Australomicroprotopus megacoxa, Myers, Alan A., Lowry, James K. & Billingham, Zac, 2016

Myers, Alan A., Lowry, James K. & Billingham, Zac, 2016, A new family, genus and species of freshwater amphipod Australomicroprotopus megacoxa gen. nov. sp. nov. (Senticaudata, Corophiidea, Microprotopoidea, Australomicroprotopidae fam. nov.) from Australia, Zootaxa 4161 (3), pp. 412-418 : 414

Australomicroprotopus megacoxa gen. nov. sp. nov.

( Figs 1–3 )

Type material. HOLOTYPE male, 4.4 mm, Victoria, Avondale Heights, Maribyrnong River (-37.769670°, 144.851200°), 5/10/2012 (AM.98902) ; Paratypes. 5 males, 4 females, same data as holotype (AM P.98903).

Other material. 1 male, Victoria, Arthurs Creek Township, Arthurs Creek (-37.584880°, 145.204600°), 22/ 04/2013 (AM P.98904) ; 3 males, 1 female Victoria, Maryvale, La Trobe River (-38.169550°, 146.484250°), 22/05/ 2012 (AM98905) ; 7 males, 3 females, Victoria, Avondale Heights, Maribyrnong River (-37.769670°, 144.851200°), 17/05/2013 (AM P.98906) ; 3 males, 1 female Victoria, Maryvale, La Trobe River (-38.170140°, 146.486080°), 19/11/2014 (AM P.98907) ; 3 males, 3 females Victoria, Meeniyan, Tarwin River (-38.578973°, 145.995254°), 5/03/2010 (AM P.98908) ; 4 males, 1 female, Victoria, Maryvale, La Trobe River (-38.165594°, 146.442693°), 28/11/2013 (AM P.98909).

Type locality. Maribyrnong River , Avondale Heights, Victoria, Australia (-37.769670°, 144.851200°).

Etymology. Named after the very large second coxa of the male.

Description. Based on male holotype, 4.4 mm.

Head. Head eye lobes subtriangular, eye round partially within eye lobe, distoventral margin moderately recessed. Antenna 1 less than half body length, peduncular articles in the ratios 3:4:2.5; accessory flagellum with three articles the terminal article rudimentary; primary flagellum subequal in length with peduncle, with 12 articles. Antenna 2 subequal in length with antenna 1; peduncular article 4 longer than 5; flagellum shorter than peduncle with 10 articles. Labrum without epistome. Mandible palp three articulate; article 3 subequal in length with article 2, spatulate with dense distal setation. Maxilla 1 inner plate with a few small distal setae; palp subequal in length with outer plate. Maxilla 2 lacking oblique setal row. Labium with rounded mandibular projections. Maxilliped palp much longer than outer plate.

Pereon. Gnathopod 1 very reduced, partially or entirely hidden behind coxa 2; coxa longer than broad narrowing distally with single distal seta; basis slender, anterior margin concave; carpus and propodus subequal in length; propodus the broader; dactylus slightly overlapping palm. Gnathopod 2 enormous; coxa strongly produced forward, very setose on lower margin; basis slender, flask-shaped, setose on anterior and posterior margins; carpus short, cup shaped; propodus nearly three times length of carpus, palm very reduced, posterior margin with one acute distal spine and one proximal rounded process constricted at the base, posterior margin clothed in long setae; dactylus very enlarged, curved, reaching beyond proximal end of propodus. Pereopods 3–4 relatively small, strongly setose; coxae deep, coxa 3 a little larger than coxa 4; dactylus short, less than half length of propodus. Pereopod 5 missing. Pereopod 6 relatively feeble; basis slender, posterior margin convex; dactylus weak. Pereopod 7 stout; basis enlarged, with broad weakly serrate posteroproximal flange; dactylus strong.

Pleon. Epimera 2–3 with small posterodistal spine. Uropod 1 peduncle with strong inter-ramal spine about one third length of peduncle; inner ramus longer than outer and subequal in length with peduncle. Uropod 2 peduncle with short inter-ramal spine a little over one quarter length of peduncle; inner ramus longer than outer and longer than peduncle. Uropod 3 peduncle short nearly as broad as long; inner ramus longer than outer and longer than peduncle. Telson broad, fleshy, each dorsolateral crest with a small spine and 4 setae.

Female (sexually dimorphic characters). Gnathopod 2 basis flask-shaped but shorter than that of male; carpus elongate but shorter than propodus; propodus narrowing distally, lacking spines or processes, palm very oblique; dactylus fitting palm.

Habitat. Lowland freshwater streams with predominantly sandy substrates.

Remarks. This is the first known freshwater example of the superfamily Microprotopoidea. It is also the first record of the superfamily from the continent of Australia. The only other known species in the superfamily from the Indo-Pacific is Microprotopus bicuspidatus Rabindranath (1971) from southern India.

Figures

FIGURE 1. Australomicroprotopus megacoxa gen. nov. sp. nov., male holotype, Victoria, Maribyrnong River.

FIGURE 2. Australomicroprotopus megacoxa gen. nov. sp. nov., male paratype Victoria, Maribyrnong River.

FIGURE 3. Australomicroprotopus megacoxa gen. nov. sp. nov., male and female paratypes Victoria, Maribyrnong River.