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A new species of Egglestonichthys from northern Australian estuaries (Teleostei, Gobiidae, Gobiinae).

Received: 02 June 2013--Accepted: 07 July 2013

Abstract

A new species, that appears to belong to the gobiid genus Egglestonichthys, is described from specimens collected from the shallow coast and estuaries of Kakadu National Park in the Northern Territory, Australia. It is unusual among gobiids in that the lower half of the pectoral-fin lacks connecting membrane between the fin rays, so that the rays are free (resembling the pectoral fm of the fishes of the family Polynemidae). Its closest relative may be E. bombylios Larson and Hoese, although its sensory papilla pattern differs from others in the genus. A key to the four known species presently placed in Egglestonichthys is provided.

Zusammenfassung

Beschrieben wird eine neue Art, die offenbar zu den Grundeln der Gattung Egglestonichthys gehort, nach Exemplaren, die an der flachen Kuste und in den Mund-ungsgebieten im Kakadu-National park des Nordterritoriums in Australien gesammelt wurden. Sie zeigen ein unter Gobiiden ungewohnliches Merkmal: die untere Halfte der Brustflossen hat keine verbindende Membran zwischen den Flossenstrahlen, sodass die Strahlen frei stehen (ahnlich wie bei den Fischen der Familie Polynemidae). Als nachster Verwandter durfte E. bombylios Larson and Hoese gelten, obwohl das Muster der Sinnes-Papillen sich von allen anderen in der Gattung unterscheidet. Beigefugt ist ein Bestim mungsschlussel zu den vier Arten, die bisher der Gattung Egglestonichthys zugeordnet werden konnten.

Resume

Une nouvelle espece, qui semble appartenir au genre de Gobiides Egglestonichthys, est decrite sur base de specimens collectes sur la Cote etroite et dans les estuaires du parc national de Kakadu, Territoire du Nord, Australie. Elle differe des autres Gobiides par le fait que la moitie inferieure des pectorales n'a pas de membranes entre les rayons, ce qui implique que ces nageoires sont libres (evoquant la pectorale des poissons de la famille des Polynemidae). L'espece la plus proche pourrait etre E. bombylios Larson et Hoese, bien que le patron de ses papilles senso-rielles differe de celles des autres membres du genre. Une c16 des quatre especes d'Egglestonichthys connues a cc jour est fournie.

Sommario

Una nuova specie, che sembra appartenere ai gobidi del genere Egglestonichthys, e descritta sulla base di esemplari raccolti in estuari e zone costiere poco profonde del Kakadu National Park nel Northern Territory, Australia. Presenta un'insolita caratteristica tra i gobidi: la meta inferiore della pinna pettorale manca di membrana di collegamento tra i raggi, che, pertanto, risultano liberi. (cio la rende simile alla pettorale dei pesci della famiglia Polynemidae). II suo parente piu prossimo potrebbe essere E. bombylios Larson e Hoese, anche se il modello di distribuzione delle papille sensoriali e diverso da tune le altre specie del genere. Viene fornita una chiave di identificazione per le quattro specie attualmente conosciute collocate in Egiestonichthys.

INTRODUCTION

In 1997, during an estuarine fish survey along the coast of Kakadu National Park, Northern Territory, specimens of an unusual small gobiid were obtained by a small beam trawl (2 m wide mouth, 6.5 mm mesh body and 1.4 mm mesh cod end). Subsequent surveys in 1998, 1999 and 2001 produced additional specimens. The fish have been tentatively identified as belonging to Egglestonichthys, a genus containing three other species of somewhat disparate appearance. Miller and Wongrat (1979) created the genus for a goby with a complex transverse papilla pattern resembling that found in some eleotrids (e.g. Eleotris), lacking lateral-line sensory pores and having a wide gill opening (to below preoperculum). Larson and Hoese (1997) described a second species (E. bombylios) and redescribed E. melanoptera Rao, originally described as a Callogobius. Miller and Wongrat (1979) provided the only published osteological information for the genus (based on the type species, E. patriciae).

The new species somewhat resembles E. bombylios Larson and Hoese, 1997, in general appearance, having reduced eyes, moderate gill opening and with some raised sensory papilla rows on the head, but differing in having a number of fin rays in the lower half of the pectoral-fin free from connecting membranes, resembling the rays of a polynemid, no scales on the cheek or opercle, as well as a sensory papilla arrangement that is unlike other species of Egglestonichthys. Although the new species has several features that differ from other Egglestonichthys, the group is so little-studied that I am reluctant to create yet another new genus based on limited information.

So far this fish is known only from coastal marine and estuarine waters within Kakadu National Park (Larson 2002) (Fig. 1). Similar beam trawl and dredging surveys have been carried out in other estuaries and harbours in the Northern Territory, but this species has not been not found. It is most interesting that this new species has not yet been collected elsewhere in the Territory, and it is possible that the fish has very specific habitat requirements.

METHODS

Measurements were taken using electronic callipers and dissecting microscope. Counts and methods generally follow Hubbs and Lagler (1970), except as indicated below. Transverse scale counts backward (TRB) are taken by counting the number of scale rows from the anal-fin origin diagonally upward and back toward the second dorsal-fin base. Head length is taken to the upper attachment of the opercular membrane. References to second dorsal and anal-fin rays includes a thin flexible spine in addition to the segmented rays. The segmented or branched caudal ray pattern (e.g. 9/8 or 9/7) is the number of segmented caudal rays attaching to the upper and lower hypural plates respectively. Vertebral counts and other osteological information were obtained by X-ray. Pterygiophore formula follows Birdsong et al. (1988). Institutional abbreviations are: AMS, Australian Museum, Sydney; NTM, Museum and Art Gallery of the Northern Territory, Darwin: QM, Queensland Museum, Brisbane; WAM, Western Australian Museum, Perth.

Egglestonichthys ulbubunitj n. sp.

Threadfin Goby

(Figs 2-4, Table I)

Table I. Morphometrics of Egglestonichthys ulbubunitj n. sp.,
expressed as percentage of SL or HL as indicated (n = 21).

                           Holotype  Mean  Maximum  Minimum

Head length in SL              29.3  30.4     33.3     27.9

Head depth in HL               69.5  67.7     75.0     61.7

Head width in HL               76.8  68.5     83.0     60.7

Body depth in SL               23.9  21.2     23.9     18.4

Body width in SL                9.3   8.6     10.4      7.0

Caudal peduncle length in      19.6  20.5     24.6     18.3
SL

Caudal peduncle depth in       13.6  11.8     13.6     10.5
SL

Snout length in HL             23.2  23.5     27.7     20.0

Eye width in HL                15.9  15.9     18.3     13.5

Upper jaw length in HL,        42.7  45.5     50.0     38.3

Interorbital width in HL       23.2  18.4     23.2     14.0

Pectoral-fin length in SL      27.9  29.0     33.7     26.7

Pelvic-fin length in SL        28.6  29.5     33.9     26.7

Caudal-fin length in SL        53.6  56.2     63.6     50.0

Longest dorsal-fin spine       13.6  15.9     19.1     13.0
in SL


Holotype: NTM S.14635-005, 28 mm SL female, off Pococks Beach, N of West Alligator Head, 1.4 m, very soft mud, beam trawl, 26 May 1998, R Williams, G. Dally, A. Pickworth and M. Gorst.

Paratypes: NTM S.17348-001, 3(26.5-30), same data as holotype; NTM S.14479-003, 1(31), centre of West Alligator River mouth, 5.5 m, mud, beam trawl, 27 May 1997, coll. R Williams and A. Pickworth; NTM S.14657-007, 4(10.5-20), off "The Rookery", East Alligator River, 7.3 m, mud, beam trawl, 2 June 1998, coll. R. Williams and G. Lindner; NTM S.15703-001, 1(18.5), 5 km offshore between Field Island and Point Farewell, 9.6 m, mud, beam trawl, coll. R. Williams, S. Morrison and D. Elphick, 12 June 2001; NTM S.16024-001, 1(28), N of West Alligator Head, 16 m, soft mud and shell grit, dredge, coll. N. Smit and party, 21 November 2004; QM 1.39101, 4(18-24), 1 km off Pococks Beach, West Alligator Head, 5 m, mud, beam trawl, coll. A. Pickworth, M. Gorst and A. Turner, 7 June 1999; AMS 1.46190-001, 2(24-27), off Midnight Point, South Alligator River, 10 m, mud and detritus, beam trawl, coll. R. Williams, S. Morrison and D. Elphick, 12 June 2001; NTM S.15289-003, 1(19), 31 km upstream from mouth of South Alligator River, 10-11 m, mud, beam trawl, coll. G. Lindner, F. Baird and G. McSkimming, 6 June 1999; WAM P. 33873-001, 1(33), Brooks Creek mouth, South Alligator River, 8-9 m, mud, beam trawl, coll. G. Lindner, F. Baird and G. McSkimming, 6 June 1999; NTM S.14441-012, 2(20-24.5), off mouth of Wildman River, 2 m, firm mud and plant detritus, beam trawl, coll. H. Larson, R Williams, A. Pickworth and M. Gorst, 28 May 1997.

Non-type material: NTM S.17479-001, 1(29), South Alligator River, 12[degrees] 12' 48.5994" 132[degrees] 24' 53.9994", in 3.5m depth over mud, beam trawl, coll. B. Pusey and M. Kennard, 27 August 2012 [frozen in the field for later identification].

Diagnosis: A small, slender, round-headed goby with small eyes, long pointed caudal fin and lower 3-7 pectoral-fin rays free from membrane; second dorsal-fin rays always 1,10; anal fin rays always 1,10; pectoral-fin rays 19-21; longitudinal scales 22-25; TRB 7-9; side of head naked, predorsal scales 9-12, extending forward to behind eyes; eyes small and dorsolateral; interorbital broad and convex; jaws oblique, with small caniniform teeth; head pores absent; reduced papillae pattern on head arranged in mostly longitudinal pattern, papillae often pointed, fleshy and may be on short raised ridges; eyes silver when alive, head and body colour pale yellowish-white, with six or seven indistinct dusky bands across nape and sides, and large oval black spot on posterior part of first dorsal fin.

Description: Based on 21 specimens, 18-33 mm SL. Counts of holotype (Fig. 2), where differing from paratypes, indicated by asterisk (in parentheses where necessary); morphometrics in Table I.

First dorsal fin VI; second dorsal-fin rays always 1,10; anal-fin rays always I,10; pectoral-fin rays 1921 (usually 20 (holotype with 20 in left fin, 21 on right); segmented caudal-fin rays 17; caudal-fin ray pattern 9/8 (one specimen with 9th upper ray split to near base); branched caudal-fin rays 8/6 (in 10), 8/7 * (in 11), 7/6 (in 1); unsegmented (procurrent) caudal-fin rays 6/6 to 8/8 (usually 7/6 or 7/7, 8/7 in holotype); longitudinal scale count 22-25 (modally 23 *); TRB 7-9 (modally 8 *; predorsal scale count 9-12 (modally 9; 11 in holotype); circ-umpeduncular scales 12 *-13 (modally 12). Gill rakers on outer face of first arch 3+11 (1), 4+11 (1), 5+11 (1). Pterygiophore formula 3-22110 * (in 15 *), 3-2310 (in 1). Vertebrae 10+16 (in 18). One epural (in 17 *), two in one specimen. Two anal pterygiophores before haemal spine of first caudal vertebra (in 18).

Head rounded in cross-section, length 27.9-33.3% (mode 30.0%) in SL; profile rounded to slightly pointed. Depth at posterior preopercular margin 61.7-75.0% (mode 66.7%) in HL. Head width at posterior preopercular margin 60.7-83.0% (mode 76.8%) in HL. Mouth terminal, oblique, forming an angle of 35-400 with body axis; jaws reaching to below posterior margin of eye or at least posterior half. Lips smooth, lower lip free, fused on either side of broad flat chin. Upper jaw 38.3-50.0% (mode 45.0%) in HL. Eye very small, placed laterally, closer to snout tip than to rear margin of preopercle, 13.5-18.3% (mode 15.9%) in HL. Snout broad and short, 20.027.7% (mode 23.2%) in HL. Interorbital very broad, flattened, 14.0-23.2%% (mode 19.0%) in HL. Body slender and compressed, depth at anal origin 18.4-23.9%% (mode 23.9%) in SL; body width at origin of first dorsal 7.0-10.4% (mode 7.0%) in SL. Caudal peduncle length 20.0-24.6% (mode 20.0%) in SL. Caudal peduncle depth 10.513.6% (mode 13.6%) in SL.

No mental fraenum; single transverse row of fleshy papillae present on chin. Anterior naris in broad, very short tube, close behind upper lip. Posterior naris rounded to oval, placed above and forward of anterior margin of eye. Gill opening moderate, extending forward to just under opercle or to mid-opercle, but not reaching posterior preopercular margin. Anterior edge of shoulder girdle (cleithrum) smooth. Gill rakers on outer face of first arch without spines, fleshy and slender, somewhat shorter than gill filaments; rakers on inner face of first arch short, stubby, without fine spines; outer rakers on other arches similar to inner face rakers. Tongue short, blunt to slightly rounded.

Outer row teeth in upper jaw small, sharp and pointed, in three rows across front and two along side; outermost row teeth larger, more curved, with largest two to six teeth on either side of symphysis. Outer row teeth in female slightly smaller than those in male. Lower jaw with two to three rows of similarly sized, small sharp teeth, none particularly large; outermost row teeth may be more upright and less curved.

Scales on head and body all cycloid. Predorsal scales small, reaching forward to close behind eyes. Cheek and operculum without scales. Pectoral base naked or with few large scales. Prepelvic area with moderately-sized scales, may be embedded.

Head pores absent.

Sensory papillae pattern on head in pattern as shown diagrammatically in Figure 3; appearing longitudinal but with few rows that appear transverse (and with some individual variation); all specimens show some damage to sensory papillae due to abrasion during trawling and subsequent handling. Papillae on head large, fleshy and often with pointed tips, in some specimens, papillae appear as two forms: vertically oriented papillae on short raised ridges, horizontally oriented papillae small and oval to round, within rounded fleshy depressions. In some specimens, papillae barely visible above skin, and can be seen through partly transparent flesh as short ridges; papillae on underside of head usually discernible above skin.

Genital papilla in male short, small, flattened, with blunt to slightly pointed tip. Genital papilla in females very short, bulbous.

First dorsal-fin low, rounded, spines barely reaching first element of second dorsal-fin origin; third or fourth dorsal spine longest, 13.0-19.1% in SL. Second dorsal and anal-fins long, pointed posteriorly, posteriormost rays of these fins usually reaching onto caudal fin. Pectoral-fin relatively narrow, pointed, 26.7-33.7% (mode 30.0%) in SL; pectoral-fin rays branched, upper and lowermost rays unbranched; lowermost three to seven (usually five to six, three in only one specimen) rays free from membrane (tips of branches of each individual branched ray joined by membrane). Pelvic-fins large (reaching anus), oval, disc-shaped, fraenum deep; fin length 26.7-33.9% (mode 28.6%) in SL. Caudal fin very long and pointed, 50.0-63.6% (mode 53.6%) in SL.

Live coloration: Only a few notes were taken when the holotype was collected: "translucent grey fat-headed goby with small silver eyes and indistinct grey cross-hatched bands across back". Figure 4 shows the freshly dead non-type specimen.

Coloration in alcohol: Background colour yellowish white, with six or seven short faint brownish saddles crossing back; first on nape before first dorsal fin and seventh at caudal-fin base (two saddles under second dorsal fin may coalesce); saddles usually joining short staggered oblique pale brownish bars or blotches along midside of body; within brownish saddles, scale margins narrowly outlined with slightly darker pigment (Fig. 4). Head and chin evenly speckled with fine brown; nape paler, may show one to three indistinct brownish bars crossing from opercle to opercle. Indistinct short brown line from front margin of eye to middle to upper jaw. Remainder of underside of head, breast and belly whitish.

First dorsal-fin translucent, anteriorly with faint brownish wedge-shaped mark extending up from second dorsal saddle; distinct black round to oval spot on posterior part of fin extending from fourth to sixth spine. Second dorsal-fin translucent to faintly brownish, fin margin narrowly unpigmented. Anal-fin translucent, with variable amounts and intensity of brown speckling along basal half of fin, usually more prominent on posterior part of fin. Pectoral-fin translucent, with faint wedge of brown speckling on upper half, an extension of an indistinct brown bar along bases of pectoral-fin rays and rear part of pectoral-fin base. Pelvic-fins translucent. Caudal-fin translucent with faint brownish speckling basally and often along membranes (mostly on lower half of fin).

Distribution: Known only from turbid estuarine and coastal habitats in the Alligator Rivers region, Northern Territory

Comparisons: This is a distinctive fish, and is unlikely to be confused with any other gobiid, especially when the pectoral fins are examined. It does not closely resemble the other species of the genus Egglestonichthys; indeed, all four described species are rather different from each other in body form and colour pattern (see Remarks and dichotomous key below).

Ecology: All specimens were obtained by 2-metre beam trawl or small dredge over (and occasionally in) very soft to firm mud (occasionally with broken shell and plant detritus such as drifts of leaves), at depths of 1-16 m. Water quality varied with the tide, from 25.8-28.4[degrees]C and 28.0-30.3[per thousand] salinity This small goby co-occurs with estuarine fishes such as small polynemids, juvenile sciaenids, engraulids and cynoglossids in this soft-substrate habitat (Larson 1999).

Etymology: Named ulbubuni, to be treated as a noun in apposition, for the Ulbu Bunidj clan in Arnhem Land, at the suggestion of senior Traditional Owner Jonathan Nadji. He stated: "My family's clan area includes the area where this fish (go by threadfin) was discovered. Our clan, Ulbu Bunidj, shares this area with Djindibi. I would like this fish to be named after our clan, which is Ulbu Bunitj".

Suggested common name: Threadfin Goby.

Remarks: This species will not key out to Egglestonichthys in Larson and Murdy's 2001 key to western Pacific gobiid genera. In fact, anyone attempting to use this key for any species of Egglestonichthys will not succeed as couplet 35b is incorrect, unfortunately (it states that head pores are present, when this is not so in Egglestonichthys; writing a working key to 76 often poorly defined genera is difficult).

As noted by Larson and Hoese (1997), there is some variation of features among the described species of this genus. Egglestonichthys ulbubunitj lacks spines on the gill rakers, as does E. bombylios. The sensory papillae pattern on the head of E. ulbubunitj is not like that of any of the other species, in that the transverse pattern is reduced and varies somewhat between specimens, although the papilla structures themselves (fleshy, partly raised on ridges) do resemble those of E. bombylios. Of the four known species of the genus, only E. patriciae and E. melanoptera are similar to each other (and could be conspecific; fresh, undamaged material is needed). Neither E. bombylios nor E. ulbubunitj greatly resemble the other two. The paucity of specimens makes further analysis difficult--one known specimen of E. patriciae, four each of E. melanoptera and E. bombylios as compared to 21 of E. ulbubunitj the smallest species (N.B. have just learned that 30 specimens of E. melanoptera have recently been collected off India; pers. comm. D. Ray, Zoological Survey of India, West Bengal). It is possible that more specimens are waiting among the trawled fish identified only as "Gobiidae" in museums.

Further material of all species will confirm whether these four odd goby taxa truly belong together as a group or not. Genetic analyses and further morphological examination will undoubtedly help disentangle them. Although it is not entirely satisfactory to assign this new species to a genus to which it may not belong, it at least flags the problem and indicates that much work remains to be done on all those small "trawl gobies" presently waiting to be examined in collections world-wide.

ACKNOWLEDGEMENTS

My many thanks to Rex Williams and Gavin Daily of the Museum and Art Gallery of the Northern Territory for their considerable help. Thanks to Charles Darwin University staff for photographing the freshly dead colouring of the small non-paratype specimen. Many thanks also to Garry Linder of Parks Australia North for all his assistance, especially with logistics; Parks Australia North staff, in particular Mick Gorst, Anna Pickworth, Buck Salau and Andrew Wellings, and Traditional Owners Joseph Bishop, Leanne Alderson and Kenny Wauchope; all of whom worked with us in collecting these peculiar fish during the Kakadu National Park estuarine fish monitoring surveys from 1997 to 2002. Their willingness and good humour made the difficult task of beam-trawling in deep mud habitats that much more enjoyable.

REFERENCES

BIRDSONG, R. S., MURDY, E. 0. & PEZOLD, F. L. 1988. A study of the vertebral column and median fin osteology in gobioid fishes with comments on gobioid relationships. Bulletin of Marine Science 42 (2): 174-214.

HUBBS, C. L. & LAGLER, K. F. 1970. Fishes of the Great Lakes Region. University of Michigan Press: Ann Arbor.

LARSON, H. K. 1999. Report to Parks Australia North, on the estuarine fish inventory of Kakadu National Park, Northern Territory, Australia. Museum and Art Gallery of the Northern Territory Research Report No. 5. 50 pp.

LARSON, H. K. 2002. Report to Parks Australia North, on estuarine fish monitoring of Kakadu National Park, Northern Territory, Australia. Museum and Art Gallery of the Northern Territory, unpublished report. 42 pp.

LARSON, H. K. & HOESE, D. F. 1997. A new species of Egglestonichthys (Pisces; Teleostei; Gobiidae) from the Indo-West Pacific, with discussion of the species of the genus. The Beagle, Records of the Museums and Art Galleries of the Northern Territory 13: 45-52.

LARSON, H. K. & MURDY, E. O. 2001. Gobiidae. Gobies. Pp 3578-3603. In: Carpenter, K. E. and Niem, V. H. (eds) FAO species identification guide for fishery purposes. The living marine resources of the western Central Pacific. Volume 6. Bony fishes part 4 (Labridae to Latimeriidae). FAO, Rome.

MILLER, P. J. & WONGRAT, P. 1979. A new goby (Teleostei: Gobiidae) from the South China Sea and its significance for gobioid classification. Zoological Journal of the Linnean Society 67: 239-257.

RAO, V. V. 1971. New gobioids from Godavari estuary. Journal of the Zoological Society of India 23 (1): 39-54.

Helen K. Larson

Museum and Art Gallery of the Northern Territory, P.O. Box 4646, Darwin, NT 0801, Australia; Museum of Tropical Queensland, 70-102 Flinders street, Townsville, Queensland 4810, Australia.

School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.

Key to the species of Egglestonichthys

1   Pelvic frenum present, may be thin (and            2
    easily damaged); body pale to brownish with
    darker bands or blotches; mouth small to large

1a  Pelvic frenum absent; fins and body generally      E. melanoptera
    plain dark brown to black; mouth large and         (Rao, 1971)
    reaching to well below eye

2   Lower 3-7 pectoral-fin rays free from fin          E ulbubunitj
    membrane; caudal-fin elongate and pointed,         n. sp.
    much longer than head; lateral scales 22-25

2a  All pectoral-fin rays contained within             3
    membrane; caudal fm not elongate and pointed;
    with at least 30 lateral scales or more

3   Papilla rows on head raised on fleshy ridges       E. bombylios
    especially around jaws, anterior cheek and snout;  Larson and
    lateral scales  31-35; eyes small (9-13 in HL)     Hoese, 1997

3a  Papilla rows on head not raised on fleshy ridges;  E. patriciae
    lateral scales 40; eyes moderate (3.5 in HL)       Miller and
                                                       Wongrat, 1979
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Author:Larson, Helen K.
Publication:aqua: International Journal of Ichthyology
Article Type:Report
Geographic Code:8AUST
Date:Jul 19, 2013
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