Discorsotheres subglobosus ( Baker, 1907 ), 2018

Ahyong, Shane T., 2018, Revision of Ostracotheres H. Milne Edwards, 1853 (Crustacea: Brachyura: Pinnotheridae), Raffles Bulletin of Zoology 66, pp. 538-571 : 554-557

publication ID

http://doi.org/10.5281/zenodo.5359739

publication LSID

lsid:zoobank.org:pub:8F3A63EE-E132-4E18-8C58-C7034BFDA4A0

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http://treatment.plazi.org/id/D33B87B4-FF90-FFB5-54CF-39AD848A7723

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scientific name

Discorsotheres subglobosus ( Baker, 1907 )
status

 

Discorsotheres subglobosus ( Baker, 1907)  

( Figs. 8 View Fig , 9 View Fig )

Pinnoteres subglobosa Baker, 1907: 179   (type locality: Gulf St. Vincent, South Australia).

Ostracotheres   (?) (‘ Pinnotheres   ’) subglobosus   . — Tesch, 1918: 287 (list).

Pinnotheres subglobosa   . — Rathbun, 1923: 96–97, fig. 1, pl. 16 fig 1. — Hale, 1927a: 173–174, fig. 174; 1927b: 312. — Silas & Alagarswarmi, 1967: 1186, 1191, 1210–1211. — Springthorpe & Lowry, 1994: 113.

Pinnotheres subglobosus   . — Tesch, 1918: 262. — Schmitt et al., 1973: 6, 8, 9, 88. — Davie, 2002: 434.

Ostracotheres subglobosus   . — Pregenzer, 1988: 17–21, figs. 1–9. — Takeda & Konishi, 1989: 1222. — Ahyong & Brown, 2003: 12. — Poore, 2004: 484, 486, fig. 154d, pl. 26H. — Ng et al., 2008: 250. — McDermott, 2009: tab. 1.

Ostracotheres subglobosa   . — An et al., 2014: tab. 1.

Type material. Lectotype: AM P151 , female (cl 10.6 mm, cw 12.4 mm), Gulf St. Vincent, South Australia, 34°53′17″S, 138°08′14″E, 17 fm [31 m], dredged, in pectens, coll. J.C. Verco. GoogleMaps   Paralectotypes: AM P102300 , 1 ovigerous female (cl 8.7 mm, cw 9.9 mm), collected with lectotype GoogleMaps   ; SAM C1390 View Materials , 4 View Materials ovigerous females (cl 7.8 mm, cw 9.3 mm to cl 8.9 mm, cw 10.4 mm), 1 parasitised female (cl 7.8 mm, cw 10.3 mm), collected with lectotype GoogleMaps   .

Other material examined (all Australia). SOUTH AUSTRALIA: AM P64674 View Materials , 2 ovigerous females (cl 8.6 mm, cw 10.6 mm; cl 9.5 mm, cw 11.7 mm), off Grange, Gulf St. Vincent, 34°54′S, 138°30′E, 15–20 m, inside scallops, 22 December 1971 GoogleMaps   ; SAM C7190 View Materials , 1 View Materials spent female (cl 8.4 mm, cw 9.5 mm), Glenelg, Gulf St. Vincent, 35°00′S, 138°30′E, on reef in Spondylus tenellus   , 37 ft [11 m], coll. N.N. Holmes, 21 September 1985 GoogleMaps   ; SAM C12812 View Materials , 2 View Materials ovigerous females (cl 6.9 mm, cw 8.8 mm; cl 7.8, cw 9.5 mm), 2 spent females (cl 6.7 mm, cw 7.9 mm; cl 7.0 mm, cw 8.4 mm), 1 female (cl 7.2 mm, cw 8.5 mm; with rhizocephalan parasite), Seacliff Reef, Gulf St. Vincent, 35°01.8′S, 138°30.6′E, from 57 scallops, coll. F. Anderson, 1 April 1982 GoogleMaps   ; SAM C12813 View Materials , 3 View Materials ovigerous females (cl 5.4 mm, cw 6.4 mm to cl 6.8 mm, cw 8.0 mm), 2 spent females (cl 5.1 mm, cw 6.0 mm; cl 6.0 mm, cw 6.7 mm), 1 female (cl 5.9 mm, cw 7.1 mm; with pair of epicaridean isopods), Gulf St. Vincent, in scallop ( Pecten bifrons   ), 40 ft [12 m], coll. N. Holmes, June 1982   ; AM E4519 , 1 ovigerous female (cl 7.3 mm, cw 9.4 mm), off Marsden Point, Kangaroo Island , 35°34′S, 137°38′E, 17 fathoms [31 m], FIS Endeavour GoogleMaps   ; SAM C11032 View Materials , 1 View Materials ovigerous female (cl 6.9 mm, cw 8.2 mm), Hardwicke Bay, Yorke Peninsula , 34°53′29″S, 137°27′12″E, from scallop, coll. L. Brake, 11 February 1983 GoogleMaps   ; USNM 205905 View Materials , 2 View Materials ovigerous females (cl 7.3 mm, cw 8.8 mm; ~ 7.1 mm, cw ~ 7.9 mm), Port Giles, Yorke Peninsula , 35°00′S, 137°46′E, from Equichlamys bifrons   , coll. A.J. Butler, 25 November 1978 GoogleMaps   ; AM P64673 View Materials , 4 ovigerous females (cl 7.1 mm, cw 8.4 mm to cl 8.6 mm, cw 10.5 mm), off Edithburgh, Yorke Peninsula , 35°05′S, 137°45′E, 9 m, broken rubble & sponges, coll. N. Coleman, 16 December 1970 GoogleMaps   ; SAM C11037 View Materials ( PCO455 photo), 1 ovigerous female (cl 6.3 mm, cw 7.2 mm), Edithburgh, Yorke Peninsula , 35°05′05″S, 137°44′45″E, 45 m, in Equichlamys bifrons   , coll. K. Gowlett-Holmes, 18 April 2005 GoogleMaps   ; WAM C15774 View Materials , 1 View Materials spent female (cl 5.2 mm, cw 6.0 mm), Edithburgh, Yorke Peninsula , 35°05′S, 137°44′E, jetty area, from Queen Scallop, coll. N. Beach, 4 March 1985 GoogleMaps   ; AM P13500 View Materials , 2 ovigerous females (cl 5.5 mm, cw 7.2 mm; cl 6.5 mm, cw 7.9 mm), Backy Point, near Whyalla, Spencer Gulf , 32°55′S, 137°48′E, from purple pecten, coll. B. Flounders GoogleMaps   ; SAM C7092 View Materials , 1 View Materials ovigerous female (cl 8.2 mm, cw 9.8 mm), opposite Nicholas Bay, between Reevesby & Partney Islands , Sir Joseph Banks Group , Spencer Gulf , 34°30′S, 136°16′E, 20 ft [6 m], sand and Posidonia   , in scallop, coll. W. Zeidler, 8 January 1984 GoogleMaps   ; SAM C12814 View Materials , 1 View Materials ovigerous female (cl 8.1 mm, cw 10.1 mm), Sir Joseph Banks Group, N Point, Marum Island, Spencer Gulf , 34°30.6′S, 136°15.0′E, 15–25 ft [4.5–7.5 m], reef, rubble, sand, sparse Posidonia   , coll. K. Gowlett-Holmes & N. Holmes, 19 January 1986 GoogleMaps   ; AM P19997 View Materials , 1 ovigerous female (cl 7.2 mm, cw 8.7 mm), Cape Donington, Spencer Gulf , 34°44′S, 136°00′E, 8 fathoms [15 m], rough bottom, coll. N. Coleman, 21 December 1970 GoogleMaps   ; SAM C11038 View Materials , 1 View Materials ovigerous female (cl 7.9 mm, cw 9.3 mm), N side of St Francis Island, Nuyts Archipelago , 32°29′35″S, 133°17′06″E, 20–30 m, in Spondylus tenellus   , coll. D. Howlett, December 1979 GoogleMaps   .

WESTERN AUSTRALIA: WAM C12228 View Materials , 1 View Materials spent female (cl 7.6 mm, cw 9.0 mm), ¾ mile S of City Beach Groin , 31°56′S, 115°45′E, in living Spondylus   shell, coll. J. Brouwer, 29 July 1961 GoogleMaps   .

Description. Female: Carapace ( Fig. 9A–C View Fig ) soft, thin, rounded-subquadrate, slightly wider than long, glabrous, surface smooth, appearing polished; strongly vaulted longitudinally, evenly rounded in lateral view; front, transverse, straight or weakly concave, slightly produced, with or without shallow transverse groove on dorsal surface immediately behind front ( Fig. 9A, N, O View Fig ); anterolateral margins, unarmed, forming bluntly rounded rim; lateral surface almost vertical; dorsal surface smooth, gently raised medially forming broad, low, rounded ridge.

Epistome ( Fig. 9D View Fig ) with narrow interantennular septum; median buccal margin with short median point. Antennular sinus slightly larger than orbit, almost transversely aligned in anterior view; antennules folded slightly obliquely. Antenna short, free antennal articles to about mid-height of eye; antennal articles 1 and 2 fused to epistome. Eyes visible in dorsal view, filling orbit, cornea pigmented.

Maxilliped 3 ( Fig. 9E View Fig ) ischiomerus surface glabrous, length about twice width; inner proximal two-thirds sinuous to weakly concave, distomesial angle obtuse, blunt; distal margin not produced beyond palp articulation; outer margin convex. Carpus slighty shorter than half propodus length. Propodus spatulate, length about twice width, distally widened, apex blunt, subtruncate. Exopod margins gently convex.

Cheliped (pereopod 1) ( Fig. 9A, F View Fig ) dactylus gently curved to straight, pollex relatively straight, apices crossing distally, without gape, irregularly, setose. Dactylus almost 0.8 × length of dorsal margin of propodus palm; outer occlusal margin with triangular proximal tooth and row of short corneous denticles and short setae extending to about midlength of dactylus, otherwise smooth; inner occlusal margin with row of short corneous denticles and short setae. Pollex ( Fig. 9G View Fig ) outer occlusal margin weakly crenulate, with 2 small, blunt triangular proximal teeth; inner occlusal margin setose, with row of small corneous denticles along proximal threefourths; inner ventral margin with row of setae. Propodus palm dorsal margin length 1.9–2.2 × height; ventral margin gently sinuous, slightly concave at base of pollex. Carpus mesial margin with setal tuft, unarmed. Merus unarmed, about as long as propodal palm.

Walking legs (pereopods 2–5) slender, smooth, similar in form ( Fig. 9A, H–M View Fig ); relative lengths: pereopod 3(both)>pereopod 4>pereopod 2>pereopod 5. Pereopod 2, 4, 5 merus to propodus unarmed, glabrous; propodus flexor and extensor margins subparallel, not widening distally; dactyli stout, half propodus length, glabrous or with few isolated setae; pereopod 2 dactylus curved, apex spiniform, slightly longer than pereopod 4–5 dactyli; pereopod 4–5 dactyli subequal, strongly falcate, apices spiniform, turning almost perpendicular to main axis. Pereopod 3 asymmetrical in length and dactyl-propodal form; “normal” pereopod 3 with merus to dactylus usually glabrous, dactylus and propodus occasionally with setose disto-flexor margin; dactylus apex spiniform, usually falcate. Longer pereopod 3 1.1–1.2 × length of “normal” pereopod 3; merus 1.4–1.5 (usually 1.5) × length of pereopod 4 merus; propodus usually slight expanded distally, distoflexor margin irregularly setose; dactylus usually longer, stouter but with shorter apex than dactylus of opposite side, setose.

Egg diameter 0.2–0.3 mm.

Hosts. Bivalves molluscs. Pectinidae   : Equichlamys bifrons ( Lamarck, 1819)   , Pecten fumatus Reeve, 1852   (as Notovola meridionalis   [ Tate, 1887]); Mytilidae   : Modiolus areolatus ( Gould, 1850)   (as Modiolaria australis   [ Gray, 1826]); Spondylidae   : Spondylus tenellus Reeve, 1856   ( Hale, 1927a, b; Pregenzer, 1988).

Remarks. Pregenzer (1988) synonymised D. subglobosus ( Baker, 1907)   (South Australia) and D. subquadratus ( Sakai, 1939)   ( Japan), although most subsequent authors have either questioned or not accepted the synonymy ( Davie, 2002; Poore, 2004; Ng et al., 2008); both species are regarded here as valid based on comparison of Australian and Japanese material. In overall appearance, the two species are very similar, including carapace shape and morphology of the pereopod and maxilliped 3; they differ chiefly in the shape of the antennular fossa. In D. subglobosus   , the upper margins of the antennular fossa are essentially transverse in anterior view, with the orbits and antennular fossae approximately transversely aligned ( Fig. 9D View Fig ). The upper margins of the antennular fossae in D. subquadratus   , however, are oblique and slope downwards toward the midline, meeting at an obtuse angle, and the orbits are positioned at a distinctly higher level than the antennular fossae ( Fig. 12D View Fig ). Also, pereopod 3 is usually proportionally more elongate in D. subglobosus   than in D. subquadratus   with the longer pereopod 3 merus 1.4–1.5 (usually 1.5) times the length of the pereopod 4 merus (versus 1.4). Males of neither D. subglobosus   nor D. subquadratus   are presently known. The smallest examined specimen of D. subglobosus   is mature (cl 5.2 mm, cw 6.0 mm; WAM C15774 View Materials ), and the largest specimen (cl 10.6 mm, cw 12.4 mm; AM P151) considerably outsizes the largest known specimen of D. subquadratus   (cl 7.5 mm, cw 9.2 mm; CBM ZC5989).

Like D. subquadratus   , the carapace of D. subglobosus   is weakly sclerotised and gently inflated longitudinally, forming a low, broad dorsomedian swelling, being broadest slightly posterior to the midlength. The swelling is much more prominent in D. camposi   and absent in D. spondyli   . Note that the dorsomedian prominence in D. subglobosus   may appear artifically prominent in poorly preserved specimens in which the branchial carapace surfaces are partially collapsed.

In most specimens of D. subglobosus   , the shorter pereopod 3 has a glabrous propodus and the typical falcate dactylus with one or two setae on the flexor margin; the longer pereopod 3 has a distally setose, often slightly expanded propodus and a straighter, blunt tipped, strongly setose dactylus ( Fig. 9H–M View Fig ). Some specimens, however, have setose propodi and dactyli on both pereopods 3 (as in the lectotype, AM P151; Fig. 9A View Fig ), although other aspects of asymmetry remain. As in the lectotype, in about 75% of specimens, the left pereopod is the longer.

Of the known species of Discorsopagurus   , D. subglobosus   appears to be most closely related to D. subquadratus   from East Asia, despite their wide geographic separation. This strongly anti-tropical distribution of this presumed cognate species pair in southern Australia and East Asia, is independently paralleled in other major marine groups, including fishes and molluscs ( Randall, 1981; Norman & Kubodera, 2006; Gill & Mooi, 2017).

Two specimens from Gulf St. Vincent are parasitised, one with a rhizocephalan ( SAM C12812 View Materials ), and another with a pair of epicaridean isopods, apparently Rhopalione sp.   ( SAM C12813 View Materials )   .

Distribution. Gulf St Vincent, Spencer Gulf and the Nuyts Archipelago, South Australia; Perth, Western Australia; 6– 45 m.

AM

Australian Museum

SAM

South African Museum

WAM

Western Australian Museum

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Pinnotheridae

Genus

Discorsotheres

Loc

Discorsotheres subglobosus ( Baker, 1907 )

Ahyong, Shane T. 2018
2018
Loc

Ostracotheres subglobosus

Ng PKL & Guinot D & Davie PJF 2008: 250
Poore GCB 2004: 484
Ahyong ST & Brown DE 2003: 12
Takeda M & Konishi K 1989: 1222
Pregenzer C 1988: 17
1988
Loc

Pinnotheres subglobosa

Springthorpe RT & Lowry JK 1994: 113
Silas EG & Alagarswarmi K 1967: 1186
Hale HM 1927: 173
Rathbun MJ 1923: 96
1923
Loc

Ostracotheres

Tesch JJ 1918: 287
1918
Loc

Pinnotheres subglobosus

Davie PJF 2002: 434
Schmitt WL & McCain JC & Davidson E 1973: 6
Tesch JJ 1918: 262
1918
Loc

Pinnoteres subglobosa

Baker WH 1907: 179
1907