Hemimysis anomala G. O. Sars, 1907

Wittmann, Karl J., Ariani, Antonio P. & Daneliya, Mikhail, 2016, The Mysidae (Crustacea: Peracarida: Mysida) in fresh and oligohaline waters of the Mediterranean. Taxonomy, biogeography, and bioinvasion, Zootaxa 4142 (1), pp. 1-70 : 11-13

Hemimysis anomala G. O. Sars, 1907

Fig. 3

Hemimysis anomala G. O. Sars, 1907 . Short selection from 306 references: Băcescu 1940; Daufresne et al. 2007; Porter et al. 2008; Wittmann & Ariani 2009; San Vicente 2010; Daneliya & Petryashev 2011; Daneliya et al. 2012; Golaz & Väinölä 2013; Wittmann et al. 2014; Roth 2015.

Material examined (all samples from Mediterranean drainage, Rhône system, leg. K. J. Wittmann). 5 M ad. 5.0– 7.4 mm, 1 F subad., 5 imm., 4 juv., southern France, left bank of the river branch Grand Rhône at Port St. Louis, at Rhône km 323.2, 43.3827N 004.8073E, altitude 0 m, sea distance 6 km , 3–4 m depth, stones and mud, v = 0 m/s, S = 0.1–3.5, 426–6300 µS/cm, 22.5–21.7°C, pH 7.63–7.28, 7.35– 6.55 mg O2/l, 11–12°d, 17–32 NTU, bottle traps exposed over night, 17/ 18 June 2009 , NHMW reg. no. 25703; 1 M ad. 6.1 mm, 1 F subad., southern France, left bank of the river branch Petit Rhône at Tiki , 43.4512N 004.3977E, sea distance 150 m , 1.5–2.5 m depth, boulders with algae and gravel, strong wind-driven ( Mistral ) waves, v = 0–0.2 m /s, S = 1.5–1.7, 3040–3480 µS/cm, 23.7– 21.6°C, pH 7.93–7.65, 7.25– 6.40 mg O2/l, 25–17 NTU, bottle traps exposed over night, 19/ 20 June 2009 ; 8 F ad. 6.4–8.6 mm, 14 M ad. 6.0– 8.7 mm, 35 F subad., 6 M subad., 53 imm., 110 juv., southern France, right bank of Rhône River, ca. 2 km south of Beaucaire, at Rhône km 269.2, 43.7876N 004.6486E, altitude 8 m, sea distance 61 km , 2–2.5 m depth, v = 0.05–0.15 m /s, S = 0.1, 356 µS/cm, 21.5°C, pH 6.9, 6.16 mg O2/l, 9°d, 99 NTU, bottle traps exposed over night, 15/ 16 June 2007 , NHMW 25702 ; 1 M ad. 7.9 mm, 1 F subad., 1 M subad., 3 imm., eastern France, right bank of Rhône River below weir near Wievroz , 45.8126N 005.0919E, altitude 179 m, sea distance ca. 352 km , 2–4 m depth, boulders and gravel, v = 0.2–0.3 m /s, S = 0.1, 294–304 µS/cm, 21.2–21.3°C, pH 7.32–6.78, 5.58– 4.77 mg O2/l, 8°d, 24–19 NTU, bottle traps exposed over night, 29/ 30 June 2009 ; 1 M imm., eastern France, left bank of Rhône River at re-confluence with its small side branch near Chateaufort , 46.9299N 005.8247E, altitude 252 m, sea distance ca. 464 km , 0.2–3 m depth, bank macrophytes, Myriophyllum , detritus, soft bottom, v = 0.1–0.3 m /s, S = 0.1, 285 µS/cm, 19.8°C, pH 8.06, 5.85 mg O2/l, 8°d, 17 NTU, hand net, 30 June 2009, day ; 175 juv., Switzerland, Lake Geneva, yachting harbour near Geneva, 46.2303N 006.1878E, altitude 371 m, sea distance ca. 531 km , 1.5–4 m depth, boulders with Myriophyllum and Zannichellia , S = 0.1, 269 µS/cm, 21.2°C, pH 8.29, 7.66 mg O2/l, 8°d, 0 NTU, hand net, 30 June 2009, day , NHMW 25704.

Description ( Fig. 3 ). Hemimysini with eyes well developed, cornea large, globular; eyestalks short ( Fig. 3 A). Antennal scale suboval, terminally rounded; inner and outer margins without spines, densely setose except for the smooth proximal half of the outer margin; terminal segment is only 3–7% scale length; antennal sympod with dorsal lobe projecting anteriorly above and shortly beyond basal segment of endopod ( Fig. 3 B). Rostrum very short, almost missing, its form sinusoid ( Fig. 3 C) or forming a terminally rounded, wide angle ( Fig. 3 A). Maxillary palpus with transversely flattened terminal margin bearing 4–6 setae and 10–13 articulate spines (spine-like setae) in between. Carapace almost smooth ( Fig. 3 C); neck, however, strengthened by cuticularized bars along median portions of the cervical sulcus; 4–6 cervical pores directly in front of this reinforcement; almost straight series of about 25–35 cardial pores transversely crossing above the heart. A framework of cuticularized bars strengthens the thoracic sternites ( Fig. 3 D); apart from this the sternites are smooth, except for a number of minute, spine-like scales on the (as usual) anteriorly directed lobe of the first thoracomere ( Fig. 3 D). First thoracic endopod without endite on merus; its epipod leaf-like, without seta ( Fig. 3 D); carpopropodus of endopods 3–8 with 5–6, (5)–6, 6, 6, 6, or 5–6 segments, respectively; claw very strong ( Fig. 3 D) in endopods 1 and 2, whereas weaker, but always distinct ( Fig. 3 E) in endopods 3–8. Basis of all thoracic exopods with well rounded outer corner; flagellum 8- segmented in exopods 1 and 8, but 9-segmented in exopods 2–7, not counting the large intersegmental joint between basis and flagellum which may be mistaken as a segment. Penes normal, of moderate size, each with 8–11 curved setae around the ejaculatory opening. Male pleopods 3–5 each with large, 2-segmented sympod; male pleopod 3 with small, unsegmented endopod, and with rudimentary, minute, knob-like exopod ( Fig. 3 F); pleopod 4 with small, 2-segmented endopod and with long, 6-segmented exopod showing two large modified setae, one each on penultimate and terminal segment ( Fig. 3 G); pleopod 5 well-developed, setose, biramous, its exopod 3- to 4- segmented, its endopod 2- to 4-segmented ( Fig. 3 H). Scutellum paracaudale well rounded, sinusoid in both sexes ( Fig. 3 J, K). Endopods of uropods with 6–9 spines in linear series from subbasal to subterminal portions of inner margin ( Fig. 3 L). Statoliths composed of vaterite. Telson rhombohedral, terminally truncate, i.e. without apical cleft ( Fig. 3 M); lateral margins each with 14–19 spines, not counting the pair of large latero-apical spines; terminal margin with 11–16 laminar, apically acute processes. Body colour bloody-red, pink to translucent, often with ivoryyellowish tinge; intensively red upon expanded chromatophores, whereas nearly translucent with numerous dark red spots upon contracted chromatophores. Apart from these short-term variations the colours become generally intensified with increasing body size (age) ( Salemaa & Hietalahti, 1993).

Bionomy. Adult body size mostly 6–11 mm, total range 5–17 mm; adult males on average slightly smaller than females. The species is strongly euryhaline, inhabiting a salinity range of S = 0–19, mostly in less than 10 m to a maximum of about 50 m depth ( Băcescu 1954, Zhuravel 1960, Komarova 1991, Kelleher et al. 1999). During daytime it is strongly photophobic, (epi)benthic, gathering in swarms in shelters on the bottom. At night it swims more actively, at a greater distance from the bottom, often up to the surface. The diurnal vertical migration is clearly determined by the factor light ( Borcherding et al. 2006). Near sunset, juveniles apparently emerge earlier at higher light levels compared to adults (Boscarino et al. 2012). Hemimysis feeds on detritus, algae, and zooplankton ( Băcescu 1954, Borcherding et al. 2006). The mysids adapt their feeding behaviour to environmental conditions and to the availability of pelagic and benthic food sources ( Marty et al. 2012). The portion of zooplankton consumed increases with increasing body size ( Borcherding et al. 2006). The omnivorous habit of the species together with voracious predatory feeding of the adults may considerably affect the zooplankton composition ( Ketelaars et al. 1999). Hemimysis is often found in the stomach of perch, pikeperch, and various other species of fish ( Kelleher et al. 1999, Borcherding et al. 2006, Brooking et al. 2010, Lantry et al. 2012). Consumption by fish may show strong quantitative variations between seasons and years (Lantry et al. 2012). In the northern Black Sea and in the northern Baltic, H. anomala breeds from April to October ( Băcescu 1954, Komarova 1991, Salemaa & Hietalahti 1993), in the alpine Lake Geneva from March to October ( Golaz & Väinölä 2013). Numbers of eggs per brood are mostly in the order of 6–35, total range 2–70, with strong variations according to body size, season, and locality ( Ketelaars et al. 1999, Borcherding et al. 2006, Pothoven et al. 2007, Marty 2008, Golaz & Väinölä 2013, Borza 2014). H. anomala is clearly a warm season breeder ( Wittmann 1984) with young being produced from spring to autumn and the overwintering generation being born in autumn and reproducing in spring. In an artificial embayment of the Hungarian Danube, it produces four generations per year and shows very high fecundity, particularly by the overwintering generation with a mean of 43 young per breeding female ( Borza 2014). Dumont & Muller (2009) reported that the species reproduces in waters of Alsace (NE-France) only three times a year, in March/April, June/July, and September/October. Here the overwintering population starts to reproduce in early March, when the water warms to 7–8°C.

Distribution ( Fig. 2 ). This Pontocaspian endemic was originally confined to the lower reach of rivers, to estuaries and to coastal 'marine' environments of the Caspian, Black, and Azov Seas ( Băcescu 1937, 1954; Derzhavin 1939; Mordukhai-Boltovskoi 1960; Băcescu et al. 1971; Komarova 1991). By intentional transplantations and by non-intentional modes of areal expansion H. anomala reached tributaries and coastal waters of the NE-Atlantic, including waters of Ireland plus England, and tributaries of the Bay of Biscay, North Sea and Baltic. It also reached tributaries of the NW-Mediterranean, Lake Aral and even the Great Lakes of North America (see ‘Discussion’).

Figures

FIGURE 2. Distribution of Hemimysis anomala G. O. Sars, 1907, and Mesopodopsis slabberi (Van Beneden, 1861), in tributaries and coastal waters of the Mediterranean and Black seas. Data original and from 135 literature sources.

FIGURE 3. Hemimysis anomala G. O. Sars, 1907, from the Rhône River at river-km 269, females with 9.2 mm (A) or 8.6 mm (J, L, M), and male with 8.7 mm (B – H, K) body length. A, habitus of female, dorsal; B, left antenna, dorsal; C, carapace expanded on slide, dorsal, pores not to scale; D, thoracic sternites 1 – 8 (ventral) with first thoracopod (caudal); E, ' tarsus' of left thoracic endopod 3, rostral; F, male pleopod 3, rostral; G, male pleopod 4, caudal; H, male pleopod 5, caudal; J, K, posterior margin of sixth pleonite in female (J) or male (K), lateral; L, right uropod, ventral; M, telson, dorsal.