Milyeringa justitia, Larson, Helen K., Foster, Ralph, Humphreys, William F. & Stevens, Mark I., 2013

Larson, Helen K., Foster, Ralph, Humphreys, William F. & Stevens, Mark I., 2013, A new species of the blind cave gudgeon Milyeringa (Pisces: Gobioidei, Eleotridae) from Barrow Island, Western Australia, with a redescription of M. veritas Whitley, Zootaxa 3616 (2), pp. 135-150 : 140-143

Milyeringa justitia , new species Larson and Foster

Barrow cave gudgeon

Diagnosis. A Milyeringa with first dorsal fin absent (remnant of single pterygiophore present in CT-scanned specimen), 6 segmented second dorsal fin rays; 6–7 segmented anal fin rays; pelvic fin rays I,3; 13–15 caudal fin rays; caudal and pectoral fin rays all unbranched; an almost naked body with greatly reduced scalation (single row of few cycloid scales present), head short with reduced numbers of rows of sensory papillae on the head and body; vertebrae 7–9+13–15 (22 in total), one pre-anal pterygiophore, one epural, last haemal spine broad, split, with sheet of bone joining forks. Restricted to subterranean aquifers accessed by wells sunk on Barrow Island, Western Australia.

Material examined. All from Barrow Island, Western Australia. HOLOTYPE: WAM P.33166-001, 19.5 mm SL male, old water supply well, L8, 20° 49’ 2.31” S 115° 23’ 41.98” E, BES 9794, coll. G. Humphreys and J. Alexander, 25 November 2009. PARATYPES: WAM P.33167-001, 19 mm SL male, old water supply well, L8, 20° 49’ 2.31” S 115° 23’ 41.98” E, BES 9795, coll. G. Humphreys and J. Alexander, 25 November 2009; WAM P.33137-001, 16 mm SL female, Anode well Q4, 20° 59’ S 115° 24’ E, BES 15152, coll. W. Hayes and J. Sherborne, 12 August 2009; WAM P.33135-001, 16 mm SL, sex uncertain, Anode well Q4, 20° 47’ 28” S 115° 23’ 57” E, BES 15151, coll. W Hayes and J. Sherborne, 12 August 2009; WAM P.33169-001, 23 mm SL female, Anode well P2, 5.2 km W of terminal tanks, 20° 46’ 40.07” S 115° 24’ 41.77” E, BES 15152, coll. W. Hayes and J. Sherborne, 6 December 2009.

Non-type material: WAM P.33165-001, anterior half of body remaining, mid-point of old water supply well, L8, Barrow Island, 20° 49’ 02.2” S 115° 23’ 42.2” E, BES 6959, coll. K. Hallett, 13 January 1999.

Description. Based on five specimens, 16–23 mm SL. An asterisk indicates counts and measurements of holotype ( Fig. 4 ).

First dorsal fin absent; second dorsal rays 6*; anal rays 6*–7; pectoral rays 12*–13; pelvic rays I,3; segmented caudal rays 13–15*, in 7/6 pattern in four, 8/ 7 in holotype; 7/6 (in 3), 7/7 (1), 8/6* (1), 9/9 (1) segmented caudal fin rays, all rays unbranched; lateral scale count 2–8*, in single row; vertebrae 7+15 (1), 9+13 (1); single large epural; one anal pterygiophore anterior to first haemal spine; last haemal spine broadened and forked (poorly ossified).

Body rather short, compressed, more compressed posteriorly; body depth at anal fin origin 15.2–18.4% of SL. Caudal peduncle moderate, length 19.5–21.3% of SL. Caudal peduncle depth 9.2–10.6% of SL. Head slightly depressed, rounded to rather square in cross-section, wider than deep at preopercular margin, head length 36.9–40.0% of SL; head depth at posterior preopercular margin 48.4–54.8% of HL; width at posterior preopercular margin 54.2–64.8% of HL. Mouth moderately large, terminal and oblique, chin tip anteriormost, jaws forming an angle of about 35º with body axis. Upper jaw length 43.8–47.5% of HL; inner margin of lips smooth; lower lip fused to chin anteriorly, side of lip free; chin flat and smooth. Anterior naris in very short tube at edge of upper lip, posterior naris with slightly narrower opening, nares joined by thin fleshy tube over nasal rosette; nares may be reduced to two low-rimmed pores joined by short tube over nasal rosette. Eyes absent. “Snout” area between tip of jaws and rear preopercular margin broad and concave, with hump behind maxillary symphysis, snout forming rounded square when viewed from above, length of snout tip to upper edge of the preopercular margin 68.8–76.7% of HL. Opercle length (upper edge of preopercle to upper margin of opercle) 25.4–31.5% of HL. Preopercular margin bony, smooth and flat. Gill opening very wide, extending to just anterior to or just below rictus. Tongue large, tip gently rounded to slightly pointed. Teeth in both jaws small, evenly sized, conical and pointed; in two rows; largest teeth at front of upper jaw and along side of lower jaw. Headpores absent. Sensory papillae on head in reduced longitudinal pattern ( Fig. 5 ); many papillae with thin narrow flap each (often missing due to their fragility). Sensory papillae on body reduced, with single uneven row of papillae along mid-side, a vertical row of few papillae anterior to hypural crease and another row on base of caudal fin just behind hypural crease; papillae on body rarely with thin narrow flap (probably due to damage) (Fig. 6).

Body mostly naked, cycloid scales in single row from caudal fin base to just below dorsal fin origin; scales embedded in skin, difficult to discern.

First dorsal fin absent. Second dorsal fin with all elements segmented and all rays unbranched; fin rays falling well short of caudal fin base. Anal fin with all rays segmented and unbranched. Pectoral fin somewhat pointed, central rays longest, 18.4–23.0% of SL; all rays unbranched. Pelvic fin length 15.2–18.9% of SL; pelvic spine very short, segmented rays all unbranched; fins very slender, pointed, spine quite short, all segmented rays unbranched, fins extending about half the distance to anus. Caudal fin oval, pointed posteriorly, central rays may be greatly elongate (often damaged); caudal fin length 18.7–28.9% of SL.

Live coloration. No information available.

Coloration in alcohol. Whitish, with transparent fin membranes (Fig. 6).

Distribution. This species is known only from Barrow Island, off the north-west coast of Western Australia. No Milyeringa has yet been reported from groundwater of the Robe or Fortescue River systems on the mainland east of Barrow Island, despite the presence there of some elements of the typical Cape Range and Barrow Island anchialine fauna, including Stygiocaris (Decapoda) , Halosbaena (Thermosbaenacea) , Haptolana (Isopoda) and Ophisternon (Synbranchiformes) (Humphreys 2008; Page et al. 2008).

Comparisons. Milyeringa justitia can be separated from M. veritas by its lack of a first dorsal fin ( M. veritas possesses a small first dorsal fin of III–IV spines), in having all dorsal and anal fin elements segmented ( M. veritas usually has an anal fin spine present), its greatly reduced scalation (with a few cycloid scales along the posterior half of the body compared to the almost complete scalation in M. veritas ), having fewer sensory papillae on the head and body (vertical rows on body present in M. veritas ; Fig. 7 ), a lower number of segmented caudal fin rays (13–15 in M. justitia and 16–17 in M. veritas ) and a slightly deeper head (mean HD 51.3% of SL in M. justitia vs 41.8% in M. veritas ). Milyeringa veritas also has a flatter, wider head in specimens over 30 mm SL, but as the largest M. justitia is only 23 mm SL, this feature cannot be compared.

Ecology. This species (as M. veritas ) is protected by state and Commonwealth fauna protection legislation. However, the highly restricted range, with a possible maximum area of occupancy of 78 km 2 (see Humphreys (2002)), of the new species and potential threats to its habitat warrant specific assessment of extinction risk. That is, it is likely to belong to a higher category of threat than that currently considered for M. veritas . The high conservation value of the subterranean fauna of Barrow Island was not recognised until the early 1990s (Humphreys 2001b).

The sparse knowledge of the habitat of Milyeringa on Barrow Island was summarised by Humphreys (2001b). Milyeringa is known from a former water bore (the type locality) and two anode protection bores in the middle of an oilfield that has been in production since about 1967 and where the water table is up to 54 m below the surface, being 3.8 to 5.8 km from the closest coast ( Fig. 8 ). A tidal range of about three metres, comparable to the ocean tide, in boreholes more than 1 km inland suggests well developed karst below the surface of Barrow Island, an observation that is supported by large voids recorded in drilling logs from oil and anode wells (Humphreys 2001b). The groundwater is an anchialine system showing marked hydrogeochemical stratification (Humphreys 2001b: see Fig. 3 for profile data from the type locality L8 and others), although not as well characterised as that on the Cape Range peninsula (Seymour et al. 2007).

Milyeringa justitia is sympatric with a range of stygiobiont crustaceans including Thermosbaenacea , Atyidae (Decapoda) , Hadziidae (Amphipoda) , Cirolanidae (Isopoda) , many copepod taxa including Ridgewayiidae (Calanoida) and it is also sympatric with a groundwater synbranchid eel, apparently an Ophisternon , but known only from a photograph, having been delivered to the surface by the detonation of an explosive charge in a seismic exploration well and the specimen was not retained (D. Moro; pers. comm. to WH, 8/9/2009).

Etymology. Whitley chose the name veritas for his species because “Truth lies at the bottom of a well” (Whitley 1964). As truth and justice are supposed to go together, we name this species justitia , from the Latin for justice, in the hope that justice helps the species to survive on Barrow Island, which has been an oilfield since 1967 and is most recently the site of the Gorgon Gas Hub development.

As M. veritas is known as the Cave Gudgeon, we suggest Barrow Cave Gudgeon as a common name for this species.

Figures

FIGURE 3. Milyeringa COI neighbor-joining tree. Collection localities of samples are in parentheses following the sample number. Red indicates the M. brooksi haplotype clade and blue indicates those individuals collected from Kudumurra Well (C- 25).

FIGURE 4. Holotype of Milyeringa justitia n. sp., WAM P. 33166 - 001, 19.5 mm SL male, Barrow Island, WA. Fins partly reconstructed; five scale pockets not illustrated (three scales remain).

FIGURE 5. Head of Milyeringa justitia n. sp., showing sensory papillae pattern and indicating flaps when intact; WAM P. 33165 - 001, head 3 mm long, twisted to left, posterior half of fish missing (taken for genetic sample). Inset shows lateral view of papilla row and flaps.

FIGURE 7. Ethanol-preserved paratype of Milyeringa justitia n. sp., WAM P. 33135 - 001, from Anode well Q 4 on Barrow Island, Western Australia. Photograph by W. F. Humphreys.

FIGURE 8. Barrow Island beam pump (nodding donkey) about 1 km from well L 8 that lies above the habitat of Milyeringa justitia n. sp., in groundwater about 54 m down. Photograph by W. F. Humphreys.