Heteromysis (Olivemysis) cocoensis, Heard Rita Vargas, 2018

Heard Rita Vargas, W. Wayne Price Richard W., 2018, Heteromysis cocoensis n. sp. (Crustacea: Mysida: Mysidae) from coastal waters of Isla del Coco, Costa Rica, Nauplius (e 2018012) 26, pp. 1-10 : 2-8

Heteromysis (Olivemysis) cocoensis n. sp. Price, Heard and Vargas

( Figs. 2–4 )

Type material. Holotype: adult male (Length [L] 3.0 mm), Costa Rica, Isla del Coco , Bahía Chatham, 5 o 32’57.89’’N 87 o 2’30.51’’W, coral rubble washings, depth 8 m, R. Vargas Castillo, coll., 26 May 2008, MZUCR 2678-03 ; Paratypes: 2 adult males (L 3.1, 2.7 mm), Costa Rica, Isla del Coco , Bajo Silverado, 5 o 32’43.75’’N 87 o 1’48.49’’W, coral rubble washings, depth 11 m, R. Vargas Castillo, coll., 26 May 2008, MZUCR 2676-37 ; 2 ovigerous females (L 3.0, 2.8mm), Costa Rica, Isla del Coco , coral rubble washings, depth 11 m, R. Vargas Castillo, coll., 26 May 2008, MZUCR 2615-06 ; 1 ovigerous female (L 3.1 mm), same collection data as holotype, MZUCR 2678-26 ; 1adult male (L 2.5 mm), Costa Rica, Isla del Coco ,north side of Isla Manuelita, 5 o 33’48.95’’N 87 o 2’51.53’’W, coral reef, coral rubble washings, depth 14.5 m, R. Vargas Castillo, coll., 26 May 2008, USNM 1484992 ; 1 ovigerous female (L 3.3 mm), same collection data as holotype, USNM 1484993 .

Additional material examined. 5 females (3 damaged), 5 males (all damaged), 4 juveniles, Costa Rica, Isla del Coco, north side of Isla Manuelita, 5 o 33’48.95’’N 87 o 2’51.53’’W, coral reef, coral rubble washings, depth 14.5 m, R . Vargas Castillo, coll., 26 May 2008, MZUCR 2682-14 ; 1 female, Costa Rica, Isla del Coco, Bajo Silverado, 5 o 32’43.75’’N 87 o 1’48.49’’W, coral rubble washings, depth 11 m, R . Vargas Castillo, coll., 26 May 2008, MZUCR 2676-07 ; 1 female, 2males (all damaged), Costa Rica, Isla del Coca, Punta Ulloa, 5 o 33’1.58’’N 87 o 1’52.82’’W, coral reef, on rocks, depth 12–15 m, J. Sibaja, coll., 14 Oct. 2007, MZUCR 2502- 08 ; 2 females (1 damaged), 3 males, Costa Rica, Isla del Coco, Punta Ulloa, 5 o 33’1.58’’N 87 o 1’52.82’’W, rock washings, R . Vargas, coll. 23 May 2008, MZUCR 2642-01 ; 1 female, 1 male, Costa Rica, Isla del Coco, Isla Cáscara, 5 o 33’3.43’’N 87 o 3’45.91’’W, coral reef, depth 32– 34 m ., J. Nivia, J, Sibaja, J. Cortes, coll., 7 Jul. 2011, MZUCR 3047-03 .

Diagnosis. Antennular peduncle, article 3 with distomedial flagellate seta possessing small tubercles distally, article 1 with distodorsal flagellate seta; thoracic endopod3 with 7–9 robust flagellate setae with microdentations on medial margin of carpopropodus; male pleopod 1 with 6 robust spiniform simple setae along distomedial and distal margins; male pleopod 3 with 6 stout flagellate setae on distal margin; male pleopod 4 with 28–36 small simple setae (no distal flagella) on distal margin; uropodal endopod armed with 2–3 spiniform setae along medial margin in region of statocyst; telson, lateral margins armed along posterior 0.3–0.4 length with 6–7 spiniform setae per margin (including apical setae); outer apical seta 3.3–5 times longer than inner; cleft depth 0.25–0.30 times telson length, cleft completely armed with 16–21 spinules.

Description. General body form ( Fig. 2A ): moderately slender; carapace with anterior margin produced into a triangular rostrum; posterior dorsal margin emarginated, partially exposing thoracic somite 8; anterolateral lobes rounded.

Antennule peduncle ( Fig. 2B ): article 1 subequal in length with article 3, distolateral epiprocess with 3–5 plumose setae, small lobe with 4 plumose setae and 1 strong, blade-like subapically flagellate seta on distodorsal margin; article 2 compressed with 2 plumose setae on distomedial border, 3–4 plumose setae near distolateral margin; article 3 with 1 thick, modified, subapically flagellate seta having small tubercles distally, 6–7 times as long as wide, and 1 long laterally directed simple seta on distomedial margin, small lobe with 4 setae on distodorsal margin, 2 short plumose setae near lateral margin; outer and inner flagella with attenuated setae along medial margins; males having moderately setose lobe on ventral surface.

Antenna ( Fig. 2C ): scale extending to or slightly beyond peduncle, 2.9–3.2 times as long as maximum width, medial margin slightly convex, lateral margin straight, apex faintly articulated, tip 0.07 times scale length, all margins setose; antennal peduncle 3-articulated; article 1 inconspicuous; article 2 is 1.3–1.4 times longer than article 3, armed with 3–4 plumose setae distomedially, 1 plumose seta on distolateral border; article 3 with 3–5 plumose setae distomedially, 3 short plumose setae along distolateral border; flagellum with attenuated setae along medial margin.

Eye ( Fig. 2A ): moderately large, oval, distal end of eyestalk slightly wider than cornea with ocular tooth on anteromedial margin; cornea large, oval, occupying distal third of eye.

Mandible ( Fig. 2D ): cutting edges typical of genus, molar processes with strong grinding surfaces on both mandibles; palp 3-articulated; article 1 small, inconspicuous; article 2 expanded medially, 2.5–3.0 times longer than article 3, lateral margin with a series of 7–8 plumose setae along entire length, medial margin with 9–11 plumose setae along entire length; article 3 with 1 long, strong pennate seta at apex and 9–12 shorter distally pennate setae along distomedial margin.

Labrum ( Fig. 2E ): typical of genus. oval, posterolateral margins rounded with dense clusters of fine setae; anterior margin not produced into a spiniform process.

Maxillule ( Fig. 2F ): outer lobe apex with 8–12 robust, weakly serrated spiniform and 3 subapical simple setae; inner lobe apex with 3 long, curved distally serrated setae, 9–11 simple and plumose setae on apex, inner, and outer margins.

Maxilla ( Fig. 2G ): typical of genus; exopod with 6–15 plumose setae, not extending beyond basal article of endopod; endopod 2-articulated, distal article moderately expanded, about 1.3 times as long as greatest width, distal and inner margins with dense series of plumose setae; sympod and sympodal endites densely armed with plumose, serrated, and simple setae.

Thoracic endopod 1 ( Fig. 3A ): short, robust; basis with large endite with stout plumose setae on medial margin; ischium and merus equally long with stout plumose setae on medial margins; carpopropodus short, with plumose and simple setae on distal margin; dactylus wider than long, with simple and plumose setae and a long, strong terminal claw; Thoracic endopod 2 ( Fig. 3B ): basis with medial endite; merus longer than combined preischium and ischium and about equal in length to combined carpopropodus and dactylus; dactylus with several stout, serrated and more slender plumoseandsimplesetae. Thoracicendopod3( Fig.3C ): ischium 0.5–0.6 times length of merus; merus 1.1–1.3 times length of carpopropodus, medial margin with a series of 7–9 short and long simple setae, lateral margin with 1-2 simple setae distally; carpopropodus, medial margin with 7–9 robust flagellate setae with microdentations, 6–8 of these setae arranged in pairs distally, 1 single seta proximally, 1 simple seta at base of each single or pair of flagellate setae, lateral margin with 3–5 short simple setae; dactylus with long, curved, robust claw on distal end.Thoracic endopod 4( Fig.3D ): merus 1.1 times length of ischium; carpopropodus 0.9 times length of merus, with 3 articles, distal 2 subequal in length, each 0.5 times as long as proximal article, dactylus small with slender claw.Thoracic endopod 5–8 ( Fig. 3 E, F ): merus 0.8–0.9 times length of ischium; carpopropodus 0.8–0.9 times length of merus, with 5–7 articles, distal 4–6 subequal in length, each 0.4–0.5 times as long as proximal article; dactylus armed with slender serrated claw.

Thoracic exopods:exopod 1 with 8 articles, exopods 2–8 with 9 articles.

Thoracic sternal processes: males with sternites 1–8 supporting median triangular spiniform processes; females with similar process on sternite 1 only.

Marsupium: females with pairs of developed oostegites on bases of the medial margins of thoracopods 7 and 8, respectively.

Penes: penes cylindrical, stiff with smooth cuticle and no discernable setae; about 6 times longer than wide; extending forward to base of thoracopod 6.

Pleopods: reduced to small uniarticulated plates in both sexes; male pleopods 2 and 5 unmodified; pleopod 1 ( Fig. 4A ) with row of 5–6 plumose setae on anterior surface (not shown in Fig. 4A ), with 6 robust, spiniform simple setae along medial and distal margins, increasing in length distally with longest seta reaching distal end of pleopod 2, lateral margin with 2–3 plumose setae, pseudobranchial lobe (exite) with 4 plumose setae; pleopod 3 ( Fig. 4B ) with row of 5–6 plumose setae on anterior surface, distal margin with 6 stout flagellate setae and 1 long plumose seta, lateral margin with 2 plumose setae, pseudobranchial lobe with 4 plumose setae; pleopod 4 ( Fig. 4C ) with row of 5–6 plumose setae on anterior surface (not shown in Fig. 4C ), distal margin with 28–36 small, simple setae (no distal flagella apparent) and 1 long plumose seta, lateral margin with 2 plumose setae, pseudobranchial lobe with 4 plumose setae.

Uropods ( Fig. 4E ): exopod 1.15–1.25 times longer than endopod, lateral margin straight, medial margin slightly convex, all margins setose; endopod linguiform with a row of 2–3 spiniform setae increasing in length distally on medial margin in region of statocyst, all margins setose.

Telson ( Fig. 4D ): length 1.0–1.1 times length of abdominal somite 6 and 0.7 times that of uropodal exopod, 1.2 times as long as maximum (basal) width; lateral margins moderately concave, armed along posterior 0.3–0.4 length with 6–7 spiniform setae per margin (apical setae included); outer apical seta 3.3–5 times longer than inner; cleft depth 0.25–0.30 times length of telson, completely armed with 16–21 spinules.

Etymology. The name refers to the type locality,

Isla del Coco.

Habitat. Heteromysis (Olivemysis) cocoensis n. sp. collected from coral rubble washings with sponges, algae, and hydroids in depths of 8–34 m. Collecting techniques were too general to determine if this species was associated with a specific host; however, many species of Heteromysis are associated symbiotically with benthic invertebrates such as sponges, anthozoans, ophiuroids, and shells inhabited by hermit crabs (see Fukuoka, 2005 for details).

Type locality. Costa Rica, Isla del Coco , Bahía Chatham, 5 o 32’57.89’’N 87 o 2’30.51’’W, coral rubble washings, depth 8 m.

Distribution. This species is known only from coral reefs in coastal waters of Isla del Cocos.

Figures

Figure 2. Heteromysis (Olivemysis) cocoensis n. sp. adult male, 3.0. mm. A. Dorsal view. B. Antennular peduncle with enlargement of modified flagellate seta. C. Antennal peduncle and scale.D.Mandibles with right palp.E. Labrum.F.Maxillule.G.Maxilla. Scale: A, 0.4 mm; B–G, 0.1 mm.

Figure 3. Heteromysis (Olivemysis) cocoensisn. sp.adult male, 3.0.mm.A,B.Thoracic endopods 1, 2. C. Thoracic endopod 3 (lateral view) with enlargement of distal end (mesial view). D–F. Thoracic endopods 4, 7, 5. Scale: A, B, D–F, 0.1 mm; C, 0.15 mm.

Figure 4. Heteromysis (Olivemysis) cocoensis n. sp. adult male, 3.0. mm. A. Pleopod 1, posterior view. B. Pleopod 3, posterior view. C. Pleopod 4, posterior view, with enlargement of distal setae. D. Telson. E. Uropod. Scale: A, 0.25 mm; B–E, 0.1 mm.