Phylladiorhynchus pusillus ( Henderson, 1885 )

Schnabel, Kareen E. & Ahyong, Shane T., 2019, The squat lobster genus Phylladiorhynchus Baba, 1969 in New Zealand and eastern Australia, with description of six new species, Zootaxa 4688 (3), pp. 301-347 : 329-334

Phylladiorhynchus pusillus ( Henderson, 1885)

( Fig. 10 , 11 , 12 )

Galathea pusilla Henderson, 1885: 407 (Twofold Bay, Australia, 275 m).— Henderson, 1888: 121, pl. 12, figs. 1, 1a, 1b ( Twofold Bay , Australia, 275 m) .— Whitelegge, 1900: 185 (off Bondi , New South Wales, 91 m) .— Grant & McCulloch, 1906: 49, pl. 4, figs. 5, 5a (part, Port Phillip Heads , Victoria) .

Phylladiorhynchus pusillus .— Davie, 2002: 66.— Poore, 2004: 238, fig. 66b (compilation, key).— Poore et al., 2008: 22 (SW Australia, 95–439 m) (part).— Rowden et al., 2010, tab. 3 (in part).

Not Galathea pusilla .— Thomson, 1899: 193, pl. 21, fig. 7 (Whanganui, Cook Strait, Paterson Inlet, 14.6 m) (= P. australis n. sp.).— Chilton, 1906: 267 (Channel Islands, Auckland, 46 m) (= P. australis n. sp.).— Grant & McCulloch, 1906: 49 (part, Mast Head Island specimen = P. spinosus n. sp.).— Chilton, 1911: 303 ( New Zealand) (= P. australis n. sp.).— Borradaile, 1916: 92 (off Three Kings Islands and off North Cape, 183– 128 m) (= P. australis n. sp.).— Hale, 1927: 80 (South Australia, 75 fathoms) (= P. australis n. sp.).— Tirmizi, 1966: 175, fig. 1 (= P. ikedai ( Miyake & Baba, 1965)) .

Not Phylladiorhynchus pusillus . — Miyake & Baba, 1967: 234, fig. 6 (East China Sea, 102–196 m) (different species, undetermined).— Haig, 1973: 282 (S of Cape Everard (Victoria), S and SW of Mt Cann (Victoria) and off St. Helens Point, Tasmania, 110–183 m) (= P. nui n. sp.).— Baba, 1991: 486–487, fig. 4e, f (different species, undetermined).— Baba et al., 2009: 287–289, figs. 263, 264 (different species, undetermined).— Lee et al., 2019: 730, figs. 3, 4 (different species, undetermined).

Not Phylladiorhynchus cf. pusillus .— Ahyong, 2007: 42 , fig. 20B, 22. (= P. nui n. sp.).

Records requiring verification:

Galathea pusilla .— Guiler, 1952: 36 (D’Entrecasteaux Channel, Tasmania).—Miyake, 1965: 635, fig. 1044 (no record).— Zarenkov, 1968: 177, fig. 22 (Victoria, Australia, 110 m).— Lewinsohn, 1969: 116 (no record).

Phylladiorhynchus pusillus .— Baba, 1969: 4 (Sagami Bay, 200–300 m).— Baba, 2005: 201, 305 (key, synonymies, Kei Islands and Japan (Sagami Bay and W of Nagasaki), 146–549 m).

Type material. LECTOTYPE: NHMUK 1888 :33 ( Henderson, 1885), male (3.0 mm), Challenger Stn. 163A, Twofold Bay , New South Wales, Australia, 36.98°S, 150.33°E, 150 fathoms (274 m), 4 Apr 1874.

Other material. Kermadec Islands, New Zealand: NIWA 118725 , 6 males (2.0– 3.2 mm), 8 females ov. (2.3–2.7 mm), Stn. TAN1612/77, Macauley Island, 30.222–30.228°S, 178.397–178.397°W, 72–101 m, 29 Oct 2016 . NIWA 135602 , 2 males (2.7, 3.5 mm), Stn. TAN 1612/97, Macauley Island, 30.247–30.248°S, 178.384–178.380°W, 125– 136 m, 31 Oct 2016 . NIWA 10633 , 1 female (2.0 mm) , NZOI Stn. K 838, Macauley Island , 30.263°S, 178.395°W, 200 m, 28 Jul 1974 . NIWA 43003 , 1 male (1.5 mm) , NZOI Stn. K 855, Cheeseman Island , 30.553°S, 178.527°W, 125 m, 30 Jul 1974 . NIWA 21207 , 4 males (1.7–3.0 mm) , NZOI Stn. K 797, north of L’Esperance Rock , 31.347°S, 178.820°W, 55 m, 19 Jul 1974 . AWMM MA125787 (ex NIWA 135601 ), 2 males (3.5, 3.7 mm), 2 females (2.0, 2.3 mm), Stn. TAN 1612/106, L’Esperance Rock, 31.364–31.367°S, 178.759–178.758°W, 90–109 m, 01 Nov 2016 . AWMM MA30532 , 1 male (not measured), K 2011-2-1 , W side South Meyer Island 29.247°S, 177.882°W, 21 m, among algae, 12 May 2011 . AWMM MA30533 , 1 male (cl 1.8 mm), K 2011-29-1 , Boat Cove, Raoul Island , 29.273°S, 177.927°W, 10 m, 15 May 2011 . AM P88923, 1 specimen (1.4 mm), K 2011-23-4 , Milne Rocks, Raoul Island , 29.282°S, 177.903°W, vertical rock wall, rocks, cobble, coarse sand & turfing algae, 21 m, 15 Jul 2011 . AWMM MA30534 , 1 female (cl 2.2 mm), K 2011-77 - 2, W side Cheeseman Island 30.535°S, 178.570°W, 24 m, 23 May 2011 .

Bay of Islands: NIWA 135611 , 1 female (2.5 mm), Stn . TAN0906 /130, 34.555–34.558°S, 173.160–173.159°E, 107– 105 m, 12 Jul 2009 . NIWA 56259 , 2 females (2.7, 2.8 mm), Stn . TAN0906 /140, 34.571–34.576°S, 173.209– 173.213°E, 117–120 m, 13 Jul 2009 . NIWA 135612 , 1 female (2.3 mm), Stn . TAN0906 /236, Bay of Islands , 34.850– 34.850°S, 173.905–173.898°E, 134– 132 m, 19 Jul 2009 . NIWA 57391 , 1 male (3.4 mm), 2 females (3.0, 3.1 mm), Stn . TAN0906 /235, 34.876–34.879°S, 173.916–173.910°E, 117– 114 m, 19 Jul 2009 . NIWA 55443 , 2 females (3.5, 3.9 mm), Stn . TAN0906 /81, 34.879–34.877°S, 173.917–173.913°E, 115– 112 m, 08 Jul 2009 . NIWA 57503 , 3 males (3.0, 3.0, 4.4 mm), Stn . TAN0906 /240, 34.979–34.980°S, 173.998–174.002°E, 85–93 m, 19 Jul 2009 . NIWA 55302 , 1 female (2.3 mm), Stn . TAN0906 /68, 35.005–35.005°S, 174.060–174.055°E, 110– 108 m, 08 Jul 2009 . NIWA 55202 , 1 male (2.8 mm), Stn . TAN0906 /60, 35.141–35.137°S, 174.290–174.289°E, 103–104 m, 07 Jul 2009 . NIWA 115200 , 1 male (3.3 mm), Stn . TAN0906 /25, 35.553–35.548°S, 174.553–174.553°E, 57– 57 m, 05 Jul 2009 .

Hauraki Gulf: NHMUK 1912 : 11.5.61 –68 (part), 3 males (2.7, 2.8, 3.4 mm), 1 female (3.1 mm) .

New South Wales, Australia: AM P76215, 1 male (5.3 mm), NSW3083, SE of Kilcare , 33.542°S, 151.374°E, 114 m, rocky reef, from bryozoan, coll. K. Attwood, 2 May 2007 . AM G2387 , 1 male (2.1 mm), 1 female (2.8 mm), 8–9.5 km off Coogee , “off Bondi”, Thetis Stn. 44, 33.95°S, 151.358°E, 91 m, fine sand, coll. E.R. Waite, 15 Mar 1898 . AM P86067, 1 male (1.7 mm), 1 female (2.4 mm), K 80-07-02 , SE of Tathra Head , 36.75–36.80°S, 150.03– 150.05°E, 64 m, trawl, 10 Jun 1980 . AM P89921, 1 male (1.7 mm) , RV Southern Surveyor Stn. SS05/94/119, E of Disaster Bay, 37.310°S, 150.065°E, 81–82 m, benthic sled, 2 Sep 1994 . AM P89915, 3 males (1.9, 2.3, 2.5 mm), Stn. SS05/94/127, E of Disaster Bay, 37.315°S, 149.993°E, 24–30 m, benthic sled, 2 Sep 1994 . NHMD-87715, 3 males (1.7, 1.7, 2.5 mm), 1 female (2.3 mm), Disaster Bay , FIS Endeavour, 30–40 fm (55–73 m), sand, mud, trawled, 1 Oct 1914 , coll. Th. Mortensen. AM P89924, 1 male (2.0 mm), 3 males (1.5–3.0 mm), 4 females (1.7–2.1 mm), 3 females (2.8, 3.0, 3.3 mm), Stn. SS05/94/94, Gabo Island, 37.585°S, 149.722°E, 25 m, trawl, 30 Aug 1994 .

Victoria, Australia: AM G5618 , 1 male (4.6 mm), Port Philip Heads , 37.967°S, 144.9°E, coll. F. E. Grant. AM G5744 , 1 male (4.9 mm), 2 females ov. (3.9, 4.1 mm), Port Philip Heads , 37.967°S, 144.9°E, coll. F. E. Grant. AM P89899, 1 male (2.3 mm) , RV Southern Surveyor Stn. SS05/94/59, Bass Strait, E of Seal Islands, 38.942°S, 148.322°E, 80–85 m, 27 Aug 1994 . AM P89900, 1 male (2.3 mm), Stn. SS 05/94/60, E of Seal Islands , Bass Strait, 38.985°S, 148.527°E, 125 m, 27 Aug 1994 .

Tasmania: AM P89928, 1 male (4.2 mm), Stn. TAS-170, Sloop Reef, Bay of Fires , 42.220°S, 148.292°E, 23 m, coll. R. Springthorpe & C. J. McCormick, 16 Apr 1991 .

South Australia: SAM C9974 , 1 female (3.1 mm) , Stn. DCE_100, du Couedic Canyon, 36.336°S, 136.623°E, 106 m.

Western Australia: MV J55116 , 2 males (2.0, 2.7 mm), Stn. SS10/2005/120, off Carnarvon , 24.619°S, 112.666°E, 100– 100 m, coll. G. C. Poore, 7 Dec 2005 . MV J55113 , 1 female ov. (2.5 mm), 1 female (2.6 mm), 6 males (2.7–3.4 mm), Stn. SS10/2005/102, off Kalbarri , 27.813°S, 113.311°E, 96–98 m, coll. G. C. Poore, 5 Dec 2005 . MV J55114 , 1 female ov. (2.9 mm), 1 male (3.0 mm), Stn. SS 10/2005/082, Jurien Bay , 29.803–29.804°S, 114.439–114.436°E, 85–92 m, 2 Dec 2005 . MV J55117 , 5 males (3.0– 3.9 mm), Stn. SS10/2005/002, off Two Rocks , 31.724°S, 115.244°E, 102 m, coll. R. S. Wilson, 18 Nov 2005 . MV55121 , 1 male (2.9 mm), Stn. SS10/05/014, off Bunbury , 33.036–33.038°S, 114.820–114.813°E, 95–99 m, 20 Nov 2005 . MV J55120 , 4 females ov. (2.1–3.1 mm), Stn. SS10/2005/15, off Mentelle , 33.98°S, 114.734°E, 97– 96 m, coll. R. S. Wilson, 21 Nov 2005 .

Diagnosis. Rostrum lateral margins convex; subapical spines present. Carapace with 4 epigastric spines of which outermost may be present as a granule and much smaller than inner pair (rarely with 6 spines); anterior metagastric ridge scale-like, medially interrupted. Abdominal tergite 3 usually without posterior transverse ridge. Thoracic sternite 3 anterior margin convex, median projection absent. Antennular article 1 with 5 spines: distomesial spine over-reaching lower distolateral spine, slightly to distinctly overreached by upper distolateral and first lateral spines. Antennal article 1 mesial process not reaching level of second lateral antennular spine; article 2 distolateral and distomesial spines subequal; article 3 with distinct distomesial spine. Maxilliped 3 merus with 1 prominent spine on flexor margin. P2–4 dactylus extensor margin without upright spines at bases of movable spines.

De s cription. Carapace: Length 0.9–[1.0] × width; transverse ridges with dense short setae, and few scattered, longer, iridescent setae. Gastric region with 4 transverse ridges: epigastric ridge medially interrupted, with 2 (rarely 3) pairs of spines in transverse row, innermost pair always prominent, largest, outer pair(s) prominent to obsolescent, sometimes indicated by minute granule; protogastric ridge uninterrupted and extending laterally to carapace margin; mesogastric ridge interrupted laterally by cervical groove; metagastric ridge medially interrupted and forming 2 arches, laterally interrupted by the cervical groove, laterally scale-like and continuing uninterrupted to lateral margin of carapace. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 2 complete, uninterrupted ridges, intervened by 3 interrupted ridges. Lateral margins medially convex, with 7 spines: 2 spines in front of (anterolateral, hepatic) and 5 spines behind anterior cervical groove (3 anterior branchial spines, 2 posterior branchial spines). Anterolateral spine well-developed, reaching lateral orbital spine, size subequal. Hepatic spine small, set slightly mesially from lateral margin. Anterior branchial spines subequal in size. Posterior branchial spines with first spine subequal to anterior branchial spines, second smaller. Rostrum length 0.4–0.6 [0.5] × pcl; length-width ratio [1.0]–1.3; distance between basal pair of rostral spines about 0.3 × carapace width; dorsal surface slightly concave; lateral margin distinctly convex, with distinct pair of sub-apical spines. Pterygostomian flap with sharp anterior spine and few small, scattered granules at upper margin near linea anomurica; entire surface with series of broken and continuous striae.

Thoracic sternum: Sternal plastron as wide as or slightly wider than long (length-width ratio [0.8]–1.0); lateral margins divergent posteriorly. Sternite 3 1.7–[2.1] × length; anterior margin convex and minutely serrated; anterolateral margins with broad granule or square.

Abdomen: Tergite 2 with 2 uninterrupted transverse ridges; tergite 3 usually with anterior ridge only, rarely with posterior ridge; tergite 4 with anterior ridge only, remainder smooth, without elevated ridges.

Eye: Eye length about 1.2 × width, peduncle distally setose, slightly expanded proximally, with few short transverse striae on lateral surface; cornea not dilated.

Antennule:Article 1 with 5 well-developed distal spines, distomesial spine well-developed, over-reaching lower distolateral spine; paired distolateral spines present; proximal lateral spine strongly developed.

Antenna: Article 1 with prominent, broad mesial process, distally overreaching peduncle. Article 2 with subequal distal spines, reaching midlength of article 3. Article 3 with distinct mesial spine, anterolaterally squared (unarmed). Article 4 unarmed.

Maxilliped 3 (Mxp3): Ischium with pronounced distal spines on both flexor and extensor margin; crista dentata with regular row of spines along entire margin. Merus slightly shorter than ischium at midline, with strong distal spines on extensor margins, subequal in size to spine at midlength on flexor margin; otherwise unarmed.

Cheliped: Length 2.7–4.7 [3.8] × pcl (males), 2.9–3.5 × pcl (females), larger specimens generally with longer chelipeds; subcylindrical, spiny, setation variable, ranging from densely plumose to sparse. Ischiomerus 1.1–1.9 [1.5] × pcl, 1.5–[2.4] × carpus length; with rows of spines, lateral and distal spines strongest. Carpus with rows of spines except for ventral surface, 1 or 2 lateral spines most prominent. Palm 0.7–[1.5] × carpus length, length-width ratio 1.6–3.2 [2.5], with 4 parallel rows of spines (2 mesial, 1 at about dorsal midline, 1 close to lateral margin, with 1 or 2 spines reaching onto proximal portion of fixed finger. Dactylus 0.6–[0.9] × palm length; usually with 1 distinct proximal spine laterally, 1 or 2 additional small spines in specimens with large chelipeds; surface with short setiferous striae and some scattered granules in large specimens; distally with row of spines along curved margin; tip excavated.

Walking legs (P2–4): Relatively robust, subcylindrical, moderately setose and spinose. Merus successively shorter posteriorly (P2 merus 1.1–1.2 length of P3, P3 merus 1.1–1.2 × length of P4 merus). P2 merus about threefourths pcl; 1.2–1.3 × P2 propodus length; length 4–5 × width. P3 merus 1.0–1.2 × P3 propodus length; length 4–5 × width. P4 merus 0.9 × P4 propodus length; length 3.4–4.0 × width. Extensor margin of P2 and P3 with regular row of spines, proximally diminishing, with prominent distal spine; P4 extensor margin irregular but unarmed; distally unarmed; ventral margins irregular and with strong distal spine on all legs; P4 lateral surface with median row of small spines, absent on P2 and P3. Carpus with 2 or 3 spines on extensor margin on P2–3, irregular but unarmed on P4; distal spine prominent on all legs; 2 or 3 spines along row below extensor margin on lateral surface on all legs; flexor margin unarmed. P2–4 propodus length 4.5–6.0 × height [loose leg of syntype slightly stouter at 4.3]; extensor margin with 3–5 proximal spines on P2–3, typically 2 on P4; flexor margin with 3–5 slender movable spines in addition to distal pair. Dactylus 0.6–0.7 × propodus length, ending in incurved, strong, sharp spine; flexor margin with 5–7 movable spines, otherwise unarmed.

Size. Male pcl 1.5–5.3 mm, female pcl 2.0– 3.9 mm, ovigerous female pcl ≥ 2.3 mm.

Colour in life. Unknown.

Parasites. Five specimens, a 3.1 mm female from South Australia (SAM C9974), a 2.4 mm female from New South Wales (AM P86067), a 2.3 mm male from Victoria (AM P89899) and a 2.6 mm female and 3.0 mm male from Western Australia (MV J5513) have kentrogonid rhizocephalan externae under the abdomen.

Genetic data. A specimen each from three samples (NIWA 57503, Bay of Islands, and NIWA 135601 and 135602 from the Kermadec Islands) has been sequenced for COI ( Table 1 ).

Di s tribution. Confirmed from southeastern, southern and western Australia (New South Wales, Victoria, Tasmania, South Australia), and the northern New Zealand mainland and Kermadec Ridge, 10– 274 m. The type record remains the deepest record for this species (274 m), although more typically, collections were made between 30 and 130 m depth.

Remarks. Phylladiorhynchus pusillus was formerly considered widespread in the Indo-West and Eastern Pacific ( Baba et al. 2008), but it is here confirmed only from New Zealand and temperate Australian waters. The majority of the specimens previously identified as P. pusillus in New Zealand and southeastern Australia belong to two new species, P. australis n. sp. and P. nui n. sp., and differences are discussed under those species above. Several records within the region remain to be verified: specimens reported by Guiler (1952) and Zarenkov (1968) could not be located in collections. Specimens examined from Western and South Australia reported by Poore et al. (2008) conform in all aspects and are identified here as P. pusillus s.s. One specimen contained in sample MV J55117 and three further samples not listed differ from all species reported here and require further study.

Records of P. pusillus from outside New Zealand and Australian waters region remain to be verified, but it seems likely that P. pusillus is restricted to the temperate southwestern Pacific and eastern Indian oceans. Figures of material reported as P. pusillus from Taiwan ( Baba et al. 2009: figs. 263, 264), the East China Sea ( Lee et al. 2019: figs. 3, 4) and New Caledonia ( Baba 1991: fig. 4e) all show a biconcave anterior margin of thoracic sternite 3, indicating that these are not referable to P. pusillus sensu stricto, but belong to other species. Two nominal species formerly placed in the synonymy of P. pusillus ( Galathea integra Benedict, 1902 , Japan; and Galathea lenzi Rathbun, 1907 , Chile) will probably also prove to be separate valid species and are currently under study by Rodríguez-Flores (pers. com.?).

Henderson (1885) described P. pusillus based on a male and two female syntypes, all in poor condition. The largest syntype, the male, is herein designated as the lectotype. The lectotype, unfortunately, has the anterior portion of the carapace fractured and only a single walking leg, presumably the left P3, remaining. Nevertheless, it matches other specimens collected off southeastern Australia (including near the type locality) that help confirm diagnostic characters for this species. Comparing the Australian lectotype with material from New Zealand, the appearance and morphometrics overlap nearly entirely. In some measurements, the single specimen appeared to be at one or the other extreme of the range (e.g., proportions of the rostrum, thoracic sternite 3 and some measurements of the chelipeds) but this is considered natural variation. Despite specimen damage, the diagnostic features of P. pusillus are clearly preserved in the lectotype: the medially broken metagastric ridge that appears as four convex striae across the carapace, a distinctly convex lateral rostral margin, the anteriorly rounded sternite 3, and the distinct mesial spines on antennal articles 2 and 3.

Variation is evident in the ornamentation of abdominal tergite 3. The majority of specimens have only a single transverse ridge on tergite 3, but a distinct posterior transverse ridge is also present in the largest specimen examined (male, 5.3 mm, AM P76215). Two other relatively large specimens (females, 3.0, 3.3 mm, AM P89924) from off Gabo Island, near the type locality, also have a posterior transverse ridge on tergite 3, albeit indistinct. The specimens otherwise agree well with other specimens of P. pusillus .

The typical two pairs of epigastric spines, which have to date been the primary recognition features of P. pusillus , exhibit previously unreported allometric variation. In small specimens, one or both of the outermost spines are sometimes yet to be fully developed, present only as a small granule. In the smallest male (NIWA 43003, 1.5 mm), the spines are very difficult to detect, even under highest magnification. Similarly, records of P. integrirostris from the Kermadec Islands ( Ahyong 2015), based on minute specimens (≤ 2.2 mm), proved referable to P. pusillus in which the outer epigastric spines were as yet undeveloped, being present only as a minute granule. At the other extreme, six epigastric spines are occasionally present as in a 2.8 mm female (AM P89924) and as figured by Poore (2004: fig. 66b). Despite the variation in epigastric spination in some specimens of P. pusillus , the species can be recognised at all sizes by the anteriorly convex rather than biconcave or medially emarginate thoracic sternite 3.

Figures

FIGURE 10. Phylladiorhynchus pusillus (Henderson, 1885), syntype male, 3.3 mm (NHMUK 1888:33): A, carapace and abdomen, dorsal view. B, sternal plastron. C, telson D, left cephalic region, showing antennular, antennal peduncles and acute anterior margin of pterygostomian flap, ventral view. E, right antennal peduncle, ventral view. F, G, left cheliped, dorsal and ventral view. H, I, right cheliped, dorsal and ventral view. J, left P2 or P3, lateral view, with detail of dactylus. Scale bars: 2 mm.

FIGURE 11. Phylladiorhynchus pusillus (Henderson, 1885), male, 4.5 mm (NIWA 57503): A, carapace and abdomen, dorsal view. B, sternal plastron. C, F, right and left antennal peduncle, ventral view. D, E, right and left antennular peduncle, ventral view. G, left Mxp3, lateral view. H, right cheliped, dorsal view. I–K, right P2–4, lateral view. Scale bars: 2 mm.

FIGURE 12. Distribution records for Phylladiorhynchus pusillus (white circles), P. spinosus n. sp. (crossed circles) and P. triginta n. sp. (black circles). Lines demarcating the EEZ for both Australia and NZ shown.