Hansenomysis lucifugus ( Faxon, 1893 )

Hendrickx, Michel E. & Hernández-Payán, José-Carlos, 2020, Rediscovery of Hansenomysis lucifugus (Faxon, 1893) (Crustacea, Mysida Petalophthalmidae) in the eastern Pacific, Zootaxa 4729 (3), pp. 416-428 : 417-422

publication ID	https://doi.org/ 10.11646/zootaxa.4729.3.8
publication LSID	lsid:zoobank.org:pub:89C630EB-81AB-4B2D-A8EB-E4F47470B0AC
persistent identifier	https://treatment.plazi.org/id/03CD667A-FFED-FFFD-4F85-3C170375BCBC
treatment provided by	Plazi
scientific name	Hansenomysis lucifugus ( Faxon, 1893 )
status

Treatment

Hansenomysis lucifugus ( Faxon, 1893) View in CoL

( Figs. 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 , 10 View FIGURE 10 , 11 View FIGURE 11 )

Scolophthalmus lucifugus Faxon, 1893: 219 ; 1895: 226, Pl. LV, Fig. 1‒1e View FIGURE 1 .― Illig, 1930: 556.―W.M. Tattersall, 1951: 243.― Gordan, 1957: 336 (list). Scolopthalmus lucifugus .―Lucas & Thiele, 1904: 482. Hansenomysis lucifugus View in CoL .― Mauchline & Murano, 1977: 57 (list).― Bravo & Murano, 1997: 234 (key).― Price, 2004: 56

(list).― Mees & Meland, 2019: listed.― Müller, 1993: 19 (list).? Hansenomysis lucifugus .― Bravo & Murano, 1997: 232, Fig. 3 View FIGURE 3 E‒G.

Material examined. TALUD XVI-B. St. 1 (28°28.3’N ‒ 115°45.2’W), May 23, 2014, 1 F (CL 12.94 mm), BS operating at 2038‒2054 m (ICML-EMU-12486) GoogleMaps ; St. 9 (29°20.89’N ‒ 115°51’W), May 31, 2014, 6 F (CL 10.53‒ 13.75 mm), BS operating at 1848‒1860 m (ICML-EMU-12487) GoogleMaps ; St. 15 (29°40.4’N ‒ 116°6’W), May 29, 2014, 1 F (CL 10.57 mm), BS operating at 2010‒2046 m (ICML-EMU-12488) GoogleMaps ; St. 20 (30°51.26’’N ‒ 116°42.18’’W), May 26, 2014, 4 F (CL 10.71‒12.79 mm), BS operating at 2075‒2090 m (ICML-EMU-12489) GoogleMaps ; St. 21 (30°49.4’N ‒ 116°47.8’W), May 28, 2014, 3 F (CL 12.20‒13.12 mm), BS operating at 2018‒2093 m (ICML-EMU-12490) GoogleMaps

Description. (based on adult females). Carapace ( Fig. 1A, B View FIGURE 1 ) long, about 3 x as long as high; frontal margin of carapace produced in an acute rostrum, triangular in dorsal view; antero-lateral margins markedly oblique; antero-lateral corners triangle-shaped, acutely produced; antero-ventral margin with a strong spine; rest of carapace without spines or lobes; cervical sulcus well marked, a distinctive linguiform sulcus posterior to cervical sulcus.

Thoracic somites ( Fig. 1A View FIGURE 1 ) 7‒8 and abdominal somites 1‒6 dorsally unarmed; 6th abdominal somite posterior margin unarmed.

Eyes ( Fig. 1B View FIGURE 1 ) fused in a single plate; cornea reduced, without pigments; peduncular plate with a pair of long, spine-like projections (horns).

Antennular peduncle ( Fig. 1B View FIGURE 1 ) long, robust, about 0.5 as long as carapace; articles 1‒2 equal in length, 3rd slightly shorter; article 1 with an oblique series of short subdistal setae; articles 1‒3 with long plumose setae on in- ner margin.

Antennal peduncle ( Figs. 1C View FIGURE 1 , 10 View FIGURE 10 A‒B) about 3/5 length of antennal scale, extending slightly beyond 2nd article of antennular peduncle; article 1 short, a minute spine on inner margin, sympod outer distal angle with one long, slender spine at base of scale; article 2 long, about 1/3 length of scale, with three distal multi-articulate setae; article 3 shorter, about 1/4 length of scale, with three distal multi-articulate setae. Antennal scale ( Fig. 1C View FIGURE 1 ) lanceolate, 4 x as long as wide, slightly overreaching anterior margin of antennular peduncle, setose all round except for proximal third of outer margin, distal edge of naked margin with three spines gradually increasing in length, scale without apical lobule.

Mandible ( Figs. 2A View FIGURE 2 , 3 View FIGURE 3 A‒F, 4A‒C) palp long, slender, 3-jointed; 1st article shortest, without spine; 2nd longer than 3rd, about 7 x as long as wide, with 21‒23 long, spine-like setae and intermixed short setae; 3rd article about 2/3 as long as 2nd, with long and short marginal setae and four long distal setae. Right mandible incisive process a curved crest with a strong basal tooth; molar process subrectangular, with small spines on margin ( Fig. 4B, C View FIGURE 4 ; mostly missing or hard to see in SEM photographs); lacinia mobilis represented by three or four small, spine-like setae (the “spine row” sensu W.N. Tatersall & O.S. Tatersall 1951) between the incisive and molar processes. Left mandible stronger than right, incisive process with a prominent tooth; lacina mobilis trifid, with two strong teeth and a weaker 3rd; molar process similar to right mandible; a short inner, conical projection at base of molar process.

Maxilla ( Fig. 2B View FIGURE 2 ) with distal segment of endopod longer than wide, densely setose on inner margin and scarcely setose on outer margin, all setae long and plumose; endites distally round, armed with plumose setae on inner margin; exopod large, reaching to proximal 1/4 of endopod distal article, with 38‒40 plumose, marginal setae.

Maxillula ( Fig. 2C View FIGURE 2 ) outer lobe (basis) armed with 13 apical, cuspidate setae, and three long, serrate-like (two lines of denticles) setae on caudal face; inner lobe with 10 apical setae, three long, strong and plumose, two indented setae, and five simple setae.

First thoracopod ( Fig. 5A View FIGURE 5 ) small and robust; exopod absent; epipod well developed; endopod with preischium long, with 11 simple, short and long setae on inner distal margin, ischium with 14 simple, short and long setae on inner margin, merus with 4 long, simple setae and several simple, short setae on inner margin, carpopropodus with one long and 2 shorter, simple setae on inner margin, dactylus short, with 2 strong distal setae and several, shorter and slender setae.

Second thoracopod ( Fig. 5B View FIGURE 5 ) robust; exopod about the same size as endopod, 16-articulated, articles with long plumose setae; preischium of endopod short, ischium without seta on outer margin, inner margin produced into a lamellar lobe armed with many short and long, simple setae, merus long, about 4 x as long as wide, inner margin armed with long, simple setae, a row of short setae parallel to marginal setae, and 3 distal, long serrate (papose) setae, series of sparse setae distally, carpopropodus about 0.5 length of merus, inner margin armed with numerous short, simple setae, 2 long distal setae, outer margin with 7 long, simple setae and a parallel series of short setae, dactylus inner margin with 3 long setae, the distal seta shorter and stronger, 2 long setae on outer margin, and additional, scattered, shorter setae.

Third to fifth thoracic appendages ( Figs. 5 View FIGURE 5 C–D, 6A) with endopods long and slender, terminal chelate-like structure well developed, rather long, surrounded by tuft of simple setae, meri equal or slightly longer (thoracopod 5) than carpopropodi; exopods shorter than endopods, with 17 or 18 articles; setae as illustrated; endopod of third thoracopod shorter than endopods of 4th and 5th. Sixth to eighth thoracopods endopods ( Fig. 6 View FIGURE 6 B–D) long and slen- der, about twice as long as exopods, dactylus and nail forming long, slender claw, meri longer than carpopropodi, entire; carpopropodi entire; exopods shorter than endopods, with 16‒19 articles; setae as illustrated.

Female (adult) with six pairs of oostegites.

Pleopods ( Fig. 7 View FIGURE 7 ) of female uniramous, well developed, increasing in size posteriorly; 1st to 4th 2-segmented, 5th about 2 x as long as 4th, 3-segmented.

Uropods ( Fig. 8A View FIGURE 8 ) long, slender; exopod equal to telson length, 2-segmented, inner and 2nd segment margins setose, outer margin with four spinose setae in distal half, and two similar spinose setae near suture of 2nd segment; endopod without statocyst, about 0.5 as wide as exopod, extending beyond distal edge of telson, 2-segmented, setose all round, without marginal spines.

Telson ( Fig. 8A, B View FIGURE 8 ) long, wide, about 1.5 times as long as 6th abdominal segment, subrectangular, unarmed in proximal 1/8, rest of margin armed with alternate short and long spinose setae, the latter about 2x as long as the short setae, two long and one short spinose setae in middle of posterior margin.

Comments. In the right mandible, a series of 3‒4 small, spine-like setae is present in the position where the lacinia mobilis of the left mandible was observed. This series of spines might be the equivalent of the “spine row” as defined by W.M. Tattersall & O.S. Tattersall (1951: 37), although the lacinia mobilis might simply be missing. Illustrations of mandibles in Hansenomysis is available for some species, including H. chini Băcescu, 1971 , and H. spenceri Băcescu, 1971 , both with a single stylet-shaped seta replacing the lacina mobilis ( Băcescu 1971), thus indicating a potential strong variation in the lacina mobilis structure within the genus.

Size. All the specimens captured were adult female, 10.53‒13.75 mm CL. The holotype is a female of 42 mm long ( Faxon 1895). From the illustration provided by Faxon (1895: Pl. LV, fig. 1), the CL of the holotype is estimated as ca. 10.3 mm. Total length of adult females examined was in the range of 35.37 to 56.74 mm.

Depth distribution. The type material, a single female, was collected in a tow net operated between surface and 1322 fathoms (2417 m) ( Faxon 1895; “Albatross” St. 3400). The material examined herein was collected at unknown depths, within the depth range of 0‒2093 m. The doubtful material from off Japan was collected in a sledge net operated at a maximum depth of 742 m ( Bravo & Murano 1997). Hansenomysis lucifugus is most probably a pelagic species, but its depth range remains unknown until opening-closing nets operated at specific depth ranges are used.

Geographic distribution. Off the Galapagos Islands ( Faxon 1893; type locality, 0°36’S ‒ 86°46’W); off the west coast of the Baja California Peninsula (see material examined) ( Fig. 9 View FIGURE 9 ); a doubtful record off Japan ( Bravo & Murano 1997).