Parvonotus meridionalis, Davie & Ng, 2024

Davie, Peter J. F. & Ng, Ngan Kee, 2024, A new genus for the small shore crab previously known as Brachynotus spinosus (H. Milne Edwards, 1853) (Crustacea: Brachyura: Varunidae), with two new species from southern Australia and Samoa, Zootaxa 5476 (1), pp. 66-81 : 68-72

Parvonotus meridionalis sp. nov.

( Figs 1–3 , 5B, D, G, I, K , 7B , 8 )

Heterograpsus spinosus . —A. Milne Edwards 1873a: 258.— Kingsley 1880: 210 [in list, specimens from Australia].— Ortmann 1894: 715.— de Man 1891: 56–58, pl. 4, fig. 15 [in part, questionably fig. 15a and otherwise not specimens from Upolu]. [Not Heterograpsus spinosus H. Milne Edwards, 1853 ].

Heterograpsus octodentatus .—Haswell 1882: 101 [in part, only specimens from the “North Coast of Tasmania ” and Port Phillip are considered to be attributable to the present species, fide F. A. McNeill in Tweedie 1927b).

Eriocheir spinosus .— Hale 1927a: 184–185, fig. 185; 1927b: 312–131, fig. 2.

Brachynotus spinosus .— Fulton & Grant 1906: 19.— Tweedie 1942: 16.— Guiler 1952: 40.— Griffin 1969a: 329.— Griffin 1969b: 88.— Davie 2002: 100.— Poore 2004: 510, figs. 163d, e, pl. 29f.

Type material. Holotype: QM-W29654, male (12.6 × 10.9 mm), Carlton River estuary, 42°53’S, 147°39’E, SE Tasmania, coll. M.W.F. Tweedie, 01.01.1941 . Paratypes: Tasmania —QM-W29652, 2 males (6.2 × 5.7; 5.5 × 5.0 mm), 3 juv. females (6.2 × 5.4; 5.2 × 4.5; 5.0 × 4.3 mm), Midway Point , 42°47’56”S, 147°31’33”E, coll. A. & M. Walsh, 25.06.2023 ; QM-W27951, male (12.0 × 10.4 mm), female (15.9 × 13.4 mm), Carlton River estuary, 42°53’S, 147°39’E coll. M.W.F. Tweedie, 01.01.1941 ; QM-W29652, 3 males (12.6 × 10.9; 12.5 × 10.5; 10.0 × 8.5 mm), 2 females (11.7 × 9.8; 10.7 × 8.8 mm), Eaglehawk Neck Bay , 43°01’S, 147°53’E, coll. Y. Fukui, 21.12.2000 ; AMP.16700, 2 males (12.8 × 10.9; 10.6 × 9.5 mm), 2 females (12.6 × 10.5; 11.7 × 10.3 mm), Pittwater, near Hobart, SE Tasmania, 42°48’S, 147°30’E, under stones on sandstone platform, coll. D.J.G. Griffin, 14.06.1962 . AM-P.107581, male (12.6 × 10.8 mm), same data as AM-P.16700; AM-P.77399, male (11.6 × 10.6 mm), 2 females (17.5 × 14.6; 15.3 × 12.9 mm), Clerk Pt., Georges Bay , 41°18’00”S, 148°19’30”E, coll. Australian Museum party, 12.04.1991 ; AM-P.16699, female (14.2 × 11.7 mm), Triabunna , east coast, supralittoral mud flats, under stones near streams, coll. D.J.G. Griffin, 17.06.1962 ; SMF-7305, male (11.6 × 10.0 mm), ovig. female (16.0 × 13.3 mm), Pittwater, near Hobart , under stones on sandstone platform, supralittoral, coll. D Griffin, 14.06.1962 ; USNM-113547, 5 males (8.4 × 7.5 to 11.8 × 10.0 mm), 2 females (10.8 × 9.0; 11.2 × 10.0 mm), 9 ovig. females (9.5 × 8.0 to 14.9 × 12.4 mm), Howden, North West Bay , south-eastern coast, coll. D.J.G. Griffin, 10 Nov. 1965 . South Australia —AM-P.86987, male (9.0 × 8.1 mm), female (14.9 × 12.5 mm), Seacliffe, Adelaide , 35°01’54”S, 138°34’08”E, low tide under boulders, coll. S. & R. Ahyong, D. Middleton, 28.01.2002 ; AM-P.90255, male (11.2 × 10.2 mm), 3 females (15.8 × 12.9; 9.3 × 8.4; 8.8 × 7.6 mm), Whyalla, east end Foreshore Beach , 33°02’26”S, 137°35’23”E, under intertidal rocks, coll. S. Ahyong, 23.04.2011 ; ZRC 2008.0113 , 2 males (8.9 × 7.8; 9.0 × 7.8 mm), Point Lowly, Whyalla, under boulders, low tide, near lighthouse, coll. S. T. Ahyong, 09.05.2005 ; QM-W12468, male (14.4 × 12.6 mm), Port Victoria, Spencer Gulf , 18.11.1983 . Victoria —MNHN-MPB-12538, male (13.1 × 11.8 mm), female (10.9 × 9.8 mm), Port Philip, donated Australia Museum , no collection date; USNM-64689, 2 males (14.5 × 12.6, 15.3 × 13.1 mm), 2 females (15.2 × 13.1; 17.1 × 13.2 mm), 2 ovig. females (14.2 × 12.8, 16.0 × 13.3 mm), Beaumaris, Port Philip, coll. M. Ward, Jan. 1926 ; AM-P.16699, female (16.7 × 14.2 mm), Shoreham, Honeysuckle Reef , 38°26’S, 145°03’E, amongst rocky rubble on platform, coll. M.J. & P.G. Littlejohn, 03.04.1971 . Non-type material: MNHNB3514 , 1 male, 1 female (specimens not measured), “Nelle Hollande, M.A. Edwards ” [previously examined by A. Milne Edwards (1873a) and de Man (1891)] .

Diagnosis. Small species (<20 mm cb). Carapace subquadrate, slightly broader than long(1.11–1.16×), flattened, surface smooth but uneven, regions moderately well-defined, cervical groove clearly marked. Anterolateral margins subparallel to slightly divergent posteriorly (greatest cb c. 1.1 × exorbital width); 4 anterolateral teeth, exorbital tooth large, outer margin almost straight, second tooth smaller but prominent, anteriorly projecting, third tooth smallest, similar shape to second; last tooth slightly larger somewhat triangular, more laterally protruding; greatest carapace breadth at last tooth. Crest marking posterolateral carapace facet runs from tip of last tooth to just above base of last leg. Front broad, shallowly bilobed, finely granulated. Postorbital lobes prominent, broad, straight to shallowly concave in dorsal view ( Figs 1A , 7B ); not strongly separated from lateral inner orbital lobes. Infra-orbital ridge finely granulate ( Figs. 1F , 2B ).

Chelipeds subequal, homochelous. Male chelipeds moderately enlarged; smooth; fingers with only slight gape when closed; chelae smooth on outer face, granular on inner face, with patch of short, matted setae at base of fingers on inner and outer surfaces. Chelae of female more slender, lacking setal patch at base of gape. Pereopods flattened, ventral margin without delineated flattened expansion on carpus and propodus ( Fig. 6G ); meri with strong anterior sub-distal spine; sparse stout, black, spine-like setae on propodi and dactyli. Males with tuft of short setae on distal half of posterior edge of propodus of P2 and P3 (absent in females or only faintly indicated on P2). P4 propodus c. 2.2 × longer than wide. P5 propodus c. 1.7 × longer than wide.

Pleon with six somites plus telson; male pleon ( Figs. 1B , 6I, K ) widest towards distal edge of laterally convex third somite; following somites smoothly tapering somite 6 noticeably less divergent with margins more nearly subparallel, c. 2.6 times wider than long ( Fig. 6I, K ); distal edge of sixth narrowing to meet telson, telson narrower than sixth, c. 1.4 times wider than long, apically rounded; fifth somite markedly concave laterally. Female pleon ( Fig. 1D ) very broad; rounded; gonopore oval, distinctly protruding ( Fig. 2J, K ). G1 ( Fig. 2H–J ) moderately stout, only slightly tapering; short groove on sternal surface towards lateral face ending in distinct lobe; strong tufts of setae mostly confined to distal part of sternal lobe and fringing projecting corneous tip; few short setae extending little way down pleonal surface somewhat medially.

Colour in life. ( Fig. 3 ) Corneas of eyes black but with numerous small white spots (even in preserved specimens). Fresh specimens range from mottled dull green, fawn, or gray through to a darker reddish brown, typically with fine pale spotting and often with larger white patches on the pereiopods. Dull green or brown with or without white markings, which may be so extensive as largely or wholly to replace the colour ( Tweedie 1942). Innumerable colour variations occur; some examples are green, others different shades of brown. Some are very dark brown with large or small white markings, while others have the whole upper surface of the carapace milk-white ( Hale 1927a). Banding of the legs is common ( Griffin 1969b).

Habitat/biology. Active scavenger. Found in the intertidal and shallow subtidal zones on a variety of habitats including rocky, muddy, and sandy shores, and under rocks or flotsam. “A common little crab, found on rocky reef or sheltering under nodules of mud and under stones at low tide” ( Hale 1927a: 185); “found along the banks of estuarine rivers (as well as on beaches and tidal flats), but apparently never enters fresh water above tidal influence. ( Hale, 1927b: 313). In estuaries and sheltered bays, intertidal towards high tide level, under small stones on beaches completely sheltered from heavy wave action ( Griffin, 1969a, b). Ovigerous females are found from July or August through to February (late winter to late summer) and are most common in November and December ( Griffin, 1969b).

Remarks. The crab fauna of the Australian shoreline has been well collected and is generally well-known. The species known as “ Brachynotus spinosus ” is considered a common small shore-crab species of temperate south-eastern Australia, extending along the east coast only as far as northern Victoria ( Fulton & Grant 1906; Davie 2002; Poore 2004). It is so common in fact, that it has been given the vernacular name of “Little Shore Crab” in Australia ( Hale 1927a; Davie 2002).

In the MNHN, Paris there are two dry specimens, one male and one female (MNHN-B3514), simply labelled as “Nelle Hollande ”, but without other data. These have been re-examined as part of the present study, and we confirm that they belong to our proposed new species Parvonotus meridionalis gen. nov., sp. nov. It seems that it would have also been these same specimens that A. Milne-Edwards (1873a) examined and identified as conspecific with Heterograpsus spinosus H. Milne Edwards, 1853 , thus first wrongly extending the range of that species from the tropical Solomon Islands to the temperate Australian southern coast.

Ortmann (1894) examined a female from the collection of the Bremen Museum, as well as two males and two females from the Museum Godeffroy, both specimen lots collected from “Ost-Australien” (east Australia) and dated 1886 and 1888 respectively. He would have followed both A. Milne-Edwards (1873a) and de Man (1891) in assuming that the Australian specimens were conspecific with Heterograpsus spinosus from Vanikoro in the Solomon Islands.

Distribution. South-eastern Australia: South Australia to Victoria and Tasmania ( Fig. 8 ).

Etymology. The species name meridionalis is from the Latin meaning southern, and refers to its distribution along the temperate southern coast of Australia. It is used as a noun in apposition.

Figures

FIGURE 1. Parvonotus meridionalis gen. & sp. nov., A, B, dorsal and ventral views of holotype male (QM-W29654), (12.6×10.9 mm), Carlton River estuary, Tasmania; C, D, dorsal and ventral views of paratype female (QM-W27951); E, frontal view of chelae of holotype male; F, frontal view showing epistome, infraorbital borders and postfrontal lobes of holotype.

FIGURE 2. Parvonotus meridionalis gen. & sp. nov., reproduction of figures from published descriptions, A, from Hale (1927a), South Australia; B–E, H–J from Griffin (1969b), male (17 mm c.b.), Pittwater, Tasmania; F, G, from Hale (1927b), male (17 mm c.b.), Kangaroo Island, South Australia. A, dorsal view of male; B, suborbital margin and lower orbit; C, third maxilliped; D, propodus and dactylus of right P2 in anterior view; E, propodus and dactylus of right P5 in posterior view; F, G, internal and external views of right male chela; H, G1 pleonal view; I, G1 tip, sternal view; J, G1 tip, pleonal view. Paratype female (QM-W27951): J, K, female left gonopore showing shape, and position on sternite (J); and in anterior lateral view showing degree of prominence (K).

FIGURE 3. Colour variation in life of Parvonotus meridionalis gen. & sp. nov.; All photographs taken within the greater Adelaide region, South Australia; specimens not collected. A, north coast of Onkaparinga; B, O’Sullivan Beach; C, Yankalilla; D, Aldinga Beach; E, Kingston Park; F, Aldinga Reef, South Coast of Onkaparinga. [Photographs copyright Matt Tank; used with kind permission]

FIGURE 5. Parvonotus samoensis gen. & sp. nov., A–C, F, G, H, holotype male (11.5×10.3 mm), RMNH.CRUS.D.1219, Upolu, Samoa, western Polynesia. C, D, paratype female (14.0×11.7 mm), same data as holotype. A, male dorsal view; B, ventral view; C, frontal view showing chelae; D, female dorsal view; E, female ventral view; F, oblique anterior view of holotype male; G, left male chela, original figure by de Man (1891); H, contemporary photograph of same holotype male chela; I, photograph of spirit specimens and label of de Man’s specimens in the RMNH.

FIGURE 6. Comparison of males of Parvonotus samoensis gen. & sp. nov. and P. meridionalis sp. nov., and comparison of P5 between all three species. A, C, F, H, J = P. samoensis sp. nov., holotype (11.5×10.3 mm), RMNH.CRUS.D.1219; B, D, G, I, K = Parvonotus meridionalis sp. nov., holotype (12.6×10.9 mm), QM-W29654; E, P. spinosus (H. Milne Edwards, 1853) comb. nov., holotype female (MNHP B11017). A, B, dorsal views; C, D, outer views of left male chela; E, F, G, anterior views of P5; H, I, sternal views; J, K, pleonal somites 5, 6 and telson.

FIGURE 7. Composite illustrations comparing dorsal morphological differences in carapace and leg proportions of female Parvonotus species. A, P. spinosus (H. Milne Edwards, 1853), comb. nov., holotype; B, P. meridionalis sp. nov., paratype female (QM-W27951); C, D, P. samoensis sp. nov., C, original figure by de Man (1891), D, contemporary photograph of paratype female (RMNH.CRUS.D.1219).

FIGURE 8. Map showing the distribution of the three recognised species of Parvonotus gen. nov. Base map courtesy of United States National Oceanic and Atmospheric Administration; used under Creative Commons licence.