Dodecas hexacentrum Mayer, 1903

Takeuchi, Ichiro & Lowry, James K., 2015, A taxonomic study on the Phtisicidae (Crustacea: Amphipoda) of New South Wales, Australia, Journal of Natural History 50, pp. 603-648 : 611-616

Dodecas hexacentrum Mayer, 1903

( Figures 4 – 6 )

Dodecas hexacentrum Mayer, 1903: 29 – 30 , pl. 1, figs 14 – 15, pl. 6 figs 33 – 34. – Stebbing, 1910b: 652. – K.H. Barnard, 1932: 306, fig. 169a. – Guiler, 1954: 539 – 542, figs 8 – 9. – McCain and Steinberg, 1970: 49. – Lowry and Stoddart, 2003: 35.

Type material

Syntypes. Male “ a ”, AM G2555 , 33°50.8 ʹ S, 151°60.7 ʹ E, off Watsons Bay, Port Jackson, New South Wales, May 1887, host sponge: Thalassodendrum rubens Lendenfeld ; 2 mature females “ b ” and “ c ”, AM P46932, 33°50.8 ʹ S, 151°60.7 ʹ E, off Watsons Bay , Port Jackson , New South Wales, May 1887, host sponge: Thalassodendrum rubens Lendenfeld ; 7 males, 7 mature females, 1 immature female and 4 juveniles, AM P46933, 33°50.8 ʹ S, 151°60.7 ʹ E, off Watsons Bay , Port Jackson , New South Wales, May 1887, host sponge: Thalassodendrum rubens Lendenfeld ; Many individuals, AM P46934, off Watsons Bay , Port Jackson , New South Wales, May 1887, host sponge: Thalassodendrum rubens Lendenfeld ; 140 individuals, AM P46935, 33°51 ʹ S, 151°16 ʹ E, off Watsons Bay , Port Jackson , New South Wales, May 1887, host sponge: Thalassodendrum rubens Lendenfeld .

Additional material examined

1 mature female, AM G2564 , 38°32 ʹ S, 145°22 ʹ E, Griffiths Point, Victoria; 1 male and 1 female, AM P22827, 33°49 ʹ S, 151°20 ʹ E, east of North Head, Port Jackson , New South Wales, 19.8 m depth, 19 February 1973, host sponge: cf . Teichonella labrinthica , Australian Museum Shelf Benthic Survey (= AMSBS); 7 males and 9 mature females, AM P22828, 33°49 ʹ S, 151°21 ʹ E, east of North Head, Port Jackson, New South Wales, 19.8 m depth, 19 February1973, host sponge: Holopsamma flavus , AMSBS; 1 mature female, AM P22829, 33°49 ʹ S, 151°20 ʹ E, east of North Head , Port Jackson , New South Wales, 19.8 m depth, 19 February1973, host: Chalinissa elegans ; 6 individuals, AM P22831, 33°49 ʹ S, 151°20 ʹ E, east of North Head , Port Jackson , New South Wales, 21.3 m depth, 20 February 1973, host: Polymastea craticia , AMSBS; 3 males and 1 mature female, AM P22832, 33°49 ʹ S, 151°20 ʹ E, east of North Head , Port Jackson , New South Wales, 21.3 m depth, host: Chalinissa elegans , AMSBS; 2 males and 5 juveniles, AM P22833, 33°49 ʹ S, 151°20 ʹ E, east of North Head , Port Jackson , New South Wales, 25.9 m depth, 26 February1973, host sponge: Polymastia craticia , AMSBS; 643 individuals, AM P22834, 33°49 ʹ S, 151°20 ʹ E, east of North Head , Port Jackson , New South Wales, 25.9 m depth, 26 February 1973, host sponge: Holopsamma flavus , AMSBS; 1 male and 1 juvenile, AM P22835, 33°49 ʹ S, 151°21 ʹ E, east of North Head , Port Jackson , New South Wales, 32.9 m depth, 23 May 1973; 1 male and 1 juvenile, AM P22836, 33°49 ʹ S, 151°21 ʹ E, east of North Head , Port Jackson , New South Wales, 30.4 m depth, 25 May 1973, AMSBS; 2 males and 2 mature females, AM P22837, 33° 50 ʹ S, 151°18 ʹ E, east of South Head , Port Jackson , New South Wales, 21 m depth, February 1974, host sponge: Holopsamma flavus , AMSBS; 1 individual, AM P22838, 33°44 ʹ S, 151°20 ʹ E, east of Long Reef , New South Wales, 15.2 m depth, 28 April 1972, AMSBS; 2 individuals, AM P22843, 33°49 ʹ S, 151°18 ʹ E, east of North Head , Port Jackson , New South Wales, 25.9 m depth, 26 February 1974, AMSBS; 1 male, AM P24371, 33°44 ʹ S, 151°22 ʹ E, east of Long Reef , Sydney , New South Wales, 32 m depth, 28 April 1972, AMSBS; 139 individuals, AM P46944, 33°50 ʹ S, 151°18 ʹ E, east of South Head , Port Jackson , New South Wales, 21 m depth, February 1974, host sponge: Holopsamma flavus , AMSBS .

Type locality

Off Watsons Bay, Port Jackson , New South Wales .

Other records

New South Wales: East of North Head and east of South Head, Port Jackson , east of Long Reef . Victoria: Griffiths Point.

Description

Based on male, syntype “ a ”, body length 14.04 mm, AM G2555. Head and pereonite 1 combined length 3.02 mm; pereonite 2, 1.60 mm; pereonite 3, 1.78 mm; pereonite 4, 2.40 mm; pereonite 5, 3.02 mm; pereonite 6, 1.78 mm; pereonite 7, 0.44 mm.

Head and pereonites robust Head smooth, rounded dorsally; eye large, protruding; head/ pereonite 1 dorsal margin slightly convex; with anteriorly pointed paired dorsodistal projections.

Antenna 1 slender; slightly shorter than body length; peduncle articles 2 and 3 subequal in length; peduncular article 3 concave along anterior margin; flagellum 0.25 × peduncular length, with seven articles; proximal article result of fusion of three articles. Antenna 2 slender; 0.33 × antenna 1 length; peduncle without setae; flagellum about 0.5 × peduncular length, with five articles.

Upper lip notched, forming shallow quadrilateral projections. Mandible right side incisor with five teeth; lacinia mobilis a reverse trapezoid plate followed by a smaller plate; palp article 2 with eight lateral setae; palp article 3 setal formula 1 – 9 – 1; left side incisor with five teeth; lacinia mobilis with five teeth, followed by a trapezoid plate; palp article 2 with six lateral setae; palp article 3 setal formula 1 – 10 – 1. Lower lip finely setose on inner and outer lobes. Maxilla 1 outer plate with six stout apical setal-teeth; palp distal margin with five triangular projections, each with one robust seta, with a row of slender setae. Maxilla 2 inner plate triangular with one apical robust and eight slender setae; outer plate elongate with eight apical setae. Maxilliped inner plate (basal endite) quadrilateral, with three stout serriform setae on expanded inner half of distal margin, with one seta on outer half; outer plate (ischial endite) oval, 0.25 × length of inner plate (basal endite), inner margin smooth, with three or four setae on inner margin; palp article 2 setose on inner margin; palp article 3 not expanded, with six lateral to distal setae; palp article 4 weakly falcate.

Pereon. Pereonite 2 with small anterolateral triangular projection, with midlateral projection, with paired anteriorly curved mid dorsal projections. Pereonite 5 longest. Gnathopod 1 propodus triangular, with three rows of submarginal setae near dorsal margin; palm begins 1/4 along posterior margin, smooth, with two robust setae (one large and one small) near corner of palm; dactylus curved. Gnathopod 2 situated in middle of pereonite 2; gill elongate, about 4 × width, 1.2 × pereonite length; coxa vestigial; basis 2.5 × length of pereonite 2; carpus 1.1 × propodus length; propodus elongate (subrectangular), large, length 2 × width, anterodistal margin straight; palm proximal projection with three robust (one large and two small) setae, palm margin straight, smooth, with broad well developed distal shelf, with one large and one small projections, without sinus.

Pereopod 3 very slender; gill length about as long as corresponding pereonite, straight; basis to carpus straight, cylindrical; basis shorter than other pereopod articles; propodus without distal palm and robust setae; dactylus spatulate, not setose. Pereopod 4 absent. Gill 4 length about 1/2 × corresponding pereonite, straight. Pereopod 5 broad; articulation between articles 1 and 2 oblique; dactylus medium length, falcate, without setae.

Pleon. Pleopod one pair, tiny. Uropod 1; peduncle elongate, about 6 – 8 × width; ramus about 4 – 5 × width; ramus 0.35 × peduncular length.

Female (sexually dimorphic characters and pereopods 6 and 7). Based on syntype “ b ”, body length 10.90 mm, AM P46932 and “ c ”, body length 5.03 mm, AM P46932, for pereopods 6 and 7. Length of head and pereonite 1 combined 1.20 mm, and each length of pereonites 2–7, 1.50 mm, 1.55 mm, 2.10 mm, 2.30 mm, 1.50 mm and 0.55 mm, respectively. Pereonite 1 lacking paired dorsodistal projections. Posterior end of pereonite 1 slightly convex. Pereonite 2 with anterolateral triangular projection, with anteriorly lateral projection, with anteriorly pointed paired mid-dorsal projections. Antenna 1 2/5 × body length. Basis of gnathopod 2 subequal to pereonite 2 length. Propodus oblong, with convex palm. Pereopod 6 with vestigial coxa; basis shorter than propodus; propodus with one pair of robust setae on proximal margin, with two robust setae along palm; dactylus falcate, not setose. Pereopod 7 similar to pereopod 6; merus shorter than basis.

Remarks

See remarks of Dodecas decacentrum .

Figures

Figure 4. Dodecas hexacentrum Mayer, 1903 from Watsons Bay, Port Jackson, New South Wales. Male, syntype, 14.01 mm, AM G2555; B, female, syntype ‘b’, 10.90 mm, AM P46932. Bar indicates 1.0 mm.

Figure 5. Dodecas hexacentrum Mayer, 1903 from Watsons Bay, Port Jackson, New South Wales. Male, syntype, 14.01 mm, AM G2555, A2; G1, P3, P5, ABD (LT); female ‘b’, syntype, 10.90 mm, AM P46932, G2, P6, ABD (V); female ‘c’, syntype, 5.03 mm, AM P46932, P7. Bars in P7, ABD (LT) (M) and ABD (V) (F) indicate 0.20 mm, those in G1, G2 (M), G2 (F), P3, P5, P6 and P7 indicate 0.50 mm and that in A2 indicates 1.0 mm.

Figure 6. Dodecas hexacentrum Mayer, 1903 from Watsons Bay, Port Jackson, New South Wales. Male, syntype, 14.01 mm, AM G2555. Bars indicate 0.10 mm.