Doryphoribius amazzonicus, Lisi, Oscar, 2011

Lisi, Oscar, 2011, Remarks on Doryphoribius flavus (Iharos, 1966), and description of three new species (Tardigrada, Hypsibiidae), Zootaxa 2834, pp. 17-32 : 22-25

Doryphoribius amazzonicus sp. nov.

( Fig. 3 )

Material examined. Holotype (slide number 5422) and one paratype (slide number 4828), mounted in polyvinyl lactophenol; Ecuador: Loreto, from a moss sample (data available from Pilato, Binda, Napolitano & Moncada, 2001).

Specific diagnosis. [Eye spots present*], reticulate sculpture on dorsal and lateral cuticle consisting of mesh delimited by ridges forming a tubercle at each crossing. Unsculptured legs with the anterior side of the first three pairs and the posterior side of the fourth pair, swollen. Bucco-pharyngeal apparatus of the Doryphoribius type; peribuccal papulae present, some of which were divided; teeth and ridges not apparent in the buccal cavity; buccal tube long and narrow; pharyngeal bulb with two macroplacoids and no microplacoid or septulum. Claws of the Isohypsibius type, slightly stout, internal claws with small basal portion, external enlarged at the very base; smooth lunules present, those of the external claws more evident; no other sclerified structures on legs.

[*] = Not visible after mounting in polyvinyl lactophenol.

Description of the holotype. Body 225.0 μm long (but it may be slightly contracted by the mounting media), colourless, eye-spots no longer visible. Reticulate sculpture on dorsal and lateral cuticle with mesh that was slightly irregular in shape and size ( Fig. 3 A in the paratype), delimited by ridges which form a tubercle at each crossing ( Fig. 3 B, arrows); the mesh increase in average size from the lateral to the dorsal cuticle and from the head to the posterior portion of the body, reaching a maximum diameter (up to 3.6 μm, pt = 10.7) between the third and the fourth pair of legs, and decrease slightly more caudally.

Anterior side of the first three pairs of legs and posterior side of the fourth pair, swollen (this character was more visible in the paratype), no sculpture on the legs.

Bucco-pharyngeal apparatus ( Fig. 3 C) of the Doryphoribius type (i.e. with rigid buccal tube with ventral lamina); peribuccal papulae present, some of which were divided; teeth were not visible in the buccal cavity of the holotype or the paratype but, as these were relatively small specimens, this detail needs to be confirmed. The buccal tube is long and slender; 33.6 μm long and 4.4 μm wide (pt = 13.1); stylets supports inserted on the buccal tube at 70.6 % of its length (pt = 70.6). Ventral lamina 20.9 μm long (pt = 62.2); pharyngeal bulb 24.4 μm by 21.2 μm with pharyngeal apophyses and two macroplacoids, neither microplacoid nor septulum present; placoid row 10.9 μm long (pt = 32.4); first macroplacoid, slightly constricted in the middle, 6.5 μm long (pt = 19.3), second macroplacoid 3.6 μm (pt = 10.7).

Claws ( Fig. 3D ) of the Isohypsibius type moderately robust, slightly different in shape and size on each leg; basal portions of inner claws small, while those of the external claws are slightly longer and enlarged at the very base. Accessory points on the main branches; smooth lunules present (those of the internal claws of the first three pairs of legs often difficult to see); no other sclerified structures on the legs. The measurements of the claws and the other metric characters are reported in Table 2.

nov.; “Styl. supp. insert.” indicates the stylet supports insertion point on the buccal tube; “% bo-le” indicates the percentage

ratio with respect to the body length (calculated for the buccal tube length, the placoid row, the claws and the largest mesh).

Holotype – slide N. 5422 (slightly contracted?) Paratype – slide N. 4828

Characters µm pt % bo-le µm pt % bo-le

Body length 225.0 - - 241.2 - -

Buccal tube length 33.6 - 14.9 33.2 - 13.8

Buccal tube width 4.4 13.1 - 3.8 11.4 -

Styl. supp. insert. - 70.6 - - 72.8 -

Ventral lamina 20.9 62.2 - 20.8 62.7 -

Placoid row 10.9 32.4 4.8 10.2 30.8 4.2

I macroplacoid 6.5 19.3 - 6.2 18.7 -

II macroplacoid 3.6 10.7 - 3.6 10.8 -

I ex. claws 11.6 34.5 5.2???

I int. claws 10.0 29.8 4.4???

II ex. claws 11.4? 33.9? 5.1????

II int. claws??? 9.4 28.3 3.9

III ex. claws 12.0 35.7 5.3???

III int. claws 10.5 31.3 4.7???

IV ant. claws??????

IV post. claws 13.0 38.7 5.8 11.8 35.5 4.9

Largest mesh 3.6 10.7 1.6 4.1 12.3 1.7 Remarks. The paratype was similar to the holotype both in qualitative and in metric characters; the measurements of some structures of the paratype (the body length which did not appear contracted) are reported in Table 2. Eggs were not found.

Etymology. The name amazzonicus (= living in Amazonia) refers to the geographic region where the specimens were collected.

Type depositories. The holotype and the paratype are deposited in the Binda and Pilato collection (Museum of the Department of Animal Biology “Marcello La Greca”, University of Catania).

Differential diagnosis. According to Michalczyk & Kaczmarek (2010), the new species should belong to the evelinae group, but the authors themselves were in doubt as to whether or not the species groups they proposed actually reflect phylogenetic relationships. Personally, I am not convinced that the characters, i.e. number of macroplacoids and presence or absence of gibbosities, chosen by the authors for splitting the genus in the four proposed groups were valid. The number of macroplacoids is usually an efficient criterion to separate species groups, though there may be some borderline situations. However, I am doubtful of defining species groups using the presence or absence of dorso-lateral and leg gibbosities (together referred to as “cuticular gibbosities”), and not considering the cuticular sculpture, i.e. the absence or presence and type of sculpture. For these reasons I found it more appropriate to compare the new species with those having two macroplacoids and a more or less similar cuticular sculpture, independent of the species groups proposed by Michalczyk & Kaczmarek (2010).

Previously, the known Doryphoribius with a true reticulate cuticular sculpture, without dorsal gibbosities and with two macroplacoids in the pharyngeal bulb, were D. flavus and D. polynettae . The new species differed from D. flavus by having less uniformly wide ridges, which form an obvious tubercle at each crossing. In addition, the new species legs were unsculptured. Doryphoribius amazzonicus sp. nov. also differed from D. flavus by having the buccal tube slightly longer with respect to the body length ( Table 5), the stylets supports inserted on the buccal tube in a slightly more caudal position ( Table 5), and clearly shorter and slightly stouter claws ( Table 5, and Figs. 1 C–D, 2E and 3D).

The new species differed from D. polynettae above all in lacking cuticular sculpture on the ventral cuticle, by having a more obvious dorsal cuticular sculpture with tubercles where the mesh crosses, neither pores nor roughness on the cuticle, swollen portions of the legs, and no teeth visible in the buccal cavity.

Bartels, et al. (2007) described D. smokiensis Bartels, Nelson, Kaczmarek & Michalczyk, 2007 , which has two macroplacoids in the pharyngeal bulb and “a sculptured dorsal cuticle without gibbosities”; in particular the sculpture consisted of a “polygonal design” and for that combination of characters the authors compared the species to D. flavus , and D. polynettae . In fact, according to Bartels (pers. comm.), the sculpturing of D. smokiensis , is not really “reticular”. In deed, Fig. 3 from Bartels, et al. (2007) shows the cuticle under phase contrast as visible bright stripes delimiting dark polygons. This, in my opinion, shows thickened areas of cuticle that should be considered as polygonal tubercles. By contrast, D. flavus , D. polynettae , and D. amazzonicus sp. nov. all have a sculpture consisting of more or less prominent ridges that form a network delimiting flat polygonal areas of cuticle, the “mesh”. Under phase contrast these are seen as dark stripes around bright polygons. Apart from the cuticular sculpture, D. amazzonicus sp. nov. differed from D. smokiensis by having eyes, swollen portions of the legs, no teeth visible in the oral cavity, far narrower buccal tube, lunules at the claw bases and other minor details.

Another Doryphoribius with two macroplacoids and a true reticulate cuticular sculpture similar to that of D. flavus , D. polynettae and D. amazzonicus sp. nov., is D. quadrituberculatus Kaczmarek & Michalczyk, 2004 , but this species has four dorsal gibbosities on the caudal end of the body. D. amazzonicus sp. nov. also differed from D. quadrituberculatus by having tubercles at the ridge crossings, swollen portions of the legs, peribuccal papulae, no teeth visible in the oral cavity and lunules at the base of the claws.

Figures

FIGURE 3. D. amazzonicus sp. nov. A, Cuticular sculpture of the caudal portion of the paratype; B, Caudal portion of the holotype, some tubercles are in focus (arrows); C, Bucco-pharyngeal apparatus of the holotype; D, Claws of the second and third pair of legs of the holotype. Scale bar = 10 µm.

FIGURE 1. D. flavus. A, Dorso-lateral teeth (arrows) of the buccal cavity of a paratype; B, Bucco-pharyngeal apparatus of another paratype; C, Claws of the second and third pairs of legs of the same paratype as Fig. 1 B; D, claws of the fourth pair of legs of the same paratype as Fig. 1 B – C. Scale bar = 10 µm.