Fageapseudes retusifrons ( Richardson, 1912 )

Błażewicz-Paszkowycz, Magdalena, Bamber, Roger N. & Cunha, Marina R., 2011, Apseudomorph tanaidaceans (Crustacea: Peracarida) from mud-volcanoes in the Gulf of Cadiz (North-east Atlantic), Zootaxa 2919, pp. 1-36 : 16-22

Fageapseudes retusifrons ( Richardson, 1912)

( Figs 10–12)

Apseudes obtusifrons Norman & Stebbing, 1886 , 88–89; pl. 18, fig. 2. [Pre-occuppied, non- Apseudes obtusifrons Haswell, 1882 ].

Apseudes retusifrons Richardson 1912 , 584.

Fageapseudes retusifrons Sieg 1983 , 99–100 (synonymy).

Material examined. 25 specimens, including three g (hermaphrodites) with brood pouches ( BMNH.2010.454- 463), Cruise TTR15, Station AT575, Mercator mud volcano, 35°17.903'N 06°38.715'W, 355 m depth, mud breccia, boxcore, 26.07.2005; coll. MRC.

Other GoC records. 8 specimens, Station AT559, Kidd mud volcano, 35°24.777'N 06°43.782'W, 552 m depth, mud, boxcore, 08.08.2004; 11 specimens, Cruise TTR14, Station AT561, Kidd mud volcano, 35°25.602'N 06°44.099'W, 526 m depth, mud, boxcore, 08.08.2004; 8 specimens, Station AT566, Fiúza mud volcano, 35°15.510'N 06°41.702'W, 414 m depth, mud breccia, TV-grab, 09.08.2004; 39 specimens, Cruise TTR15, Station AT576, Mercator mud volcano, 35°17.657'N 06°39.129'W, 428 m depth, mud, boxcore, 26.07.2005. All coll. MRC.

Description. Body ( Fig. 10 A, B) glabrous, dorsoventrally flattened, elongate, 5.7 mm long, eight times as long as wide, narrower posteriorly. Cephalothorax trapezoidal, as long as wide, anterior margin straight and centrally cleft, laterally advanced at attachment of antennules, lateral margin indented anterior to branchial chambers. Eyes absent; eyelobes modified to prominent spine-like apophyses directed anterolaterally. Six free pereonites; pereonite 1 laterally rounded (bulbous), half length of cephalothorax; pereonites 2 to 6 with slender, laterally directed spine-like apophyses anterolaterally, bulbous posterolateral swellings above attachment of coxae and smaller lateral spine-like apophyses just anterior to coxal swellings; pereonites 2 and 6 subequal in length, 1.25 times as long as pereonite 1, pereonites 3, 4 and 5 subequal in length, 1.7 times as long as pereonite 1 (all pereonites respectively 2.2, 1.4, 1.0, 0.9, 0.9 and 0.9 times as wide as long); ventral hyposphenia present on all pereonites except where penial tubercle developed on pereonite six; some specimens without hyposphenia on pereonites 3 and 4. Pleon twice as long as cephalothorax, of five free subequal rectangular pleonites bearing pleopods (easily detached), plus pleotelson; pleonites 1.5 times as wide as long, laterally expanded by spiniform apophyses. Pleotelson long and slender, widest posteriorly, 0.4 times length of whole pleon, 2.7 times as long as wide.

Antennule ( Fig. 11 A). Peduncle 4-articled, proximal article elongate, 4.1 times as long as wide, outer margin with tufts of penicillate setae proximally and at midlength, and one subdistal simple seta; second article 0.3 times as long as article 1, with distal pair of penicillate setae, and sparse inner and outer simple marginal setae; third article three-quarters length of second, with inner and outer simple distal setae; fourth article one-third as long as third, with one distal seta. Main flagellum of six segments, segments 3, 4 and 6 bearing single aesthetascs; accessory flagellum of two segments.

Antenna ( Fig. 11 B) proximal peduncle article without apophyses; article 2 bearing elongate squama with nine simple marginal setae of varying lengths; peduncle article 3 as long as wide, with one seta; articles 4 and 5 equal in length, and 4.5 times as long as article 3, with one and five distal penicillate setae respectively. Flagellum of four segments.

Mouthparts. Labrum ( Fig. 11 C) rounded, simple, distally setulose; sharp epistome present. Right mandible ( Fig. 11 E) bearing pointed, crenulated pars incisiva, setiferous lobe with six bifurcate setae, pars molaris strongly recurved, distally pointed and with fine denticulations; mandibular palp of three articles, proximal article twice as long as wide and naked, article 2 slightly curved, 2.7 times as long as article 1 with five simple inner setae in distal quarter; article 3 one-quarter length of article 2 with three shorter and one longer distal simple setae. Left mandible ( Fig. 11 D) as right but with slender, crenulate lacinia mobilis. Maxillule ( Fig. 11 F) inner endite with five finely setulate distal setae; outer endite with eleven distal spines and two subdistal setae, outer margin finely denticulate; palp of two stout articles, proximal article with outer denticulations, distal article with five distal setae, each terminating in a rounded, setulose bulb. Maxilla ( Fig. 11 G) with serrations on outer margin; outer lobe of moveable endite with two mesially plumose setae on outer margin and five simple or mesially plumose distal setae; inner lobe of movable endite with 13 simple setae; outer lobe of inner endite with five trifurcate spines and adjacent row of four stout plumose setae; inner lobe of fixed endite with rostral row of 18 setae guarding two longer and stouter plumose setae. Labium ( Fig. 11 H) with distally-denticulate outer margin and naked distal margin, palp with dense lateral setules and three simple distal setae. Maxilliped ( Fig. 11 I) basis with one proximal and one distal short setae; palp article 1 with two stout, plumose distal setae; palp article 2 about twice as long as wide, with eight simple and three plumose setae on inner margin, outer margin with simple distal seta; palp article 3 with two shorter and four longer setae in two rows along inner margin; palp article 4 with six distal setae. Endite ( Fig. 11 I’) with compound (finely denticulate) inner caudodistal seta, slender simple subdistal seta and slender, spatulate, distal spines, and six coupling hooks. Epignath ( Fig. 11 J) large, cup-shaped, with inner lobes and finely denticulate distal seta.

Cheliped ( Fig. 12 A) slender. Basis 2.3 times as long as wide, dorsal margin with proximal plumose seta and two fine, simple distal setae, ventrally with two plumose setae in proximal half, stout spine in distal half and subdistal plumose seta; exopodite absent. Merus reflexed, narrowing proximally, with single dorsodistal plumose seta, ventral shoulder with spine-like apophysis with three adjacent simple setae. Carpus 3.4 times as long as wide, with two longer and four shorter simple setae along ventral margin, single fine dorsodistal simple seta. Chela fingers as long as palm, ventral margin with three setae, dorsal margin sparsely setose; cutting edge of fixed finger with row of four setae alongside seven distal “teeth”, triangular proximal apophysis with adjacent tuft of three setae, distal claw sharply pointed; dactylus with five fine setae but no apophyses on cutting edge, three subdistal setae.

Pereopods: Pereopod 1 ( Fig. 12 B) with pronounced spine-like apophysis on coxa. Basis slender, 4.8 times as long as wide, with sparse setae along dorsal and ventral margins and longer ventrodistal seta; exopodite absent. Ischium with two simple ventrodistal setae. Merus less than half as long as basis, with two midventral setae, ventrodistal spine and adjacent seta, and three dorsodistal simple setae. Carpus 0.8 times as long as merus, ventrally with four slender, curved spines, dorsally with four setae in distal half and slender dorsodistal spine. Propodus just shorter than merus, ventral margin with five spines, dorsally with three setae in distal half and slender dorsodistal spine. Dactylus with two dorsal fine setae and two ventral denticulations; unguis one-third as long as dactylus, both together 0.9 times as long as propodus.

Pereopod 2 ( Fig. 12 C) more slender than pereopod 1. Coxa without spiniform apophysis. Basis 5.1 times as long as wide with fine dorsoproximal seta. Ischium with one ventral seta. Merus 0.2 times as long as basis, with three distal setae. Carpus elongate, 2.3 times as long as merus, with two simple and one plumose ventral setae in distal half, paired dorsodistal setae and inner distal seta. Propodus two-thirds as long as carpus, with three ventral strong setae and three dorsodistal fine setae. Dactylus slender with fine mid-dorsal seta, unguis slender, almost as long as dactylus, the two together 1.35 times as long as propodus.

Pereopod 3 ( Fig. 12 D) similar to pereopod 2, but basis with proximal penicillate setae, carpus without ventral plumose seta, propodus with slender dorsodistal spine longer than dactylus.

Pereopod 4 ( Fig. 12 E) basis 4.8 times as long as wide, with single dorsoproximal and midventral penicillate setae; ischium with one ventral and two dorsal setae; merus just less than half as long as carpus, with three ventrodistal and one dorsodistal setae; carpus with ventrodistal to distal crown of seven setae more than half as long as propodus; propodus 0.9 times as long as carpus, with mid-dorsal penicillate seta, dorsodistal tuft of four shorter and one longer finely denticulate setae and denticulate spine adjacent to dactylus; dactylus plus claw as long as propodus.

Pereopod 5 ( Fig. 12 F) proximally similar to pereopod 4, carpus with two ventrodistal and two dorsodistal setae; propodus 0.7 times as long as carpus, with ventrodistal row of nine short leaf-like, bilaterally-setulose spines; dactylus and unguis slender, together longer than propodus.

Pereopod 6 ( Fig. 12 G) similar to pereopod 5, but ventrodistal leaf-like propodal spines extending around distal margin of article.

Pleopods uniramous ( Fig. 12 H) or biramous (cf. Bäcescu & Guţu 1971, fig. 2). Basis elongate, naked; rami from one-third as long to as long as basis with one to four distal setae.

Uropod ( Fig. 12 I) biramous, both rami filiform, multi-segmented. Basis with one seta distally; exopod less than half as long as endopod, with six segments; endopod elongate, 1.7 times as long as pleotelson, with about 10 segments.

Oostegites, when present, occur on pereopods 1 to 4.

Remarks. The present material is taken from depths between 355 and 552 m, slightly south-west of the typelocality which is “west of the Straits of Gibraltar ” (35°50’N 05°26’W) at 234 m ( Norman & Stebbing 1886); other records are from the Mediterranean, off Monaco and Corsica ( Bäcescu & Guţu 1971; Stephensen 1915) and Libya (Bamber, unpubl.) with an overall recorded range of 220 m to 740 m.

Owing to the rediscovery of this species in the close vicinity of the type-locality, we have redescribed it in detail above. The description agrees with both the incomplete description of Norman and Stebbing (1886, as Apseudes obtusifrons ) and that of Bäcescu & Guţu (1971) based on material from the Mediterranean.

Fageapseudes retusifrons is a sequential protogynous/simultaneous hermaphrodite: the specimens above labelled g have oostegites and a male penial tubercle, and usually (but not always) biramous pleopods. Less mature specimens (including juveniles and some with oostegites or a brood-pouch) are without the tooth-like apophysis on the cheliped fixed-finger, and have fewer, often uniramous pleopods, or no pleopods at all.

Jóżwiak and Błażewicz-Paszkowycz (2007) described a new genus, Collossella , for their Antarctic species C. suprema , and included Apseudes bicornis Kudinova-Pasternak, 1973 in their new genus (this species having been moved previously to Fageapseudes by Bäcescu 1978b). The two genera were distinguished on the basis of the presence ( Collossella ) or absence ( Fageapseudes ) of an exopodite on the cheliped (absent on pereopod 1 in both), the presence of five pairs of pleopods ( Collossella ) or fewer pairs of reduced pleopods ( Fageapseudes ) in females, the presence of four ( Collossella ) or only one ( Fageapseudes ) pair of oostegites, the presence of two ( Collossella ) or four ( Fageapseudes ) segments in the antennular accessory flagellum (although two are shown for Fageapseudes by Bäcescu & Guţu 1971), and the presence of spines and setae ( Collossella ) or spines only ( Fageapseudes ) on the ventral margin of the carpus of pereopod 1.

In fact, the present material of F. retusifrons shows oostegites present on each of pereopods 1 to 4, two segments in the antennular accessory flagellum, as well as the intraspecific variability in pleopod development.

In addition to the species mentioned above, Bamber (2007b) described Fageapseudes brachyomos from the Kurile-Kamchatka Trench. F. brachyomos has an exopodite on the cheliped (like Collossella ), as well as an exopodite on pereopod 1 (like no other species of these genera), five pairs of pleopods (like Collossella ), four segments in the antennular accessory flagellum (like Fageapseudes sensu Jóżwiak & Błażewicz-Paszkowycz, 2007 but not F. retusifrons ), and both spines and setae on the ventral margins of both carpus (like Collossella ) and propodus (like no other species of these genera) of pereopod 1, falling quite between the “distinctions” of these two genera.

It is therefore concluded that Collossella is a junior synonym of Fageapseudes , a genus in which the cheliped and pereopod 1 are with or without exopodites (depending on the species), with two to four segments in the antennular accessory flagellum (depending on the species), four pairs of oostegites, and interspecific variation in the length of the articles and of the setation/spination of pereopod 1.

Family Sphyrapodidae Gu ţ u, 1980

Subfamily Sphyrapodinae Gu ţ u, 1980

Figures

FIGURE 11. Fageapseudes retusifrons, A, antennule; B, antenna; C, labrum; D, left mandible, distal; E, right mandible; F, maxillule; G, maxilla; H, labium; I, maxilliped with I’, detail of endite; J, epignath. Scale lines = 0.1 mm for A, B, H – J; 0.01 mm for C – G.

FIGURE 12. Fageapseudes retusifrons, A, cheliped; B to G, pereopods 1 – 6 respectively; H, pleopod; I, uropod. Scale lines = 0.5 mm for A – G, 0.1 mm for H, I.