Phreatobius sanguijuela, Luis Fernandez, Lisandro J. Saucedo, Fernando M. Carvajal-Vallejos & Scott A. Schaefer, 2007

Luis Fernandez, Lisandro J. Saucedo, Fernando M. Carvajal-Vallejos & Scott A. Schaefer, 2007, A new phreatic catfish of the genus Phreatobius Goeldi 1905 from groundwaters of the Itenez River, Bolivia (Siluriformes: Heptapteridae)., Zootaxa 1626, pp. 51-58 : 53-56

Phreatobius sanguijuela new species

(Figs. 2-3)

Holotype. UMSS 1785, 42.1 mm SL, Bolivia, Departamento Santa Cruz, Río Iténez basin, Comunidad de Porvenir, artificial well, 6 m depth near Río Paraguá, 172 m elevation, 13º 59' 14.44'' S, 61º 32' 27.05'' W, collected by L. Saucedo, 1 June 2006.

Paratypes. MNKP 5373, 2 specimens: 27.8-32.3 mm SL, same data as holotype.

Diagnosis. Assigned to Phreatobius among siluriform genera based on the possession of the following combination of characters: dorsal and ventral procurrent caudal-fin rays extended rostrally, dorsally reaching a vertical position on dorsal-fin base posterior to dorsal-fin insertion, ventrally continuous with anal fin (Fig. 2A); caudal fin round; all anal-fin rays unbranched; mouth prognathous, with jaws displaced dorsally on head; adductor mandibulae muscle hypertrophied, covering most of skull and inserting posteriorly onto first neural spine (Fig. 2B); first pectoral-fin ray soft, not spinous; bright red in life. Uniquely diagnosed relative to its congener by the absence of eyes (versus eyes present, minute; Fig. 3), presence of 25-34 dorsal procurrent caudal fin rays (versus 42-50); 14-16 ventral procurrent caudal fin rays (versus 22-26); 45-46 vertebrae (versus54-59).

Description. Morphometric data for the holotype and paratypes presented in Table 1. Body round in cross section from head through dorsal-fin origin, gradually more compressed posteriorly, tapering to caudal fin. Dorsal and ventral trunk profiles nearly straight from head to base of caudal fin. Body depth nearly uniform through middle of anal-fin length, narrowing to caudal-fin base. Dorsal head profile markedly wider than trunk, due to hypertrophied jaw adductor musculature (Fig. 2B). Integument of head and body thick, underlain with thick layer of round, adipose bodies individually visible under stereomicroscope; myotomes and intermuscular septa not externally visible.

Head slightly depressed, longer than broad in dorsal view. Snout blunt in dorsal and lateral views. Mouth prognathous, lower jaw extending further anteriorly than upper jaw. Cleft of mouth straight. Lower jaw projected dorsally, its ventral surface markedly convex. Upper jaw strongly depressed, its depth one-third or less than that of lower jaw in lateral view. Mouth as wide as head, its lateral margins strongly curved posteriorly; mouth corner at vertical though anterior third of head length. Upper lips narrow, well defined laterally by fold of integument. Lower lip poorly defined, mostly continuous with ventral surface of head. Eyes absent (Fig. 2B). Branchiostegal membranes mostly free, narrowly attached to isthmus anteriorly at midline, with wide and almost free branchial openings; posterior origin of membranes located immediately dorsal to origin of pectoral fin.

Maxillary barbel long and thin, reaching to slightly beyond posterior margin of pectoral-fin base. Outer mental barbel longer than maxillary barbel, reaching pectoral-fin base or posterior third of pectoral fin. Inner mental barbel shortest, when extended parallel to body reaching to point slightly posterior to margin of branchial membrane; its origin slightly anterior to that of lateral mental barbel. All barbels with fine round tips.

Anterior naris prolonged as tube of integument directed anterodorsally, about twice as long as wide, narial opening small, round, located close to upper lip. Posterior naris large, anterior margin crescentic and framed by low rim of elevated integument, located close to base of maxillary barbel but not continuous with its margin. Distance between two posterior nares slightly greater than that between anterior nares.

Cephalic sensory canals comprised of three pores dorsally on anterior snout region near nares. Anterior pair (pore I of Reichel 1927: fig. 3, 305) closely spaced relative to one another along midline, positioned mesially to base of anterior nares. Mid-posterior pair (pore II) located posteromesially to posterior nares. Posterior pair (pore III) located posterolaterally to posterior nares and aligned with maxillary barbel base. Two laterosensory pores visible in lateral view. Anterior-most (pore V) located approximately at median lateral line of body, posterior (pore VI) located slightly laterodorsally. One large pore (IV) located posterolaterally close to end of head. Anterior portion of mandibular canal with two pores (VII, VIII) located ventrally close to barbel and two posterior (IX, X) pores located laterally. Pores of epiphyseal branch absent. Infraorbital canal absent. Laterosensory canal system absent along most of body, restricted anteriorly to short tube with two pores.

Pectoral fin small, base short; four rays total, all soft, first ray unbranched; last ray markedly shorter than anterior rays. Pectoral-fin insertion approximately horizontal. Pelvic fin with four* (n=2) or five (n=l) rays, one or two branched, all projecting beyond fin membrane. Pelvic fin reaching or covering anus, not reaching anal fin. Dorsal-fin margin straight and short, with seven rays (n=3), none, one or three* branched, all soft; fin origin closer to tip of snout than to base of caudal fin, positioned slightly anteriorly to vertical through pelvic fin origin, its posterior insertion approximately at middle of SL. First dorsal-fin pterygiophore inserted posterior to neural spine of vertebra 13. Anal fin straight in profile and long, with 19 (n=2) and 20* (n=l) unbranched rays. Anal-fin origin located slightly posterior to anus and vertical through dorsal fin origin. First anal-fin pterygiophore inserted on centrum 18. Anal-fin continuous posteriorly with ventral procurrent caudal fin rays, fins clearly demarkated by slight indentation along membranous fin margin. Caudal fin margin nearly round, continuous dorsally and ventrally with procurrent rays. Principal caudal-fin rays eight branched plus two unbranched* (n=2) or nine branched plus 2 unbranched (n=1), all soft. Dorsal procurrent caudal-fin rays 25, 31 and 34*. Ventral procurrent caudal fin rays 14, 15, 16*; almost vertically aligned, rays becoming gradually longer posteriorly. Caudal peduncle markedly expanded in area of procurrent rays, like a single extended fin. Vertebrae 45 (n=1) and 46* (n=2). Pleural ribs one or three*.

Pigmentation in alcohol: All specimens nearly whitish, without trace of red coloration characteristic of living specimens. Holotype and largest paratype with pigment concentration along midline of body, forming thin midlateral line (Fig. 2A). Tubelike extension of anterior naris white. All barbels white. Pectoral, pelvic, dorsal, anal, and caudal fins, as well as region corresponding to dorsal and ventral procurrent caudal fin rays, lack dark pigment. Coloration in life: Body bright red, slightly translucent, not whitish as in preserved specimens. Outline of vertebral column visible along post-abdominal region. Gut contents evident as dark shadows along ventral translucent region of abdomen.

Etymology. The specific name sanguijuela is the local name for these catfishes in this area of Bolivia, treated here as a noun in apposition to the generic name.

Distribution. Phreatobius sanguijuela is known only from artificial wells of 6 m depth at Comunidad de Porvenir, near Río Paraguâ (Fig. 1). The Río Paraguâ forms part of the headwaters of the Río Itenéz in eastern Santa Cruz Department, northeastern Bolivia.

Habitat. The artificial wells where P. sanguijuela were collected are separated from the Río Paraguâ main channel by approximately 2 km. The wells range in depth from 6 to 12 m with a diameter of approximately one meter, with surface openings covered and sidewalls unfinished. The bottom consists of unconsolidated sand and reddish lime. The water is transparent and water depth is about 1 m. The specimens were captured using a bucket during the dry season (June) and they become much less frequent during the rainy season. Water is used locally for human consumption and the catfish are captured incidentally and killed, often mistaken for parasitic leeches (“sanguijuelas”) due to their bright, blood-red coloration.

Discussion

The sensitivity of some stygofaunal species to pollution renders them excellent biological monitors and indicators of declining water quality (Hancock et al. 2005). Contamination from sewage, metals, inorganic chemicals, and pesticides has reduced diversity in various stygofaunal communities. Hypogean fishes are likewise susceptible to many threats from environmental degredation, overexplotation of natural resources, and hydrological manipulation. For example, pressure from scarcity of resources and economic isolation serves to endanger the endemic phreatic catfish Silvinichthys bortayro in northwest Argentina (Fernandez 2005). Similarly, in this particular region of Bolivia, the soils are nutrient poor and relegate local communities to heavy reliance on cattle ranching. Mining activities represent another environmental threat. A gold mine located in the San Simon Mountains approximately 100 to 130 km from the wells producing the new species discharges contaminated water into the Río Itenéz in the extraction process. Understanding the biology of phreatic fishes will aid local efforts to manage groundwater resources, support appropriate legislation for its protection and sustainable use, and spawn collaborative, multi-scale research projects in the new field of ecological hydrogeology. Increased knowledge of and appreciation for these fishes on behalf of the local people must become an important priority as well. Informal communication with the peoples of the Porvenir region indicate that the locals regard P. sanguijuela as a parasitic threat to human health, due to its blood-red color and vermiform shape. For these reasons, and perhaps because the fishes are mistaken for leeches, the fishes are killed upon incidental capture when extracting drinking water. Indigenous knowledge is a valuable source of information on the status and trends of individual species and incorporated into the process of resources management by local communities (Hellier et al. 1999). Such information would be of particular value when no alternative sources, such as detailed taxonomic surveys, are available.

Finally, discovery of a new Phreatobius species separated by some 2000 km distance from its sole congener suggests that phreatic fishes are most certainly much more common and widely distributed than previously thought. A combination of active survey of existing wells and use of baited traps may be required in efforts to expand our knowledge of phreatic fishes. The presumed limited vagility of Phreatobius is also likely untrue. Although there are no estimates of population size, and while the extent of the distribution of local populations is unknown, extreme geographic isolation of a small number of local populations is unlikely, given the persistence of populations over time.