Exosphaeroma agmokara, Bruce, 2003

Bruce, N. L., 2003, New genera and species of sphaeromatid isopod crustaceans from Australian marine coastal waters, Memoirs of Museum Victoria 60 (2), pp. 309-369 : 328-333

publication ID	https://doi.org/ 10.24199/j.mmv.2003.60.28
persistent identifier	https://treatment.plazi.org/id/038D87F1-FFC2-FFEE-FF72-FE214068FA23
treatment provided by	Felipe
scientific name	Exosphaeroma agmokara
status	sp. nov.

Treatment

Exosphaeroma agmokara View in CoL sp. nov.

Figures 14–17 View Figure 14 View Figure 15 View Figure 16 View Figure 17

Material examined. Holotype. Male (7.7 mm), Broken Head, NSW, c. 28º42´S, 153º37´E, 30 Mar 1980, intertidal, on rocks at sand-rock interface, N.L. Bruce ( QM W26727 ). GoogleMaps

Paratypes. 6 males (7.0–7.4, immature 5.4, 5.6 mm), 5 females (ovigerous 5.8, 5.9, non-ovigerous 5.7–6.6 mm), 3 mancas (3.9–5.0 mm), same data as holotype ( QM W8573 ) GoogleMaps .

Description of male. Body 1.8 times as long as greatest width, ovate, widest at pereonite 5; dorsal surfaces smooth, anteriorly with fine ridges. Cephalon anterior margin without transverse ridges, ventral rostral process weakly developed, not visible in dorsal view. Head about one-third as long as pereonite 1, p ereonite 1 about 1.5 times as long as pereonite 2; pereonite 2>3=4>5<6<7; pereonite 7 laterally shorter than 6, longer than pereonite 6 at median point. Pleon laterally about twice as long as pereonite 7, with sublateral ‘keys’. Pleotelson strongly vaulted, posterior margin produced to acute apex; ventral margin anteriorly excavate.

Antennule peduncle article 1 1.4 times as long as wide, about 2.4 times as long as article 2, anterior and posterior margins convex; article 3 about two-thirds as long as article 1, 2.5 times as long as wide, 1.6 times as long as article 2; flagellum 16-articled, extending to posterior of pereonite 1, about 2.8 times as long article 3. Antenna relatively robust, peduncle articles 1 and 2 short, article 1 anterior margin with mass of setae, combined lengths about equal to that of article 5; article 3 about 1.2 times as long as article 4; article 4 about 0.6 as long as article 5, articles 3–5 collinear; flagellum about 1.4 times as long as peduncle, extending to middle of margin of pereonite 3, with 17 articles.

Epistome anteriorly truncate, anterior lateral margins straight, diverging to mid point, then narrowing to medial constriction. Left mandible incisor with 3 cusps, lacinia mobilis with 3 cusps, spine row of 7–8 curved serrate spines; right mandible with 3 indistinct cusps, spine row of 2 broad-based multidigitate spines, 11 serrate spines; molar process round, crushing surface strongly ridged; palp articles 1 and 2 subequal in length, article 2 distolateral margin with 16 finely biserrate setae; article 3 with 18 biserrate setae, terminal 2 setae being longest. Maxillule mesial lobe with 4 long, strongly CP RS, lateral lobe with 10 RS on gnathal surface, twelfth seta set between these; 4 lateral-most and mesial-most RS simple, others strongly serrate. Maxilla lateral lobe and middle lobe each with 9 curved finely serrate RS respectively, mesial lobe with about 20 serrate and biserrate RS, many of which are weakly spatulate, proximal seta longest. Maxilliped endite lateral margin strongly convex, distal margin with 1 simple RS at sublateral angle, 5 curved CP RS, 8 mesially bent CP RS; distomesial margin with 5 large stout CP RS, increasing in size proximally; palp articles 2–5 with about 26, 30, 30 and 24 setae respectively.

Pereopod 1 with inferior margin of distal half of ischium and entire margin of merus to propodus with dense setulose fringe; basis about 2.8 times as long as greatest width, approximately twice as long as propodus; superior margin with 3 close-set short simple setae at midpoint; ischium 0.8 times as long as basis, 2.3 times as long as greatest width, superior margin weakly setulose with 4 prominent acute simple setae; merus short, about 0.3 times as long as ischium, about 0.7 times as long as greatest width, superior distal angle with 5 acute long simple setae, inferior margin with 5 setae distal-most only being long and extending beyond setulose fringe; carpus 0.8 times as long as wide, inferior margin with 1 long seta and distally with 1 RS; propodus 2.0 times as long as greatest width, 0.7 times as long as ischium, inferior margin with 2 setae and distally with 1 RS; dactylus 0.8 times as long as propodus, unguis inferior margin with prominent serrate cuticular scales, secondary unguis recurved simple. Pereopods 2–7 subsimilar, pereopod 7 slightly shorter than pereopod 6. Pereopod 2 basis 2.4 times as long as greatest width, inferior proximal margin and submarginal surface with setulose fringe; inferodistal angle with single simple seta, superior margin with widely spaced small setae; ischium 0.8 times as long as basis, 2.3 times as long as greatest width, superior distal margin with 4 prominent simple setae, inferior margin with setulose fringe at distal angle only; merus about half as long as ischium, superior distal angle with 2 long simple seta, inferior margin with dense setulose fringe with 4 short and 1 long simple seta; carpus slightly (1.1) times longer than merus, 1.6 times as long as greatest width, anterodistal angle with 2 small simple seta, inferior margin with dense setulose fringe, with 5 long simple setae; propodus 0.9 times as long as ischium, superior distal angle with 3 setae one of which is palmate, inferior margin with dense setulose fringe, with 8 simple setae none of which greatly exceed length of setulose fringe; dactylus 0.4 as long as propodus. Pereopods 5–7 similar, longer and with more RS than pereopods 1 and 2, pereopod 7 noticeably more slender that pereopod 6. Pereopod 7 basis 4.2 times as long as greatest width, inferodistal angle with single simple seta, superior margin with 4 widely spaced small setae, distally with group of 4 palmate seta, proximal inferior margin with setulose patch; ischium 0.6 times as long as basis, 2.9 times as long as greatest width, proximal superior margin with 4 prominent long simple setae, inferior distal angle with 1 short simple setae; merus half as long as ischium, superior distal angle truncate, with 5 long simple setae, inferior distal margin with setulose fringe with 2 simple setae; carpus 1.3 times as long as merus, anterodistal margin with 8 acute biserrate and 3 simple RS, inferior margin with setulose fringe with 4 simple setae, inferior distal angle with 2 stout biserrate RS; propodus about as long as ischium, 4.8 times as long as wide, inferior margin setulose but less dense than merus and carpus, distally with 2 short simple RS, superior distal angle with 1 simple and 1 palmate seta; dactylus 0.4 as long as propodus.

Penes slender, 4.5 times as long as basal width; separated by about twice basal width of penial process, angled mesially, weakly curved.

Pleopod 1 exopod and endopod with c. 35 and 27 PMS respectively, exopod proximolateral RS prominent; endopod 0.7 as long as exopod, 1.5 times as long as greatest width. Pleopod 2 exopod and endopod with c. 42 and 30 PMS respectively; appendix masculina 12 times as long as wide, distally highly folded and glandular in appearance, apically rounded, Pleopod 3 exopod and endopod with c. 45 and 19 PMS respectively; exopod transverse suture entire. Pleopod 4 endopod with prominent thick ridges, lateral, exopod transverse suture entire, distal margin with 3 short simple setae, lateral margin with continuous evenly spaced fine simple setae. Pleopod 5 both endopod with feeble thickenings, without raised ridges, lateral margin with evenly spaced fine simple setae; exopod with 4 scale patches, 3 distal to suture, lateral margin with numerous evenly spaced simple setae, with obscure proximal lobe. Uropod exopod extending slightly beyond endopod, about 3 times as long as wide; endopod about twice as long as wide; both rami with lateral margins evenly convex distal margin evenly rounded.

Female. Similar to male.

Size. Males 7.0– 7.7 mm, ovigerous females 5.8 5.9 mm, non-ovigerous females, 5.7–6.6 mm, mancas 3.9–5.0 mm.

Etymology. From Greek agmo (break) and kara (head), alluding the type locality; noun in apposition.

Distribution. Known only from the type locality, Broken Head, northern NSW.

Remarks. Many species of Exosphaeroma (Appendix) are similar. Exosphaeroma agmokara sp. nov. is best identified by the posterior margin of pereonite 7 being weakly produced to form a median point which overrides pleonite 1, the evenly rounded uropodal rami which extend to about the end of the pleotelson (i.e. not extending noticeably beyond nor falling short of the pleotelson apex), the apex of the pleotelson being weakly produced and acute, the narrowly truncate anterior margin of the epistome and, in the male, by the distal margin of the appendix masculina being bent with the subdistal part being heavily folded (concertina-like).

No Australian species of Exosphaeroma has pereonite 7 produced to form a median point, while E. serventii Baker, 1928 has the uropodal exopod distally acute; E. bicolor Baker, 1926 has the uropodal exopod longer than the endopod and distally acute, and an anteriorly rounded epistome; E. laevis ( Baker, 1910) has an anteriorly acute epistome; E. aliae Baker, 1926 has a broadly subtruncate pleotelson and anteriorly acute epistome; and E. varicolor Barnard, 1914 has proportionally wider uropods, the pleotelson bearing two short anteriorly-positioned submedian ridges.

Similar species are the larger E. gigas ( Leach, 1818) ( Brandt and Wägele, 1989) from the Southern Ocean, E. obtusum ( Dana, 1853, sensu Hurley and Jansen, 1978) from New Zealand and E. pallidum Barnard, 1940 from South Africa. Of these only E. obtusa has pereonite 7 forming a median point but can be distinguished by the widely truncate epistome, more bluntly rounded uropodal rami and the subdistal margins of the pleotelson being convex rather than straight. The shape of pereonite 7 is not mentioned in the poorly-known E. pallidum , which can be separated from E. agmokara by having lanceolate uropodal rami.