Microcanthus joyceae Whitley, 1931

Tea, Yi-Kai & Gill, Anthony C., 2020, Systematic reappraisal of the anti-equatorial fish genus Microcanthus Swainson (Teleostei: Microcanthidae), with redescription and resurrection of Microcanthus joyceae Whitley, Zootaxa 4802 (1), pp. 41-60 : 53-57

Microcanthus joyceae Whitley

East-Australian Stripey

Figures 2C , 3B 1 , 4 , 8–11 ; Table 2

Chaetodon strigatus [non Cuvier 1831].— Steindachner 1866: 435 (Port Jackson, Australia).— Macleay 1881: 387 (Port Jackson, New South Wales).— Ogilby 1886: 16 (Clarence River, New South Wales; not distribution or synonymy).

Neochaetodon vittatus [non Castelnau 1873].— Castelnau 1879: 350 (list, Port Jackson, Australia).

Microcanthus strigatus [non Chaetodon strigatus Cuvier 1831 ].— Cockerell 1915: 43 (Queensland, description of scales).— McCulloch 1929: 248 (New South Wales distribution only; not synonymy).— Gill & Reader 1992: 208 (Elizabeth Reef, Tasman Sea).— Francis 1993: 162 (checklist, in part, eastern Australia, Lord Howe and Norfolk Islands only).— Kuiter 1993: 215 (distribution in part, colour photo).— Kuiter 1996: 204 (distribution in part, colour photo).— Randall et al. 1998: 216 (description, distribution in part, colour photo).—Johnson 1999: 738 (checklist).— Hoese & Bray 2006: 1324 (checklist, in part, eastern Australian distribution only).

Microcanthus joyceae Whitley 1931: 111 , pl. 13, figs 4–5 (type locality, Shellharbour, New South Wales, Australia; holotype AMS IA.4012; Figure 8 ).— Whitley 1964: 46 (checklist).— Kuiter & Kuiter 2018: 188 (colour photos; distribution).

Microcanthus howensis Whitley 1931: 112 , pl. 13, fig. 2 (type locality, Lord Howe Island ; holotype AMS IA.4018).

Diagnosis. Microcanthus joyceae shares similar body proportions and meristic counts to M. strigatus , but can be distinguished from Microcanthus strigatus in having the fifth body stripe relatively straight, without an inflection, and in lacking spots and short dashes on the breast and lower body ( Figures 8 , 9 & 11 ).

Description. Dorsal-fin rays XI,16 (15–17); anal-fin rays III,14 (13–14); pectoral-fin rays 16/16 (15–17); upper procurrent caudal-fin rays 9 (8–9); lower procurrent caudal-fin rays 8 (7–9); total caudal-fin rays 32–35; diagonal rows of scales in lateral series 56 (49–58); circumpeduncular scales 26 (26–28); gill rakers 16–17; branchiostegals 7. Frequency distributions of numbers of dorsal-, anal- and pectoral-fin rays, and numbers of circumpeduncular scales and diagonal rows of scales in lateral series are presented in Table 2.

Body laterally compressed, moderately tall and roughly circular in lateral view, dorsal-fin origin to pelvic-fin origin 54.1–59.8% SL; head small 31.6–35.1% SL; snout acute 7.8–10.8% SL; eye large 12.0–14.1% SL; interorbital region naked, 8.3–11.4% SL in width.

As percentage of SL (based on 25 specimens, 61.7–112.2 mm SL): predorsal length 44.2–51.5; prepelvic length 43.0–49.5; dorsal-fin origin to pelvic-fin origin 54.1–59.8; pelvic-fin origin to anal-fin origin 27.6–33.6; dorsal-fin origin to anal-fin origin 65.5–72.7; spiny dorsal-fin base length 35.3–44.4; soft dorsal-fin base length 22.2–30.3; anal-fin origin to dorsal-fin terminus 36.9–43.6; anal-fin base length 21.2–29.6; mid-dorsal fin to anal-fin origin 49.9–59.1; dorsal-fin terminus to dorsal end of caudal peduncle 8.7–11.0; anal-fin terminus to ventral end of caudal peduncle 6.9–10.1; anal-fin terminus to dorsal end of caudal peduncle 15.9–18.6; dorsal-fin terminus to ventral end of caudal peduncle: 16.3–19.9; first anal-fin spine 7.2–10.7; second anal-fin spine 16.2–22.4; third anal-fin spine 11.1–15.0; pectoral-fin length 24.4–27.7; pelvic-fin length 24.7–30.6; pelvic-fin spine 13.9–17.2.

Etymology. The species is named after Joyce K. Allan, who provided Whitley with illustrations of this species for his original description. To be treated as a noun in the genitive case. While Whitley did not provide a common name in his description, he alluded to its vernacular name, the “Stripey,” commonly used by locals in New South Wales, Australia. Since the use of this name is pervasive throughout the region, we choose to retain it in part as the common name, proposing the usage of “East-Australian Stripey” instead to distinguish M. joyceae from M. strigatus .

Distribution and habitat. Microcanthus joyceae is known from the eastern coast of Australia, from southern Queensland to New South Wales, reaching its southernmost limit at the southern border of New South Wales. It also occurs in New Caledonia, Lord Howe Island, and Norfolk Island (see Remarks; Figure 4 ). Juveniles and young adults are often seen in rock pools and rocky shores at depths of up to 5 m ( Figures 9 & 10 ). Adults are more commonly seen near rocky reefs, though are common in harbours, embankments, and under piers, where they occur in large groups ( Figure 11 ).

Remarks. In the original description of Microcanthus joyceae, Whitley (1931) made note of the difference in stripe pattern, and the smaller overall size in comparison with M. strigatus from Asia. He further commented that M. joyceae attains a maximum size of 150 mm, compared with the maximum size of 200 mm in M. strigatus . In examination of specimens of M. joyceae (n = 25), our largest specimens measured 108.5 mm (Byron Bay, NSW; AMS IB. 2518) and 112.2 mm (Lord Howe Island, NSW; AMS I. 1797–1798), compared with the largest from East Asia (n = 38) at 157.3 mm (Kagoshima, Japan; KAUM-I. 80597). While there is an apparent correlation in size differences, we cannot discount the possibility of sampling bias. Results from a detailed morphological study, however, confirms Whitley’s observation in that M. joyceae lacks the inflected anal-fin stripe and spot pattern on the lower abdomen frequently observed in M. strigatus ( Tea et al. 2019) .

In the same publication, Whitley (1931) treated Microcanthus from Lord Howe Island as a separate species, M. howensis , primarily on the basis of having thinner stripes that extend only half-way across the soft-dorsal and anal fins. Our morphological data set for specimens of the southwest Pacific contains three Lord Howe Island individuals (AMS I. 1797–1798), including the holotype of M. howensis (AMS IA.4018), examination of which revealed no apparent differences in meristic, morphometric, or coloration characters. Similarly, photographs of Lord Howe Island individuals taken in the field showed no differences from M. joyceae in colour pattern, disagreeing with Whitley’s description. However, given the morphologically cryptic nature of this group and the lack of comparative genetic material from this region, we refrain from commenting on the status of M. howensis until more material becomes available. We provisionally treat M. howensis as a synonym of M. joyceae , based on the geographic proximity of Lord Howe Island to mainland eastern Australia.

Material examined. NEW SOUTH WALES, AUSTRALIA: Lake Macquarie , Swansea Channel, Pelican, AMS

I.48994-001 (11: 61.7–72.8 mm SL); Byron Bay, AMS IB.2518 (108.5 mm SL); Kingscliff, Cudgera Creek, AMS

I.41846-001 (4: 19.5–41 mm SL, cleared and stained); Lord Howe Island, AMS IA.4018 (51.3 mm SL; holotype of M. howensis ); Lord Howe Island, AMS I. 1797–1798 (2: 92.7–112.2 mm SL); Shellharbour, AMS IA.4012 (86.5 mm SL; holotype of M. joyceae ); QUEENSLAND, AUSTRALIA: eastern tip of Sabina Point, AMS I.34301-015 (2: 76.9–97.0 mm SL); Moreton Bay, AMS IB.6348 (92.5 mm SL); Wide Bay, AMS I.10989 (2: 77.9–104.5 mm SL); One Tree Island, AMS I.20463-027 (4: 82.1–89.4 mm SL).

Figures

FIGURE 1. X-radiograph of Microcanthus strigatus, KPM-NI 24269, 73.8 mm SL, Yakushima Island, Japan. Radiograph by A. Hay.

FIGURE 2. Genera of Microcanthidae. Tilodon and Neatypus are monotypic. A) Tilodon sexfasciatus, in situ photograph from Blairgowrie, Victoria, Australia; B) Neatypus obliquus, in situ photograph from Bunbury, Western Australia; C) Microcanthus joyceae, in situ photograph from Magic Point, Maroubra, New South Wales, Australia; and D) Atypichthys strigatus, in situ photograph from Henry Head, Botany Bay, New South Wales, Australia. Photographs by S. Schulz (A), C. Mark (B), and E. Schlogl (C & D).

FIGURE 3. Lateral-line scales of: A) Scorpis lineolatus (Scorpididae), AMS I.48993-001, 55.3 mm SL; B) Microcanthus joyceae (Microcanthidae), AMS I.48994-001, 64.2 mm SL; C) Atypichthys strigatus (Microcanthidae), AMS I.48992-001, 93.9 mm SL. Drawings on right show portion of lateral line and adjacent scales. Lateral-line scales are show in dark grey; scale bars indicate 2 mm. Photographs by Y.K. Tea; drawings by A.C. Gill.

FIGURE 4. Phylogenetic relationships and population structure for Microcanthus. A) Tree inferred using maximum likelihood and Bayesian inference based on mitochondrial 16S, COI and control region. Numbers at nodes indicate posterior probabilities inferred using Bayesian analysis in MrBayes and likelihood bootstrap support from a maximum-likelihood analysis in RAxML. Atypichthys (not shown) was used as the outgroup. B) Geographic distribution of Microcanthus. Geographic distributions of Microcanthus are colour coded as follow: Blue—East Asia (M. strigatus); Yellow—Hawaii (M. strigatus); Pink—Western Australia (M. strigatus); Purple—Southwest Pacific (M. joyceae). C) Bayesian clustering plots for 82 individuals of Microcanthus from populations of M. strigatus from East Asia, Hawaii and Western Australia, and M. joyceae from the southwest Pacific. The most likely number of partitions was K = 3 (LnP = -184055). The second most likely number of partitions was K = 4 (LnP = -187956). For discussion of phylogenetic relationships and population genetics of Microcanthus, see Tea et al. (2019).

FIGURE 8. Microcanthus joyceae, holotype, AMS-IA. 4012, 86.5 mm SL, Shellharbour, New South Wales, Australia. Note the lack of a prominent inflection on the lower anal-fin stripe. Photograph by Y.K. Tea

FIGURE 9. Microcanthus joyceae, in situ photograph from Shelly Beach, Manly, New South Wales, Australia. Note the anal-fin stripe without a downward inflection, and the lack of spots on the lower abdomen. Photograph by E. Schlogl.

FIGURE 10. Newly settled recruit of Microcanthus joyceae, ca. 12 mm SL, in situ photograph from Forresters Beach, New South Wales, Australia. Juveniles often recruit in rock pools. Photograph by A.C. Gill.

FIGURE 11. Microcanthus joyceae, in situ photograph from Fly Point, Port Stephens, New South Wales, Australia. Photograph by: E. Schlogl.