Jassa, , Vader & Krapp, 2005

Key to the world species of Jassa (both sexes) 6

1 Gnathopod 2, basis, at least the distal part of the anterolateral margin bearing a fringe of setae (at least some setal lengths 20–40% or more of the maximal basis width) (e.g., Figs 15 View FIGURE 15 , 28 View FIGURE 28 , 78 View FIGURE 78 , 88 View FIGURE 88 and 102 View FIGURE 102 ) (fringe alsopresent in juveniles but may be less pronouncedthanin adults...e.g., see Fig. 102 View FIGURE 102 ) ............................................................... 2

- Gnathopod 2, basis, setae short, minute or absent (setal lengths <20% of the maximal basis width) (e.g., Figs 37 View FIGURE 37 , 85 View FIGURE 85 , 95 View FIGURE 95 and 104 View FIGURE 104 )............................................................................................... 13

2 Gnathopod 2, propodus, anteroproximal margin with a row of long setae (setal length Ẑthe maximal basis width). Gnathopod 1, carpuswithoutasetaorclusterofsetaeattheanterodistaljunctionofthepropodus ( Figs 67 View FIGURE 67 and 68 View FIGURE 68 ) ... J. staudei Conlan, 1990

- Gnathopod 2, propodus, setae on the anteroproximal margin short or absent (setal length <65% of the maximal basis width). Gnathopod 1, carpus, seta(e) at the anterodistal junction of the propodus present or absent (may be slightly medial or lateral and aslongasthecarpusorveryshort) (e.g., Figs 15 View FIGURE 15 , 22 View FIGURE 22 , 65 View FIGURE 65 and 88–90 View FIGURE 88 View FIGURE 89 View FIGURE 90 ) ................................................3

3 Gnathopod 2, female, palmsinuous (e.g., Figs 88 View FIGURE 88 , 97 View FIGURE 97 and 102 View FIGURE 102 ).....................................................4

- Gnathopod 2, female, palmconcave (e.g., Figs 15 View FIGURE 15 , 26 View FIGURE 26 , 29 View FIGURE 29 and 65 View FIGURE 65 )..................................................6

4 Gnathopod 1, basis, anterior margin with a row of spine-like setae; carpus, anterodistal margin with a single or cluster of setae at thejunctionof thepropodus ( Figs 88–90 View FIGURE 88 View FIGURE 89 View FIGURE 90 ) ................................................. J. alonsoae Conlan, 1990

- Gnathopod 1, basis, anteriormarginwithoutarowof spine-likesetae ( Figs 85 View FIGURE 85 and 102 View FIGURE 102 ) ................................5

5 Gnathopod 1, carpus, anterodistal margin with a seta or cluster of setae at the anterodistal junction of the propodus (seta(e) ~40% thelengthof the carpus) ( Fig. 85 View FIGURE 85 ) ......................................................... J. myersi Conlan , 19907

- Gnathopod 1, carpus, anterodistal margin without a seta or cluster of setae at the junction of the propodus ( Fig. 102 View FIGURE 102 ).......... .................................................................................... J. gruneri Conlan, 1990

6 Uropod 1, peduncular spinous process that extends ventrally from the peduncle and underlies the rami very short (±10% of the lengthof thelongest ramus) ( Fig. 65 View FIGURE 65 ) ................................................... J. borowskyae Conlan, 1990

- Uropod 1, peduncular spinous process that extends ventrally from the peduncle and underlies the rami at least 25% to 50% the lengthofthelongestramus (e.g., Figs 42 View FIGURE 42 , 88 View FIGURE 88 and 99 View FIGURE 99 ) ............................................................7

7 Gnathopod 1, carpus with a seta or cluster of setae at the anterodistal junction of the propodus (seta or setal cluster may be slightly lateralormedialandshortoraslongasthe carpus) (e.g., Figs 15 View FIGURE 15 , 22 View FIGURE 22 , 29 View FIGURE 29 , 31 View FIGURE 31 , 62 View FIGURE 62 and 81 View FIGURE 81 ) ................................8

- Gnathopod 1, carpuswithoutasetaorclusterofsetaeattheanterodistaljunctionofthepropodus ... J. monodon ( Heller, 1866)

8 Gnathopod 1, carpus, seta or cluster of setae at the anterodistal junction of the propodus short (length <25% of the length of the carpus) andslightlymedialorlateral ( Figs 15 View FIGURE 15 and 31 View FIGURE 31 )............................................................9

- Gnathopod 1, carpus, seta or cluster of setae at the anterodistal junction of the propodus long (length 25–50% of the length of the carpusor longer) andslightlymedialorlateral ( Figs 22 View FIGURE 22 , 29 View FIGURE 29 , 62 View FIGURE 62 and 81 View FIGURE 81 ).............................................10

9 Telson, tip bearing a seta or setae extending between the third uropods (these setae are in addition to the usual upright setae at each lateral cusp and are visible when the uropods are pressed downwards and away from the telson). Antenna 2, thumbed males and adult females of any size without plumose setae on the posterior margin of article 5 and the flagellum (though setae may look finely pectinate). Gnathopod 2, propodus of major form thumbed male, thumb conical, tip acute, spine or spine group on the posteriormarginattheoriginof thethumbabsent (character statesdifferintheminor form) ( Figs 31–33 View FIGURE 31 View FIGURE 32 View FIGURE 33 ) ................... ..................................................................................... J. valida ( Dana, 1853)

- Telson, tip without apical setae (though the usual upright setae at each lateral cusp are present). Antenna 2, large thumbed males and adult females, with dense plumose setae on the posterior margin of article 2 and the flagellum. Gnathopod 2, propodus of major form thumbed male, thumb wide, tip squared, spine or spine group on the posterior margin at the origin of the thumb absent (character statesdifferintheminor form) ( Figs 15–16 View FIGURE 15 View FIGURE 16 )..................................... J. marmorata Holmes, 1905

10 Gnathopod 2, basis and propodus, anterior marginal setae abundant and plumose ( Figs 62–63 View FIGURE 62 View FIGURE 63 ). Mandibular palp, article 2, with a fringeof setaeonthedorsalmargin ( Fig. 64 View FIGURE 64 ) ................................................. J. oclairi Conlan, 1990

- Gnathopod 2, basis and propodus, anterior marginal setae sparse and simple ( Figs 22 View FIGURE 22 , 28 View FIGURE 28 and 78 View FIGURE 78 ). Mandibular palp, article 2, withoutafringeofsetaeonthedorsalmargin ( Figs 27 View FIGURE 27 , 30 View FIGURE 30 and 82 View FIGURE 82 ) ................................................11

11 Telson, tip bearing apical seta or setae in addition to the usual upright seta or setae at each lateral cusp ( Fig. 28 View FIGURE 28 ).............. .................................................................................... J. morinoi Conlan, 1990

- Telson, tipwithoutapical setae, onlywiththeusualuprightsetaorsetaeateachlateralcusp ( Figs 22 View FIGURE 22 and 78 View FIGURE 78 ) ..............12

12 Antenna 2, large thumbed male and large adult female, peduncular article 5 and flagellum, posterior margin bearing dense plumose setae ( Figs 22 View FIGURE 22 and 23 View FIGURE 23 ). Gnathopod 2, propodus of major form male, thumb tip acute; spine or spine group on the posterior margin at the origin of the thumb absent (although present in small thumbed males) ( Figs 22 View FIGURE 22 and 23 View FIGURE 23 ). Gnathopod 1, female propodus, palm straight to shallowly concave. Gnathopod 2, female propodus, maximum width about 50% of maximum length, palmar anglenotclosetothedefining spines; spinestightly clustered ( Fig. 26 View FIGURE 26 ) ........................... J. slatteryi Conlan, 1990

- Antenna 2, thumbed male and large adult female, peduncular article 5 and flagellum setae not plumose (though may be microscopically pectinate) ( Fig. 81 View FIGURE 81 ). Gnathopod 2, propodus of major form male, thumb tip angled posteriorly, spine or spine group on the posterior margin at the origin of the thumb present ( Fig. 78 View FIGURE 78 ). Gnathopod 1, female propodus, palm convex. Gnathopod 2, female propodus, maximum width about 65% of maximum length, palmar angle close to the defining spines; spines sequential

6 This key is limited by incomplete knowledge of J. kimi , J. laurieae , J. monodon and J. shawi . Sufficient information for J. kimi , J. monodon and J. shawi allow for their inclusion but Jassa laurieae has been excluded because its characteristics are unknown posterior of pereon segment 4. See Table 11 and Remarks section for J. laurieae for distinguishing character states.

7 J. myersi appearstwiceinthekeybecausethesetalfringeontheanterolateralmarginofthebasisofgnathopod 2 canbe interpreted as being present or absent due to the sparseness of the setae on some individuals

( Fig. 81 View FIGURE 81 ) ............................................................................. J. carltoni Conlan, 1990 13 Uropod 1, peduncular spinous process that extends ventrally from the peduncle and underlies the rami short (<10% of the length of thelongest ramus) (e.g., Figs 65 and 83). Onlyknownfromthe Northeastern Pacific................................14

- Uropod 1, peduncular spinous process that extends ventrally from the peduncle and underlies the rami at least 25% to 50% the lengthofthelongestramus) (e.g., Figs 42 View FIGURE 42 , 88 View FIGURE 88 and 99 View FIGURE 99 ). Notknownfromthe Northeastern Pacific ........................15

14 Gnathopod 1, carpus, seta or setal cluster at the anterodistal junction of the propodus about 35% of the length of the carpus. Gnathopod 2, female propodus, palmsinuous ( Fig. 85 View FIGURE 85 ) ............................................ J. myersi Conlan, 1990 - Gnathopod 1, carpus, seta or setal cluster at the anterodistal junction of the propodus minute (<15% of the length of the carpus) and slightly medial. Gnathopod 2, female propodus, palm concave, palmar defining angle acute and close to the defining spines ( Fig. 83) ............................................................................... J. shawi Conlan, 1990 15 Pereopods 5–7, anterior margin of the propodus, spines strong and spine row extending half or more of its full length, propodus expandedornotexpanded forgrasping ( Figs 92, 95 and 99). .....................................................16

- Pereopods 5–7, anterior margin of the propodus, spines mostly on the distal half, propodus not expanded for grasping (e.g., Figs 42 View FIGURE 42 , 48 View FIGURE 48 , 93 View FIGURE 93 and 96 View FIGURE 96 )........................................................................................18

16 Gnathopod 1, carpus, seta or setal cluster at the anterodistal junction of the propodus about 1/3 the length of the carpus and slightly lateral and medial. Body length at maturity 15–25 mm (thumbed males and females with setose brood plates) ( Fig. 99 View FIGURE 99 )........ .................................................................................... J. ingens ( Pfeffer, 1888) - Gnathopod 1, carpus without a seta or setal cluster at the anterodistal junction of the propodus. Body length at maturity 5–9 mm (thumbedmalesandfemaleswithsetosebroodplates) ( Figs 92 and 95) ............................................17

17 Pereopods 5–7, anterior margin of the propodus expanded proximally for grasping. Antenna 2, thumbed male, posterior margin of article 5 andflagellumdenselyclothedinplumose setae. Gnathopod 2, female, palmof thepropodussinuous ( Fig. 95 View FIGURE 95 ) ........ .................................................................................... J. fenwicki Conlan, 1990 - Pereopods 5–7, anterior margin of the propodus not expanded proximally for grasping. Antenna 2, thumbed male, posterior margin of article 5 and flagellum without plumose setae (though setae are minutely barbed). Gnathopod 2, female, palm of the propoduswithadistinctledgedistalof thepalmardefiningspines ( Fig. 92) .......................... J. justi Conlan, 1990 18 Gnathopod 1, carpus with a seta or setal cluster at the anterodistal junction of the propodus (length about 25% of the carpus length) ( Fig. 93)............................................................................ J. thurstoni Conlan, 1990 - Gnathopod 1, carpus without a short seta or setal cluster at the anterodistal junction of the propodus (e.g., Figs 42–43), or if seta present, length <15% of thecarpuslength (e.g., Figs 60 and 96). ..................................................19

19 Mandibular palp, article 2 withafringeof setaeonthedorsalmargin ( Figs 47 View FIGURE 47 and 53 View FIGURE 53 ) ................................20

- Mandibular palp, article 2 withoutafringeofsetaeonthedorsalmargin ( Figs 41 View FIGURE 41 , 61 View FIGURE 61 and 98 View FIGURE 98 ) ...........................21

20 Uropod 3, inner ramus bearing 1 or 2 spines centrally in addition to the usual spine at the tip ( Fig. 42 View FIGURE 42 ). Antenna 2, large adult male and female, posterior margin of peduncular article 5 and flagellum article 1 bearing dense plumose setae ( Figs 42–43 View FIGURE 42 View FIGURE 43 ) (these absentinsmall juveniles). Gnathopod 2, female propodus, palmarangle bulbous, distantfromthedefiningspines ( Fig. 44 View FIGURE 44 ). .... .................................................................................. J. falcata ( Montagu, 1808) - Uropod 3, inner ramus without central spines (only the usual spine at the tip) ( Fig. 48). Antenna 2, large adult male and female, posterior margin of peduncular article 5 and flagellum article 1 without plumose setae ( Fig. 48) (although setae may be minutely barbed) ( Fig. 50). Gnathopod 2, female propodus, palmarangle acute, close tothedefining spines ( Figs 51 and 52) ........... ................................................................................. J. herdmani ( Walker, 1893) 21 Gnathopods 1 and 2, basis, anteriormarginbearingafringeof setaeorspines ( Fig. 104) ......... J. hartmannae Conlan, 1990 - Gnathopods 1 and 2, basis, anterior margin without an obvious fringe of setae or spines (setae minute or restricted distally ( Figs 37, 60 and 96) ..........................................................................................22

22 Gnathopod 2, female, palm sinuous ( Fig. 97 View FIGURE 97 ). Gnathopod 2, propodus of the major form thumbed male, thumb short with acute tip, spineorspinegroupontheposteriormarginattheoriginof thethumb onaledge ( Fig. 96 View FIGURE 96 ). Southern Hemisphere ......... .......................................................................... J. kjetilanna Vaderand Krapp, 2005 - Gnathopod 2, female, palm concave ( Fig. 37). Gnathopod 2, propodus of the major form thumbed male, thumb long with rounded or incised tip, spine or spine group on the posterior margin at the origin of the thumb residual or absent ( Figs 39 and 60). Northern Hemisphere ............................................................................................23

23 Antenna 2 markedly larger than antenna 1, width up to 2x the width of antenna 1 in the thumbed male. Gnathopod 2, propodus of themajorformthumbedmale, thumbtipnotincised ( Fig. 60 View FIGURE 60 ). North Pacific ............................... J. kimi n. sp.

- Antenna 2 not markedly larger than antenna 1, width up to 1.5x the width of antenna 1 in the thumbed male. Gnathopod 2, propodusof themajorformthumbedmale, thumbtipincised ( Figs 37–39 View FIGURE 37 View FIGURE 38 View FIGURE 39 ). North Atlantic.................. J. pusilla ( Sars, 1894)

Functionalmorphology

Live animal observations on J. marmorata , J. slatteryi , J. falcata and J. herdmani demonstrated the flexibility of the animals and the uses of various appendages and setae (Supplementary Table S11). For example, the first gnathopods could reach sufficiently to clean most of the head, using the medial setae on the propodus, and they were also essential for cleaning the antennae. The carpus, propodus and dactyl could be twisted to function as a plate for the maxillipeds, which then scraped particles from the medial setae for processing by the buccal mass. The setal cluster at the anterodistal junction of the carpus with the propodus, consistently long, short or absent in the 24 species and therefore useful for species identification, appeared to rub the maxillipeds and other mouthparts as well as the anterior medial margin of gnathopod 2. Thus, the setal cluster appeared to have a feeding and cleaning function in conjunction with the medial setae on the propodus. The sequential operation of the buccal appendages was also elucidated, with the upper lip moving in synchrony with the mandible and the maxilla 1 with the maxilliped. While the antenna 2 could provide the same function as antenna 1 in suspension feeding, it also was used as a prod to collect detritus as well as a fighting appendage. Assessment of tube occupation showed that pereopods 3–4 secreted the tube matrix, pereopods 5–7 and the uropods provided purchase, and the pleopods created a posterior to anterior current. Individuals were able to swim by taking a streamlined position with antennae stretched anteriorly but quickly returned to a substrate when released in the water. When J. slatteryi and J. marmorata were provided with a choice of the green alga Ulva , a hydroid or a glass surface for residence, almost all adult females, juvenile females and juvenile males constructed a tube within two days of introduction to a glass bowl and hydroids were the preferred substrate for both species (Supplementary Table S12). No individuals built tubes on the glass surface. Tube appearance was also found to differ with the substrate ( Fig. 105 View FIGURE 105 ), being sewn together among hydroids ( Fig. 105a View FIGURE 105 ), elongated on a hard substrate ( Fig. 105b View FIGURE 105 ) or compacted in dense colonies ( Figs 105 View FIGURE 105 c–e).

Cryptic colouration was variable ( Fig. 106 View FIGURE 106 ), with hatchlings being clear ( Fig. 106a View FIGURE 106 ) and juveniles more pigmented ( Fig. 106b View FIGURE 106 ) but not as fully as adults ( Figs 106 View FIGURE 106 c–l). Colouration varied from chocolate brown to red, depending on the substrate colour, and certain consistencies in patterns were found in the species observed ( J. borowskyae , J. staudei , J. marmorata , J. carltoni , J. falcata and J. herdmani ). The brown banding was widest on the dorsum of segments 3 and 4 ( Figs 106c, e View FIGURE 106 ) and the antennae were banded brown/orange and white ( Figs 106d View FIGURE 106 , f–l). The larger second gnathopods also had dark-light patterns ( Figs 106 View FIGURE 106 f–l) while the smaller legs were less pigmented ( Figs 106 View FIGURE 106 h–l). In the J. staudei and J. marmorata major males photographed, the mottled pattern on the second gnathopods was similar ( Figs 106f, g, i View FIGURE 106 ); so too were the eye-like patterns on the dorsum of segment 2 (visible in J. staudei , Fig. 106e View FIGURE 106 ), which also occured in J. marmorata and J. falcata (not shown). While the second antennal flagella of J. staudei and J. marmorata were only brown banded on segment 1 ( Figs 106f, i, k View FIGURE 106 ), in J. falcata and J. herdmani , all segments were banded to give a candy-cane pattern ( Fig. 106h, j, l View FIGURE 106 ). The wing-shaped pigmentation on the dorsum (visible in J. borowskyae , Fig. 106c View FIGURE 106 ) was intraspecifically variable, though it has been observed in some specimens of J. marmorata and J. falcata . The lateral extensions on the dorsum of segment 4 in the photographed juvenile J. carltoni ( Fig. 106b View FIGURE 106 ) have also been seen in juvenile J. marmorata . The stronger pigmentation on the dorsum of segment 5 in the photographed J. borowskyae ( Fig. 106c View FIGURE 106 ) has also been seen in J. slatteryi (not shown). Afew individuals of J. falcata collected from Audrassalas, France and J. herdmani from Helgoland, Germany were bright turquoise ( Fig. 105f View FIGURE 105 ). The individuals did not appear to behave any differently from the brown and white mottled individuals.

DNAanalysis

The CO1 fragment was amplified or retrieved from 10 out of the 24 currently known Jassa species. The overall mean distance was 0.21 (0.01 SE) with and without Hemijassa goniamera , exemplifying the generally high genetic divergence within the genus. Excluding H. goniamera , which as expected displayed a higher average distance (0.242), the highest distances were found between J. slatteryi and J. herdmani as well as between J. morinoi and J. falcata (0.257 and 0.252 respectively), with the latter being the one with highest average distance (0.233; Table 15). In contrast, the lowest average distance was found in J. marmorata (0.181) which also displayed the lowest pairwise distances with J. valida , J. slatteryi and J. kimi (0.142, 0.152 and 0.154, respectively; Table 15).

The CO1 gene revealed high saturation in the genus Jassa , resulting in long branches and low resolution. Nonetheless, both analyses confirmed the basal position of H. goniamera as a sister taxon to the genus Jassa , which was otherwise monophyletic ( Fig. 107 View FIGURE 107 ). Despite the fact that the ML did not retrieve good support for the nodes belonging to Jassa (not shown), both phylogenies displayed a similar topology, clearly dividing the genus into two main clades that were supported by the BI (100–99% posterior probability). One clade was composed of the primarily European and North Atlantic species ( J. herdmani , J. falcata , J. pusilla and J. laurieae ) whereas the other clade comprised Pacific ( J. kimi and J. staudei ) and trans-hemisphericspecies ( J. marmorata , J. slatteryi , J. morinoi and J. valida ).