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