Pereionotus thomsoni Stebbing, 1899

Coleman, Oliver & Lowry, James K., 2012, The genus Pereionotus (Crustacea, Amphipoda, Phliantidae) from Australia, Zootaxa 3486, pp. 63-88 : 64-69

Pereionotus thomsoni Stebbing, 1899

( Figs 1–3 )

Pereionotus thomsoni Stebbing, 1899: 417 , pl. 35A.— Barnard & Karaman, 1991: 587. – Lowry & Stoddart, 2003: 222 (catalogue).

Palinnotus thomsoni Stebbing, 1900: 16 .

non Palinnotus thomsoni .— J.L. Barnard, 1972: 295, figs 176–179 (= Pereionotus dieteri sp. nov.).

non Palinnotus thomsoni japonicus Hirayama, 1987: 35 , figs 244–246 (= Pereionotus hirayamai sp. nov.)

non Pereionotus thomsoni . — Coleman, 2009b: 766 , figs 1–2, pl. 5C (= Pereionotus yongensis sp. nov.)

Type material. Neotype male, 2 mm, AM P.88036, south of Port Stephens, Boat Harbour, New South Wales, Australia (32°46'59" S 152°06'E), mixed broad leafed brown algae, by hand on snorkel, M. Capa & C. Fraser, 14 March 2006, NSW 2989.

Additional material examined. 30+ specimens, AM P.81997, south of Port Stephens, Boat Harbour, New South Wales, Australia (32°46'59" S 152°06'E), mixed broad leafed brown algae, by hand on snorkel, M. Capa & C. Fraser, 14 March 2006, NSW 2989; 1 juvenile, AM P.81961, Golf Course Bommie, 500 m NE of Ulladulla Head, New South Wales, Australia (35°20'29"S 150°29'12"E), turf algae, P.B. Berents & K.B. Attwood, 0 2 May 1997, NSW 1293; 1 juvenile, AM P.81959, 50 m east of Sullivan's Reef, Ulladulla, New South Wales, Australia (35°21'19"S 150°29'22" E), turf algae, 23 m depth, A. Murray, 5 May 1997, NSW 1329; 3 specimens, AM P.81960, southern end of Lighthouse Reef, Ulladulla, New South Wales, Australia, (35°22'08"S 150°29'19" E), red algal turf, A. Murray, 30 April 1997, NSW 1274; 3 specimens, AM P.81958, 50 m east of Sullivan's Reef, Ulladulla, New South Wales, Australia (35°21'19"S 150°29'22"E), rock surface, 23 m depth, P.B. Berents & R.T. Springthorpe, 5 May 1997, NSW 1323; 2 specimens, AM P.81962, 1.5 km south of Tathra Head, New South Wales, Australia (36°43'59"S 149°59'17"E), from tops of boulders covered with algal turf, R. Springthorpe, 17 May 1995, NSW 1083; 5 specimens, AM P.81963, Merimbula, Merimbula (Long) Point, south-east of wharf, New South Wales, Australia (36°54'04"S 149°55'47"E), Herdmania momus attached to boulders, A. Murray, 15 May 1995, NSW 1053; 1 specimens, AM P.81964, south east of wharf, Merimbula (Long) Point, Merimbula, New South Wales, Australia (36°54'04"S, 149°55'47" E), orange/brown finger sponge, P.B. Berents, 15 May 1995, NSW 1043; 2 specimens, AM P. 81966, 500 m south of Tathra Head, New South Wales, Australia (36°43'44"S 149°49'46"E), sediment layer from rock shelf, R. Springthorpe, 16 May 1995 NSW 1067; 1 specimen, AM P.81965, south east of wharf, Merimbula (Long) Point, Merimbula, New South Wales, Australia (36°54'04"S, 149°55'47"E), amongst small boulders, K.B. Attwood, 15 May 1995, NSW 1051; 1 specimen, AM P.81967, south east of wharf, Merimbula (Long) Point, Merimbula, New South Wales, Australia (36°54'04"S 149°55'47"E), Ecklonia sp., K.B. Attwood, 15 May 1995, NSW 1052; 2 specimens, AM P.81969, 10 m west of Little Beach boat ramp, Port Stephens, New South Wales, Australia (32°43'12"S 152°09'36"E), on Padina sp., 0.5 m depth, C. Fraser, by hand on snorkel, 10 Mar 2006 NSW 2921; 1 specimen, AM P.81970, south of Smoky Cape, south side of Fish Rock, New South Wales, Australia, (30°56'28"S 153°05'58"E), sand from gutter, 22 m depth, airlift on SCUBA, R. Springthorpe, 11 February 2002, NSW 1843; 1 specimen, AM P.81968, north-east side of Cabbage Tree Island, north-east of Port Stephens, New South Wales, Australia (32° 41' 06" S, 152° 13' 36" E), brown algae and rocks, 16.4 m depth, K.B. Attwood & C. Fraser, 0 8 March 2006, NSW 2874; 15 specimens, AM P.81971, small bay N of Boat Harbour, south of Port Stephens, New South Wales, Australia, (32°46'59"S 152°06'E), Lobophora variegata ?, 1–2 m depth, M. Capa & C. Fraser, 14 March 2006, NSW 2987; 1 specimen, AM P.81973, Bay of Islands, Victoria, Australia (38°35'S 142°49'30"E), red algae, 2–5 m depth, R. Springthorpe & P.M. Berents, 28 April 1988, VIC 27; 1 specimen, AM P.81972, Henty Reef, Apollo Bay, Victoria, Australia (38°47' S 143°40'30"E) kelp holdfasts encrusted with sponges, bryozoans, 4–5 m depth, P.B. Berents & R.T. Springthorpe, 25 April 1988, VIC 13; 2 specimens, AM P.18213, west end of reef, Long Reef, Collaroy, New South Wales, Australia (33°44'S 151°19'E), P. Hutchings, 16 November 1970; 1 specimen, AM P.81974 Lord Howe Island, New South Wales, Australia (31°29'17"S 159°9'19"E), M. McArthur, 25 April 2008; 2 specimens, AM P.82001, Montague Island, New South Wales, Australia (36°15'S 150°14'E), washed from algae, A. Kuiter, December 1978; 13 specimens, AM P.81996, Australia, New South Wales, Esmerelda Cove, Broughton Island, north east of Port Stephens (32° 37' 19" S, 152° 19' 10" E) sloping rock reef with ledges, Stypodium sp.?, 17 m depth, by hand on SCUBA, C. Fraser, 12 March 2006, NSW 2951; 2 adults, 2 juveniles, AM P.81995. Burrill Rocks, Ulladulla New South Wales, Australia (35°23'23"S 150°28'14"E), debris around boulder, K.B. Attwood, 0 7 May 1997, NSW 1350; 1 specimen, NMV J59351 , Point Nepean, Nepean Bay, Victoria, Australia (38°18'24''S 144°39'28''E), 5–6 m depth, leg, T.D. O'Hara & Plummer, 8 April – 25 May 1998, Quadrat/ SCUBA; 2 specimens, NMV J 61089 , Point Nepean, Cheviot Beach, Victoria, Australia (38°18'S 144°40'E), 3.5–5 m depth, T.D. O'Hara & Plummer, 31 March 1998, Quadrat, SCUBA; 10 specimens, NMV J 60906 , off East Cape Conran, Sailor's Grave, Victoria, Australia (37°48'13''S 148°44'41''E), 4–5 m depth, T.D. O'Hara, Plummer & Hirst, 15 April 1998, Quadrat/ SCUBA.

Diagnosis. Dorsal keel consisting of subequal evenly rising dorsal humps on pereonites 2–7. Antenna 1 peduncular article 2 as long as wide. Coxae 1–4 with very few short setae on the distal margins. Pereopods 1–4 propodi with additional robust seta half-way on the posterior margin and similar robust setae on the anterior margin of the propodi of pereopods 5–7.

Description. Based on male, 2 mm. Body ( Fig. 1a ) laterally not much expanded, coxae not much laterally splayed. Protrusions on the lateral faces of the pereonites missing. With shallow dorsal keel, each carina on pereonites 2–7 wide and dorsally truncate; on pereonite 1 a rounded process anteriorly, about as wide as 1/3 the length of the segment, posteriorly a shorter, wide truncate protrusion. Carinae on pereonites 5–6 slightly drawn out posteriorly; on pereonite 7 wide and dorsally truncate, those on pleonite segments similar to that on pereonite 7.

Head small, shorter than pereonite 1; eyes produced on rounded dorsal processes. Antenna 1 ( Fig. 1b ) peduncle article 1 as wide as long, twice as wide as article 2, with subapical rounded dorsal lobe, small seta in characteristic notch halfway on medial margin; peduncular article 3 half the width of article 2; short 2-articulate flagellum with long terminal aesthetascs. Antenna 2 ( Fig.1d ) slender, peduncular article 5 subequal or only weakly longer than article 4; article 4 1.5x as long as article 3. Upper lip ( Fig. 1e ) apically truncate. Mandibles ( Fig. 1f, g ) with dentate incisors and 3 raker spines. Lower lip ( Fig. 1c ) with truncate apical margin and short mandibular lobes. Maxilla 1 ( Fig. 1h ) with minute nonsetose inner lobe; outer lobe with 6 robust setae of differing width; uniarticulate, inconspicuous, flat palp, reaching the apex of the outer plate. Maxilla 2 ( Fig. 1j ) plates separate only apically; with inner plate almost 3 times as wide as outer plate. Maxilliped ( Fig. 1i ) inner plate apically truncate with 3 nodular setae and few slender setae; outer plate long, ending in a mediodistal tip; palp 3-articulate, slender, slightly shorter than outer plate.

Pereon. Pereopod 1 ( Fig. 2a ) coxa subrectangular; basis slightly expanded distally; ischium longer than merus; merus triangular, about the length of carpus; propodus as long as merus and carpus combined, anterior margin convex, posterior margin straight with 2 robust setae, inner face of propodus with row of stout apically setulose setae; dactylus falcate with long unguis. Pereopod 2 ( Fig. 2b ) coxa wider than that of pereopod 1; basis distally expanded, anterior margin straight, posterior margin convex; mid diameter of ischium half the width of distal basis region; merus and carpus as for pereopod 1; propodus somewhat more slender and longer compared to pereopod 1 and without row of robust setae on inner face, 1 medial and 1 apical robust seta on the posterior margin; dactylus as for pereopod 1. Pereopod 3 ( Fig. 2c ) coxa similar in shape to that of pereopod 2, but wider; basis subrectangular; ischium as in pereopod 2; merus with straight posterior margin and convex anterior margin, distal margin oblique; carpus slightly expanded distally, apical margin straight; propodus and dactylus subequal to that of pereopod 2. Pereopod 4 ( Fig. 2d ) coxa widest with angular short lobe posteromarginally; basis to merus as for pereopod 3; propodus slightly more slender and longer compared to pereopod 3, with similar robust setae as on preceding pereopods; dactylus as for pereopod 3. Pereopod 5 ( Fig. 2e ) coxa much wider than long, wider than the width of the basis, bilobed, posterior lobe slightly longer and wider than anterior one; basis anteromarginally straight, with wide rounded posterior lobe, expanded ventrally and partly covering the ischium, which is about as wide as long; merus drawn out into rounded posterodistal lobe; carpus as long as merus, slightly expanded distally; propodus and carpus as long as in pereopod 4, but propodus with 2 robust setae anteromarginally. Pereopod 6 ( Fig. 3a ) coxa as wide as long, narrower than basis width; basis to dactylus subequal to that of pereopod 5. Pereopod 7 ( Fig. 3b ) coxa smallest; basis with small posteromarginal lobe, distal margin oblique; ischium subrectangular, with 1 robust seta anterodistally; merus with 2 robust setae anterodistally, posterodistal lobe slightly shorter than that of pereopod 6; carpus shorter than that of pereopod 6, with 2 robust setae on anterior margin; propodus with 3 robust setae on anterior margin: dactylus as for pereopod 6.

Pleon. Pleopods 1–3 with slender rami. Pleopod 1 ( Fig. 3h ) with subrectangular peduncle, 2.2x as long as wide, with 2 coupling hooks; outer ramus slightly longer than inner. Pleopod 2 ( Fig. 3g ) peduncle as long as wide, with 2 coupling hooks. Pleopod 3 ( Fig. 3f ) peduncle wider than long with a tapering medial process ending in an apex with 2 coupling hooks. Uropod 1 ( Fig. 3e ) peduncle longer than rami, slightly expanded distally; rami subequal, with nodular seta on the tip. Uropod 2 ( Fig. 3c ) peduncle slightly longer than inner ramus, outer ramus inserted more proximally and somewhat shorter than inner ramus, both rami apically with nodular setae. Uropod 3 hidden under the triangular telson ( Fig. 3d ).

Variation. The material from Montague Island (AM P.82001) has longer coxae 1 and several specimens of the sample from Broughton Island (AM P.81996) have their first coxae drawn out posterolaterally.

Sexual dimorphism. Female body much wider than male habitus. Uropod 1 peduncle as long as inner ramus, outer ramus shorter than inner, both rami longer than in male and terminal nodular setae minute. Uropod 2 peduncle shorter and more slender than in male, ramus more slender, outer ramus lacking.

Remarks. For comparison of P. thomsoni and the similar P. dieteri sp. nov. see table 1 and for differences to similar species see discussion.

Distribution. Australia: New South Wales, Victoria, Lord Howe Island.

Figures

FIGURE 1 a – j: Pereionotus thomsoni Stebbing, 1899, neotype male, 2 mm, AM P. 88036. a) habitus, b) antenna 1; c) lower lip; d) antenna 2; e) upper lip; f, g) mandibles; h) maxilla 1; i) maxilliped, j) maxilla 2. Scale bars: a) 200 µm; b – j) 100 µm.

FIGURE 2 a – e: Pereionotus thomsoni Stebbing, 1899, neotype male, 2 mm, AM P. 88036. a) pereopod 1; b) pereopod 2; c) pereopod 3; d) pereopod 4; e) pereopod 5. Scale bars: a – e) 100 µm.

FIGURE 3 a – h: Pereionotus thomsoni Stebbing, 1899, neotype male, 2 mm, AM P. 88036. a) pereopod 6; b) pereopod 7; c) uropod 2; d) telson; e) uropod 1; f) pleopod 3; g) pleopod 2; h) pleopod 1. Scale bars: a – h) 100 µm.