Exosphaeroma pentcheffi, 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 : 28-34

Taxon classification Animalia Isopoda Sphaeromatidae

Exosphaeroma pentcheffi sp. n. Figures 13, 14, 15, 16, 24, 28

Material examined.

HOLOTYPE ♂ (4.6 mm): California, Los Angeles County, Palos Verdes Peninsula, Pt. Fermin, shore at Paseo del Mar, ~0.5 mi. W of Gaffey Street, 33.71°N, 118.3°W, mid-low intertidal, chipping overhanging rock with hammer and Phragmatopoma tubes on underside of rock, 0.99 m depth, fixed and preserved in 95% ethanol, 27 Mar 2004, coll. R. Wetzer, N.D. Pentcheff, and LMU students. RW04.030.1, LACM CR-2014.10.

PARATYPES: Allotype ♀ (4.6 mm) (whole animal figured): shore at Paseo del Mar, ~0.5 mi. W of Gaffey Street, 33.71°N, 118.3°W, mostly barnacles, some algal turf, medium to high intertidal, paint scraper, fixed and preserved in 95% ethanol, 16 Feb 2004, coll. R. Wetzer. RW04.002.1, LACM CR-2014.11. 1 ♂ accidently destroyed after being imaged (RW04.255, LACM CR-2014.12), 1 ♂, 3 ♀ (RW04.030.2), plus 1 ♀ (4.6 mm) prepared as SEM: RW04.030.3, LACM CR-2014.10. 3♀(RW04.002.2), plus 1 ♂ (RW04.002.3) and 1 ♀ (RW04.002.4) prepared for SEM: shore at Paseo del Mar, ~0.5 mi. W of Gaffey Street, 33.71°N, 118.3°W, mostly barnacles, some algal turf, medium to high intertidal, paint scrapper, fixed and preserved in 95% ethanol, 16 Feb 2004, coll. R. Wetzer. RW04.002, LACM CR-2014.11. 1 ♂ (5.1 mm), 2 ♀: shore at Paseo del Mar, ~0.5 mi. W of Gaffey Street, 33.71°N, 118.3°W, found in bottom of bucket with sea stars, mid- to low intertidal, fixed and preserved in 95% ethanol, 16 Feb 2004. Loyola Marymount University Invertebrate Class, N.D. Pentcheff, coll. E. Pattison and K. Stanley. RW04.003.1, LACM CR-2014.13.

Description of male.

Body length 1.8 width; pereonites 5-6 each with 7 longitudinal rows of strong tubercles, pereonite 7 with strong median process with 3 lateral tubercles (Figures 13A, B; 24A, D). Pleon with 1 medium tubercle on posterior margin, on either side of longitudinal axis (Figures 13A, B; 24A, D). Pleotelson length 0.85 width, dorsal surface with 3 strong medial tubercles on either side of the longitudinal axis, with 1 strong medial tubercle between the longitudinal axis and lateral margin, pleotelson covered with numerous, additional, small tubercles; ventrolateral ridge extending posteriorly 0.80 of total length, with long setae (Figures 13A, B; 24A, C, D).

Antennula peduncle article 1 length 1.4 width, anterior medial margin with 2 palm setae; article 2 length 1.1 width, inferior distal margin with 3 palm setae; article 3 length 3.1 width; flagellum with 9 articles (Figure 14B). Antenna reaching anterior margin of pereonite 2, peduncle article 1 with fine, simple setae on superior margin; flagellum with 11 articles (Figure 14A).

Left mandible incisor with 4 cusps; lacinia mobilis with 3 cusps; lacinia mobilis spine row comprised of 8 curved, serrate spines, and 1 curved, robust, simple spine (Figure 14C). Right mandible incisor with 3 cusps; spine row comprised of 7 curved, serrate spines; crushing surfaces strongly ridged, with 1 serrate spine (Figure 14D). Maxillula mesial lobe with 4 circumplumose RS; lateral lobe with 10 long, curved, pectinate RS, gnathal surface with 1 curved, simple RS (Figure 14G). Maxilla mesial lobe with 1 long, straight RS, and 8 plumose RS on gnathal surface; middle lobe with 8 long, curved, pectinate RS; lateral lobe with 5 long, curved, pectinate RS (Figure 14F). Maxilliped endite distal surface with 7 plumose setae, and 3 simple RS; distomesial margin with 1 coupling hook, and 3 large stout plumose setae; palp article 2 distal apex with 6 long, simple RS; article 3 distal apex with 8 long, simple RS, lateral distal angle with 1 long, simple RS; article 4 distal apex with 7 long, simple RS; article 5 distal apex with 7 long, simple RS (Figure 14E).

Pereopod 1 (Figure 15A) basis superior margin without palm setae, 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 0.50 ischium length, superior distal angle with 3 long, simple setae; carpus inferior distal angle with 1 long, simple seta; propodus length 2.7 width, 1.0 ischium length, superior distal angle without long, simple setae, inferior margin with 1 long, simple seta; dactylus length 1.4 width, length 0.36 propodus length, inferior margin without setal scales, distal margin with 4 simple setae (Figure 15A). Pereopod 3 (Figure 15B) basis superior margin with 1 palm seta, inferior distal angle with 2 long simple setae, inferior proximal margin with setal patch present; ischium length 3.1 width, superior margin with 6 long, simple RS, inferior distal angle with 2 long, simple RS, and with setal patch present; merus lobate, length 2.2 width, 0.73 ischium length, superior distal angle with 4 long, simple RS, inferior margin covered in setal mat; carpus superior margin with 1 long, simple seta on distal angle, inferior margin with setal mat, and 3 long, simple setae; propodus weakly curved, length 3.2 width, 1.8 carpus length, superior distal margin with 1 palm seta, inferior margin covered in setal mat; dactylus length 1.6 width, length 0.30 propodus length, inferior margin without scales, distal margin with 4 long, simple setae (Figure 15B). Pereopod 7 (Figure 15C) basis superior margin with 1 palm seta, inferior proximal margin with setal patch, inferior distal angle with long, simple setae absent; ischium length 2.8 width, superior margin with 2 long, simple RS; merus lobate, merus length 2.1 width, merus length 0.63 ischium length, superior distal angle with 4 RS, inferior margin with setal mat, inferior distal angle with biserrate setae absent; carpus length 2.3 width, carpus length 1.1 merus length, inferior margin with setal mat, superior distal angle with a cluster of 8 long, biserrate setae, superior distal angle with a cluster of 2 long, simple, RS, inferior distal angle with a cluster of 3 long, biserrate setae; propodus weakly, curved, length 5.0 width, length 1.6 carpus length, inferior margin first 0.33 with setal mat, superior distal angle with 2 long, simple setae, inferior margin with 2 long, simple setae, and with palm setae absent; dactylus length 1.7 width, dactylus length 0.22 propodus length, inferior margin without fine scales, distal margin with 3 long, simple setae (Figure 15C).

Penial process length 3.0 basal width (Figure 24B).

Pleopod 1 peduncle length 0.56 width, with a cluster of 3 coupling hooks; endopod mesial margin covered in fine, simple setae; exopod length 1.7 width, ventral surface with fine, simple setae (Figure 16A). Pleopod 2 appendix masculina distally narrowing to an acute rounded tip, length 15 basal width (Figure 16B). Pleopod 3 peduncle with a cluster of 3 coupling hooks, distolateral angle with 2 large, simple setae (Figure 16C). Pleopod 4 peduncle length 0.46 width, distolateral angle with 1 large, simple seta; endopod distal apex without plumose setae; exopod distal margin with 2 simple setae (Figure 16D). Pleopod 5 exopod proximolateral margin with palm setae absent; exopod with transverse suture starting laterally moving mesially, incomplete; exopod with 4 scale patches (Figure 16E). Uropod exopod length 2.4 width; rolled proximolateral margin weakening moving toward lateral, distal margin; mesial margin with evenly spaced fine simple setae; endopod length 2.8 width, extends past exopod, distal apex with short, simple setal patch, dorsal surface covered with numerous small tubercles, mesial margin with evenly spaced fine simple setae (Figures 16F; 24A, C, D).

Description of female.

Body length 2.3 width; pereonites 2-6 each with 7 longitudinal rows of strong tubercles, pereonite 7 distomesial margin convex with strong median process, and 3 lateral tubercles (Figure 24E, F). Pleon with 1 posterior strong tubercle on either side of longitudinal axis (Figure 24E, F). Pleotelson length 0.61 width, dorsal surface with 3 strong medial tubercles on either side of the longitudinal axis, with 1 strong medial tubercle between the longitudinal axis and lateral margin, pleotelson covered with numerous, additional, small tubercles (Figure 24E, F). Uropod exopod proximolateral margin rolled; endopod length 3.6 width, extends past exopod, dorsal surface covered with numerous small tubercles, mesial margin without setae (Figure 24E, F).

Size.

Largest ♂ 6.8 mm, largest ♀ 4.6 mm.

Colour.

No chromatophores: preserved specimen pale buff, whitish.

Remarks.

Exosphaeroma pentcheffi sp. n. unlike the other Exosphaeroma species in this 'species flock’ lacks strong sexual dimorphism and is unique in that females shares the same dorsal ornamentation as males; males differ from females in having slightly stronger tubercles, longer pleotelson and longer uropods. Females of Exosphaeroma pentcheffi sp. n. are the only females of this 'species flock’ that can reliably be identified at the species level. Exosphaeroma pentcheffi sp. n. males can be identified by: pereonites 5 and 6 having 7 longitudinal rows of strong tubercles, pereonite 7 with a strong median process with 3 lateral tubercles; pleotelson dorsum with 3 strong medial tubercles on either side of the longitudinal axis, with 1 strong medial tubercle between the longitudinal axis and lateral margin, pleotelson covered with numerous, additional, small tubercles (Figures 13A, B; 24A, D, E, F). 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 13 and 24).

Distribution.

California, Los Angeles County, Palos Verdes Peninsula.

Etymology.

This beautiful species is named for N. Dean Pentcheff, expert isopod collector, superb field and dive buddy, travel companion and IT support par excellence. Dean is commended for his reliable patience, support and solid friendship.