Mesopodopsis slabberi ( Van Beneden, 1861 )

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 : 6-10

Mesopodopsis slabberi ( Van Beneden, 1861)

Fig. 1

Short selection from 39 synonymy statements with a total of 425 references:

Podopsis Slabberi Van Beneden, 1861 : Marcusen 1867; Marion 1894; Masi 1906; Hess 1910. Mysis Slabberi : Goës 1864.

Podopsis pontica Czerniavsky, 1870 : nomen nudum (in synonymy lists often cited as 1869). Macropsis Slabberi : Sars 1877; Carus 1885; Gourret 1894; Sudry 1910; Percival 1929 (partim: 102).

Podopsis (Mesopodopsis) Slabberi : Czerniavsky 1882a, 1887.

Podopsis (Parapodopsis) Goësi Czerniavsky, 1882a .

Podopsis (Parapodopsis) cornuta Czerniavsky, 1882a, 1887 .

Podopsis (Parapodopsis) Goesi : Czerniavsky 1887.

Parapodopsis cornuta: Butchinsky 1885, 1890 ; Sowinsky 1894; Retzius 1910; Knipowitsch 1925.

Parapodopsis cornutum: Kowalevsky 1889 ; Gaskell 1908.

Macropsis slabberi: Scott 1888 ; Graeffe 1902; Zimmer 1915b; Mazoué 1931; Nekrasova & Rakitina 1968.

Leptocaris Slabberi : Aurivillius 1898a, 1898b.

Mesopodopsis Slabberi : Norman & Scott 1906; Norman 1907; Colosi 1929; Fage 1933; Nouvel 1943.

Podopsis slabberi: Van der Sleen 1920 ; Gauthier 1928; Stammer 1932 (partim: 562).

Mesopodopsis slabberi: W. M. Tattersall 1922, 1927 (partim: Port Said); Colosi 1929; Băcescu 1941; Ariani 1967; Daneliya 2002; Kocataş et al. 2003; San Vicente 2010; Wittmann et al. 2014.

Material examined ( southern France , hand net, leg. K. J. Wittmann, if not stated otherwise; among 85 Mediterranean samples inspected, only those from salinity S <5 are listed). 27 F ad. 7.5–9.5 mm, 97 M ad. 6.5–9.6 mm, 106 F subad., 30 M subad., 58 imm., 16 juv. (additional ~30,000 specimens sorted only by taxon), accompanied by 2 Limnomysis benedeni and 3 Diamysis lagunaris , estuary of the Petit Rhône at Tiki, near Rhônekm 337.5; southern bank, 43.4514N 004.3976E, sea distance 180 m, 0.2–1.2 m depth, taken from filiform green algae on boulders, v = 0 m/s, S = 2.2, 4080 µS/cm, 23.7°C, pH 7.71, 7.50 mg O2/l, 14 NTU, 19 June 2009, NHMW reg. no. 25699; 1 F ad. 11.1 mm, Canal d'Arles à Fos, at corner with the canal Liaison Rhône - Fos, 43.4663N 004.8338E, sea distance 7 km, altitude 0 m, 0.3–1.5 m depth, from boulders and concrete walls with filiform algae, and from mud, v = 0 m/s, S = 3.4, 6490 µS/cm, 23.1°C, pH 7.42, 5.75 mg O2/l, 43 NTU, 17 June 2009; 37 F ad. 7.3–9.2 mm, 1 M ad. 6.8 mm, 28 F subad., 13 M subad., 335 imm., 1312 juv., Départment Gard, Canal du Rhône à Sète, at canal-km PK 48 (= K.21), 43.5880N 004.2168E, sea distance 9 km, altitude 0 m, 0.3–1.5 m depth, from bank vegetation, filiform algae, and stones, v = 0 m/s, S = 3.4, 6370 µS/cm, 25.9°C, pH 7.18, 3.29 mg O2/l, 9°d, 66 NTU, 15 June 2007, NHMW 25701 ; 76 F ad. 11.4–14.5 mm, 3 M ad. 8.6–11.6 mm, 1 F subad., 2 M subad., North Adriatic drainage, Italy, delta of Po River, mouth branch Po di Goro, 44.7960N 012.3915E, sea distance 800 m, 0.5–1.2 m depth, from shoots and roots of Phragmites , and from wood, v = 0.05–0.2 m /s, S = 1.4, 2880 µS/cm, 14.2°C, pH 7.67, 9.21 mg O2/l, 28 NTU, 14 Apr. 2012, leg. Ariani & Wittmann, NHMW 25700 .

Description ( Fig. 1 ; Mediterranean materials only, adult females 5–15 mm, males 4–12 mm). Mysini with eyes well developed, cornea globular; eyestalks smooth, cylindrical, 3–4 times as long as cornea ( Fig. 1 A). Peduncle of antennula much more stout in males ( Fig. 1 A) than in females, seta at antero-lateral corner of basal segment in males much shorter than in females; male antennula with accessory flagellum ( Fig. 1 A) having 3–4 small setae curled with their slender distal portions around the basis of the large, straight, smooth, terminal seta; this flagellum and the appendix masculina extend to about same length when stretched anteriorly, not taking account of setae. Antennal segment posteriorly elongate giving the cephalic region its remarkably slender appearance. Antennal scale length subequal to antennular peduncle; scale slender, terminally narrowing, bluntly ending; inner and outer margins densely setose, without spines; apical segment is 13–19% scale length, this segment with 5 plumose setae ( Fig. 1 A). Rostrum short, subtriangular with wide angle, anteriorly well rounded ( Fig. 1 A). Lacinia mobilis of right mandible with 2 large and 4–9 small teeth; median segment of mandibular palp with setae over the distal 62–93% of its length. Carapace smooth ( Fig. 1 A, B), antero-laterally with a pair of spines; carapace with clear cervical constriction, nonetheless cervical sulcus weak, visible only in situ ( Fig. 1 A), but not so in detached material ( Fig. 1 B); total of 20–30 cardial pores in a double wing-like arrangement ( Fig. 1 B, C) as typical for the genus, absence of cervical pores.

Thoracic sternite 1 medially with dense fields of minute hairs, sternite 2 much less hairy, sternites 3–8 medially smooth ( Fig. 1 D); in accordance with the slender body shape of the animals, the sternites are narrow, laterally delimited by holdfasts for the coxae of the thoracopods; in females the distance between these holdfasts increases from sternite 4 to sternite 8 ( Fig. 1 D), thus providing additional space for the marsupium and its content. First thoracic endopod with a large, setose endite from the basis plus a small, often indistinct, endite from the coxa; its epipod elongate, tongue-like, terminally rounded, without seta ( Fig. 1 D); dactylus of endopods 1, 2 setose; claw missing in endopods 1–8; tarsus of endopods 3–7 with 5–8 segments, tarsus of endopod 8 with 4–7 segments; basal to penultimate segments of tarsus 3 each with modified seta at outer distal border, this seta basally barbed and distally armed with minute spines ( Fig. 1 E)—such a seta only on penultimate segment of tarsus 8, yet with the spines larger and more recurved, no such setae on tarsi 4–7; these last tarsi with basally barbed setae (without spines) on their basal segments but not on their terminal 2–4 segments. Basis of all thoracic exopods with well rounded outer corner; flagellum 8-segmented in exopods 1 and 8, whereas 9-segmented in exopods 2–7, not counting the large intersegmental joint between basis and flagellum which may be mistaken as a segment. Large marsupial plates on thoracopods 7, 8; the smaller first oostegites with posterior lobe bearing a number of long, backwards directed setae that are spinose on their distal half; a number of such setae but no such lobe on the large second oostegites; a posterior lobe with only 2 (1–3) such setae present ( Fig. 1 D) also on the sympod of thoracopod 6 in females only. Penes normal, large, each with semicircle of only 4–5 smooth, weakly curved setae anteriorly close to the ejaculatory opening; brush of 3–7 large, barbed setae on the outer face at 31–45% penis length from tip; inner margin with area of acute (in part hair-like) scales.

All pleopods of females and pleopods 1, 2, 5 of males reduced to undivided endopods with indistinct outer apophysis; male pleopods 3, 4 ( Fig. 1 F, G) each with large, 2-segmented sympod, terminal segment of each sympod with area of scales similar in arrangement and relative position to that on the penis; endopod of male pleopods 3, 4 with distinct, setose apophysis directed outwards in subbasal position; male pleopod 3 ( Fig. 1 F) with comparatively large, unsegmented endopod, and with clearly shorter, somewhat reduced, 2- to 3-segmented exopod; pleopod 4 ( Fig. 1 G) with minute, 2- to 3-segmented endopod and with long, 3-segmented exopod, the latter showing a large modified seta plus a much shorter one on its short terminal segment ( Fig. 1 G). On each side of the pleon, the scutellum paracaudale represents a roughly triangular plate with acute tip and undulate upper and lower margins ( Fig. 1 H, J); the scutellum is forward displaced from the posterior margin of the sixth pleonite by slightly less than its own length. Endopod of uropods with blunt projection above statocyst and with one spine below statocyst ( Fig. 1 K). Statoliths composed of fluorite. Telson shorter than last abdominal somite, hirsute shortly behind basal corners, terminally ending with two lateral and one median lobe ( Fig. 1 L), the latter 3–5 times the length of the lateral lobes; only distal 28–60% of lateral margins armed with 3–8 spines, not counting the larger spine at the tip of each lateral lobe; margin of medio-terminal lobe with 20–36 densely set spines (spine-like laminae).

Distribution ( Fig. 2 ). This mysid is known from coastal marine and brackish waters of the Ponto-Azov, Mediterranean and Baltic Seas, and of the NE-Atlantic from Norway to Morocco (59°N-33°N). It occurs in anhaline to hyperhaline conditions, with main occurrence in meso- to polyhaline waters, very rarely found in freshwater. Nonetheless it may be abundant also in coastal marine environments ( Mees et al. 1993). According to Vilas et al. (2006) it shows strong osmoregulatory capability in the range of S = 7–29, with elevated oxygen consumption already at S = 6. Brood pouch young tolerate only more narrow ranges of salinity compared to adults ( Greenwood et al. 1989). Brun (1967) reported Mesopodopsis slabberi from the chlorinity range of 0.5–21‰ (salinity 0.9–38) in the estuary of the Grand Rhône (NW-Mediterranean). For records made by Aguesse & Bigot (1960) in the Rhône delta see below, chapter on Neomysis integer . The above-listed own samples of M. slabberi from the deltas of the Rhône and Po Rivers are in the salinity range of 1.4–3.4. Pesta (1935) reported this species from S = 1.3 in a brackish drain at the Island of Corfu (NE-Mediterranean). None out of 85 Mediterranean samples inspected by us were below this value (S = 1.4–43; 1974–2012).

In the Tamar River estuary at the E-Atlantic coast of SW-England, M. slabberi shows a less wide salinity distribution (S> 5) compared with the co-occurring N. integer ; there is differential distribution of age stages versus salinity, and the population shows a down-estuary movement in winter ( Moffat & Jones 1993, Moffat 1996). In accordance with this, M. slabberi tends to disappear in winter when salinity decreases to values below S = 5 and water temperature below 10°C in a warm-temperate estuary at the coast of Portugal ( Azeiteiro et al. 1999). Its abundance along the Westerschelde estuary at the Dutch-Belgian border is primarily correlated with temperature ( Rappé et al. 2011), whereas primarily with salinity in the Guadalquivir (SW-Spain; Fernández-Delgado et al. 2007) and Gironde (W-France; Castel 1993, David et al. 2005) estuaries.

This species appears to be also rare in fresh-waters draining into the Black Sea. Dedju & Polischtuk (1968) listed it for fresh and brackish, near-deltaic waters of the Danube River , with main occurrence in the "polyhaline" (= probably 'mesohaline' according to the Venice System ) reach. Similarly , Băcescu & Dumitrescu (1958) found masses in oligo- to mesohaline waters off Danube mouth branches. Upon our own sampling in Black Sea coastal waters, thousands of M. slabberi were found in oligo- to mesohaline coastal waters, but only one adult female in true fresh-water (NW-Black Sea , Danube Delta, Canal Tătaru, 45.0765N 029.6342E, sea distance 1.4 km, 0.3–4.7 m depth, S = 0.0–0.1, 376 µS/cm, snorkel diver operated net, 24 June 2008, leg. K. J. Wittmann) . At that coast this mysid species has been found for almost a century ( Borcea 1926; Bâcescu 1940, 1954; Teodorescu-Leonte 1977; Begun & Gomoiu 2007) in the oligohaline waters of the perimarine Lake Sinoe ( Danube Predelta ). Begun & Gomoiu (2007) demonstrated great faunal changes with respect to the 1950–70 s, and attributed this to freshwater input enhanced by humans. The mysids Mesopodopsis slabberi and Paramysis kroyeri (Czerniavsky, 1882) now tend to disappear during episodic freshening of the lake water, and inversely to recolonize this lake upon periods of seawater intrusion through a narrow canal. From their observations, Begun & Gomoiu (2007) concluded that both species are episodically found in fresh-water but are not capable of forming stable populations there.

For the complex history of the taxonomy of M. slabberi see ‘Discussion’.

Figures

FIGURE 1. Mesopodopsis slabberi (Van Beneden, 1861) from the oligohaline reach of the Po di Goro, a mouth branch of the Po River, males with 8.6 mm (A) or 10.7 mm (F – H, L), and female with 13.5 mm (B – E, J, K) body length. A, anterior body region of adult male, dorsal view; B, carapace expanded on slide, dorsal; C, detail of (B) showing cardial pore group, dorsal; D, thoracic sternites (ventral) with caudal faces of left thoracopods 1 and 6; E, ' tarsus' of third thoracopod, rostral face; F, male pleopod 3, rostral; G, male pleopod 4, caudal; H, J, posterior margin of sixth pleonite in male (H) and female (J), lateral; K, uropods, ventral; L, telson, dorsal.

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.