Muvi schmallenbergi gen. nov., sp. nov. (Crustacea, Tanaidacea) from the southeast Australian coast, with comments on the distribution and habitat preferences of Chondropodinae

Key to the genera of the subfamily Chondropodinae (modified after Gut¸u, 2008)

• 1 - Rostrum with marginal denticlesJulmarichardia Guţu, 1989

• - Rostrum without marginal denticles 2

• 2 - Pereopod-1 propodus cylindrical, much longer than thick or the length of the carpus3

• - Pereopod-1 propodus wide, not much longer than thick or the length of the carpus 4

• 3 - Uropod peduncle with strong apophysis dorsallyBamberus Stępień & Błażewicz, 2013

• Uropod peduncle without strong apophysis dorsallyChondropodus Guţu, 2006

• 4 - Antennule inner flagellum bi-segmented5

• - Antennule inner flagellum multi-segmented 6

• 5 - Cheliped exopod tri-articled, with terminal setae Calozodion Gardiner, 1973

• Cheliped exopod uni-articled, without terminal setae Vestigiramus Guţu, 2009

• 6 - Antennule inner flagellum equal in length to outer flagellum Muvi gen. nov.

• Antennule inner flagellum shorter than outer flagellum 7

• 7 - Pereopod-1 exopod with last article round (and large), having more than 20 plumose marginal setaeTrichapseudes Barnard, 1920

• - Pereopod-1 exopod with last article normal (elongated), having clearly less than 20 plumose marginal setae 8

• 9 - Five pairs of pleopodsHoplopolemius Sganga & Roccatagliata, 2016

• - Three pairs of pleopods Zaraza Guţu, 2006

Muvi schmallenbergi sp. nov.

urn:lsid:zoobank.org:act:14743564-C6F2-42CE-A181-CE30F5C5A2C2

(Figs. 1–3)

Material examined. Holotype female (MNV J74649), 4.5 mm, SLOPE 99, Victoria, Off Portland, 38° 31′ 34″ S, 141° 58′ 46″ E, depth 49.6 m, 11 May 1994, Smith-McIntyre grab, coll. G.C.B. Poore. Paratype, female (MNV J74648), 5.9 mm, the same locality, dissected on slides.

Diagnosis. As for the genus.

Etymology. The new species is dedicated to Barbara Schmallenberg.

Description of female (body of holotype, appendages from paratype)

Body (Figs. 1A, 1B) 4.5 mm long. Cephalothorax 21% of total body length; rostrum triangular and pointed (Figs. 1A, 2C); eyelobes pointed with visual elements (Figs. 1A, 1B). Pereon 47% of total body length; pereonites length-width ratio 0.3, 0.4, 0.5, 0.5, 0.5 and 0.3; pereonites 2–5 with dorsoproximal apophyses on lateral margin. Pleon 32% of total body length; pleonites equal in length, about 0.2 L:W, with pointed lateral margins; pleotelson just longer than the last three pleonites combined.

Antennule (Fig. 2A) peduncle article-1 2.1 L:W and 1.9x article-2, with four simple and two penicillate setae on the inner margin and one simple, one plumose seta, and four penicillate setae on the outer margin; single apophysis present in the outerodistal corner; article-2 1.2 L:W and 1.9x article-3, with five simple and two penicillate setae subdistally; article-3 as long as wide, with two simple setae distally; common article short and naked; flagella subequal, each with 12 segments, setation as figured (no aesthetasc present).

Antenna (Fig. 2B) peduncle article-1 short and naked; peduncle article-2 1.7 L:W and 3x article-3, with three minute distal and subdistal setae; squama narrow, 4.5 L:W, with simple subdistal seta and three distal setae; peduncle article-3 0.8 L:W and 0.7x article-4, with two long simple setae distally; article-4 1.2 L:W and 0.9x article-5, with three penicillate distal setae; article-5 1.4 L:W, with two short simple, two long simple, and two penicillate setae distally, and one mid-length simple seta; flagellum of six segments, setation as figured.

Mouthparts. Labrum (Fig. 2D) rectangular with numerous minute setae on distal and lateral margins. Right mandible (Fig. 2E) incisor with four well-calcified triangular teeth; outer margin with tubercles and with minute setae distally. Left mandible (Fig. 2F) outer margin with distally setulose tubercles; incisor with four distal teeth; lacinia mobilis as long as incisor, with four teeth, setiferous lobe with four complex-tip setae; molar broad, distally serrated; palp (Fig. 2G) article-1 1.1 L:W, with five inner setae; article-2 2.1 L:W with outer margin serrated, two simple distal setae and row of about 14 inner setae starting from the middle of the article, decreasing in length towards the distal end of the article; article-3 3.7 L:W, with five outer setae and a row of about 18 setae along the inner margin. Maxillule (Fig. 2H) inner endite with five setae distally (at least three setulated), inner and outer margins serrated, outer margin with tuft of setae and subproximal tubercle; outer endite with eleven spines (one appearing serrated), outer margin setulated. Maxilla (Fig. 2I) outer lobe of moveable endite with two subdistal simple setae and six distal serrated setae, outer margin with microtrichiae; inner lobe of moveable endite with ten serrated setae distally; outer lobe of fixed endite distally with three tri-furcated and three serrated setae; inner lobe of fixed endite with 22 setae (at least five of them serrated). Labium (Figs. 2J, 2K) outer and inner margins with setation distally; palp (Fig. 2K) lateral margins setulated, distally with three simple spines.

Maxilliped (Fig. 2L) coxa naked. Basis 1.1 L:W, with laterodistal seta and three subdistal long setae, additionally outer margin with teeth and inner margin with proximal microtrichiae. Palp article-1 0.4 L:W, with long simple seta on inner margin and one simple seta and two plumose setae on outer margin; article-2 1.2 L:W, with two rows of setae on inner margin (first with 11 setae and second with five setae, at least one seta plumose), and two long laterodistal setae; article-3 about as long as wide, with row of about 10 setae along inner margin (at least one plumose); article-4 1.3 L:W, with row of nine distal setae (at least five of them serrated) and one outer seta. Endite (Fig. 2M) outer margin setulated; inner margin with three coupling hooks and five short plumose setae; distal margin with nine short plumose setae/spines (some with complex tip) and one long plumose seta; subdistal seta simple (not leaf-like).

Cheliped (Fig. 3A) basis 1.1 L:W, with plumose dorsodistal seta, simple seta ventroproximally, one spine ventrally at mid-length and four long setae ventrodistally; exopod of three articles, article-3 with nine plumose setae (drawn as simple for figure clarity); merus 1.2 L:W and 0.7x basis, with one simple seta, one plumose seta, four spines and apophysis ventrally; carpus 0.9 L:W and 1.2x merus, with row of seven setae along dorsal margin, three setae ventrally and distal apophysis; propodus 0.9 L:W and 1.8x carpus, with three short setae dorsally, three setae on outer surface, and one serrated inner spine near dactylus insertion; fixed finger about 0.8x propodus, with two proximal outer setae, four setae ventrally, cutting margin with two long setae near dactylus insertion, four setae distally and small teeth accompanied with minute setae in proximal half; dactylus just longer than fixed finger with two subdistal setae, and row of teeth and spinules along the cutting edge.

Pereopod-1 (Fig. 3B) coxa long and with smooth margins, with two setae; basis 2.2 L:W and 2.0x merus, with two ventral setae and four ventrodistal setae, row of plumose (five) and simple (five) setae along dorsal margin; exopod of three articles, article-3 with 11 plumose setae; ischium with three ventrodistal setae; merus 1.3 L:W and 1.1x carpus, with one dorsodistal spine, one ventrodistal spine, four ventral and three dorsal setae, and four setae on inner surface; carpus 1.1 L:W and 1.1x propodus, with two ventrodistal spines, three setae ventrally, one short seta distally and six setae dorsally; propodus 1.5 L:W and 1.5x dactylus, with three spines and four setae ventrally, and with two spines and two setae dorsally; dactylus 2.9 L:W and x 2.0 unguis, with one dorsal seta and ventral apophysis; dactylus and unguis combined as long as propodus.

Pereopod-2 as peropod-3 (not figured).

Pereopod-3 (Fig. 3C) coxa with one seta; basis 2.1 L:W and 1.8x merus, with tuft of three setae ventrodistally, one simple seta, three penicillate setae dorsally, and three simple setae ventrally; ischium with two ventrodistal setae; merus 1.7 L:W and 1.3x carpus, with one small spine and one larger spine ventrodistally, one dorsodistal seta, one ventral seta, and two ventrodistal setae; carpus 1.2 L:W and 0.65x propodus, with one ventral subproximal spine, two ventrodistal spines, one short seta, two long setae, and three spines dorsodistally; propodus 2.5 L:W and 1.5x dactylus, with three ventroproximal spines, one ventrodistal spine, one dorsal subdistal spine, one dorsodistal spine, one ventral seta, two short ventrodistal setae, two dorsal setae, and one dorsodistal seta; dactylus 3.2 L:W, with ventral tooth, ventrodistal seta, and two dorsal setae; unguis about 0.5x dactylus; together about as long as propodus.

Pereopod-4 (Fig. 3D) coxa with two penicillate setae; basis 2.1 L:W and 2.0x merus, with one ventroproximal seta, two short setae, and one long seta ventrodistally, and two simple setae and three penicillate setae dorsally; ischium with three ventrodistal setae; merus 1.5 L:W and 0.9x carpus, with two short ventrodistal spines, two ventral setae, one ventrodistal seta, and two long dorsodistal setae; carpus 1.8 L:W and as long as propodus, with two short spines and one longer dorsal spine, two ventrodistal spines, two ventrodistal setae, and three dorsodistal setae; propodus 3.3 L:W and 2.0x dactylus, with one penicillate dorsal seta and eight serrated setae distally; dactylus damaged, 2.0x unguis, with two short setae ventrally.

Pereopod-5 (Fig. 3E) coxa with one simple seta and one plumose seta; basis 2.3 L:W and 2.2x merus, with simple ventroproximal seta, one mid-length ventral seta, one plumose seta and three simple setae ventrodistally, dorsal margin with one simple seta, five plumose setae and three penicillate setae; ischium with one plumose seta and one short simple seta ventrodistally; merus 1.7 L:W and as long as carpus, with one short ventrodistal spine, one plumose ventral seta, one simple ventrodistal seta, and one plumose dorsodistal seta; carpus 1.5 L:W and 0.8x propodus, with four spines increasing in size along ventral margin, and one dorsodistal spine, one plumose dorsal seta, and one plumose seta and two simple dorsodistal setae; propodus 2.0 L:W and 1.7x dactylus, with two ventral spines, three ventrodistal serrated minute spines, one serrated dorsodistal spine, and one dorsodistal plumose seta; dactylus with mid-length minute ventral spine, medially and dorsally with one seta, combined length of dactylus with that of unguis 0.9x propodus.

Pereopod-6 (Fig. 3F) basis 3.1 L:W and 3.4x merus, with two dorsal plumose setae and four ventral plumose setae; ischium with one ventrodistal plumose seta; merus 1.3 L:W and 0.6x carpus, with one subdistal plumose seta dorsally and two ventrodistal plumose setae; carpus 1.9 L:W and 0.9x propodus, with two ventrodistal spines, one dorsodistal spine, one ventrodistal simple seta, one distal simple seta, and one dorsodistal plumose seta; propodus 2.2 L:W and 1.2x dactylus, with one mid-length spine ventrally, and at least nine minute serrated spines ventrodistally and dorsodistally, and one dorsal mid-length penicillate seta; dactylus with ventrodistal seta, ventral serration, and three dorsal setae; dactylus with mid-length minute ventral spine, medially and dorsally with one seta, combined length of dactylus with that of unguis 1.1x propodus.

Pleopods (Fig. 3G) basal article 1.7 L:W, with one distal plumose seta; endopod just longer than exopod, with two plumose setae subdistally, seven plumose setae distally, and one dorsal seta, and one ventral mid-length seta; exopod with eleven plumose setae along distal end and one plumose ventroproximal seta.

Uropod (Fig. 3H) basal article 1.8 L:W, with seven simple setae distally; exopod of three segments, segment-2 with two distal setae, segment-3 with three distal setae; endopod 3.7x exopod, of seven segments, some with mid-length setae apparently indicating segment fusion; segment-3 with two distal setae; segment-4 with four mid-length setae, and two penicillate setae, and three simple setae distally; segment-5 with two mid-length setae, and two penicillate setae, and two simple setae distally; segment-7 with two penicillate setae and four simple setae distally; other segments naked.

Distribution. Muvi schmallenbergi is known only from the type locality, offshore Portland (Australia), from a depth of 49.6 m and habitats rich in red algae.

Distribution of Chondropodinae

Geographical distribution

Chondropodinae are most diversified in the Atlantic and represented by 17 species. The highest number of species (six) has been recorded for the relatively restricted areas of the Eastern Gulf of Mexico, Cuba, Haiti, and Southeast Mexico (Richardson, 1902; Gardiner, 1973; Guţu, 1984, 2002, 2006b, 2009). Furthermore, five Chondropodinae are known from East African coasts (Barnard, 1914, 1920; Guţu, 1989b, 2014), and four species were found in West Africa (Guţu, 2006a; Menioui, 2013). The genera of Chondropodinae are widely distributed and usually present in more than one marine basin. For example, Julmarichardia was found in the Mozambique Channel, on the Malaysian coast, in Northwest Australia, and in the Northeast Atlantic. Calozodion was found on the Brazilian coast, off Angola, off Mauritania, in Malaysia, in the Caribbean Sea, and in the Gulf of Mexico (Figs. 4 and 5). Two non-monotypic genera of Chondropodinae, Vestigiramus and Chondropodus, have a restricted distribution. Vestigiramus is represented by three species that occur along the East coast of South America, and Chondropodus, with two species, has been recorded from the coast of Mauritania. The distribution of Chondropodinae is clearly limited to tropical, subtropical, and, to some extent, temperate waters; likewise, they are entirely absent in higher latitudes (Figs. 4 and 5). The most northerly record is held by Julmarichardia dollfusi situated in the subboreal zone (latitude 49° N) off Jersey in the Northeast Atlantic (English Channel) (Guţu, 1989a). Until now, the most southerly records of Chondropodinae have been made by Barnard, who described Julmarichardia deltoides from the Great Fish Point Lighthouse (Port Alfred, South Africa) and Trichapseudes tridens offshore of East London (South Africa) (approximately 33°S; coordinates are not specified in the original descriptions) (Barnard, 1914; Barnard, 1920). As of this record, Muvi schmallenbergi is the southernmost record of the subfamily, found at approximately 38°S. The Atlantic sectors of the Arctic and the Antarctic are among the most studied areas of the World Ocean (Sieg, 1986b; 1986c; Bird, 2010; Błażewicz-Paszkowycz, 2014; Jakiel, Stępień & Błażewicz, 2018); thus, the absence of the Chondropodinae in polar regions cannot be explained by biased sampling efforts.

The longitudinal gradient in diversity, observed in many groups of marine invertebrates (decapods, gastropods, and bivalves) or vertebrates (e.g., fishes), point to a peak in the tropics and a decrease towards the poles (Clarke & Crame, 2010; Rabosky et al., 2018). The highest diversity around the equator is justified by the larger area and the longer evolutionary time of the tropical regions, where diversity is supported by higher rates of speciation and lower extinction rates (Mittelbach et al., 2007; Brown, 2014). Cenozoic glaciations interrupted by interglacial events are stated as the main factor responsible for extinctions of shallow-water taxa in polar regions (Clarke & Crame, 2010; Thatje, 2012). Recolonization of the vacant habitats of the Antarctic shelf is assumed to be limited for tropic or temperate fauna because of their physiological adaptation to warmer waters (Thatje, 2012; Brown, 2014). Hence, Brown (2014) remarked that tropical species and lineages have a long evolutionary history in relatively equable environments and may not tolerate several abiotic stresses (e.g., low temperature and extreme seasonality).

The pantropical and pantemperate distribution of Tanaidacea and their absence in high latitudes has previously been reported for most shallow-water families of Apseudomorpha (Błażewicz-Paszkowycz, 2014) and some plesiomorphic families of Tanaidomorpha, such as Tanaididae, Pseudozeuxidae, Paratanaidae, and Leptocheliidae (Błażewicz-Paszkowycz, Bamber & Anderson, 2012). Sieg (1992) stated that tropical or temperate Tanaidacea that became extinct during glaciations were replaced by deep-sea taxa because of similar temperature regimes in the abyssal and the Antarctic shelf (polar emergence). He argued that tanaidaceans which evolved before the Eocene were theoretically “ready” to colonize vacant Antarctic habitats and that the Antarctic shallow-water tanaidaceans are dominated by phylogenetically young taxa which lack functional eyes, evidencing their deep-sea origin (Sieg, 1992). Błażewicz-Paszkowycz (2014) has supplemented Sieg’s hypothesis by indicating that some tanaidaceans might have survived the glaciations in the deeper shelf or slope refugia or colonized the Antarctic via the Scotia Arc. This idea is strongly supported by the presence of representatives of typically tropical families in Antarctica, such as Paratanais oculatus (Paratanaidae), Allotanais hirsutus (Tanaididae), and Synapseudes aflagellatus (Metapseudidae).

The Arctic is less thermally isolated than the Antarctic, which is surrounded by the Antarctic Circumpolar Current (ACC). Furthermore, it is supported by the transitional zones to the south, where the temperate Atlantic waters merge and mix with the polar waters (Loeng et al., 2005; Stepanjants et al., 2006). Also, warm water masses transported to the Arctic by the Atlantic currents promote the distribution of temperate fauna to the polar zone (McBride et al., 2014; Csapó, Grabowski & Węsławski, 2021). Although the Arctic has a more recent history of glaciation, dated to about 2.5 Ma, than the Antarctic (>20 Ma), the paucity of the temperate and tropical fauna in the Northern Hemisphere is comparable to that of the Southern Hemisphere. Although in the Arctic, the tanaidaceans share some species with the temperate Atlantic and are characterized by a lower level of endemism (Sieg, 1986a), tropical/temperate shallow-water apseudomorphs are still underrepresented, including Chondropodinae (Stępień, Pabis & Błażewicz, 2018) and plesiomorphic families of Tanaidomorpha.