posterior half of top of head with single longitudinal row and irregular, transverse or obliquely directed papillae distributed mid-medially, posterolateral to brain, and dorsally above each opercle. Preopercular mandibular series consisting of multiple lines of transverse papillae medial to longitudinal line extending from near anterior end of lower jaw to lateral opercular margin ( Fig. 3 C). Two dorsolateral rows of papillae, one above and the other just posterior to base of pectoral fin. Single longitudinal row of papillae on each side of middorsal ridge above and just posterior to base of pectoral fin. About five vertical to transverse rows of papillae extending from midlateral region of each side to ventromedial region of abdomen distributed approximately equally between pectoral-fin insertion and urogenital papilla. Additional irregularly spaced vertical rows of papillae distributed along sides of body from plane passing through second dorsal and anal fins to caudal peduncle.

First dorsal-fin origin anterior to midpoint of body and vertical through tip of adducted pelvic rays, pre-spinousdorsal fin length 42.7–50.0% SL, base of fin 6.7–13.4% SL. Origin of second dorsal fin about equal with or slightly posterior to vertical plane passing through urogenital papilla, slightly anterior to origin of anal fin. Base of second dorsal fin 7.4–18.2% SL, longer than that of spinous dorsal but less than anal-fin base length. Both second dorsal and anal fins high, sinuous, broadly rounded, middle branched rays longest. Anal fin long, base length 11.4–19.8% SL, origin slightly posterior to urogenital papilla, insertion slightly posterior to that of second dorsal fin. Caudal fin pointed to lanceolate, middle rays longest (sometimes considerably longer than others), terminal ends of rays frayed in some specimens (see Fig. 1 A; in comparison, species of Dormitator have a broadly rounded fin, and species of Eleotris , Gobiomorus , and Guavina have a semi-truncate to rounded fin). Bases of pelvic fins apposed but fins separate (as in other eleotrids, compared to fused in most gobiids), jugular, anterior to plane passing through origin of pectoral-fin rays but about equal with anterior edge of thick anteromedial pectoral-fin musculature, posterior to symphysis of opercular membranes. Pelvic fin relatively long and ribbon-like, pointed, middle to posterior branched rays longest, tip of appressed fin not reaching to genital papilla. Pectoral-fin base obliquely vertical, origin (dorsal edge) slightly posterior to insertion (ventral edge), basal portion surrounding proximal radials projecting from body as fleshy appendage. Pectoral fins elongate and produced with filamentous rays, most pronounced in larger individuals, middle branched rays longest, tips of appressed fins reaching well posterior to anal-fin origin.

Coloration in preservative.— Head and body without pigmentation, uniformly white to yellowish and opaque in appearance. Fins translucent or transparent. Internal organs and musculature yellowish to amber; muscle bands evident where not obscured by squamation.

Etymology.— The specific epithet is a patronym to honor our good friend and colleague Thomas L. Morris, discoverer and collector of this new species, renowned cave diver and speleobiologist, intrepid explorer, and respected conservationist devoted to the protection of karst habitats and their associated biotas.

Distribution and habitat.— Caecieleotris morrisi is currently known from only a single cave system beneath Presa Miguel Alema'n reservoir, northern State of Oaxaca, Mexico, located along the east side of the Sierra Mazateca front range ( Fig. 4 ). The lake is sometimes also referred to as Temascal, name of an adjacent municipality (also known as Nuevo Soyaltepec) and associated hydroelectric plant. This artificial impoundment was created following the construction of Presa (=dam) Miguel Alema'n, a large dam on the Tonto River, major headwater tributary of the R'ıo Papaloapan draining into the southwestern Gulf of Mexico. Construction of the dam began in 1949 and filling of the reservoir was completed in 1955. The 830 m (2,723 ft) long dam and 9,300 km 2 (3,591 mi 2) reservoir provides hydroelectricity, flood control, and irrigation supply. The dam is operated in conjunction with the Cerro do Oro Dam (and associated 220 km 2, 85 mi2 reservoir) located on the Santo Domingo River, which is joined to Presa Miguel Alema'n reservoir by a short, narrow channel. The Tonto and Santo Domingo rivers join to the south of the city of San Juan Bautista Tuxtepec to form the R'ıo Papaloapan, Mexico's second largest river (mean annual discharge 3.73310 4 m 3; Miller et al., 2005).

The cave entrance at the type locality lies at a depth of about 6.1 m (20 ft) beneath a rocky bluff along the shoreline of the lake. Immediately within the cave, the depth descends to about 27.4 m (90 ft) before rising to a depth of about 12.2 m (40 ft) where it then levels off. Divers with the collecting party observed flowstone in the cave (sheet-like mineral deposits typically composed of calcite). This suggests that prior to impoundment the entrance might have been a highwater, wet season overflow, and that a lower (now deeper) entrance might exist that could have been a perennial artesian spring in pre-reservoir conditions (Tom Morris, pers. comm.). In addition to this cave the dive team explored a submerged sulfur spring nearby where, as expected, no higher taxa were observed.

Conservation status.— All cavefish species of North America are in some level of jeopardy due to endemic distributions and the vulnerability of subterranean habitats to land-use changes and environmental perturbations ( Jelks et al., 2008), as is the general case with cavefishes globally ( Proudlove, 2001, 2006). Higher taxonomic groups (genera and families) with obligate cave-dwelling species have disproportionately high levels of imperilment in comparison to groups comprised primarily of epigean forms. Stygobitic ictalurids ( Prietella lundbergi , P. phreatophila , Satan eurystomus , and Trogloglanis pattersoni ) are considered endangered, and the number of at-risk species in other families is high relative to the total number of taxa in each group or the number distributed in North America: a single species ( Typhliasina pearsei ) of Bythitidae (100%), the Amblyopsidae (6 of 7 species, 86%; although Typhlichthys represents a species complex according to Niemiller et al., 2012), and the Heptapteridae (6 of 9, 67%; Jelks et al., 2008; Chakrabarty et al., 2014). Insofar as C. morrisi is presently known only from the type series collected over two decades ago and nothing is known regarding distribution or population abundance, it is strictly conjecture to speculate about conservation status of the species. However, there have been extensive hydrologic modifications in the region of the type locality, and the biologically rich State of Oaxaca has undergone extensive land-use changes over the last few decades. These changes include widespread deforestation ( Vela'zquez et al., 2003) that is projected to continue into the future ( G'omez-Mendoza et al., 2006), one of many factors known to degrade and threaten subterranean habitats ( Bichuette and Trajano, 2010). Within central Mexico many endemic fishes are considered imperiled ( Dzul-Caamal et al., 2012). Given current and projected land-use conditions, it may be prudent for the Mexican government to consider protective status for C. morrisi under the Norma Oficial Mexicana (NOM; SEMARNAT, 2010), pending further exploration and studies to evaluate population status, distribution, and ecology of this unique species.

DISCUSSION

The Gobiiformes is diagnosed by at least 14 putative synapomorphies ( Wiley and Johnson, 2010) identified from among a broad suite of osteological and myological characters that have been extensively examined by various investigators in efforts to determine relationships within this species-rich order as well as to explore possible relationships of the Gobiiformes with other percomorph groups (e.g., Springer, 1983; Hoese and Gill, 1993; Johnson and Brothers, 1993; Winterbottom, 1993; Thacker, 2009; Gill and Mooi, 2012). A comprehensive morphological analysis of C. morrisi is beyond the scope of the present study. Furthermore, suboptimal quality of the only cleared-and-stained specimen (CS; 28.2 mm SL, presumably a juvenile or subadult) and lack of specimens exhibiting a complete series of ontogenetic stages precludes a detailed evaluation of many of these characters. Nevertheless, certain character states observed in the CS specimen confirm that the new taxon is a gobiiform: pelvic intercleithral cartilage is present; ventral intercleithral cartilage is present; hypurals 1 and 2 are fused; hypurals 3 and 4 are fused to each other and to the urostyle; the dorsalmost pectoral ray articulates with the posterior margin of the dorsal-most actinost and lacks a medial enlarged articular base; infraorbital bones consist of paired lacrimals and the second element is apparently reduced or absent; supraneurals are absent; and sensory papillae are distributed extensively on the head and body.

Placement of C. morrisi in the Eleotridae is provisional on the basis of a limited number of readily observable characters. Monophyly of the family as currently recognized is questionable, and the group is generally defined by plesiomorphic rather than derived characters ( Hoese, 1984; Thacker, 2009). Typically, species of Eleotridae , Butidae , Rhyacichthyidae , and Odontobutidae are separated from the Gobiidae and Gobionellidae in having six (versus five) branchiostegal rays ( Hoese, 1984; Hoese and Gill, 1993; Thacker, 2011; Gill and Mooi, 2012). Specimens of the type series of C. morrisi exhibit unusual variation of 4–6 (modally 6) branchiostegals, with an asymmetrical number on each side in at least one individual; the small anterior elements are difficult to discern in alcohol-preserved specimens, but a reduced number may be related to developmental truncation as a result of extreme troglomorphy. As in most other eleotrids, C. morrisi also has separate pelvic fins, unlike the majority of other gobiiforms. Also, as is characteristic of other eleotrids ( Hoese and Gill, 1993), C. morrisi appears to have procurrent cartilages of the caudal fin elongated posteriorly and extended over the anterior epural(s). Unusual variation observed in some meristic and mensural characters of the type series may be attributable, in part, to developmental truncation as result of troglomorphy, contortion of preserved specimens, inaccurate counts or measurements (difficult given the lack of pigmentation and small body size), or a combination of factors.

The discovery of C. morrisi brings to 13 the number of described stygobitic gobiiforms worldwide, and to four the number of Eleotridae , with an additional undescribed cave sleeper reported from Guam ( Table 1 ). Most notably, C. morrisi represents the only cave-adapted sleeper known from Atlantic Ocean drainages, with all others confined to the Indo-Pacific region. Two of the four described cave sleepers ( Oxyeleotris caeca and O. colasi ) occur on the island of New Guinea and are thought to be related to each other, as well as to O. fimbriata , an epigean species that is distributed widely in New Guinea and northern Australia ( Allen, 1996). There is also molecular evidence supporting monophyly of O. colasi with the epigean O. marmorata (type species of the genus) and O. lineolata , in a phylogenetic analysis that included eight other Indo-Pacific and eastern Atlantic gobiiforms ( Pouyaud et al., 2012). Bostrychus microphthalmus is a cave eleotrid from Sulawesi that appears to be most similar morphologically to B. sinensis , a wide-ranging tropical Indo- Pacific species that most commonly occurs in mangroves and estuaries, and occasionally enters fresh water, along with other congeners that occur in or are confined to fresh waters ( Hoese and Kottelat, 2005). In the molecular analysis by Pouyaud et al. (2012), B. sinensis appears as the sister taxon to the monophyletic Oxyeleotris . Other molecular phylogenetic studies have demonstrated that cave gudgeons of the genus Typhleotris ( T. madagascariensis , T. mararybe , and T. pauliani ), endemic to karst systems in southwestern Madagascar, are the sister group to Milyeringa ( M. justitia and M. veritas ), endemic to similar cave habitats in northwestern Australia ( Chakrabarty et al., 2012). The phylogenetic position of Milyeringa within the Gobiiformes has been questioned (reviewed by Larson et al., 2013), and some authors place the genus in the Eleotridae (references in Table 1 footnote), but the nuclear DNA evidence suggests a distinct relationship with eleotrids and supports recognition of the group at the family level, Milyeringidae ( Tornabene et al., 2013; Thacker et al., 2015). We should note that attempts to extract and amplify DNA from specimens of C. morrisi failed, possibly due to exposure to formalin at some stage of preservation.

The aforementioned cave-adapted species share convergent characters that are common to stygobitic fishes and that are the subject of extensive study, i.e., loss or reduction of eyes and pigmentation, hyper-development of non-optic sensory systems, and other morphological features associated with a hypogean lifestyle. Among the cave-dwelling eleotrids and milyeringids there is a gradation of these morphological characters (see Diagnosis), suggesting that considerable differences exist between taxa based on divergence times from ancestral lineages and concomitant time that selective forces have been acting during cave existence. Indeed, a remarkable ancient sister-group relationship and the widely disjunct Malagasy-Australian distribution of the milyeringids reveals the historical extent to which individual lineages may be subjected to similar evolutionary processes acting independently in the hypogean environment ( Chakrabarty et al., 2012).

The pronounced troglomorphic features of C. morrisi , namely the near complete loss of eyes, absence of all pigmentation, and well-developed neuromast/sensory papillae system suggest that this species has an ancient history of living in darkness. Based on geography alone, it is unlikely that C. morrisi shares a close relationship with other described cave gobiiforms. It is most parsimonious to infer that C. morrisi shares a common ancestral lineage with one or more species of extant eleotrids in the westcentral Atlantic, particularly those species ranging in the Gulf of Mexico and western Caribbean, but gross morphological features do not provide insight into possible relationships. However, biogeographical patterns from multiple taxonomic groups provide evidence of historical linkages between freshwater faunas of the R'ıo Papaloapan drainage and the Central American/ Neotropical realm ( Huidobro et al., 2006; Quiroz-Martinez et al., 2014). The R'ıo Papaloapan is part of the Papaloapan- Coatzacoalcos division of the Usumacinta ichthyofaunal province ( Miller et al., 2005). Within this major province fish diversity is great, with over 200 described species, over half of which are restricted to fresh waters; of those permanent freshwater species, at least 18 are thought to be derived from marine ancestors. About one quarter of the R'ıo Papaloapan ichthyofauna is endemic, including two species of cave hepapterids ( Rhamdia reddelli and R. zongolicensis ). Moreover, considered in its entirety, the Usumacinta ichthyofaunal province is occupied largely by taxa of Middle or South American derivation ( Miller et al., 2005; Matamoros et al., 2015). Thus, possible phylogenetic affinities of C. morrisi with taxa outside of the Gulf of Mexico or circum-Caribbean region cannot be precluded.

Mexico has six extant, epigean eleotrid species in Gulf Coast drainages: Dormitator maculatus , Eleotris amblyopsis , Eleotris perniger , Erotelis smaragdus , Gobiomorus dormitor , and Guavina guavina (Castro-Aquirre et al., 1999; Miller et al., 2005). An additional five eleotrid species occur on the Pacific Slope of Mexico: Dormitator latifrons , Eleotris picta , Erotelis armiger , Gobiomorus maculatus , and Gobiomorus polylepis . Caecieleotris morrisi exhibits a generalized eleotrid shape with a depressed head and elongate, slightly compressed body, and perhaps is most similar in shape to species of Eleotris and Erotelis . However, the very large spatulate-shaped head of C. morrisi is more typical of some of the other cave gobiiforms and is especially similar to that of Oxyeleotris (see Allen, 1996:fig. 3; Pouyaud et al., 2012:figs. 2–3), most likely relating to convergence in these cave obligates. Future study may not only be informative in determining the phylogenetic relationship of C. morrisi with other Atlantic or Pacific eleotrids, but could provide interesting clues about biogeography, as well as placing into an evolutionary context information gleaned about convergence in morphology and other aspects of the biology of cave-adapted sleepers.

The discovery of C. morrisi in southcentral Mexico is not surprising given the number of endemic hypogean species of other freshwater taxa in the region and the many stygobitic fishes documented elsewhere in Mexico ( Hubbs, 1938) and karst regions of the eastern and central United States, Caribbean, and Neotropics ( Proudlove, 2006). Central Mexico has a notable subterranean invertebrate fauna, especially decapod crustaceans that have invaded cave systems independently and that are thought to have been derived from surface or marine ancestors with affinities to cavernicolous species in the United States, Central America, and the western Caribbean region ( Hobbs et al., 1977; Hobbs, 1994; Hobbs and Lodge, 2010). Among countries of the world, Mexico ranks third (behind China and Brazil) in number of known hypogean fish species, with about 12 valid species and several additional taxa of unresolved taxonomic status (e.g., infraspecific populations of Astyanax and Rhamdia ). This number represents approximately 7% of stygobitic fishes worldwide ( Proudlove, 2010). In Mexico, as is the case globally, most hypogean fishes are ostariophysans. Caecieleotris morrisi is thus a unique taxon in representing the only known obligate cave gobiiform in the Western Hemisphere.

Figures

Fig. 1. Holotype of Caecieleotris morrisi, CNPE-IBUNAM 19073, 34.1 mm SL, sex undetermined, in lateral (A), dorsal (B), and ventral (C) views.

Fig. 2. Neurocranium in dorsal view of (A) Caecieleotris morrisi (UF 101173, paratype) and (B) Eleotris perniger (UF 27603). Abbreviations: e, eye; f, frontal; o, anophthalmic orbital region, illustrating thin, rod-like ossification in (A) in comparison to broad, laminar shelf in (B). Scale bars = 5 mm.

Fig. 3. Pattern of sensory head papillae series on head of Caecieleotris morrisi, drawn from composite of UF 101173 (31.6 mm SL, paratype) and CNPE-IBUNAM 19073 (34.1 mm SL, holotype) in lateral (A), dorsal (B), and ventral (C) views. Dorsal fin omitted from (B). Scale bar = 5 mm.

Fig. 4. Map of Presa Miguel Alemán and vicinity, Oaxaca, Mexico, type locality (vertical arrow) of Caecieleotris morrisi. Source: Wikimedia Commons (http: // en. wikipedia. org / wiki / File: Papaloapanrivermap. png).

Tables

Table 2. Measurements and meristic counts of type specimens (n = 11) of Caecieleotris morrisi. Range, mean, and standard deviation (SD) of measurements include values for the holotype.

	Holotype
	CNPE-IBUNAM 19073	Range	Mean	SD
Standard length (SL, mm)	34.1	19.3–34.1	27.0	4.9
Percent SL
Head length (HL) Pre anal-fin length	34.4 60.1	29.2–42.5 56.5–67.8	35.6 62.4	3.2 3.5
Pre spinous-dorsal fin length	45.5	42.7–50.0	46.1	2.0
Pre rayed-dorsal fin length Pre pelvic-fin length	60.1 30.8	58.5–61.9 29.8–33.9	59.9 32.1	1.2 1.2
Pre pectoral-fin length	29.3	28.8–35.6	31.1	2.1
Pectoral-fin origin to spinous dorsal-fin origin Body depth at pelvic-fin origin	8.0 17.6	7.8–11.8 14.2–18.6	9.4 16.4	1.1 1.6
Caudal peduncle depth	7.8	7.4–8.4	7.9	0.3
Caudal peduncle length Caudal peduncle width Body width at pectoral-fin origin	17.6 4.4 13.5	17.6–28.4 2.9–5.4 11.6–17.4	24.3 3.9 14.2	3.5 0.7 1.9
Pectoral-fin length Pelvic-fin length Anal-fin base length	42.2 21.1 13.5	30.8–42.2 15.0–21.1 11.4–19.8	34.8 17.2 14.7	3.3 1.9 2.8
Spinous dorsal-fin base length Rayed dorsal-fin base length	9.4 15.0	6.7–13.4 7.4–18.2	9.9 14.7	2.0 2.8
Percent HL
Head width	63.4	54.1–68.2	62.7	4.9
Upper jaw length Lower jaw length	36.1 37.4	27.0–40.9 28.1–45.5	31.2 33.1	4.2 5.0