Gnorimosphaeroma oregonense (Dana, 1853)

Wetzer, Regina, Wall, Adam & Bruce, Niel L., 2021, Redescription of Gnorimosphaeroma oregonense (Dana, 1853) (Crustacea, Isopoda, Sphaeromatidae), designation of neotype, and 16 S-rDNA molecular phylogeny of the north-eastern Pacific species, ZooKeys 1037, pp. 23-56 : 23

publication ID	https://dx.doi.org/10.3897/zookeys.1037.63017
publication LSID	lsid:zoobank.org:pub:4BB4E90C-0EB8-47D6-B5AF-C6F5E954140F
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scientific name	Gnorimosphaeroma oregonense (Dana, 1853)
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Gnorimosphaeroma oregonense (Dana, 1853) Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9

Gnorimosphaeroma oregonense Abbreviated synonymy (detailed synonymies given by Richardson (1905), Menzies (1954), and Kussakin (1979).

Spheroma oregonensis Dana, 1853: 778, Atlas plate 52x.

Exosphaeroma oregonensis .- Richardson, 1905: 296, figs 315, 316.

Neosphaeroma oregonense .- Monod, 1932: 76, fig. 74.

Gnorimosphaeroma oregonensis oregonensis .- Menzies, 1954: 406, figs 5, 7A-E, 12.

Material examined.

Neotype ♂ (8.5 mm): Canada, British Columbia, Vancouver, Stanley Park , 49.294°N, 123.155°W, mid intertidal, hand, fixed and preserved in 95% ethanol. 7 Jul 2010, coll. Regina Wetzer & N. Dean Pentcheff. Collection ID: RW10.003. LACM:DISCO:7028. GoogleMaps

Additional material examined from the same lot as the neotype.

♀ Non-type with mancas (6.0 mm) LACM:DISCO:11164; ♂ (8.5 mm) LACM:DISCO:11161; subadult ♂ with penes beginning, without appendix masculina (6.0 mm) LACM:DISCO:11162; plus additional 20+ adults, juveniles, and mancas in this lot.

Body parts and appendages figured are as indicated in figure legends.

Description of male neotype.

Body length 2.4 × width; widest at pereonite 6; pleotelson length 0.6 × width, distal margin broad and weakly convex. (Figs 1A, B View Figure 1 , 2A View Figure 2 ). Pleotelson length 0.66 × width.

Antennula peduncle article 1 length 1.3 × width; article 2 as long as wide; article 3 length 2.6 × width, inferior distal margin with one palm seta; flagellum with 13 articles, 11 basal articles with aesthetascs and small simple seta (Figs 2A View Figure 2 , 3A View Figure 3 , 4A View Figure 4 ). Antenna reaching slightly beyond anterior margin of pereonite 2; peduncle article 4 length 2.3 × width, flagellum with 14 articles, setation as figured (Figs 2A View Figure 2 , 3B View Figure 3 , 4B View Figure 4 ). Clypeus and labrum as in Figs 3A View Figure 3 , 8B View Figure 8 .

Left mandible incisor with 4 cusps; lacinia mobilis with a single cusp; lacinia mobilis spine row comprised of 4 serrate spines; crushing surfaces ridged (Fig. 4C View Figure 4 ). Right mandible incisor with 3 cusps, spine row comprised of 7 serrate spines (Fig. 4D View Figure 4 ). Maxillula mesial lobe with ca. 4 spines; lateral lobe with ca. 8 spines (Fig. 4F, E View Figure 4 , respectively). Maxilla mesial lobe with 5 simple setae and 6 plumose RS on gnathal surface; middle lobe with 2 simple setae and 1 pectinate RS; lateral lobe with 2 simple setae, and 1 pectinate RS (Fig. 4G View Figure 4 ). Maxilliped endite distal surface with 7 plumose setae; distomesial margin with 3 plumose setae; palp article 2 distal apex with 9 long, simple RS; article 3 distal apex with 11 long, simple RS, lateral distal angle with 2 long, simple RS; article 4 distal apex with 15 long, simple RS, lateral distal angle with 1 long, simple RS; article 5 distal apex with 13 long, simple RS (Fig. 4H View Figure 4 ).

Pereopod 1 (Figs 5A View Figure 5 , 7C View Figure 7 ) basis inferior distal angle with 1 long, RS, inferior proximal margin with setal patch; ischium length 1.6 × width, inferior medial margin with setal patch; merus lobate, 0.74 × ischium length, superior distal angle with 4 long, RS; carpus inferior medial margin with 1 robust, serrate, trident seta; propodus length 2.1 × width, 1.1 × ischium length, inferior margin with 3 robust, serrate, trident seta, and 3 plumose setae; dactylus length 1.2 × width, length 0.33 × propodus length, distal margin with 4 simple setae (Figs 5A View Figure 5 , 7C View Figure 7 ). Pereopod 2 (Fig. 5B View Figure 5 ) basis inferior distal angle with 1 long, simple RS, inferior medial margin with setal patch; ischium length 2.2 × width, inferior medial margin with 12 long, simple RS, inferior distal angle with single simple RS; merus lobate, length 1.6 × width, 0.69 × ischium length, superior distal angle with cluster of 7 simple RS, distal medial margin with one palm seta; carpus length 1.2 × merus length, 2.5 × width, superior margin with 4 robust, biserrate setae on distal angle, inferior margin 2 palm setae; propodus weakly curved, length 2.6 × width, 1.2 × carpus length, superior distal margin with a palm seta; dactylus length 1.2 × width, length 0.27 × propodus length, inferior margin with scales, distal margin with 3 long, simple setae (Fig. 5B View Figure 5 ). Pereopods 3-6 progressively less setose (not figured). Pereopod 7 (Figs 5C View Figure 5 , 7B View Figure 7 ) basis inferior medial margin with setal patch, inferior distal angle with 1 long, simple seta; ischium length 3.2 × width, inferior distal angle with 1 palm seta; merus lobate, merus length 1.3 × width, merus length 0.42 × ischium length, superior distal angle with 1 trident seta, inferior distal angle with 1 biserrate seta and 1 palm seta; carpus length 1.8 × width, carpus length 1.3 × merus length, superior distal angle with a cluster of 5 long, biserrate setae, inferior distal angle with a cluster of 1 long, biserrate seta, and 1 long, trident seta; propodus weakly curved, length 3.2 width, length 1.5 carpus length, superior distal angle with 1 simple seta, and 1 palm seta, inferior margin with 2 long, trident setae; dactylus length 1.3 × width, dactylus length 0.21 × propodus length, distal margin with 3 simple setae (Figs 5C View Figure 5 , 7B View Figure 7 ).

Penial processes length 3.8 × basal width; close set (Fig. 6A View Figure 6 ).

Pleopod 1 (Fig. 6B View Figure 6 ) peduncle length 0.38 × width with 4 coupling hooks; exopod length 1.5 × width, 1.1 × endopod length. Pleopod 2 (Fig. 6C View Figure 6 ) peduncle length 0.34 × width with 3 coupling hooks, appendix masculina length 8.5 × width, 1.1 × length of endopod, straight, proximally and medially slightly swollen, distally narrowing. Pleopod 3 (Fig. 6D View Figure 6 ) peduncle length 0.34 × width with 3 coupling hooks. Pleopods 1-4 exopods and endopods with PMS as figured (note: not all drawn, but indicated). Pleopod 4 (Fig. 6E View Figure 6 ) endopod and exopod subequal, exopod with transverse suture. Pleopod 5 (Fig. 6F View Figure 6 ) endopod and exopod subequal, endopod length 1.5 × width, exopod length 2.1 × width with 1 distal scale patch and 2 medial lateral scale patches.

Uropod extending to posterior margin of pleotelson. Exopod 0.83 × as long as endopod, 2.7 × as wide; apex narrowly rounded; mesial margin with continuous row of PMS. Endopod 3.8 × as long as wide, lateral margin weakly convex, apex bluntly rounded.

Description of female.

Body length 2.4 × width (Figs 2B View Figure 2 , 3A, B View Figure 3 , 7A View Figure 7 , 8A-C View Figure 8 , 9A, B View Figure 9 ). Pleotelson length 0.66 × width (Fig. 8C View Figure 8 ). Uropodal endopod (Figs 8C View Figure 8 , 9B View Figure 9 ) as in male, longer than exopod, endopod just barely extending to posterior margin of pleotelson. Gravid female (Figs 3B View Figure 3 , 9B View Figure 9 ) estimated to be able to brood 8-10 mancas.

Size.

Largest ♂ to 8.5 mm, largest ♀ to 6 mm. Dana (1853) gave no measurements. Fee (1926: 8, 9) records the largest specimens as being "ca. 1 cm. long; one-half as long as wide."

Color.

When preserved in ethanol, specimens quickly become pale buff to whitish.

Distribution.

British Columbia, Vancouver to California, San Francisco.

Remarks.

The species occurs only in fully marine habitats in the intertidal to an unknown depth. A single lot indicated that it was collected by night light, and another that specimens were collected on floats among fouling organisms. None of the material examined indicates depth.

Kussakin (1979) reported G. oregonense from Alaska, Popov Island to San Francisco Bay, California. Kussakin (1979) figured G. oregonense from the collections of the Zoological Institute of the Academy of Sciences of the USSR. He noted that it is widely distributed with males reaching a length of 12 mm and females up to 8 mm, and that it occurred widely from Alaska to California. It is not clear what the specific localities of the figured specimens were ( Kussakin 1979: 407) nor of those deposited in the Russian collections. We were unable to locate and access these specimens. Kussakin reported that the specimens he examined were predominantly littoral, but can be sublittoral to 22 m, on rocks, under rocks, less often on sand, and sometimes in empty shipworm tubes. Kussakin remarked it is a good swimmer, and sometimes turns up in night light samples. It can tolerate salinities as low as 9‰. Since we were not able to re-examine Kussakin’s specimens, we cannot verify that the Gnorimosphaeroma he identified are the same species as G. oregonense from the type locality and described here. Furthermore, our genetic data clearly distinguishes between fully marine and low salinity specimens and recognizes these as distinct species (see below). We do not include Kussakin’s specimens in the synonymy ( Gnorimosphaeroma oregonense : Kussakin, 1979: 406, figs 260-262.)