Orthotheres haliotidis Geiger & Martin 1999
Creators: name: Ng, Peter K. L.
name: Ho, Ping-Ho
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pinnotheridae
Orthotheres
Orthotheres haliotidis

description: Orthotheres haliotidis Geiger & Martin, 1999
(Figs. 4–6)
Pinnixa faba – Haswell, 1882: 113; Grant & McCulloch, 1906: 6, 23; Schmitt et al., 1973: 108 (list); Davie, 2002: 431 (list). [not Pinnixa faba (Dana, 1851)].
Orthotheres haliotidis Geiger & Martin, 1999: 273, figs. 1–7; Ng et al., 2008: 250 (list); Ahyong & Brown, 2003: 10.
Material examined. 2 ovigerous females (12.7 × 8.8 mm, 12.3 × 7.9 mm) (AM P3155), in Haliotis asinina, Masthead Island, 23°32’S 151°44’E, Queensland, Australia, coll. A.R. McCulloch & E. Le G. Troughton, no date; 1 ovigerous female (14.0 × 9.9 mm) (AM P64672), North West Island, Capricorn Group, 23°18’S 151°42’E, Queensland, Australia, coll. M. Ward, December 1929; 1 ovigerous female (10.0 × 7.0 mm) (AM P72222), Heron Island, 23°26’S 151°55’E, Queensland, Australia, coll. J. Bishop, no date; 1 male (7.4 × 6.7 mm), 1 ovigerous female (11.4 × 7.9 mm) (AM P72223), in branchial cavity of Haliotis asinina, Heron Island, 23°26’S 151°55’E, Queensland, Australia, coll. M.L. Kok, 8 April 1963; 1 male (6.3 × 6.1 mm), 1 ovigerous female (13.7 × 9.3 mm) (QM), almost certainly from Queensland, no other data.
Diagnosis. Female: Carapace transversely ovate, wider than long, width to length ratio 1.41–1.55; dorsal surface smooth, glabrous, distinctly convex; front projecting slightly anteriorly beyond orbits, entire, margin gently sinuous with shallow median concavity (Fig. 4B; 5A). Eyes small, just visible in dorsal view; mobile, completely filling orbit (Fig. 5A). MXP3 outer surface with numerous short setae; dactylus elongate, inserted distinctly before base of propodus; propodus about 2 times length of dactylus, cylindrical, as long as subovate carpus; carpus inserted on inner surface of ischiomerus, just below distal margin; ischiomerus long, articles completely fused, anteromesial angle of merus distinctly angular from lateral view; exopod relatively stout, ca. 2/3 length of ischiomerus, flagellum 2–segmented (Fig. 5B, D). Anterior thoracic sternum wide sternites 1, 2 completely fused. Chela long; mesioventral margin distinctly setose; outer surfaces of palm, fingers (except for distal and marginal parts) almost smooth; ventral parts of inner surface with numerous setae which do not obscure surface; fingers ca. half length of palm; dactylus occlusal margin with large triangular subproximal tooth, with 4 or 5 denticles behind it; pollex occlusal margin with 1 subproximal tooth, with 3 or 4 denticles behind it (Fig. 6M). Ambulatory legs short, left and right sides symmetrical; P2–P4 merus relatively long; P5 propodus elongate; no natatory setae present; relative lengths of meri P2<P3=P4>P5; dactylus short with prominently hooked tip, ventral margin lined with short setae; P3 and P4 dactylus relatively shorter, broader, dorsal margin carinate, ventral surface gently but prominently concave surface (Fig. 6 E–K). Abdomen wide, extending to buccal region, covering bases of ambulatory legs; telson deeply recessed into distal margin of somite 6 with gently sinuous distal margin (Fig. 5G, H).
Male: Carapace circular, slightly wider than long, width to length ratio 1.10; dorsal surface smooth, gently convex; front distinctly projecting anteriorly, margin gently sinuous (Fig. 4A). Eyes distinctly visible in dorsal view (Fig. 4A). MXP3 as in female. Anterior thoracic sternum relatively wide sternites 1, 2 fused, with shallow concave suture (towards buccal cavity) separating from sternite 3; sternites 3, 4 fused, with very shallow groove separating them; sternopleonal cavity reaching to just before suture between sternites 3/4. Chela relatively stout, shorter than in female; occlusal margin of fingers with subproximal tooth (larger in dactylus) and 4 or 5 denticles behind it (Fig. 6L). Ambulatory legs short, left and right sides symmetrical; P5 propodus long; no natatory setae present; relative lengths of meri P2=P3=P4>P5; dactylus short with prominently hooked tip, ventral margin lined with short setae; P3 and P4 dactylus with ventral surface gently concave (Fig. 6 A–D). Abdomen relatively narrower; telson semicircular (Fig. 5F). G1 relatively stout, distal third gently distinctly bent outwards, tip without distinct large opening (Fig. 5 I–L). G2 short, with rounded tip; exopod stout, shorter than endopod (Fig. 3M).
Remarks. The present specimens agree well with the description and figures of Geiger & Martin (1999) whose specimens were from Queensland and Western Australia (see also Ahyong & Brown, 2003). The MXP3 ischiomerus depicted by Geiger & Martin (1999) appears to be dimorphic although the authors did not discuss it. The inner distolateral margin of the ischiomerus of the male paratype was shown as almost straight and sloping, with the edge angular (Geiger & Martin, 1999: figs. 3A, 4A, B) whereas that of the female holotype was figured as evenly convex with the edge rounded (Geiger & Martin, 1999: fig. 4C). The condition of the male paratype agrees well with those observed for the present series of specimens for both sexes, and there is no dimorphism observed. It is possible the female holotype figured by Geiger & Martin (1999: fig. 4C) is anomalous in this character or the structure was figured at an angle. Geiger & Martin (1999: fig. 3) shows a gently curved G1 with a relatively short distal part although Geiger & Martin (1999: fig. 7) indicates a G1 more like the present one (Fig. 5I, K), with the distal part more elongated and curved at right angles. The median part of the G1 looks as if it has a low indentation (cf. Geiger & Martin 1999: fig. 7B) but this appears to be an artifact of the SEM process.
For comparisons with O. turboe and O. baoyu n. sp., see remarks for the latter species.
description: Published as part of Ng, Peter K. L. & Ho, Ping-Ho, 2016, Orthotheres baoyu, a new species of pea crab (Crustacea: Brachyura: Pinnotheridae) associated with abalones from Tungsha Island, Taiwan; with notes on the genus, pp. 229-241 in Raffles Bulletin of Zoology 64 on pages 234-236, DOI: 10.5281/zenodo.4502042