Syrrhoe affinis Chevreux, 1908

Fuchs, Luisa, Coleman, Charles Oliver & Loerz, Anne-Nina, 2019, The genus Syrrhoe (Crustacea, Amphipoda, Synopiidae) from the North Atlantic, Evolutionary Systematics 3 (1), pp. 85-108 : 85

Syrrhoe affinis Chevreux, 1908 Figs 1, 2, 3, 4, 5

Syrrhoe affinis Chevreux, 1908: p. 7, fig. 4. - Sexton 1911: 202, pl. 3, figs 1-8. - Chevreux 1919: 574. - Chevreux 1927: 86, pl. 7, fig. 27. - Chevreux 1935: 98, pl. 13, fig. 7. - J.L. Barnard 1972: 53. - Ledoyer 1977: 411, fig. 30. - G. Karaman 1986: 136, figs 8-10; fig. 11, 1-2. - Ruffo 1993: 715, fig. 492 Syrrhoe (?) affinis J.L. Barnard, 1961: 80, fig. 49. Lörz and Coleman 2013, figs 44-49, 103-112

Material examined.

1 male (illustrated and described), 10 mm, 1 female, UM/BIO stations, HB-2016-01-21-2, Hjeltefjorden v. Stureterminalen, 60°37 ’48” N, 4°52 ’5” E, 230 m, 21.1.2016, RP sledge, ZMBN 127919; 1 female, 5 mm; UM/BIO stations, HB-2016-01-21-3, Hjeltefjorden v. Stureterminalen, 60°37 ’48.4” N, 4°52 ’5.’’ E, 230 m, 21.1.2016, RP sledge, ZMBN 112491; 2 males, 9 mm and 8.7 mm, 1 female, MAREANO 2013, R961-710, 64°10 ’11” N, 8°5 ’50” E, 345 m, 05.10.2013, large VW grab, ZMBN 127921; 1 male, MAREANO 2013, R911-695 GR, 63°34 ’22” N, 7°25 ’24” E, 302 m, 4.10.2013, large VW grab, ZMBN 127923; 42 females, 30 males, 120 without sex determination, MAREANO 2012, R997-31, 62°30 ’30” N, 5°35 ’17” E, 277-282 m, 2.10.2012, RP sledge, ZMBN 127927; 19 females, 5 males, 42 without sex determination, MAREANO 2013, R911-101, 63°34 ’42” N, 7°25 ’11” E, 305-308 m, 4.10.2013, RP sledge, ZMBN 127924; 11 males, 12 females, 43 without sex determination, MAREANO 2012, R1046-35, 62°22 ’9” N, 4°27 ’47” E, 193 m, 3.10.2012, RP sledge, ZMBN 127926; 5 males, 9 females, 105 without sex determination. MAREANO 2012, R1013-23, 63°18 ’49” N, 6°39 ’14” E, 225-226 m, 26.9.2012, RP sledge, ZMBN 127929; 1 female, MAREANO 2013, R1238-97, 62°44 ’54” N, 3°1 ’59” E, 567-569 m, 24.9.2013, RP sledge, ZMBN 127925.

Description

based on: male, 10 mm, ZMBN 127919.

Head. Head slightly produced. Eyes invisible, no trace of ommatidea, unpigmented or not present; rostrum short, reaching half the length of article 1 of antenna 1; lateral cephalic lobe present, truncate. Antenna 1 (Fig. 1b) article 1 with a distally curved tooth; article 2 without distomedial tooth, subequal to article 1; article 3 subequal to article 1, shorter than article 2; accessory flagellum 3-articulate, almost reaching end of first flagellar article, 2nd article of accessory flagellum shorter than half the length of 1st accessory flagellar article, minute 3rd article with terminal plumose seta and (broken off) stout seta; flagellum shorter than pereon, 17 articles. The accessory flagellum in female specimens is longer than the 1st flagellum article, it consists of a large basal article and a minute second article. Antenna 2 (Fig. 1d) slightly surpassing pereon segment 7; flagellum broken off, but at least 27 articles. Labrum (upper lip) (Fig. 1e) entire, rounded. Mandible (Fig. 1c), incisor multidentate (worn down, number unknown); left lacinia mobilis wide, 5?-dentate (wide, 6-dentate on right side); accessory setal row on the left side distally with 3 blade like stout setae and 3 plumose setae proximally (with 2 blade like setae and 3 plumose setae on the right mandible); molar small, columnar, weakly triturative, with strongly serrate margin; mandibular palp 3-articulate, terminal article minute, with 5 very long stout setae. Maxilla 1 (Fig. 2a) inner plate with 7 long and distally 2 shorter plumose setae; outer plate with 11 apical robust setae lined with denticles; palp article 2 outer margin smooth, with apical and medial setation. Maxilla 2 (Fig. 1f) outer plate slightly longer than inner plate; inner plate width more than 2 × outer plate. Maxilliped (Fig. 2 b–e) inner plate truncate distally with some mediodistal and distal setae, 1 robust setae on inner distal angle and 3 on anterior face distally; outer plate somewhat surpassing second palp article, lined with stout setae distomarginally and mediomarginally; palp 4 articulate, 2nd article longest, 3rd article slightly expanded distally, 4th article with long unguis, slender.

Pereon. Pereonite 1-6 dorsally, dorsolaterally and laterally smooth. Pereonite 7 without carination, but posterior margin mid-dorsally serrate, with short mid-dorsal point; additional small mid-dorsal hump prior to posterior margin absent; posterolateral corner angular and not produced. Gnathopod 1 (Fig. 3a, b, d) nearly rectipalmate; coxa slightly expanded distally, apex distally truncate, strongly directed anteriorly; basis longer than carpus; carpus subrectangular, with long setae along posterior margin (fine structure as in Fig. 3b); propodus palm transverse, defined by 1 serrate robust seta and additional robust seta; unguis curved. Gnathopod 2 (Fig. 3c, e, i, j) coxa tapering distally; basis longer than carpus; carpus with serrate setae along distal half of the the posterior margin; propodus palm nearly oblique, defined by 1 serrate robust seta and 1 additional robust seta; dactylus of gnathopod 2 well developed, unguis short, less than or subequal to length of dactylus. Pereopod 3 (Fig. 4a) coxa anterodistal lobe present, subacutely produced, surpassing posterior head margin, posterodistal lobe present, truncate, half the depth of the coxa, posterodistal margin smooth; basis slightly wider than ischium, long plumose setae on anterior and posterior margins; ischium subquadrate, 1/4 of merus length; merus, carpus, propodus subequal in length, setae on posterior margins; dactylus rather straight with slender unguis. Pereopod 3-4 coxa pelagont. Pereopod 4 (Fig. 4b) coxa shorter than coxa 3, lobate in shape, curved posteriorly, posterior margin with well-developed lobe; ischium subquadrate, 1/4 of merus length; merus, carpus and propodus subequal in length, setae on posterior margins, dactylus rather straight, unguis slender. Pereopod 5-7 (Fig. 5 a–c) basis anterodistal corner weakly curved and pointed, posterior margin serrate. Pereopod 5 and 6 coxa bilobate, posterior lobe larger than anterior lobe; basis subovoid, expanded, posterodistal lobe weakly developed, not extending past ischium. Pereopod 7 (Fig. 5c) coxa wider than long, posteroventrally pointed; basis oval, posterodistal lobe well developed, rounded, extending below ischium; merus drawn out posterodistally, merus, carpus and propodus successively longer, strongly setose antero- and posteromarginally; dactylus rather straight.

Pleon. Pleonites 1-2 posterodorsal margin serrate, without carination, posterior margin mid-dorsally with short point.

Pleonite 3 (Fig. 1a) posterior margin mid-dorsally not produced, margin serrate. Epimeron 1 and 2 posterior margin smooth, posterodistal corner weakly pointed. Epimeron 3 (Fig. 1a) posterior margin serrate, smooth un-serrate, convex margin at dorsolateral part of epimeron; posteroventral corner rounded.

Urosomite 1 (Fig. 1a) mid-dorsal posterior margin serrate. Urosomite 2 (Fig. 1a) mid-dorsal posterior margin serrate. Urosomite 3 mid-dorsal posterior margin smooth. Uropod 1 (Fig. 3f) peduncle with long distolateral process, longer than half the length of outer ramus; inner ramus longer than peduncle; apical robust setae on tip of both rami present. Uropod 2 (Fig. 3g) peduncle with laterodistal process (much shorter and more bulky than that on peduncle of uropod 1) apical robust setae on tip of outer ramus present. Uropod 3 (Fig. 3k) length exceeding uropods 1-2. Telson (Fig. 3h) almost reaching end of uropod 3 rami, 3 × as long as wide; with no setae along the lateral margin, without apical slender setae; lobes abutting, deeply cleft 90%.

Distribution.

Atlantic Ocean, off Morocco, 460-888 m (type locality); New Zealand, Chatham Rise, Challenger Plateau, Tasman Sea, 418-610 m; Mediterranean Sea, 180-360 m; Arctic North Atlantic, 193-569 m.

Remarks.

Lörz and Coleman (2013) noted a morphological variance in the Pacific material of S. affinis , not related to sampling depth or gender of the animals, of larger specimens having a mid-dorsal long thin process on pereonites 7 and pleonites 1-2. This was also observed in the Arctic specimens studied herein.

This species was recorded by J.L. Barnard (1961) from New Zealand waters. Barnard placed a question mark before the species name as he doubted that a species originally described from the Atlantic coast off Morocco could occur in New Zealand waters. We share this hesitation, but could not detect any morphological differences in the material from Chevreux and material collected this century in the Pacific. Preserved specimens appear to have no eyes, there is not a trace of pigments but in some specimens of the Pacific material the outlines of eyes appear to be visible.

The present specimens of S. affinis from the North Atlantic differ minutely from the Pacific material by having urosomite 2 postero-dorsomarginally serrate (vs smooth), but the serration of urosomite 2 could have been less developed and therefore overlooked in populations from other regions. In Barnard’s (1961) illustration of the Pacific material there is one tooth on this segment. In Ruffo (1993) the illustration of the Mediterranean material, identified as S. affinis , shows at least 2 teeth on this segment.