Austrotheres pregenzeri, Ahyong, 2018

Ahyong, Shane T., 2018, Revision of Ostracotheres H. Milne Edwards, 1853 (Crustacea: Brachyura: Pinnotheridae), Raffles Bulletin of Zoology 66, pp. 538-571 : 547-550

Austrotheres pregenzeri new species

( Figs. 5 , 6 )

Ostracotheres holothuriensis . — Pregenzer, 1988: 21–28, figs. 10–16, 12a, 17–19. — Poore, 2004: 484, 486, fig. 154c, g, pl. 26H. — Ng et al., 2008: 250. (Not O. holothuriensis [ Baker, 1907]).

Pinnotheres holothuriensis . — Davie, 2002: 433. (Not P. holothuriensis Baker, 1907 ).

Type material (all New South Wales, Australia). Holotype: AM P72226, female (cl 10.5 mm, cw 10.2 mm), S of Point Stephens lighthouse, Port Stephens , 32°45′02″S, 152°11′35″E, 14 m, from Herdmania sp. , NSW1488, coll. S. Keable et al., 31 May 1998 . Paratypes: AM P80529, 1 ovigerous female (cl 10.4 mm, cw 9.1 mm), SW side Boodelbah Island , E of Port Stephens, 32°42.4998′S, 152°13.5258′E, 10–13 m, from Herdmania sp. encrusted with hydroids, sloping boulder reef meeting flat sand bottom, NSW2905 (photo 16), coll. S. Keable et al., 10 March 2006 ; AM P63040, 1 male (cl 4.9 mm, cw 4.6 mm), 1 ovigerous female (cl 8.6 mm, cw 7.7 mm), Kurnell Pier , Botany Bay, 34°00.2′S, 151°12.5′E, 7 m, from pylons/pilings , BB KP1 P2-7 , NSW Fisheries / CRIMP Survey , 21 Oct 1998 .

Other material examined (all Australia). QUEENSLAND: MNHN-IU-2008-12984 (B9780), 1 ovigerous female (cl 9.8 mm, cw 9.0 mm), Heron Island, coll. A.J. Bruce, 1968.

NEW SOUTH WALES: QM W18368, 1 male (cl 6.1 mm, cw 5.6 mm), ‘ The Needles’ , Julian Rocks, Byron Bay, 28°36′08″S, 153°37′07″E, 12 m, fringing reef, from Herdmania grandis , coll. J. Kennedy, 2 February 1993 ; AM P101806 , 1 ovigerous female (cl 8.5 mm, cw 7.7 mm), NW end South Solitary Island , 30°12.116′S, 153°15.978′E, 17.4 m, steep incline with large drab boulders encrusted with fixed growth, from Herdmania sp. NSW2808, coll . R. Springthorpe , 1 February 2005 ; AM P58218, 1 juvenile female (cl 3.9 mm, cw 3.7 mm), bulk liquids berth, Botany Bay , 33°58.5′S, 151°12.6′E, 3 m, from pylons/pilings , BB KP1 P1-3 , NSW Fisheries / CRIMP Survey , 19 October 1998 ; AM P63041, 1 spent female (cl 7.2 mm, cw 6.2 mm), Channel Marker 4, Botany Bay, 33°59.3′S, 151°12.6′E, 3 m, from pylons/pilings , BB CH 4 P1-3, NSW Fisheries / CRIMP Survey , 21 October 1998 ; AM P58219, 1 ovigerous female (cl 8.4 mm, cw 7.8 mm), Kurnell Pier , Botany Bay, 34°00.0′S, 151°12.5′E, 7 m, from pylons/pilings , BB KP1 P3-7 , NSW Fisheries / CRIMP Survey , 21 October 1998 ; AM P63135, 1 juvenile female (cl 4.6 mm, cw 4.2 mm), dorsally beyond eye; antennal articles 1 and 2 fused to epistome. Eyes filling orbit, cornea pigmented .

Maxilliped 3 ( Fig. 6D ) margins and surface with short setae; ischiomerus length about 2.3 × width; inner, proximal twothirds weakly concave, distomesial angle obtusely rounded; distal margin produced slightly beyond palp articulation; outer margin strongly convex. Carpus half propodus length. Propodus spatulate, length about twice width, distally widened, apex blunt, rounded. Exopod margins convex.

Port Kembla, 34°28.3′S, 150°57.5′E, outer side of eastern breakwater, 7 m, from pylons/pilings, PK EBO Qual, NSW Fisheries/ CRIMP Survey , 16 May 2000 ; NMV J13221 , 3 ovigerous females (cl 6.4 mm, cw 5.7 mm; cl 9.9 mm, cw 8.9 mm; cl 11.5 mm, cw 10.6 mm), Shellharbour , 34°35′S, 150°52′E, coll. J.E. Watson, 1975 ; AM P101807 , 1 ovigerous female (cl 7.8 mm, cw 7.2 mm), NW of Bass Point, under gravel loader jetty, Shellharbour , 34°35′29.91″S, 150°53′07.53″E, 10 m, scrapings including small Herdmania grandis and small encrusting orange bryozoan, NSW3908, 2 May 2010 ; ZRC 2018.1067 , 1 male (cl 2.9 mm, cw 2.8 mm), 1 ovigerous female (cl 8.6 mm, cw 7.6 mm), NW of Bass Point, under gravel loader jetty, Shellharbour , 34°35′29.91″S, 150°53′07.53″E, 10.6 m, from Herdmania grandis, NSW 3924, 2 May 2010 .

Description. Female: Carapace ( Fig. 6A, B ) subcircular to longitudinally subovate, slightly longer than wide, lateral margins rounded to slightly flattened, longitudinally vaulted, profile rounded in lateral view; front slightly produced, subtruncate, broadly rounded, medially straight or weakly emarginated; anterolateral margins defined, coarsely irregular; dorsal surface rugose, regions weakly inflated across anterior half of carapace, demarcated by shallow grooves, surfaces rugose, irregularly, coarsely tuberculate, granulate, most pronounced in largest specimens; epigastric region slightly raised, anterior ridge prominent, transverse, anteriorly divided into four by short emarginations; posterior half of surface smooth or with scattered granules.

Epistome ( Fig. 6C ) with broad triangular interantennular septum; median buccal margin with obtuse median point. Antennular sinus larger than orbit; antennules folded slightly obliquely. Antenna short, free antennal articles not extending Cheliped (pereopod 1) ( Fig. 6A, E ) outer surface largely glabrous. Dactylus and pollex relatively straight, crossing distally, without gape, with row of short setae. Dactylus as long as dorsal margin of propodus palm, occlusal margin with 2 small teeth; surfaces smooth. Pollex occlusal margin irregular, crenulate, with low blunt tooth at midlength; inner ventral margin setose; inner surface of palm with short scattered setae. Propodus palm dorsal margin length 1.3–1.5 × height; ventral margin distinctly weakly concave at base of pollex. Carpus mesial margin with brush of setae, unarmed; merus unarmed, stout, shorter than propodus.

Walking legs (pereopods 2–5) similar ( Fig. 6F–I ); relative lengths: pereopod 2≈pereopod 3>pereopod 4>pereopod 5; smooth, sparsely setose; pereopod 2 propodus with row of short flexor marginal setae; pereopod 3–4 propodus with row of long natatory setae near extensor margin, extending onto dorsal surface of carpus, each article with row of natatory setae on flexor margin, with short row of distal flexor marginal setae; pereopod 5 propodus flexor margin and distal meral flexor margin setose. Meri unarmed, length 3.5–3.9 × height (pereopods 2–4), about 3.4 × height (peroepod 5). Propodi unarmed, 3.2–3.8 × height. Dactyli similar, stout, strongly curved, falcate, evenly tapering, apices spiniform, corneous; flexor margin sparsely setose proximally; pereopod 2–4 dactyli 0.6 × propodus length; pereopod 5 dactylus 0.7 × propodus length.

Egg diameter 0.3–0.4 mm (in preservative).

Male: Similar to female but smaller maximum size, carapace tuberculation less pronounced ( Fig. 6K ). Cheliped palm with shallow, irregular pitting; palm dorsal margin length 1.2–1.3 × height. Abdomen narrow ( Fig. 6N ), distally tapering, widest at somite 3; somite 6 weakly trapezoid, slightly wider than long, about as along as telson; telson slightly wider than long, apex rounded to subtruncate. G1 with long setae along central one-third of margins, small tuft of short setae on step proximal to gently sinuous, glabrous, finely tapering, lanceolate tip ( Fig. 6O, P ). G2 short, simple, about one-fourth G1 length; exopod absent ( Fig. 6Q ).

Hosts. Ascidians, Pyuridae : confirmed from Herdmania grandis ( Heller, 1878) but reported from H. momus ( Savigny, 1816) ( Pregenzer, 1988) . Kott (2002), however, showed that H. grandis in temperate Australia has been mistaken for the tropical H. momus . Pregenzer’s (1988) host records of H. momus are probably based on H. grandis .

Etymology. Named after Charles Pregenzer, for his contributions to the knowledge of Australian pinnotherids. Charles was the first to report specimens of this new species, albeit under the name A. holothuriensis .

Remarks. Review of type and other material of A. holothuriensis shows that the species is restricted to southern Australia between Victoria and Western Australia. Previous records of A. holothuriensis from New South Wales ( Pregenzer, 1988) are referable to A. pregenzeri new species, presently known only from eastern Australia between southern Queensland central New South Wales. The two species thus have discrete distributions ( Fig. 5 ), with that of A. pregenzeri encompassing the Peronian and Solanderian provinces, and A. holothuriensis corresponding largely to the Flindersian Province and extending slightly into the Solanderian Province at Shark Bay, Western Australia ( Ahyong, 2017).

Austrotheres pregenzeri differs from A. holothuriensis in carapace ornamentation. In contrast to the smooth carapace with weakly indicated epigastric ridges of A. holothuriensis , the carapace surface of A. pregenzeri is rugose and epigastric ridges marked ( Fig. 6A, B, K ). The carapace of male A. pregenzeri is irregularly rugose and granular, with shallow demarcations between regions, but in females, ornamentation is much more elaborate. Female A. pregenzeri have pronounced carapace regions on the anterior half, covered in granules or irregular nodules. Surface ornamentation tends to be nodulose and isolated in smaller specimens, becoming increasingly coalesced and also more granular in the largest specimens. Small scattered granules are also present on the posterolateral and posterior margins of the carapace in the largest specimens. Although the rugose carapace ornamentation is most pronounced in the largest specimens, the smallest juvenile female examined (cl 3.9 mm, AM P58218) already has low irregular granules and weakly developed rugosities on the anterolateral surfaces of the carapace; by cl 4.6 mm (AM P63135), the distinctive carapace ornamentation is well developed. Likewise, carapace rugosity is evident in the smallest male examined (cl 2.9 mm, ZRC 2018.1067).

Morphological variation is slight in A. pregenzeri apart from the allometric changes in carapace ornamentation. Juvenile females have a more prominent front than adults, somewhat resembling that of males, and up to about 4 mm cl, have a narrow, male-form abdomen. Females are ovigerous by at least cl 6.4 mm, with a rounded, expanded abdomen. The smallest male examined (cl 2.9 mm, AM P101808) is sexually mature, with fully developed gonopods.

Austrotheres pregenzeri is commensal with ascidians, but a number of specimens were collected in the open, amongst algae and other biofouling. Austrotheres pregenzeri probably frequently spends time outside of the host as is probably also the case for A. holothuriensis .

Distribution. Known only from eastern Australia, from scattered localities between Heron Island, Queensland, and Shellharbour, New South Wales; 3–17.4 m.

Figures

Fig. 5. Distribution of species of Austrotheres new genus. (■) A. holothuriensis (Baker, 1907) new combination; (●) A. pregenzeri new species.

Fig. 6. Austrotheres pregenzeri new species. A–J: female holotype, cl 10.5 mm, cw 10.2 mm, Port Stephens, AM P72226. K–Q: male paratype, cl 4.9 mm, cw 4.6 mm, Botany Bay, AM P63040. A, K, dorsal habitus; B, carapace, right lateral view; C, cephalothorax, anterior view; D, M, right maxilliped 3; E, right cheliped, anterior view; F–I, right pereopods 2–5; J, female abdomen; L, left cheliped, anterior view; N, male abdomen; O, right G1, sternal view; P, right G1 tip, mesial view; Q, right G2, sternal view. Scale: A–B, J = 2.0 mm; C–I, K, L, N = 1.0 mm; M = 0.5 mm; O–Q = 0.25 mm.