Arabunnachiltonia murphyi, King, Rachael A., 2009

King, Rachael A., 2009, Two new genera and species of chiltoniid amphipods (Crustacea: Amphipoda: Talitroidea) from freshwater mound springs in South Australia, Zootaxa 2293, pp. 35-52 : 39-44

Arabunnachiltonia murphyi n. sp.

Figures 2–4

Material Examined. Holotype, SAM C6823, Male, 2.0 mm, Strangways Spring, South Australia, 29°09.5'S 136°33.3'E, Coll. W. Zeidler and K. Gowlett-Holmes, 24 September 1989. Allotype, SAM C6824, Female, 2.0 mm, collected with holotype. Paratypes, SAM C6825, 20 males and 5 females, collected with holotype. Other material: SAM C6826, Strangways Spring, South Australia, 29° 9' 33.912" 136° 32' 49.02", Coll. N. Murphy and M. Guzik, 2 November 2007. SAM C6827, Francis Swamp, South Australia, 29° 07.25'S 136° 17.0'E, Coll. W. Zeidler and K. Gowlett-Holmes, 25 September 1989. SAM C6828, Francis Swamp, South Australia, 29° 9' 33.4434" 136° 18' 22.6794", Coll. N. Murphy and M. Guzik, 2 November 2007.

Type Locality. Strangways Springs, South Australia.

Description. Holotype male. Length, 2.0 mm. Head (fig. 2A) about as long as deep. Antenna 1 (fig. 2B) peduncular article 1 1.3 times as long as broad; peduncular article 2 about 0.6 times length of article 1, slightly longer than broad; peduncular article 3 similar length to article 2, twice as long as broad; flagellum slightly longer than peduncle, of eight articles, with one ventral aesthetasc on the proximal margin of the last two articles. Antenna 2 (fig. 2C) about 0.6 times length of antenna 1; peduncular article 1 broader than long; peduncular article 2 longer than article 1, about as long as broad; peduncular article 3 longer than article 2, twice as long as broad; flagellum slightly longer than peduncle, of seven articles.

Upper lip (fig. 2G) broader than long, apically bluntly rounded, with numerous short setae along apical margin. Lower lip (fig 2H) with rounded lateral lobes, apical margins rounded, apical and inner margins with numerous short setae. Left mandible (fig. 2J) with incisor of five teeth, lacinia mobilis of four teeth, spine row of three plumose setae and triturative molar. Right mandible (fig. 2I) with incisor of six teeth, lacinia mobilis of three teeth, spine row of two plumose setae and triturative molar with a long plumose seta. Maxilla 1 (fig. 2F) outer plate with nine setulate robust setae; inner plate with two long apical plumose setae. Maxilla 2 (fig. 2E) outer plate with an apical row of 12 simple setae; inner plate with an apical row of 11 simple setae, with a plumose seta on the inner lateral margin below the apical row. Maxilliped (fig. 2D) inner plate apical margin with three short spine-like robust setae, with plumose seta along apical and inner lateral margins; outer plate with numerous simple setae along apical and inner lateral margins; palp articles 1 and 2 similar width, palp article 2 with numerous simple setae on inner lateral margin; palp article 3 not as broad as articles 1 and 2, with numerous simple setae on inner lateral and distal margins; palp article 4 short, about half as broad as article 3, with unguis and simple setae on distal margin.

Gnathopod 1 (fig. 3A) coxa distal margin with 19 short simple setae, ventral margin with one plumose seta at mid length; basis, ischium, and merus ventral margins with setae; carpus with ventral-lateral lobe and row of eight setulate setae becoming longer distally, dorsal-distal margin with long settulate setae, inner face with a single plumose seta; propodus rectangular in shape, around two times as long as broad, ventral-distal corner with two robust setae (near where tip of dactylus touches), ventral-distal margin (adjacent to dactylus length) with short robust and long simple setae, dorsal-distal margin with long simple setae, inner face with five robust plumose setae; dactylus curved, fitting against ventral-distal corner of propodus, with dorsal plumose seta. Gnathopod 2 (fig. 3B) coxa distal margin with 17 short simple setae, ventral margin with two plumose setae at mid length; basis dorsal and ventral margins with setae; ischium and merus with scattered setae on ventral margins; propodus 1.3 times as long as broad, with proximal lobe covering distal margin of carpus, ventral-distal corner marked with a robust seta on each of the inner and outer faces, ventral-distal groove present on inner face to accommodate the tip of the dactylus, ventral distal margin with numerous apically bifid robust setae (similar size as those marking the ventral distal corner). Pereopod 3 (fig. 3C) coxa distal margin with 15 short simple setae; basis dorsal and ventral margins with setae; ischium ventral margins with setae; merus with distinct dorsal-distal lobe (not especially strong), dorsal margin with simple seta, dorsal-distal margin with long setae, ventral-distal margin with long simple setae; carpus ventral margin with three apically bifid robust setae and scattered simple setae; propodus ventral margin with five apically bifid robust setae in four groups (distal seta smallest); dactylus dorsal margin with plumose seta, ventral margin with simple seta, unguis present. Pereopod 4 (fig. 3D) coxa without distinct proximal excavated corner, distal margin with 22 short simple setae; basis dorsal and ventral margins with setae; ischium ventral margins with setae; merus with distinct dorsal-distal lobe (not especially strong), dorsal margin with long simple seta, dorsal-distal margin with long setae; carpus ventral margin with two apically bifid robust setae and scattered simple setae; propodus ventral margin with six apically bifid robust setae in four groups (distal seta smallest); dactylus dorsal margin with plumose seta, ventral margin with simple seta, unguis present. Pereopod 5 (fig. 3E) coxa anterior lobe with four short setae, posterior lobe with eight short simple setae; basis about as long as broad, dorsal margin with four apically divided robust setae along length, dorsal-distal margin with two robust setae, ventral margin subtly crenulated and with 14 short simple setae along length; ischium dorsal-distal margin with distal robust setae; merus with weak postero-distal lobe, dorsal margin with robust setae in four clusters, ventral margin with robust setae in three clusters; carpus shorter than merus, dorsal margin with robust setae in three clusters, ventral margin with robust setae in one distal cluster; propodus similar length to merus, dorsal margin with seven apically divided robust setae in four clusters (distal seta smallest), distal margin with long simple setae; dactylus with plumose seta on ventral margin, unguis present. Pereopod 6 (fig. 3F) coxa ventral margin with six short simple setae; basis slightly longer than broad, dorsal margin with four apically divided robust setae along length, distal end of dorsal margin with two robust setae, ventral margin subtly crenulated and with 10 short simple setae along length; ischium dorsal margin with distal robust setae; merus with weak postero-distal lobe, dorsal margin with robust setae in four clusters, ventral margin with robust setae in three clusters; carpus shorter than merus, dorsal margin with robust setae in three clusters, ventral margin with robust setae in one distal cluster; propodus similar length to merus, dorsal margin with seven apically divided robust setae in four clusters (distal seta smallest), distal margin with long simple setae; dactylus with plumose seta on ventral margin, unguis present. Pereopod 7 (fig. 3G) ventral margin with five short simple setae; basis as long as broad, dorsal margin with four apically divided robust setae along length, distal end of dorsal margin with two robust setae, ventral margin subtly crenulated and with 13 short simple setae along length; ischium dorsal margin with distal robust setae; merus with weak postero-distal lobe, dorsal margin with robust setae in three clusters, ventral margin with robust setae in three clusters; carpus shorter than merus, dorsal margin with robust setae in three clusters, ventral margin with robust setae in two distal clusters; propodus similar length to merus, dorsal margin with seven apically divided robust setae in four clusters (distal seta smallest), distal margin with long simple setae; dactylus with plumose seta on ventral margin, unguis present

Pleopods 1–3 similar, unmodified (as in Chiltonia ), peduncle inner margins with two distal retinacula (coupling hooks).

Uropod 1 (fig. 3H) peduncle distinctly longer than rami, dorsal margin with six robust along the length of the outer margin and three along the inner margin; outer ramous distal margin with four robust setae of varying lengths; inner ramous with single seta at mid length, distal margin with five robust setae of varying lengths. Uropod 2 (fig. 3J) peduncle similar length to rami, dorsal margin with three long robust setae; outer ramous slightly smaller than inner ramous, distal margin with five robust setae of varying lengths; inner ramous with two robust setae at mid length, distal margin with six robust setae of varying lengths. Uropod 3 (fig. 3K) with one article, distal margin with one short robust seta, one long robust seta apically and three shorter robust setae subapically.

Telson (fig. 3I) slightly broader than long, apically blunt with three robust setae around each distal corner.

Female. Length, 2.0 mm. Similar morphology to male except for the following.

Antenna 1 (fig. 4C) flagellum of nine articles, with one ventral aesthetasc on the proximal margin of the last four articles. Antenna 2 (fig. 4D) flagellum of seven articles.

Gnathopod 1 (fig. 4A) coxa distal margin with 19 short simple setae, ventral margin with three plumose seta at midlength; carpus with ventral-lateral lobe and row of seven setulate setae becoming longer distally; propodus almost rectangular in shape, around 2 times as long as broad, ventral-distal corner with two robust setae (near where tip of dactylus touches), ventral-distal margin (adjacent to dactylus length) with long and short simple setae, dorsal-distal margin with long simple setae, inner face with six robust setae; dactylus curved, fitting against ventral-distal corner of propodus, with dorsal plumose seta. Gnathopod 2 (fig. 4B) coxa distal margin with 12 short simple setae; basis dorsal and ventral margins with setae; ischium and merus with setae on ventral margins; carpus with ventral-lateral lobe and row of seven setulate setae becoming longer distally; propodus almost rectangular in shape, 2 times as long as broad, ventral-distal corner with two robust setae (near where tip of dactylus touches), ventral-distal margin (adjacent to dactylus length) with long and short simple setae, dorsal-distal margin with long simple setae, inner face with three robust plumose setae; dactylus curved, fitting against ventral-distal corner of propodus, with dorsal plumose seta.

Pereopod 3 (fig. 4E) propodus ventral margin with six apically bifid robust setae in five groups (distal seta smallest). Pereopod 4 (fig. 4F) propodus ventral margin with seven apically bifid robust setae in five groups (distal seta smallest).

Oostegites present on coxae 2 to 5 (figs. 4G–J) to form the marsupium, margins with scattered curved hooks.

Etymology. Named for Dr Nick Murphy (School of Earth and Environmental Sciences, The University of Adelaide), who conducted the molecular work that prompted this study and provided specimens.

Remarks. No exceptional morphological variance was recorded among the populations of this species. Mature females of this species were often but not always larger than males. Larger females exhibited greater setation on pereopods 3 and 4 (figs. 4E, F).

A. murphyi n.sp. has been recorded at only two springs sites (Strangways and Francis Swamp), despite examination of numerous spring samples from central Lake Eyre region. It would thus seem to have restricted distribution.

Figures

FIGURE 2. Arabunnachiltonia murphyi n. sp., holotype male, 2.0 mm. A, whole body, lateral view; B, antenna 1; C, antenna 2; D, maxilliped; E, maxilla 2; F, maxilla 1; G, upper lip; H, lower lip; I, right mandible; J, left mandible. Scales: 1 (A), 0.1 mm; 2 (B – C), 0.1 mm; 3 (D – J), 0.05 mm.

FIGURE 3. Arabunnachiltonia murphyi n. sp., holotype male, 2.0 mm. A, gnathopod 1 (with enlargement); B, gnathopod 2 (with enlargement); C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pereopod 7; H, uropod 1; I, uropod 2; J, telson; K, uropod 3 (right and left). Scales: 1 (A – B), 0.1 mm; 2 (C – G), 0.1 mm; 3 (H – J), 0.5 mm.

FIGURE 4. Arabunnachiltonia murphyi n. sp., allotype female, 2.0 mm. A, gnathopod 1 (with enlargement); B, gnathopod 2 (with enlargement); C, antenna 1; D, antenna 2; E, distal end of pereopod 3; F, distal end of pereopod 4; G, oostegite on pereonite 2; H, oostegite on pereonite 3; I, oostegite on pereonite 4; J, oostegite on pereonite 5. Scales: 1 (A – B), 0.1 mm; 2 (C – D), 0.1 mm; 3 (E – F), 0.1 mm; 4 (G – J), 0.1 mm.