Boreomysis arctica ( Krøyer, 1861 )

Hernández-Payán, J. C. & Hendrickx, M. E., 2024, The genus Boreomysis G. O. Sars, 1869 (Peracarida, Mysida, Mysidae) in western Mexico, Zootaxa 5418 (5), pp. 501-527 : 503-513

publication ID	https://doi.org/ 10.11646/zootaxa.5418.5.4
publication LSID	lsid:zoobank.org:pub:668564FD-5AB7-458F-9449-EB6071E2DB7D
DOI	https://doi.org/10.5281/zenodo.10793981
persistent identifier	https://treatment.plazi.org/id/03C187C0-3E6F-FF98-7391-FF214ABAFE1A
treatment provided by	Plazi
scientific name	Boreomysis arctica ( Krøyer, 1861 )
status

Treatment

Boreomysis arctica ( Krøyer, 1861) View in CoL

( Figures 1‒8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Mysis arctica Krøyer, 1861: 34 , pl. 1, fig. 5a‒f.

Boreomysis arctica View in CoL .—G.O. Sars 1869: 330 (passim); 1872: 264; 1879: 10, pl. 11‒13; 1883: 9.— Zimmer 1909: 53, figs. 71‒ 74.—W.M. Tattersall & O.S. Tattersall 1951: 132, fig. 22.— Gordan 1957: 341 (list, complete synonymy).— Birstein & Tchindonova 1958: 284, fig. 10.— Ii 1964: 41.— Mauchline & Murano 1977: 49 (list).— Lagardère & Nouvel 1980: 385.— Austin 1985: 560 (list).— Kathman et al. 1986: 104.— Laubitz 1986: 15.— Müller 1993: 22.— Price 2004: 56 (list).— Petryashov 2005: 2 (list); 2009: 77, pl. 3, figs. 4, 6.— Hernández-Payán & Hendrickx 2020: 52 (table 1).

Arctomysis arctica Czerniavsky, 1887: 7 .

Boreomysis tregouboffi Băcescu, 1941a: 12 ; 1941b: 168.

Material examined. 13 males; 12 females. Ovigerous females were not collected.

TALUD IV. St. 20 (24°27’24” N, 108°35’16” W), August 25, 2000, 1 male ( CL 9.09 mm) and 2 females ( CL 7.39, 10.67 mm), BS operated at 1500‒ 1540 m ( ICML-EMU-12573 ) GoogleMaps .

TALUD VII. St. 4 (22°03’18” N, 106°34’42” W), June 5, 2001, 1 male (damaged), GoogleMaps BS operated at 1200‒1230 m ( ICML-EMU-12574- A ); St. 12 (23°18’18” N, 107°26’48” W), June 6, 2001, 1 male ( CL 8.52 mm), GoogleMaps BS operated at 1040‒1120 m ( ICML-EMU-12574- B ); St. 13 (23°30’18” N, 107°44’00” W), June 6, 2001, 2 males ( CL 12.23 mm; one damaged) and 2 females (damaged), GoogleMaps BS operated at 1400‒1450 m ( ICML-EMU-12575- A ); St. 19 (24°16’12” N, 108°23’42” W), June 7, 2001, 1 female ( CL 9.97 mm), GoogleMaps BS operated at 1160‒1180 m ( ICML-EMU-12575- B ); St. 26 (24°25’24” N, 109°05’21” W), June 8, 2001, 1 female ( CL 6.73 mm), GoogleMaps BS operated at 1180‒1220 m ( ICMLEMU-12576- A ); St. 33-B (26°06’30” N, 110°06’42” W), June 9, 2001, 2 males ( CL 9.03, 10.37 mm) and 1 female ( CL 6.55 mm), GoogleMaps BS operated at 1260‒1300 m ( ICML-EMU-12576- B ) GoogleMaps .

TALUD VIII. St. 3 (24°32’36” N, 109°30’30” W), April 16, 2005, 1 female ( CL 13.12 mm), BS operated at 1600 m ( ICML-EMU-12577- A ); GoogleMaps St. 10 (24°58’12” N, 110°16’06” W), April 17, 2005, 3 males ( CL 10.50‒10.89 mm) and 1 female ( CL 8.08 mm), BS operated at 1500 m ( ICML-EMU-12577- B ) GoogleMaps .

TALUD X. St. 18 (27°09’06” N, 111°46’54” W), February 12, 2007, 1 male ( CL 10.66 mm) and 1 female ( CL 7.07 mm), BS operated at 1526 m ( ICML-EMU-12578 ) GoogleMaps .

TALUD XII. St. 15 (17°25’33” N, 102°07’20” W), March 30, 2008, 1 male ( CL 12.12 mm), BS operated at 2080‒2125 m ( ICML-EMU-12579 ) GoogleMaps .

TALUD XVI-B. St. 8 (29°23.8” N, 115°45.2” W), May 24, 2014, 2 females ( CL 11.19-11.83 mm), BS operated at 1448 m ( ICML-EMU-12580- A ); St. 9 (29°20.89” N, 115°51” W), May 31, 2014, 1 male ( CL 12.50 mm), BS operated at 1854 m ( ICML-EMU-12580- B ) .

Description. Carapace ( Fig. 1A, B View FIGURE 1 ) elongated, produced anteriorly to form subtriangular rostrum ending in an acute point, reaching about half the length of antennula article 1; anterolateral margins sharply produced; cervical sulcus well marked dorsally; posterodorsal margin reaching to posterior margin of ultimate thoracic segment.

Eyes ( Fig. 1A, B View FIGURE 1 ) large, circular; cornea wider than long, strongly convex, without ocular process on upper surface.

Antennular peduncle ( Fig. 1B‒D View FIGURE 1 ) robust; article 1 rectangular, concave in lateral view, 6 short setae in middle of outer margin, inner margin with 3 thick setae on distal edge and 5 short setae on distal outer margin; article 2 smaller than the other two, 3 short setae on outer margin; article 3 longer than wide, distal margin with small protuberance with 3 short setae in middle of flagella.

Antennal peduncle ( Fig. 1E View FIGURE 1 ) about 0.5 times length of scale, articles 1‒3 subequal in length; article 1 with a prominent thorn on outer margin; article 2 with 4 distal setae on external margin; article 3 with 6 long distal setae on inner margin and 1 on outer margin. Antennal scale ( Fig. 1B, E View FIGURE 1 ) long, slender, extending beyond distal edge of antennular peduncle by about 0.5 its length, about 4.5 times as long as wide, outer margin straight, without setae, inner margin setose; apical tooth well-marked, overreaching truncate apex by its entire length; a minute distal suture at inner corner.

Labrum ( Fig. 2A View FIGURE 2 ) subcircular, semi-symmetrical, posterior margin bilobed, with short, simple setae (left) and finely pitted (right).

Mandibles ( Figs. 2B View FIGURE 2 , 3A‒F View FIGURE 3 ) palp long, broad proximally; article 1 short, without setae; article 2 longer than article 3, about 3 times broader proximally than distally, outer margins setose; article 3 slightly shorter than article 2, about 5‒6 times as long as broad, comb-shaped setae on distal 2/3 of inner margin, proximal 1/3 with a series of setae almost 2 times as long as distal setae, 4 long, plumose sub-marginal setae and sub-distal, long, simple seta; outer margin with 6 simple setae in proximal 1/3. Right mandible ( Figs. 2B View FIGURE 2 , 3A‒C View FIGURE 3 ) well developed, incisor process robust, composed of chitinous ridge with 4 strong teeth, second bifid; lacinia mobilis well developed between incisor process and par centralis, represented by 2 rows of small spinal setae, first row smaller than second, with smaller number of spines; pars centralis formed by a series of 8 strong apical setae united at their base; molar process subrectangular, longer than wide, with a series of parallel lamellae on crushing surface formed by small, sharp spines attached at their base, a series of small pores on edge of molar process. Left mandible ( Figs. 2B View FIGURE 2 , 3D‒F View FIGURE 3 ) incisor process composed of 1 chitinous ridge with 4 teeth; lacinia mobilis very well developed, consisting of 5 teeth, 4 in row, 2 outermost stronger and more prominent, 1 strong central tooth; pars centralis represented by series of 7 long lamellae with broad base, spiny on their margins; molar process similar to right mandible.

Maxillula ( Fig. 2C View FIGURE 2 ) external lobe armed with 13 robust apical setae, 9 long, plumose setae on ventral surface; inner lobe with 4 long, plumose apical setae, 5 short plumose setae on inner margin, 1 simple, short setae on outer margin, and 4 short simple setae on ventral surface.

Maxilla ( Fig. 2D View FIGURE 2 ) with narrow, tapering exopodite, armed with 34 simple marginal setae; proximal endopodite article with 4 simple setae, distal article circle-shaped, densely setose on both margins, setae long, plumose; 3 subrectangular endites, distal margins with simple and plumose setae; protopod with dense covering of long, simple setae, interspersed with 7 long, plumose setae.

Thoracopod 1 ( Fig. 4A View FIGURE 4 ) short, thin; gnathobase of endopod with well-developed elongated lobe, 1 series of long plumose setae on outer margin; pre-ischium with 6 plumose setae; ischium with 7 long plumose setae on inner margin, 2 short simple setae on ventral face, outer margin without setae; merus short, broad, with 16 long, plumose setae on inner margin, several single setae on outer margin and on ventral surface; carpo-propodus short, with 4 simple setae on inner margin, several single setae on outer margin, and few setae on ventral surface; dactylus short, triangular with several setae on margins and ventral face; nail curved, shorter than dactylus, distal half with setulae; exopod more than 2 times as long as endopod, 22-articulated, each article with long plumose setae.

Thoracopod 2 ( Fig. 4B View FIGURE 4 ) endopod longer than first, shorter than 3 and 4; endopod elongated, not distally subchelated; short, naked pre-ischium; ischium armed with long, simple setae on inner margin; merus and carpo-propodus armed with a series of long, simple setae on inner margin; dactylus with simple setae, 1 series of 6 short, serrated setae on inner margin; exopod slightly shorter than endopod, 23-articulated, each article with long, plumose setae.

Thoracopods 3‒8 ( Figs. 4C, D View FIGURE 4 , 5A‒D View FIGURE 5 ) similar; elongated endopod; pre-ischium naked; ischium and merus with long, simple setae on inner margin; carpus with 1 series of long and short setae on inner margin; propodus divided into 2 subsegments, proximal shorter than distal; dactylus and nail forming long claw; exopod shorter than endopod, 24-articulated, each article with long, plumose setae.

Penis ( Fig. 5E View FIGURE 5 ) elongated, about 3 times as long as wide, slightly wider distally, distally covered with moderately long setae.

Abdominal somites 1‒6 without spines ( Fig. 1A View FIGURE 1 ).

Male pleopods ( Fig. 6A‒E View FIGURE 6 ) biramous, well developed; exopods multi-articulated (23‒29 articles), longer than corresponding endopods, 2‒5 with long, plumose setae in both margins, first with plumose setae on outer margin only; first pleopod endopod uniarticulated, a well developed elongated lobe, about 1/3 the length of the corresponding exopod, tapering distally, 16 short, comb-like simple setae on proximal half of inner margin, 2 rows of long plumose setae (8 + 5) on ventral surface. Pleopods 2‒5 endopods multi-articulated (21‒23 articles), pseudobranchial lobes short, about 1/2 length of first endopod, falciform, outer margin with small bump at about mid-length, bump armed with 4 long, simple setae.

Uropods ( Fig. 7A View FIGURE 7 ) long, thin; exopod about 1.2 times telson length, about 5.3 as long as wide, about 1.2 times as long as endopod, outer margin armed with 2 similar robust setae; endopod about 6.6 as long as wide, inner margin armed in proximal third with 2‒3 robust setae.

Telson ( Fig. 7B View FIGURE 7 ) linguiform, about 3.3 times as long as wide, maximum width about 2.6 times minimum width; margins proximal 1/3 naked, remaining 2/3 with 32‒41 setae, including long setae and intermediate clusters of 2‒5 shorter setae; distal cleft ( Fig. 8A‒C View FIGURE 8 ) V-shaped, deep, about 1/7 of total telson length; base of cleft wide, rounded, without slit; inner margins of cleft armed with 23‒26 robust setae each, setae increasing in size towards distal part of the cleft, spine-like, closely set, articulated at base; 3 long, robust setae on each lobe of apex, middle seta longest.

Females. Marsupium of female comprised of 7 pairs of oostegites. Female pleopods ( Fig. 6F‒J View FIGURE 6 ) uniramous, well developed, increasing in size posteriorly, long and plumose setae on inner margin, 1 series of short, simple setae at their base.

Size (Material examined). Males, CL 8.52‒12.50 mm; females, CL 6.55‒13.12 mm.

New records in Mexico. Boreomysis arctica is now recorded in the Mexican Pacific, in 13 locations: ten in the central and southern Gulf of California, two off the west coast of the Baja California Peninsula, and one off the SW coast of Mexico ( Fig. 9 View FIGURE 9 ), thus indicating it is a widespread and rather frequent species in western Mexico. Hernández-Payán & Hendrickx (2020) briefly included B. arctica in a list of species of mysids known to occur in western Mexico, referring to the same material reported in detail herein.

Geographic distribution. Widely distributed in the boreal waters of the Arctic Ocean, extending southward on eastern slope from Norway to British Isles, Bay of Biscay and Mediterranean (W.M. Tattersall 1951); from western Greenland to New England shores in East Atlantic (W.M. Tattersall & O.S. Tattersall 1951). In North Pacific, B. arctica is found off coast of Japan, to Sea of Okhotsk, Bering Sea and extends its distribution to coast of California (“Albatross” station 4541). Widely distributed off western Mexico ( Fig. 9 View FIGURE 9 ) (this study).

Bathymetric distribution. Because stratified (discrete) samples were not available during our studies, the material examined herein were collected at unknown depths during sampling operations within the water column, from surface to 1040‒2125 m (all caught with a BS). According to Hargreaves (1997), B. arctica occurs between 497 and 955 m depth, with maximum abundance between 555 and 925 m.

Remarks. The materials examined herein fit well with the descriptions of B. arctica by various authors. This includes: the eye with a large, circular cornea, the relative length of the rostral spine, the length-width proportion of the antennal scale, its truncate tip and extension of its distal, marginal spine, the long uniarticulated endopod of the male first pleopod, about 1/3 the length of the corresponding exopod, the shape and proportions of the telson, and the presence of two or three setae on the uropodal endopod margin (G.O. Sars 1879, W.M. Tattersall & O.S. Tattersall 1951).

Boreomysis arctica differs from the other species recorded in the eastern Pacific by one or several of the following characters: antennal scale slender; eye cornea wide, crescent-shaped, peduncle without ocular tubercle; male pleopod 1 endopod long, oval-shaped, densely setose; three long setae on the inner margin of the uropodal endopod; base of the telson cleft rounded; margins of telson with mixed short and long setae.