Phylladiorhynchus integrirostris ( Dana, 1852 )

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 : 315-317

Phylladiorhynchus integrirostris ( Dana, 1852)

( Fig. 6 )

Galathea integrirostris Dana, 1852: 482 (type locality: Kure Atoll, Hawaiian Islands, by present neotype designation).—Dana, 1855: pl. 30, figs. 12a, 12b.

Not Phylladiorhynchus integrirostris .— Ahyong, 2007: 42, fig. 21 (Lord Howe Rise, 72–82 m) (= P. triginta n. sp.).— Macpherson, 2008: 293 (Dampier Archipelago, W Australia, intertidal– 24 m) (= P. spinosus n. sp.).

Type material. NEOTYPE: BPBM S13201 , female ov. (1.5 mm), Kure Atoll, Stn. KUR-R-11, coll. S. Godwin, 26 Sep 2002.

Other material examined. Hawaiian Islands: NHMD-87703, 1 male (2.2 mm), Honolulu, ca. 5 m, coral, 5 May 1915, Th. Mortensen. NHMD-87707, 1 male (1.8 mm), Honolulu, 10–40 m, coral, 5 May 1915, Th. Mortensen. NHMD-87702, 1 female ov. (2.0 mm), Honolulu, 20–80 m, 5 May 1915, Th. Mortensen. BPBM S5106 , 1 female (1.9 mm), Waikiki , estimated 21.27°N, 157.83°W, 18 feet depth (5.5 m), coll. H. Tuttle, 1 Jan 1945 . BPBM 1272 , 2 males (1.7, 1.9 mm), Laysan , estimated 25.77°N, 171.73°W, coll. Thaanum & Bell, April 1923 . BPBM S13213 , 1 male (1.3 mm), Pearl and Hermes Atoll, Stn. PHR-R-11, coll. S. Godwin, 22 Sep 2002 . BPBM S13218 , 1 female ov. (1.5 mm), 1 male (1.3 mm), Pearl and Hermes Atoll, Stn. PHR-R-15, coll. S. Godwin, 29 Sep 2002 . BPBM S13210 , 1 male (1.4 mm), Kure Atoll, Stn. KUR-R-09, coll. S. Godwin, 26 Sep 2002 .

Diagnosis. Rostrum lateral margin convex; subapical spines present. Carapace with 2 epigastric spines; anterior branchial margin with 2 spines; hepatic spine absent. Thoracic sternite 3 anterior margin biconcave, with obtuse median projection. Antennular article 1 with 5 well-developed spines: distomesial spine large, reaching or overreaching upper distolateral spine, distinctly overreached by first lateral spines; second lateral spine smallest but always distinct. Antennal article 1 distomesial spine overreaching peduncle but not reaching second lateral antennular spine; article 2 distal spines subequal, lateral spine reaching midlength of article 3; article 3 with small mesial spine distally. 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 slightly exceeding 0.9 × width; transverse ridges with dense short setae, and few scattered, long, iridescent setae. Gastric region with 4 transverse ridges; epigastric ridge medially interrupted, with 1 pair of submedian spines; protogastric ridge uninterrupted, extending laterally to carapace margin; mesogastric ridge uninterrupted and nearly reaching first lateral branchial spine; metagastric spine medially minutely broken, otherwise uninterrupted, nearly reaching second lateral branchial spine. Mid-transverse ridge uninterrupted, preceding cervical groove indistinct, followed by 2 or 3 uninterrupted ridges, 1 or 2 short ridges laterally, not extending onto cardiac region. Lateral margins slightly convex, with 4 or 5 distinct spines (anterolateral, 2 anterior branchial, 2 or 3 posterior branchial). Anterolateral spine well-developed, almost reaching anteriorly to level of sharp lateral orbital spine; remainder of anterolateral margin unarmed. Anterior branchial spines subequal. Posterior branchial spines progressively diminishing, anterior 2 always distinct, third spine (if present) weakly indicated. Rostrum 1.2–1.4 × as long as broad, length 0.3 × pcl, width nearly 0.3 × carapace width; lateral margins slightly to distinctly convex, sub-apical spines distinct; dorsal surface concave, with scattered setae. Pterygostomian flap anterior margin ending in blunt tooth, without sharp spine; surface with series of uninterrupted striae, unarmed.

Thoracic sternum: Sternal plastron width 1.3 × length, lateral margins divergent posteriorly, maximum width at sternite 7. Sternite 3 width slightly exceeding twice length; anterior margin biconcave with blunt, obtuse median projection; lateral margins rounded.

Abdomen: Tergite 2 with anterior and posterior transverse ridges; tergites 3 and 4 with anterior ridge only; tergites 5 and 6 smooth, without elevated ridges.

Eye: Eye length 1.3 × width, peduncle distally setose, surface with few short transverse striae; cornea not dilated, maximum diameter subequal to basal rostrum width.

Antennule: Article 1 with 5 well-developed distal spines; distomesial spine large, reaching or overreaching distolateral spine; paired distolateral spines present; proximal lateral spine smallest, always distinct.

Antenna: Article 1 with broad distomesial spine, overreaching peduncle but not reaching lateralmost antennular spine. Article 2 distal spines subequal, lateral spine reaching midlength of article 3. Article 3 with small mesial spine distally. Article 4 unarmed.

Maxilliped 3 (Mxp3): Ischium with prominent distal spines on both extensor and flexor margins; crista dentata with regular row of spines along entire margin. Merus 0.8 × length of ischium at midline, with prominent distal spines on extensor margin and midlength of flexor margin, subequal in size, otherwise unarmed.

Cheliped: Short, total length 2.5–3.0 × pcl in both sexes; subcylindrical, spiny and setose. Ischiomerus 1.0–1.2 × pcl, about twice length of carpus; covered with setiferous striae and spines, mesial spines prominent. Carpus with rows of spines, 1 or 2 mesial spines most prominent. Palm 1.0–1.3 × carpus length, height-width ratio 1.6–1.8, with 4 parallel rows of spines (1 lateral, 1 at about dorsal midline, 1 close to mesial margin and 1 mesial); base of dactylus finger with small spine. Pollex with 1 small proximal spine along external margin; occlusal margin dentate, with prominent, sharp triangular process at midlength. Dactylus subequal in length or slightly shorter than palm; external proximal margin with distinct spine and serrations, distal margin smooth; occlusal margin with distinct or indistinct triangular median processes, distally with row of spines along curved margin; tip excavated; surface with short setiferous striae.

Walking legs (P2–4): Relatively stout, subcylindrical, moderately setose and spinose. Merus successively short- er posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus). P2 merus 0.7 × pcl, length about 4 × width, 1.2 × longer than propodus. P3 merus length 3.6 × width, about as long as P3 propodus; P4 merus length 3.8 × width, 0.9 × propodus length. Extensor margin of P2–3 with regular row of spines, proximally somewhat diminishing, distal spine prominent; P4 without distinct spines, distal spine minute; flexor margin with prominent terminal spines; surface with short striae. Carpus of P2 with 3 spines on extensor margin, distal strongest; P3–4 without distinct spines along extensor margin, terminal spine small; surfaces smooth, at most minutely granulate at setal insertions. P2–4 propodus stout, length about 5 × height; extensor margin typically with 2 proximal spines on P2–3, unarmed on P4; flexor margin with 1–5 slender movable spines in addition to distal pair. Dactylus 0.6 × propodus length, ending in incurved, strong, sharp spine; flexor margin with 5 or 6 movable spines, otherwise unarmed.

Size. Males 1.3–2.2 mm pcl, females 1.5–2.0 mm pcl, ovigerous females ≥ 1.5 mm.

Colour in life. Unknown.

Genetic data. COI sequence data was kindly provided by Paula C. Rodríguez-Flores (Museo Nacional de Ciencias Naturales (MNCN-CSIC) and Centre d’Estudis Avançats de Blanes (CEAB-CSIC), Spain) for P. integrirostris s.s. from Hawaii. The sequences are>10% divergent from all other species sequenced in the New Zealand region ( Table 1 ).

Di s tribution. Known with certainty only from the Hawaiian Islands; 5–40 m depth.

Remark s. Phylladiorhynchus integrirostris ( Dana, 1852) , originally described from the Sandwich Islands (=Hawaiian Islands), has been widely reported from across almost the entire Indo-West Pacific, from South Africa to the Hawaiian Islands, identified based on the presence of only two epigastric spines. However, examination of specimens with two epigastric spines from throughout the putative range of P. integrirostris revealed more than 10 distinct species, with P. integrirostris s.s. currently known with certainty only from the Hawaiian archipelago (Rodríguez-Flores et al. unpublished). All other previous records of P. integrirostris require verification. The original type material of P. integrirostris , however, is now lost ( Baba et al. 2008) and given the uncertainty in the taxonomy of the species, we herein designate a specimen from the Hawaiian Islands (ov. female, 1.5 mm, BPBM S13201 ) as the neotype of Galathea integrirostris to fix the identity of the species.

Present results indicate that P. integrirostris does not occur in New Zealand or Australian waters. Previous records of P. integrirostris from the Kermadec Islands ( Ahyong 2015) and from off Lord Howe Island ( Ahyong 2007) are referable to P. pusillus and P. triginta n. sp., respectively. Phylladiorhynchus integrirostris most closely resembles the two New Zealand species, P. spinosus n. sp. and P. triginta n. sp., but is distinguished from all species of the genus by the following combination of characters: the particularly small size (pcl ≤ 2.2 mm), a single pair of epigastric spines (shared only with P. spinosus n. sp. and P. triginta n. sp.), the absence of hepatic spines on the lateral carapace margin (present in both P. spinosus n. sp. and P. triginta n. sp.), presence of only two anterior branchial spines on the lateral carapace margin (three present in both P. spinosus n. sp. and P. triginta n. sp.), the mesogastric ridge is continuous between the first anterior branchial spines (laterally broken in both P. spinosus n. sp. and P. triginta n. sp.), the metagastric ridge is minutely interrupted medially (continuous in P. spinosus n. sp. and broken into four striae in P. triginta n. sp.), the dorsal surface of abdominal tergite 3 and 4 is smooth, without a posterior transverse ridge (shared with P. triginta n. sp. but with a posterior transverse ridge on both tergites 3 and 4 in P. spinosus n. sp.), and the P2–4 dactylar flexor margin does not bear a row of fixed spines ( P. spinosus n. sp. has a fixed perpendicular spine at the base of each movable spine, absent in P. triginta n. sp.).

Figures

FIGURE 6. Phylladiorhynchus integrirostris (Dana, 1852), neotype female ov., 1.5 mm (BPBM S13201): A, carapace, abdomen and an exemplified egg, dorsal view. B, anterior part of sternal plastron. C, pterygostomian flap, lateral view. D, right cephalic region, showing antennular and antennal peduncles, ventral view. E, right Mxp3, lateral view. F, G, left and right cheliped, dorsal view. H–J, right P2–4, lateral view. Scale bars: 2 mm.