Culexiregiloricus trichiscalida, Gad, 2009

Gad, Gunnar, 2009, Culexiregiloricus, a new genus of Nanaloricidae (Loricifera) from the deep sea of the Guinea Basin (Southeast Atlantic) *, Zootaxa 2096 (1), pp. 33-49 : 37-44

publication ID	https://doi.org/ 10.11646/zootaxa.2096.1.5
persistent identifier	https://treatment.plazi.org/id/2565965F-A63B-0012-FF4A-A622FD69FABC
treatment provided by	Felipe
scientific name	Culexiregiloricus trichiscalida
status	sp. nov.

Treatment

Culexiregiloricus trichiscalida View in CoL sp. nov.

Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 (ventral view, dorsal view, photos of details)

Measurements in Table 1

Type material: Holotypic postlarva, DIVA 2 station 76, MUC 05 (mounted on slide SMF 16897) .

Type locality: Guinea Basin I, 00°50’00’’ S, 05°35’00’’ E, depth 4,141 m, 19.03.2005 GoogleMaps .

Etymology: The species name trichiscalida means hairy scalids.

Description. Holotypic postlarva ( Figs. 1 View FIGURE 1 ; 2 View FIGURE 2 ; 3A View FIGURE 3 ; 4A View FIGURE 4 ) being a fully extended specimen filled with granular tissue. Body length from tip of mouth tube to caudal end, sums up to 285 µm. Maximum diameter of trunk in middle of lorica, is 110 µm. Species of medium size with urn-shaped, rounded, and well-defined lorica. Body divided into mouth cone, introvert, subdivided thorax, and abdomen armoured with massive lorica. Abdomen not compressed dorsoventrally.

Anterior body part composed of non-extendable, unstalked, rigid mouth cone ( Figs. 1 View FIGURE 1 ; 3B View FIGURE 3 , 4A View FIGURE 4 ), extruded and separated transversally from introvert by constriction and row of 8 cuticular plates.

Mouth cone divided into 2 parts ( Fig. 1 View FIGURE 1 ): mouth cone itself, as short proximal basal section (mc) with cuticle peeled off (as an artefact, see Figs. 3B View FIGURE 3 , 4A View FIGURE 4 ) and mouth tube (mt) as long and narrow terminal section. Mouth cone basally surrounded by 8 oral furcae (fc) as supporting structures; 8 oral ridges (or) present, which frame each furca on both sides; furcae as well as oral ridges of identical structure. Mouth tube narrow, funnellike and longer than proximal mouth cone. Mouth opening (mo) terminal on mouth tube. Internal buccal structures well visible starting with 6 small oral stylets (os) arranged ringwise inside mouth. All 6 oral stylets articulating with internal cuticular layer. Mouth cone with long, narrow buccal channel which starts with a closing apparatus behind ring of oral stylets and extending into long well-sclerotized buccal tube (bu), which is partly stiff and partly flexible. Buccal tube 12% longer than mouth cone and extending through brain down to large, round, and muscular pharynx bulb, its inner cuticular layer with characteristic fine transverse single striae or annulation (ann). Posterior part of buccal tube indistinctly triradiate in section, with extra sclerotized longitudinal edges. Buccal tube ends in triradiate prepharyngeal armature composed of 3 primary supporting elements longitudinally fused along their entire lengths with buccal tube. All primary elements also fused transversally forming 3 plates as outer pyramidal unit covering supporting elements of armature. Posteriorly armature with manubrium, anchored deeply inside pharyngeal bulb. In extended specimen (as in holotypic postlarva) pharyngeal bulb located deeply inside trunk at level of interthorax. The 3 corners of triradiate myoepithelial pharyngeal lumen paved with 5 rods of cuticular placoids, which are connected longitudinally with each other.

Spherical introvert (in, Figs. 1 View FIGURE 1 ; 2A, B View FIGURE 2 , 4A View FIGURE 4 , 5 View FIGURE 5 ) densely covered with 7 rows or circles of scalids (6 th row of spinoscalids only developed as protoscalids). First row (cr 1) has 8 more anteriorly oriented clavoscalids, not stronger sclerotized than following spinoscalids.

Clavoscalids ( Fig. 1 View FIGURE 1 ) uniform in structure, but ventral pair slightly smaller; all of them divided into 4 segments; 1 st segment (sg 1) enlarged, oval in section, short and united with swollen base, connected via joint with introvert; 2 nd segment (sg 2) very long, flattened laterally, narrowing posteriorly and covered densely by tiny trichoids (tc); last 2 segments (sg 3, sg 4) small and narrow; terminal segment spine-like. Next rows have spinoscalids oriented posteriorly and with enlarged bases. Fully developed spinoscalids of third to 7 th rows arise from small arched basal plates (bs).

Second row (sr 2) consists of 16 spinoscalids of 2 different types ( Fig. 1 View FIGURE 1 ). Nine being leg-like type A scalids (sr 2 a), longer than clavoscalids and covered densely with trichoids. They consist of 4 segments; 1 st segment (sg 1) enlarged, with separate base, and proximal fringe of small spinules; 2 nd segment (sg 2) as long as 1 st one, narrow and stalk-like; 3 rd segment (sg 3) short end even narrower; 4 th segment (sg 4) spine-like and of same length as third one; distinct hinge joint present between first and second segments. Type A spinoscalids alternat with 7 smaller and shorter type B spinoscalids (sr 2 b) consisting of only 2 segments; 1 st segment bulbous and with fringe of spinules; 2 nd segment rigid, filiform and with numerous fine hairy spinules (ba) scattered over entire length like barbs of a feather. Alternating arrangement of sr 2 -spinoscalids irregular ventrally at midline and dorsally beside midline ( Figs. 2 View FIGURE 2 , 5 View FIGURE 5 ), where 2 type A spinoscalids stand close together, and where 1 type B spinoscalid is lacking.

Third row (sr 3) of scalids also has 16 spinoscalids of 2 different types ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ), but without irregularities in alternating arrangement, because they are equal in number. Both spinoscalid types of this row similar in appearance to type A spinoscalids of 2 nd row but composed of 3 segments only. First segment of 8 type A spinoscalids (sr 3 a) enlarged, with hinge joints at border to 2 nd segment, this segment filiform, covered with trichoids, and 4 times longer than 1 st segment; 3 rd segment spine-like. Eight type B scalids (sr 3 b) clearly shorter than type A spinoscalids; 1 st segment bulbous with dorsal fringe of spinules; 2 nd segment long, filiform, and equipped with tiny spinules; 3 rd segment as long as 2 nd one, sickle-like, basally with ventral tooth, and with numerous fine long hairy spinules scattered over entire length; hinge joints between 2 nd and 3 rd segments bearing 2 lateral spines.

Fourth (sr 4) and 5 th (sr 5) rows each with circle of 30 uniform spinoscalids ( Figs. 1 View FIGURE 1 , 3c View FIGURE 3 ) which are more filiform and hair-like than spinoscalids of 2 nd and 3 rd rows. All of these consist of 3 segments; basal segment short and slightly enlarged; 2 nd and 3 rd segments elongated, connected via indistinct hinge joints. Long spinoscalids of 6 th (sr 6) row are missing (which is a characteristic feature of postlarvae in general, see discussion), only developed as 30 wart-like protoscalids located in distinct gap between 5 th and 7 th rows (marked with an arrow in Fig. 3C View FIGURE 3 ). 7 th row (sr 7) has 30 bristle-like spinoscalids, which are not divided into segments, but with enlarged bases and long filiform distal parts which have lateral margins covered with fine trichoids. Eighth row of scalids with 30 small, distinct and posteriorly oriented sharply pointed, tooth-like protrusions.

Thorax ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ) subdivided into 3 subregions: antero-, inter-, and posterothorax. Anterothorax (th 1) with 1 st row of 15 thoracic basal plates, zone between this row of basal plates and the next with flexible cuticle. Basal plates of 1 st row scale-like, located immediately behind 8 th row of scalids of introvert, so that there is no clear separation between introvert and thorax. Seven triangular type A basal plates (bp 1 a) of 1 st thoracic row alternate with 8 type B basal plates (bp 1 b) which have double tooth-like appearance.

The next 2 rows of basal plates ( Fig. 1 View FIGURE 1 ) constitute the interthorax (th 2) or neck, and carry 8 single and 7 paired trichoscalids arising from 2 rows of basal plates. Eight type A basal plates (bp 2 a) are small in size, smooth, and shield-like carry single type A trichoscalids (tr a), which have enlarged angular bases (absent from the 2 midventral ones). Type A basal plates alternate with 7 type B basal plates. Upper basal plates of 2 nd row (bp 2 b) are large and trapeziform, whilst lower basal plates of 3 rd row are hexagonal. All trichoscalids indistinct and similar in structure: narrow, flat, with finely serrated lateral margins and with capillary central channel running inside the median axis, indistinct erect margin present perpendicular to central channel equipped with spinules; tips ending indistinctly in 4 spinules.

Upper type B trichoscalids (tr 1 b) connects with basal plates via small triangular shafts, lower type B trichoscalids (tr 2 b) inserting directly on basal plates and being slightly shorter than upper ones. Upper and lower type B trichoscalids appear as “paired trichoscalids” with separate, not fused, bases. Third row has only 7 trapeziform type B basal plates (bp 3 b), which carry trichoscalids. Midventrally, there are 2 single lower slightly smaller type A trichoscalids on both sides of central axis; middorsally, there is a pair of upper and lower type B trichoscalids.

In summary, the number and arrangement of scalids (cs = clavoscalids, ss = spinoscalids) in rows (cr = row of clavoscalids, sr = row of spinoscalids) on the introvert and of basal plates (= bp) together with trichoscalids (= tr) on the thorax can be expressed in the following formula:

Figure 5 View FIGURE 5 demonstrates the arrangement of scalids on the introvert as a polar coordinate diagram.

Transition zone between interthorax and loricate abdomen ( Fig. 1 View FIGURE 1 ) formed by short and flexible posterothorax (th 3) not having any appendages or plates, but having thin cuticle and being as wide as interthorax.

Abdomen ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ) massively armoured with sclerotized lorica (lo), divided longitudinally into 8 plates and 8 intercalary plicae (ip). Lorica slightly depressed dorsoventrally, surface of cuticle completely covered with distinct square-like ( Fig. 3E View FIGURE 3 ) as well as honeycomb ( Fig. 3F View FIGURE 3 ) ultrasculpture (us). Plates with reinforced lateral margins (rfl, Fig. 2 View FIGURE 2 ). Plicae have distinct reinforced and folded lateral margins as primary folds and longitudinally subdivided along median axis by weakly developed secondary fold. Anterior margins of intercalary plicae form 2 crescents in some of their corners they are folded so tightly together that it appears as additional small “spikes” (see Fig. 3D View FIGURE 3 and in Fig. 4A View FIGURE 4 , but proof of their absence is given in Fig. 4B View FIGURE 4 ). Plates and plicae penetrated by small pores (gp), which connect with unicellular subcuticular epidermal glands. Each plate with 2–8 transversal undulations (upwellings of cuticle, tu, Fig. 1 View FIGURE 1 ; 2 View FIGURE 2 , 4B View FIGURE 4 ) and armed with lorica spikes (ls, Figs. 3D View FIGURE 3 ) of medium size along anterior edge.

Schema of lorica structures of 1 body half, from ventral plate (vp) to middorsal plate (dp), other body half identical because of bilateral symmetry (dlp = dorsolateral plate, lp = lateral plate, ip = intercalary plica).

All spikes of same structure and length ( Figs. 1 View FIGURE 1 , 3D View FIGURE 3 ); with 1 indistinct window (ws, part of thin translucent cuticle), lateral and transversal reinforcements of thicker cuticle (bridge of lorica spikes, bg); internally along their entire length spikes equipped with 1 long duct (gd) of subcuticular epidermal gland. Large, shield-like, ventral plate ( Fig. 1 View FIGURE 1 ) laterocaudally with indistinct locking apparatus (ea), caudal end of plate flanked by massive cuticular longitudinal ridge-like protrusion (pr). Eight distinct papillate flosculi (fl) present on dorsal lorica ( Fig. 2 View FIGURE 2 ) near caudal end, 3 of them forming a cluster on both dorsolateral plates (lp2, lp2'). Dorsal plate narrow anteriorly becoming wider posteriorly and ends as though cut off, bearing two additional papillate flosculi (fl, Fig. 2 View FIGURE 2 ); in caudal half lateral margins folded up and extending over remaining portion of plate. Well-defined, small, and pointed anal cone (ac) with terminal anus (an).

Remarks: The body cavity of the holotypic postlarva investigated is filled with granular cells and tissue, which is strongly coloured by Bengal Pink so that no clear view can be gained on the internal organs, except for the highly dense buccal structures and the strong and muscular pharyngeal bulb.

Differential diagnosis. The lorica of Culexiregiloricus trichiscalida gen. et sp. nov. strongly resembles the lorica of Spiniloricus turbatio ( Heiner & Neuhaus 2007) . In both species the lorica is composed of 8 mostly narrow plates plus 8 intercalary plicae. Apart form this similarity the lorica of S. turbatio is equipped with short spikes and additional spikes in each corner in the anterior part of the plates ( Heiner & Neuhaus 2007), which are lacking in C. trichiscalida gen. et sp. nov. In C. trichiscalida the reinforced anterior margins of most intercalary plicae are folded so tightly together that it appears to have additional small ’spikes’ as demonstrated in Figs. 3D View FIGURE 3 and 4A View FIGURE 4 . However, the CLSM image with higher solution and slight 3D effect ( Fig. 4B View FIGURE 4 ) shows that this impression of small ‘spikes’ is an artefact. The intercalary plicae as thinner, wide, and loose parts of cuticle between the plates may be a general feature of postlarvae belonging to the Nanaloricidae ( Heiner & Neuhaus 2007) , because the adults developing inside have a larger body size than the postlarvae they moult from ( Gad 2004a, b; Kristensen & Gad 2004, Heiner & Neuhaus 2007). Despite the lorica, S. turbatio share more similarities with Nanaloricus -species (see genus diagnosis in Heiner & Neuhaus 2007) than C. trichiscalida gen. et sp. nov., which is more closely related to Armorloricus -species (see Table 3).

Length of: Length of: Length of:

Body (total) 285 Lorica 135 tr1 30

Mouth cone 85 Lorica spikes 6 tr2 30

Mouth tube 40 cr 1 67 tr3 25

Buccal tube 95 sr 2 a / sr 2 b 75 / 50 Maximum width of:

Oral stylets 7 sr 3 a / sr 3 b 80 / 66 Buccal tube 2

Internal armature 12 sr 4 75 Lorica 110

External furca 15 sr 5 70 Ventral plate 45

Introvert 30

– Other plates 22–30

Thorax (unit of) 50 sr 65 Plicae 8–13 Anterothorax 22 7 Diameter of:

sr 8 7

Interthorax 13 Pharynx bulb 30 Posterothorax 15

There are 3 genera of Nananloricidae known so far which contain species that all have a short basal section of the mouth cone with 8 oral furcae and oral ridges of identical size and structure. Furthermore the terminal section of the mouth cone is drawn out to a long and slim mouth tube (in species of the genera Nanaloricus and Spinoloricus the mouth cone itself is long and the mouth tube very short, nearly as if not present; additionally the oral furcae and oral ridges are of different length and in the case of Nanaloricus - species also of different structure, compare Kristensen & Gad 2004 and Heiner & Neuhaus 2007). Apart from this most obvious character, the genera Armorloricus , Phoeniciloricus , and Culexiregiloricus gen. nov. share the following features:

(1) prepharyngeal armature equipped with manubrium

(2) lorica spikes with single gland ducts lacking reservoirs (and with “windows”)

(3) ventral lorica plate narrow and outer lateral margins of ventrolateral plates folded up.

A differential diagnosis on generic level is given for all “long-mouth-tube species” in the form of a comparison of the distinguishing features in Table 2.