Brachina invasa, Barnard & Williams, 1995

Barnard, J. Laurens & Williams, W. D., 1995, The taxonomy of freshwater Amphipoda (Crustacea) from Australian fresh waters: Part 2, Records of the Australian Museum 47 (2), pp. 161-201 : 194-197

Brachina invasa n.sp.

Figs 21 - 23

Etymology. From Latin, invadere, invader, referring to its stranding from marine sources.

Type locality. Parachilna Creek, Flinders Ranges , South Australia .

Material examined. HOLOTYPE ( Australian Museum, P44073), female "y" 5.S 3 mm, in type series collected 29 August 1976, WD. Williams collector, from interstitial waters. ALLOTYPE (Australian Museum, P44074), same sample, male "ZOO 4.55 mm. Other material from type series ( PARATYPES), female "x" (P44075) 4.63 mm, female "a" (P44076) 4.09 mm, juvenile "boo (P44077) 2.S 6 mm and 129 other specimens (P44078, sample number 770). Other material: Parachilna Creek, Flinders Ranges , South Australia, 3 March 1979, sample number 1066 (P44079), WD. Williams collector , surface waters, 1 female (P44071). Same locality, 3 March 1979, sample number 1075 (P440S0), WD. Williams collector , 5 specimens. Same locality, 4 March 1979, sample number 1074 (P440S1), WD. Williams collector , from inflowing spring to creek, 37 specimens. Mount Chambers Creek, off Gorge, Flinders Ranges , South Australia, 25 August 1976, sample number 771 (P440S2), WD. Williams collector , 3 specimens. Brachina Creek , near Aroona turnoff, Flinders Ranges , South Australia, 3 March 1979, sample number 1073 (P44083), W.D. Williams collector, 7 specimens .

Diagnosis. As in the genus.

Description of holotype (female "y"). Body: pleon (Fig. 23) poorly armed dorsally, armament bilateral, total dorsal setae on pleonites 1- 6 = 2-2-2-2-0-0, spinules on pleonites 4- 6 = 0-2-0; length, 5.83 mm.

Head ( Fig. 21 ): rostrum obsolescent; cephalic lobes weak, founded (illustrated) or weakly subangular, eyes in death absent.

First antenna: length 0.62 of body, 1.6 second antenna, flagellum longer than peduncle, peduncular articles 1-2 longest, article 3 shortest, setae sparse, distoventral corner of article I with strong spine, flagellum with 21 articles, lacking conspicuous aesthetascs; accessory flagellum 3-articulate, scarcely exceeding apex of article I of primary flagellum, articles uniform after first 4, sparsely setulate. Second antenna: length 0.4 body; peduncle longer than flagellum, article 4 slightly longer than 5, articles 3, 4 and 5 with poor ventral setation; flagellum 10-articulate, poorly setose ventrally, lacking calceoli.

Upper lip ( Fig. 21 ): apical margin evenly rounded, connection to epistome and epistome itself symmetrical, epistome with anterior keel. Lower lip ( Fig. 21 ): inner lobes absent. Left mandible ( Figs 21 -23): palp article 2 with 2 apical setae, article 3 absent; incisor 5+ toothed, lacinia mobilis 4-toothed, 3 setose accessory blades; molar bearing plumose seta, several combed or brushy basal setae, other pubescence. Right mandible ( Fig. 22 ): incisor 5-toothed; lacinia mobilis bifid, narrow, denticulate; accessory blades of 3 plumose spines. Left first maxilla ( Fig. 21 ): palp article 2 with 5 thin apical spines and 4 subterminal facial or apicolateral setae, outer plate with 7 spines, most denticulate; inner plate with 5 apical setae. Right first maxilla ( Fig. 21 ): palp symmetrical with left first maxilla; outer plate with 8 (aberrant) spines. Second maxilla ( Fig. 21 ): outer plate outer apical margin without spinule, apicomedial margin of inner plate with 6 marginal thick setae. Maxilliped ( Figs 21 , 22 ): palp article 3 lacking setae on inner edge, no lateral setae, face with linear row of 3 setae, apex not strongly produced, not rugose; inner plate ( Fig. 22 ) with 4 thick spines and several plumose setae apically, medial row of 4 plumose setae, and I ventrofacial spine.

First gnathopod ( Fig. 22 ): coxal plate with 9 short setules anteriorly and apically, no posteroventral setule; article 4 without posterior hump; carpus slightly elongate, not lobate; propodus subrectangular (trapezoidal), longer than wide, posterolateral angle rounded and weakly bulbous, posterior edge with I acclivity and I set of setae, with 2 medial and 3 lateral spines (in the way we interpret these spines compared to other species other species in our work), lateral spines slightly elongate, palm transverse, convex, minutely serrate: dactylus reaching end of palm. Second gnathopod ( Fig. 22 ): much enlarged; article 5 short and weakly lobate, article 6 almond-shaped, palm oblique, palmar corner with I lateral hadziid seta (see Barnard & Barnard, 1983) and 2 mediofacial spines, posterior margin with 3 setose acclivities, setae ofhadziid or eriopisellid form; dactyl strongly curved, fitting palm; coxal plate with 10 setules.

Pereopods ( Figs 22 , 23): coxa 3 with 9 anteroapical setules, coxa 4 emarginate, with 10 anteroventral setules and I posteroventral setule; pereopods 3--4 longer than gnathopod 2, pereopod 3 longer than 4, articles 4-5 weakly setose posteriorly, posterior spine formula on article 6 = 2-2-2-2 and 2-2-2-2; pereopods 5-7 similar, but progressively longer, each with 2 locking spines; coxae 5-6 bearing setule on posteroventral margin of posterior lobes, on pereopod 5 article 2 weakly expanded and minutely lobate posteroventrally, no lobe on pereopods 6-7, bearing thin short posterior setae in serration notches; dactyls of pereopods 3- 7 with one facial setule at nail margin plus 2 setules more marginally. Gills of coxae 2-6 paddle-shaped, weakly pediculate, of pereopod 6 reduced, about half as long and one quarter as voluminous as gill 4, gill sizes progressively small in order: 4, 3, 2, 5, 6. Oostegites slender but lacking setae.

Sternal (gills) processes: None.

Epimera (Fig. 23): each epimeron with small posteroventral tooth, posterior margins weakly convex, with 1-1-4 posterior setules, epimeron I naked below, epimera 2-3 with facial spine formula of 1-2. Pleon (Fig. 23): each dorsolateral posterior margin of pleonites 1- 3 with following setal formula, I-I-I, pleonites 4- 6 with dorsolateral spine formula of 0-1-0. Uropod 3 strongly extending beyond uropods I and 2 in entire animal, uropod lengths relative to uropod I: uropod 2 = 0.60, 3 = 1.3. Pleopods: retinacula 2 per pleopod, no accessories; peduncles of 1-3 with I lateral, I basal and no other setae, outer rami shorter than inner by length of 2 inner articles, outer with 9-9-9 articles, inner with 8-8-8 articles, setae on basal articles = 4-1-1-4, 3-1-1-3, 2-1-1-3, bifid basomedial setae on inner rami = 3-2-2 (of the total of 4-3--3 setae present on basal article).

First uropod (Fig. 23): peduncle length 1.4 rami; I large basofacial spine on outer face; outer margin with 2 apicodistal spines besides row of 3 dorsal spines, with 3 spines medially; rami of subequal length, only inner ramus with 2 rows of marginal spines in formula of 2-2, each ramus with 4 apical spines. Second uropod (Fig. 23): peduncle about 1.0 length of inner ramus, with 3 dorsolateral spines, medial margin with one apical spine; outer ramus shorter than inner, with 2 dorsal spines, only inner with 2 rows of marginal spines in formula of 1-2, apices with 3 and 4 spines each. Third uropod (Fig. 23): peduncle length 0.36 outer ramus, longer than urosomite 3, with one medial spine, one dorsolateral and 2 ventrolateral spines; outer ramus proximal article with 3 lateral and 3 medial ranks of 3-4 spines each, apicolateral corner with 3 spines, apicomedial corner with 3 spines; article 2 small. Telson (Fig. 23):

0.80 as long as wide, scarcely shorter than urosomite 3; cleft 100 percent of its length; apices each with spine in apicolateral notch, 2 apical spines on medial side of apical cusp, 1 apicomedial spine, 2 apicolateral penicillate setules, and each lobe with single member or pair of lateral (or partly dorsal) spines at M.37.

Description of allotype (male "z"). Body: length 4.55 mm. Like female but gnathopod 2 slightly and many other body parts less setose mainly owing to slightly smaller body size or lesser maturation. Gills 2 and 3 heavily infested with surficial protozoans.

Description of other material. Specimen "a" ( Fig. 21 ): female, length 4.09 mm.

Specimen "x": female, length 4.36 mm. Left mandible with 4 rakers. Outer plate of left and right maxillae 1 with 7 spines (thus holotype aberrant).

Specimen "b": juvenile, length 2.86 mm. All taxonomic characters identifiable; examples showing lesser development than adults as follows: primary flagellum of antenna 1 with 12 articles, of antenna 2 with 6 articles; tooth on palm of gnathopod 2 rudimentary, one medial defining spine only, defined laterally with one hadziid seta joined by 2 thin setules, posterior margin of propodus with 2 setal positions, anterior margin with 4 setal positions; posterior armament formula on article 6 of pereopod 3 = e-e-ss; article 1 of uropod 3 with 2 lateral and 3 medial spine sets; telson with only 3 apical spines on each lobe plus normal setules.

Illustrations. Left mandible of holotype with dotted seta added in place where right seta present ( Fig. 22 ); other specimens with this seta present on left mandible. Holotype selected because of completeness of all legs but bearing two aberrations: eight spines on outer plate of one maxilla 1 and lack of left molarial seta.

Distribution. South Australia, Flinders Ranges, in streams, springs.

Figures

Fig. 21. Brachina invasa n.sp., holotype, female "y" 5.83 mm (all drawings except those indicated); female "a" 4.09 mm.

Fig. 22. Brachina invasa n.sp.,holotype,female " y"5. S3mm