Bircenna thieli, Hughes, Lauren Elizabeth & Loerz, Anne-Nina, 2019

Hughes, Lauren Elizabeth & Loerz, Anne-Nina, 2019, Boring Amphipods from Tasmania, Australia (Eophliantidae: Amphipoda: Crustacea), Evolutionary Systematics 3 (1), pp. 41-52 : 41

Bircenna thieli sp. nov. Figs 4, 5, 6, 7, 8

Type material.

Holotype female, 6 mm, dissected, 2 slides, AM P.100645; paratype 1 b female, 7.5 mm, dissected, 3 slides, AM P.100646; paratypes 9 specimens, AM P.100647 (4 gravid females, 1 non-gravid female, 2 males, 2 juveniles).

Paratypes, SEM stubs: ZMH-K 45992, 5.5 mm (stub 2, entire animal); ZMH-K 45993, 5.4 mm, (stub 3, entire animal); ZMH_K-45994, (stub 4, head, urosome, body); ZMH-K 45995, 6.3 mm (stub 6 specimen at edge); ZMH-K 56619 (stub 5, mouthparts).

Bicheno, Tasmania, Australia, 41°52 ’28” S, 148°18 ’13” E, from macroalga Durvillaea potatorum ( Labillardière) Areschoug, 1854, 20 September 2015, coll. M. Thiel.

Etymology.

Named for Martin Thiel in recognition of his extensive contribution to Crustacea studies and specifically the collection of material studied here.

Type locality.

Bicheno, Tasmania, Australia.

Description.

Body shape subcylindrical, head rounded. Cephalic sinus absent. Eyes round. Pereonite 1 ventral margin with collar. Coxae 1-5 small and discontiguous. Antennae 1 length subequal to antenna 2; flagellum with 5-7 articles. Antenna 2 flagellum with 5-6 articles. Upper lip rounded. Lower lip inner and outer lobes rounded; inner lobes apically setose. Mandible lacking palp; left incisor with 8 teeth, lacinia mobilis weakly developed; right mandible incisor with 6 teeth, 30% larger than left mandible. Maxilla 1 lacking palp; inner and outer plates slender, similar in width, with stout apical setae. Maxilliped inner plate long, subequal in length to outer plate, extending halfway along palp article 2, with 4 apical robust setae; palp 4-articulate, article 4 blunt.

Gnathopod 1 coxa bilobate, twice as broad as deep; ischium two-thirds of basis length, length twice breadth; merus and carpus subequal, length twice breadth; propodus parachelate, length 2.8 times breadth, palm pollex length subequal to width, subtriangular, apically acute; dactylus unguiform. Gnathopod 2 similar to gnathopod 1, with articles slightly greater in length; coxa small, subrectangular, twice as broad as deep; merus and carpus subequal, length twice breadth; propodus parachelate, length 3.4 times breadth, palm pollex length subequal to width, subtriangular, apically acute; dactylus unguiform. Pereopods 3-4 similar; coxae subrectangular (irregular); merus expanded anterodistally, anterodistal lobe with many small slender setae. Coxa 1, 2 and 3 less wide than their pereonite. Pereopods 5-7 increasing in length. Pereopod 5 basis subrectangular, posterior margin expanded, evenly convex; merus and carpus with posterior distal lobe well developed with many small slender setae; dactylus unguiform. Pereopod 6 basis as wide as long, posterior margin expanded subquadrate; merus and carpus with posterior distal lobe well developed with many small slender setae; dactylus unguiform. Pereopods 7 length twice the depth of pereonite 7; basis rounded, posterior margin convex, anterodistal lobe reaching beyond ischium; merus and carpus with posterior distal lobe well developed with many small slender setae; dactylus unguiform. Pleopods 1-3 biramus.

Epimeral plates 1-3 rectangular in shape. Epimeron 3 posterior margin pectinate, corner produced rounded. Urosomite 1 twice length of fused urosomites 2 and 3. Urosomite 3 posterior margin between uropod 2-3 produced acute to subacute. Uropod 1 peduncle shorter than outer ramus; outer ramus about two-thirds the length of inner ramus. Uropod 2 peduncle longer than outer ramus; outer ramus about 40% of inner ramus. Uropod 3 rami absent, subquadrate, with row of apical setae. Telson fleshy, deeply cleft, subquadrate; each lobe with a few apical setae.

Remarks.

The presence of the collar on pereonite 1 ventral margin places this species in the genus Bircenna . Bircenna thieli sp. nov. is most similar to B. macayi Lörz et al. 2010 from New Zealand. These species differ in the pereopods 5 to 7 merus posterodistal lobe which in more broad in B. thieli sp. nov. The epimeron 3 in B. thieli sp. nov. is produced rounded with the posterior margin pectinate, while in B. macayai . the margin is unproduced and smooth.

Bircenna thieli sp. nov. is similar to B. fulva Chilton, 1884 based on the uropods 1 and 2 but the proportions are different in the length, with the outer ramus much shorter than the peduncle in B. thieli sp. nov.

Bircenna thieli sp. nov. can be distinguished from B. hinojosai sp. nov. with which it co-occurs by the absence of paired rounded carina on urosomite 1. The pereopod 7 basis of B. thieli sp. nov. has an angled posteroventral margin, while in B. hinojosai sp. nov. this margin is broadly rounded. Coxa of gnathopod 2 subrectangular in B. thieli sp. nov. and subtriangular in B. hinojosai sp. nov.