Thymichthys politus (Richardson) Last & Gledhill Csiro, 2009

Last, Peter R. & Gledhill Csiro, Daniel C., 2009, A revision of the Australian handfishes (Lophiiformes: Brachionichthyidae), with descriptions of three new genera and nine new species 2252, Zootaxa 2252 (1), pp. 1-77 : 59-64

Thymichthys politus (Richardson) , new combination

Figs 1 , 2 , 5 , 23 – 25; Tables 6 – 10

Cheironectes politus Richardson, 1844a: 133–134 ; holotype whereabouts unknown; from Port Arthur, Tasmania [original description].

Chironectes politus: Günther, 1861: 183 [amendment of generic name].

Brachionichthys politus: Johnston, 1883: 121 [new combination].

Sympterichthys politus: Paxton et al., 2006: 648 [new combination].

Neotype. CSIRO H 4118–01 , 61.4 mm SL, Actaeon Islands, D'Entrecasteaux Channel , Tasmania, 43° 34'S, 147° 00'E, 5 m, 6 Apr. 1985.

Additional material. 7 specimens (28–90 mm SL): CSIRO H 782–01 , 67.3 mm SL, off Forestier Peninsula , Tasmania, 42° 52'S, 147° 57'E, 10–12 m, Jun. 1987 ; CSIRO H 4114–08 , 49.8 mm SL, Tasmania, no other data ; CSIRO T 4 , 65.9 mm SL, off Forestier Peninsula , Tasmania, ca. 42° 52'S, 147° 57'E, 20 m , 1983; CSIRO T 1997–01 , 57.8 mm SL, and CSIRO T 1997–02 , 60.2 mm SL, Actaeon Islands, D'Entrecasteaux Channel , Tasmania, ca. 43° 32'S, 147° 00'E, 8 m, 19 Apr. 1980 ; QVMT 2009 :5:2, 90 mm SL, southern Tasmania, no other data ; TMH D 928 , 28.1 mm SL, off Bridport, Bass Strait , Tasmania, 40° 58'S, 147° 25'E, 15 Oct. 1950 .

Diagnosis. Member of the genus Thymichthys with a combination of the following characters: esca large, 45–65% (mean 52%) of illicium length (including esca); illicium short, thick and fleshy, without dermal spinules, length 14–17% SL, 3–3.4 times in head length, well separated from upper jaw (pre-illicial length 3.3–7.9% SL); eye of moderate size, 6.9–9.3 times in head; body variably covered with small, close-set flattened warts but lacking well-developed dermal flaps; posterior margins of warts usually with a small, sharp, prostrate spine (mostly embedded with its tip sometimes visible); scales deeply embedded, widely spaced; second dorsal-fin rays 16–17, fin base 63–71 (mean 67)% SL; length of second dorsal-fin spine 0.7–1 times length of longest ray of second dorsal fin; 9–10 anal-fin rays; 9 (rarely 10) pectoral-fin rays; body variable shades of red, usually paler ventrally; often bluish or blackish near dorsal tips of pectoral and pelvic fins, and along margins of dorsal, anal and caudal fins.

Description (data for neotype precedes other material). D1 2 (2, n=7); D2 17 (16–17); A 10 (9–10); Pc 9 (9–10, rarely 10); Pv i, 4 (i, 4); C 1 (0–1, rarely 0) + 6 (6–8, mainly 6) + 2 (1–2, rarely 1) = 9 (9); Vt 9 (8–10, rarely 8) + 14 (12–14, mainly 14) = 23 (22–24, rarely 24).

FIGURE 23. Collection localities for: A. Thymichthys politus , neotype () and additional material (•); B. T. verrucosus , holotype () and additional material ().

Body relatively elongate, moderately compressed; upper anterior margin strongly convex and elevated slightly; profile truncate to weakly convex above mouth (pre-illicial snout almost vertical); margin below first dorsal fin almost straight, usually with a deep notch above posterior aspect of eye; upper margin of eye not close to dorsal margin of head; nape usually humped; profile of head suboval when viewed anteriorly; anterior ventral profile strongly convex, sometimes flattened between pelvic fins; abdomen not expanded; caudal peduncle short, length 4.5 (2.1–5.9)% SL. Head length 46 (48–52)% SL; snout very short, length 6.8 (5.9–6.4) times in head; eye of moderate size, diameter 6.9 (7.3–9.3) times in head length; gill opening small, papilliform, aperture subequal to size of pupil, located slightly above and behind insertion of pectoral fin. Nostril aperture sizes, position and protrusibility variable (often indistinct from surrounding pores of the cephalic sensory system); usually large, well separated (anterior opening slightly closer to upper jaw than to posterior opening); anterior opening usually tubular and fringed distally (sometimes pore-like); posterior opening usually tubular, located close to orbit at horizontal level of mid eye and posterodorsally to anterior opening. Mouth small to moderate in size, terminal, not protractile; upper jaw oblique, 3.8 (3.7–4.9) in head; lips thin, not fleshy, partly recessible into shallow, circumoral groove and connected slightly forward of or below anterior margin of eye; angle of jaw not retractable into a groove; tongue well developed, rounded apically. Teeth small, villiform, in narrow bands in both jaws; band in lower jaw slightly broader near symphysis than in upper jaw; vomer edentate.

*Distance from the base of the third dorsal-fin spine to the origin of the second dorsal fin.

Skin usually thick, flabby and corrugated; body covered over most of surface with small, flattened wartlike protuberances or papillose ridges (sometimes altered through preservation, see CSIRO T 4); warts close set, their posterior margins sometimes with a short, sharp, spine tip protruding (most scales and their associated spines fully embedded in skin); rudimentary dermal flap sometimes present on mid-arm of pectoral fin (rudimentary in neotype), thallate, irregular in shape, much smaller than gill opening when present; dermal filaments poorly represented on ventrolateral surface of body. Fin rays and their associated membranes without evidence of scales or spines; illicium naked, covered with thick, fleshy skin with papillose ridges. Scales of acoustico-lateralis system bicuspid, with small central pore flanked by slender apical spinules; spinules horseshoe-shaped, much longer than spinules of body scales; arranged in well defined series; best defined on head (below lower jaw, and below and above eye) and in a single row extending along mid-upper trunk more or less parallel to dorsal margin.

Illicium terminal on snout; well separated from upper jaw, its insertion confluent with origin of first dorsal fin; short and thick, 3.4 (3.0–3.2) times in head, 1.5 (1.1–1.5) times in length of second dorsal-fin spine; when depressed, apex of esca reaching to about base of third dorsal-fin spine; illicium not retractable into obvious fleshy groove beside first dorsal fin; esca large with short, thallate filaments, 2.0 (1.5–2.2) times in length of illicium; filaments dense, matted; illicial base indistinct, obscured by skin. First dorsal fin not greatly elevated, its base with long posterior membrane; second dorsal-fin spine distinctly recurved, originating at base of illicium, distinctly longer than third spine; posterior membrane terminating above or behind level of insertion of pelvic fin, interdorsal distance short, exceeding snout length; first dorsal-fin base 3.2 (2.0–2.8) times in second dorsal-fin base. Second dorsal fin rays tallest anteriorly; fin margin not indented, decreasing slightly in height posteriorly, anterior rays much taller than penultimate posterior rays; rays simple; fin base elongate, 72 (63–69)% SL; longest ray of second dorsal fin 0.92 (0.74–0.96) times in longest dorsal-fin spine; fin membrane relatively thick, usually fully or partly concealing bases of fin rays. Anal fin moderately tall; penultimate posterior fin rays subequal to those anteriorly; length of anal-fin base 1.9 (1.6–1.8) times in length of second dorsal-fin base. Pectoral fin extended, arm-like, radials elongate, robust; extending posteriorly for almost an eye diameter behind gill opening; fin rays filamentous distally, short, membranes deeply incised, increasingly so posteriorly, tips highly flexible. Pelvic fin short, robust; rays thick and fleshy, rather deeply incised; anterior spine short, embedded and indistinct; fin located on ventral surface, usually directed ventrolaterally; its base aligned horizontally; interpelvic space broad, flat to weakly concave. Caudal fin relatively short, margin narrowly rounded; length 2.9 (2.6–3.2) times caudal peduncle depth.

Coloration. In life: Two primary colour morphs exist but both are dominated by reddish tones. A bright red morph (CSIRO H 782–01, see Fig. 25A ) is uniform vivid red (burgundy) over body and fin bases; outer parts of dorsal, caudal, anal, and pectoral fins bluish and white, sharply demarcated from reddish basal part of fins by a black edge; bluish and white areas confined to about half to a third of soft dorsal, anal and pectoral fins, covering most of caudal fin, and as two notches on first dorsal fin; pelvic fin mostly whitish; extremities of pectoral and pelvic fins red tipped; eye reddish pink; illicial stem red, esca pink. A mottled morph, which includes the neotype (CSIRO H 4118–01, see Fig. 24A ), is less strikingly coloured: pink with extensive reddish patches and spots, densest over head and upper body; fins translucent pink, rich red with bluish areas, or consistent with body colour.

In preservative: Reddish areas fading to pinkish or white; bluish and black areas become dusky, brownish or black.

Size. To at least 90 mm SL (ca. 136 mm TL); smallest specimen examined 28.1 mm SL. Size of newly hatched young and egg capsule diameter unknown.

Distribution. In widely disjunct populations; collected off the Forestier Peninsula (ca. 42° 50'S, 147° 57'E) and Actaeon Islands, D'Entrecasteaux Channel (ca. 43° 30'S, 147° 03'E), southeastern Tasmania; also a single specimen from Bass Strait, off northern Tasmania (ca. 40° 58'S, 147° 25'E). Occurs demersally inshore at depths of about 1– 20 m.

Etymology. Epithet based on polio, Latin for polish, in reference to its ‘shining reddish brown appearance’. Vernacular name: Red Handfish (Last et al., 2007).

Comparisons. Thymichthys politus is the only reddish coloured handfish with a warty skin, a slender body, and a short illicium with a large esca. It is distinguished from its closest relative, T. verrucosus , in the comparison section for that species.

Remarks. An imperfect figure ( Fig. 1C ) of a handfish, presumably of T. politus , was published in Dr Ross’s Van Diemen’s Land Annual for 1835. Richardson (1842) referred to this figure and named a reddish handfish collected by amateur naturalist, Mr T. Lempriere near the penal colony of Port Arthur, as Cheironectes (incorrect spelling of Chironectes ) politus . Richardson provided brief details of colour and noted the unusual spinous dorsal and pectoral-fin shapes of this specimen. However, a formal description of this handfish was not completed until two years later ( Richardson, 1844a, b).

It appears that T. politus was not uncommon at Port Arthur (Tasman Peninsula) in the early 1800’s. Richardson (1844) quoting Lempriere (from a compiled list of fishes collected) wrote ‘its colour is red, with spots, and all that I have seen were of the same size’ – inferring that he had seen multiple specimens. However, T. politus may have undergone a major population decline at Port Arthur. There has been an active dive business in the area and substantial other independent commercial and recreational diving effort around Port Arthur and its environs since the 1980s but only two reported local observations of T. politus have surfaced (Gowlett-Holmes, pers. comm.).

The Tasman Peninsula specimens, which were not retained, apparently resembled the mottled colour morph – figured by Edgar et al. (1982) based on a specimen collected from the D’Entrecasteaux Channel and conforming to Richardson’s (1844a) description of the holotype: ‘shining reddish brown, with minute paler marblings or reticulations’. The holotype suffered fin damage in the voyage from Australia to England ( Richardson, 1844a) and was subsequently lost ( Paxton et al., 1989). Hence, in the absence of other material from Port Arthur, the neotype is based on the mottled morph (rather than the bright red morph) pending a molecular investigation of the conspecificity of these forms.

The collection method used by Lempriere was not discussed by Richardson but it is most likely to have been using a dip net over rock and weed substrates at low tide. A large population of T. politus , consisting of hundreds of individuals of the bright red morph, was discovered on an inshore reef at Primrose Sands (Frederick Henry Bay) in the 1990s (Gowlett-Holmes, pers. comm.). Individuals were found near the outer reef edge in 5 m depth but were also common in wading depths near the shore where they could have been easily collected using dip nets. Their habitat on the Primrose Sands reef consisted mainly of stands of the green alga Caulerpa trifaria and other mixed algae. More recently, this substrate has been almost totally destroyed by an infestation of the native sea urchin ( Heliocidaris erythrogramma ) and no handfishes have been seen there since.

Most museum specimens of T. politus , as well as those observed by divers, have been about 60–70 mm SL. However, a large specimen from an unknown locality off southern Tasmania (QVM T 2009:5:2), was much larger (ca. 90 mm SL). This individual is very elongate and differs from both other forms of T. politus in being dark brown and white in preservative.

Figures

FIGURE 1. Early illustrations of brachionichthyids, reproduced courtesy of the Tasmaniana Library (State Library of Tasmania): A. Brachionichthys hirsutus illustrated by W. Gould (ca. 1832), figured as a ‘Walking Fish’; B. Brachionichthys hirsutus (bottom specimen), illustrated by L. Meredith, figured as a ‘Tortoiseshell Fish (Cheironectes politus)’ in Tasmanian Friends and Foes (1880); and C. Thymichthys politus, copper engraving by T. Bock, figured as ‘Fish caught at Port Arthur’ in Dr Ross’s ‘Van Diemen’s Land Annual’ for 1835.

FIGURE 2. Illustrations of the illicium and esca of: A. Brachionichthys australis, CSIRO H 4114–07, 55.8 mm SL; B. Brachionichthys hirsutus, CSIRO T 7, 78.9 mm SL; C. Brachiopsilus dianthus sp. nov., CSIRO H 4995–01, holotype, 99.5 mm SL; D. Brachiopsilus dossenus sp. nov., NMV A 29405–002, holotype, 65.0 mm SL; E. Brachiopsilus ziebelli sp. nov., CSIRO T 1993–01, holotype, 101.5 mm SL; F. Pezichthys amplispinus sp. nov., CSIRO H 4460–01, 37.2 mm SL; G. Pezichthys compressus sp. nov., CSIRO H 4447–01, holotype, 42.4 mm SL; H. Pezichthys eltanini sp. nov., LACM 11516–1, holotype, 30.0 mm SL; I. Pezichthys macropinnis sp. nov., CSIRO H 5317–02, holotype, 20.5 mm SL; J. Pezichthys nigrocilium sp. nov., CSIRO H 6154–01, holotype, 40.8 mm SL; K. Sympterichthys moultoni sp. nov., CSIRO H 3773–03, holotype, 45.1 mm SL; L. Thymichthys politus, CSIRO H 782–01, 67.3 mm SL; M. Thymichthys verrucosus (tasselled morph), CSIRO T 5, 51.3 mm SL; and N. Thymichthys verrucosus (eastern form) CSIRO H 3781– 01, 63.5 mm SL.

FIGURE 5. Skin morphology of: A. Thymichthys politus, CSIRO H 782–01 (x50); B. Thymichthys verrucosus, SAMA F 4750 (x40), showing a dermal flap. All images orientated as a view of mid-upper body on left side (i.e. anterior part to left).

FIGURE 24. Thymichthys politus, lateral view of: A. CSIRO H 4118–01, neotype, 61.4mm SL; and B. illustration of holotype (whereabouts unknown), reproduced from Richardson (1844a), courtesy of University of Tasmania Archives (image reversed).

FIGURE 25. Thymichthys politus colour morphs: A. composite illustration of the ‘bright red’ morph by R. Swainston; and B. unpublished painting by Lady Lefroy of a ‘red handfish’, presumably the mottled morph, presented to R.M. Johnson in the late 19th C. Reproduced courtesy of University of Tasmania Archives.