Exosphaeroma aphrodita Boone, 1923

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 : 34-40

Taxon classification Animalia Isopoda Sphaeromatidae

Exosphaeroma aphrodita Boone, 1923 Figures 17, 18, 19, 20, 25, 28

Exosphaeroma aphrodita Boone, 1923. - Bruce 2003: 369. - Espinosa and Hendrickx 2006: 238. - Brusca et al. 2007: 537. - Bruce and Schotte 2012: online.

Material examined.

LECTOTYPE, here designated: 1 ♂ USNM 1251667 with mandibles dissected: California, San Diego County, La Jolla, Scripps Institute pier pilings, 6 Nov 1915. USNM Acc. No. 53848, #1045-1-4. Identified as Exosphaeroma amplicauda by P.L. Boone.

PARALECTOTYPES: 5 ♂ (USNM 1251667), with mandibles dissected. USNM 53848.

Non-type Material: 1 ♂: Scripps, ~ 32.87°N, ~ 117.26°W, littoral in algae, March 1938, coll. Olga Hartman and Loyola e Silva. USNM 1251668. 1 ♂ (RW01.002.1), 1 ♂, 3 ♀, (RW01.002.2) plus 1 ♂ (RW01.002.3) and 3 ♀ (RW01.002.4) prepared as SEM: Scripps Institute of Oceanography, beneath seaward end of Scripps Pier, ~ 32.87°N, ~ 117.26°W, to 8 m, among detritus at base of pilings, water temp. 59 °F, SCUBA, fixed and preserved in 95%, 7 Jan 2001, coll. T. Haney. RW01.002, LACM CR-2014.14. 1 ♂ (broken): San Diego, pilings, 1 Jul 1996. USNM Acc. No. 180084, Sta. No. 256. USNM 1251669.

Description of male.

Body length 2.0 width; pereonites 5 without ornamentation, pereonite 6 with 1 lateral weak tubercle, pereonite 7 with weak median process, and paired weak lateral tubercles (Figures 17A, B; 25A, C). Pleon with 1 medium tubercle on either side of longitudinal axis (Figures 17A, B; 25A, C). Pleotelson length 0.89 width, dorsal surface with 1 anterior median strong tubercle and 2 weak medial tubercles; ventrolateral ridge extending posteriorly 0.75 of total length, with long setae (Figures 17A, B; 25A, B, C).

Antennula peduncle article 1 length 1.5 width, anterior medial margin with palm setae absent; article 2 length 1.3 width, inferior distal margin with 1 palm seta; article 3 length 2.9 width; flagellum with 8 articles (Figure 18B). Antenna reaching posterior margin of pereonite 3, peduncle article 1 superior margin without palm setae; flagellum with 12 articles (Figure 18A).

Left mandible incisor with 2 cusps; lacinia mobilis with 2 cusps; lacinia mobilis spine row comprised of 6 curved, serrate spines (Figure 18C). Right mandible incisor with 4 cusps; spine row comprised of 5 curved, serrate spines; crushing surfaces strongly ridged (Figure 18D). Maxillula mesial lobe with 5 circumplumose RS; lateral lobe with 6 long, curved, pectinate RS (Figure 18F). Maxilla mesial lobe with 3 long, curved RS, and 6 plumose RS on gnathal surface; middle lobe with 8 long, curved, pectinate RS; and 7 long, curved RS; lateral lobe with 3 long, curved, pectinate RS (Figure 18G). Maxilliped endite distal surface with 2 plumose setae; distomesial margin with 1 coupling hook; palp article 2 distal apex with 1 long, simple RS; article 3 distal apex with 3 long, simple RS, lateral distal angle with 1 long, simple RS; article 4 distal apex with 3 long, simple RS, lateral distal angle with 1 long, simple RS; article 5 distal apex with 3 long, simple RS (Figure 18E).

Pereopod 1 (Figure 19A) basis superior margin with 1 palm seta, inferior distal angle with 1 long, simple seta, inferior medial margin setal patch absent; ischium length 2.3 width, superior margin with 3 long, simple setae, inferior distal angle without long, simple setae; merus 0.40 ischium length, superior distal angle with 3 long, simple setae; carpus inferior distal angle with 1 long, simple seta; propodus length 2.1 width, 0.60 ischium length, superior distal angle with 1 long, simple seta, inferior margin with 3 long, simple setae; dactylus length 1.5 width, length 0.55 propodus length, inferior margin distal 0.67 covered with scales, distal margin with 2 simple setae (Figure 19A). Pereopod 3 (Figure 19B) basis superior margin without palm setae, inferior distal angle with 1 long simple seta, inferior proximal margin with setal patch absent; ischium length 3.2 width, superior margin with 3 long, simple RS, inferior distal angle with 1 simple RS, and with setal patch absent; merus lobate, length 1.4 width, 0.56 ischium length, superior distal angle with a cluster of 3 RS, inferior margin covered in setal mat; carpus length 0.90 merus length, 1.9 width, superior margin with 1 long, simple seta on distal angle, inferior margin with setal mat, and 1 long, simple seta; propodus weakly curved, length 3.2 width, 2.0 carpus length, superior distal margin with 1 palm seta, inferior margin first 0.67 covered in setal mat; dactylus length 1.3 width, length 0.45 propodus length, inferior margin with scales, distal margin with 3 long, simple setae (Figure 19B). Pereopod 7 (Figure 19C) basis superior margin with 2 palm setae, inferior proximal margin with setal patch, inferior distal angle with long, simple setae absent; ischium length 3.7 width, superior margin with 1 long, simple RS; merus weakly lobate, merus length 2.0 width, merus length 0.65 ischium length, superior distal angle with 2 RS, inferior margin with setal mat, inferior distal angle with biserrate setae absent; carpus length 2.9 width, carpus length 1.1 merus length, inferior margin with setal mat, superior distal angle with a cluster of 6 long, biserrate setae, superior distal angle with a cluster of 2 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 4.2 width, length 1.3 carpus length, inferior margin with setal patch, superior distal angle with 1 long, simple seta, inferior distal margin with simple, setae absent, and with 1 palm seta; dactylus length 2.0 width, dactylus length 0.27 propodus length, inferior margin with scales starting medially moving distally, distal margin with 2 simple setae (Figure 19C).

Penial process length 3.1 basal width (Figure 25B, D).

Pleopod 1 peduncle length 0.42 width, with a cluster of 4 coupling hooks; endopod mesial margin lightly covered in fine, simple setae; exopod length 1.6 width, ventral surface without fine, simple setae (Figure 20A). Pleopod 2 appendix masculina apically narrowly rounded, length 13.0 basal width (Figure 20B). Pleopod 3 peduncle with a cluster of 3 coupling hooks, distolateral angle with 3 large, simple setae (Figure 20C). Pleopod 4 peduncle length 0.61 width, distolateral angle with 1 large, simple seta; endopod distal apex 1 large, plumose seta; exopod distal margin with 2 plumose setae (Figure 20D). Pleopod 5 exopod proximolateral margin with 1 palm seta; exopod with transverse suture entire; exopod with 3 scale patches (Figure 20E). Uropod exopod length 2.4 width; rolled proximolateral margin weakening moving toward lateral, medial margin; mesial margin without setae; endopod length 3.1 width, extends past exopod, mesial margin without setae (Figures 20F, G; 25A, B, C).

Description of female.

Body length 2.9 width; pereonites 1-7 without tubercles, pereonite 7 distomesial margin weakly convex (Figure 25E, F). Pleon with 1 weak posterior tubercle on either side of longitudinal axis (Figure 25E, F). Pleotelson length 0.65 width, dorsal surface without visible tubercles; posterior margin of pleotelson acuminate (Figure 25E, F).

Uropod exopod rolled proximolateral margin rolled weakly; endopod length 3.4 width, extends past exopod, mesial margin without setae (Figure 25E, F).

Size.

Largest ♂ 8.3 mm, largest ♀ 8.7 mm.

Color.

No chromatophores: preserved specimen pale buff, whitish.

Remarks.

Exosphaeroma aphrodita can best be identified by: pereonite 5 without ornamentation, pereonite 6 with one lateral weak tubercle, pereonite 7 with weak median process, and paired weak lateral tubercles; pleotelson dorsum with one anterior median strong tubercle and two weak medial tubercles. Exosphaeroma aphrodita is strongly sexually dimorphic; females lack dorsal tubercles on the pereonites. Weak pereon tubercles are visible only with SEM and not necessarily evident with light microscopy. Tubercles visible with light microscopy are figured in the line drawings (compare Figures 17 and 25).

Exosphaeroma aphrodita , considered nomen dubium by Brusca et al. (2007), is here revalidated. Pearl Lee Boone described this species and several other isopods and tanaids without providing figures ( Boone 1923, pp. 147-156). The original description states that "the type and additional material were collected at La Jolla, California and are in the collections of the United States National Museum." We examined all of the USNM material available. We conclude that the species is valid.

Distribution.

California, San Diego–La Jolla.