Exosphaeroma russellhansoni, Wall, Adam R., Bruce, Niel L. & Wetzer, Regina, 2015

Wall, Adam R., Bruce, Niel L. & Wetzer, Regina, 2015, Status of Exosphaeromaamplicauda (Stimpson, 1857), E. aphrodita (Boone, 1923) and description of three new species (Crustacea, Isopoda, Sphaeromatidae) from the north-eastern Pacific, ZooKeys 504, pp. 11-58 : 25-28

Taxon classification Animalia Isopoda Sphaeromatidae

Exosphaeroma russellhansoni sp. n. Figures 9, 10, 11, 12, 23, 28

Material examined.

HOLOTYPE: ♂ (7.0 mm): Washington, Puget Sound, Seattle, Puget Sound Naval Supply Depot, Smith Cove, ~ 47.5°N, ~ 122.2°W, under rocks in sand, 11 Aug 1973. A.0030, coll. E.W. Iverson. RW04.010.1, LACM CR-2014.6.

PARATYPES: Allotype gravid ♀ (6.7 mm): same data as holotype, LACM CR-2014.6. 1 ♂ dissected, appendages figured (RW04.010.3), 1 ♂ (RW04.010.4, LACM CR-2014.6.4) and 2 ♀ (6.7 mm RW04.010.5, LACM CR-2014.6.5) prepared as SEM, plus ~70 additional specimens (all life stages RW04.010.6): same locality as RW04.010, LACM CR-2014.6. 3 ♀ (7.2 mm), 1 subadult ♂: south end of San Juan Island, Cattle Point, 48.451°N, 122.967°W, rocky intertidal barnacles from Semibalanus cariosus , fixed and preserved in 95% ethanol, 7 Apr 2004, coll. R. Wetzer & N.D. Pentcheff. RW04.036.1, LACM CR-2014.7. 1 ♂ (7.9 mm), 1 subadult intermolt: northeast of San Juan Island, Reuben Tarte County Park, 48.612°N, 123.098°W, scrapings of vertical rock surface in intertidal, fixed and preserved in 95% ethanol, 9 Apr 2004, coll. R. Wetzer & N.D. Pentcheff. RW04.041.1, LACM CR-2014.8. 6 ♂ (8.3 mm), 4 ♀ (8.7 mm), 2 ♂ dissected for mandibles and figured: San Juan Island, old man’s farm, ~ 48.6°N, ~ 122.9°W, under rocks, 30 Jul 1950. USNM Acc. No. 187867, coll. L. Peternick and P. Illg. USNM 1251666. 3 ♂, 1 gravid ♀, 1 subadult: San Juan Islands, False Bay, 1 Aug 1975, transferred to 95% ethanol 5 Oct 2012, coll. R.R. Hessler. RW12.215.1, LACM CR-2014.9.

Description of male.

Body length 1.6 width; pereonite 5-6 each without ornamentation, pereonite 7 with weak median process (Figures 9A, B; 23A, D). Pleon with 1 medium tubercle on either side of longitudinal axis (Figures 9A, B; 23A, D). Pleotelson length 0.65 width, dorsal surface with 2 small anterior tubercles; ventrolateral ridge entire, with long setae (Figures 9A, B; 23A, C, D).

Antennula peduncle article 1 length 1.2 width, anterior medial margin with 1 palm seta; article 2 length 1.2 width, inferior distal margin with 3 palm setae; article 3 length 2.9 width; flagellum with 9 articles (Figure 10B). Antenna reaching medium margin of pereonite 2, peduncle article 1 with numerous fine simple setae on anterior posterior margin; flagellum with 13 articles (Figure 10A).

Left mandible incisor with 3 cusps; lacinia mobilis with 2 cusps; lacinia mobilis spine row comprised of 6 curved, serrate spines; crushing surfaces strongly ridged, with 2 serrate spines (Figure 10E). Maxillula mesial lobe with 4 circumplumose RS; lateral lobe with 9 long, curved, pectinate RS (Figure 10F). Maxilla mesial lobe with 6 plumose RS on gnathal surface; middle lobe with 4 long, curved, pectinate RS; lateral lobe with 4 long, curved, pectinate RS (Figure 10D). Maxilliped endite distal surface with 11 plumose setae; distomesial margin 2 coupling hooks, and 2 large stout plumose setae, and 1 large simple RS; palp article 2 distal apex with 15 long, simple RS; article 3 distal apex with 17 long, simple RS, lateral distal angle with 1 long, simple RS; article 4 distal apex with 8 long, simple RS, lateral distal angle with 1 long, simple RS; article 5 distal apex with 9 long, simple RS (Figure 10C).

Pereopod 1 (Figure 11A) basis superior margin with 1 palm seta, inferior distal angle with 1 long, simple seta, inferior medial margin setal patch present; ischium length 1.9 width, superior margin with 3 long, simple setae, inferior distal angle with 1 long, simple seta; merus 0.45 ischium length, superior distal angle with 3 long, simple setae; carpus inferior distal angle with 1 long, simple seta; propodus length 2.3 width, 0.93 ischium length, superior distal angle without long, simple setae, inferior margin with 1 long, simple seta; dactylus length 1.5 width, length 0.46 propodus length, inferior margin covered with scales, distal margin with 3 simple setae (Figure 11A). Pereopod 3 (Figure 11B) basis superior margin with 1 palm seta, inferior distal angle with 1 long simple seta, inferior proximal margin with setal patch absent; ischium length 2.4 width, superior margin with 5 long, simple RS, inferior distal angle with 1 simple RS, and with setal patch absent; merus lobate, length 0.95 width, 0.4 ischium length, superior distal angle with a cluster of 5 simple RS, inferior margin covered in setal mat; carpus length 1.3 merus length, 1.4 width, superior margin with 1 long, simple seta on distal angle, inferior margin with setal mat, and long, simple setae absent; propodus weakly curved, length 2.6 width, 1.7 carpus length, superior distal margin with 1 palm seta, inferior margin first 0.67 covered in setal mat; dactylus length 1.2 width, length 0.33 propodus length, inferior margin proximal half with scales, distal margin with 3 long, simple setae (Figure 11B). Pereopod 7 (Figure 11C) basis superior margin with palm setae absent, inferior proximal margin with setal patch absent, inferior distal angle with 1 long, simple seta present; ischium length 3.0 width, superior margin with 10 long, simple RS; merus lobate, merus length 1.7 width, merus length 0.53 ischium length, superior distal angle with 9 RS, inferior margin with setal mat, inferior distal angle with biserrate setae absent; carpus length 2.5 width, carpus length 1.3 merus length, inferior margin with setal mat, superior distal angle with a cluster of 7 long, biserrate setae, superior distal angle with a cluster of 3 long, simple, RS, inferior distal angle with a cluster of 5 long, biserrate setae, inferior distal angle with 1 long, simple RS; propodus weakly curved, length 4.0 width, length 1.2 carpus length, inferior margin with setal mat absent, superior distal angle with 2 long, simple setae, inferior distal margin with 3 long, simple setae, and with palm setae absent; dactylus length 1.6 width, dactylus length 0.24 propodus length, inferior margin with scales, distal margin with 2 simple setae (Figure 11C).

Penial process length 2.7 basal width (Figure 23B).

Pleopod 1 peduncle length 0.41 width, with a cluster of 4 coupling hooks; endopod mesial margin lightly covered in fine, simple setae; exopod length 1.8 width, ventral surface without fine, simple setae (Figure 12A). Pleopod 2 appendix masculina proximally swollen, distally narrowing, distal end curving mesially, apex weakly hooked mesially, length 11.4 basal width (Figure 12B). Pleopod 3 peduncle with a cluster of 3 coupling hooks, distolateral angle with 2 long, simple setae (Figure 12C). Pleopod 4 peduncle distolateral angle with fine setal patch; endopod distal apex 1 large, plumose seta; exopod distal margin without setae (Figure 12D). Pleopod 5 exopod proximolateral margin with palm setae absent; exopod with distal transverse suture starting laterally, incomplete; exopod with 4 scale patches (Figure 12E). Uropod exopod length 2.4 width; rolled proximolateral margin weakening moving toward lateral, medial margin; mesial margin without setae; endopod length 2.7 width, extends past exopod, mesial proximal margin with setal patch (Figures 12F; 23A, C, D).

Description of female.

Body length 2.7 width; pereonites 1-7 without tubercles, pereonite 7 distomesial margin convex (Figure 23E, F). Pleon with 1 weak posterior tubercle on either side of longitudinal axis (Figure 23E, F). Pleotelson length 0.75 width, dorsum without tubercles; posterior margin of pleotelson acuminate (Figure 23E, F). Uropod exopod proximolateral margin rolled weakly; endopod length 3.7 width, extends past exopod (Figure 23E, F).

Size.

Largest ♂ 8.3 mm, largest ♀ 8.7 mm.

Color.

Without chromatophores. Preserved specimen pale buff, whitish.

Remarks.

Exosphaeroma russellhansoni sp. n. is morphologically most similar to Exosphaeroma amplicauda but can be easily distinguished by: pereonite 5-6 each without ornamentation, pereonite 7 with weak median process (Figures 9A, B; 23A, D). Appendix masculina distal end curving mesially, apex weakly hooked mesially, length 11.4 basal width (Figure 12B).

Exosphaeroma amplicauda is distinguished by: pereonites 5 and 6 with one weak median tubercle, and one weak lateral tubercle; pereonite 7 with weak median process and paired lateral tubercles (Figures 1A, B; 21A, D). Appendix masculina distal end curving mesially, straightening at distal tip, length 15.4 basal width (Figure 4B). Exosphaeroma russellhansoni sp. n. is strongly sexually dimorphic; females lacking dorsal tubercles on pereonites 1-7. Weak pereon tubercles are visible only with SEM, but not necessarily evident with light microscopy, and therefore are omitted from line drawings (compare Figures 9 and 23).

Distribution.

Washington, Puget Sound and San Juan Island.

Etymology.

Named to honor Russell Kenneth Hanson, ARW’s only maternal uncle who has shaped the person Adam is today by so graciously sharing with Adam his insatiable curiosity, life-long pursuit of perfection and tireless work ethic.