Doryphoribiidae Gąsiorek, Stec, Morek & Michalczyk, 2019

Rocha, Alejandra, Doma, Irene, Reyes, Andrea Gonzalez & Lisi, Oscar, 2020, Two new tardigrade species (Echiniscidae and Doryphoribiidae) from the Salta province (Argentina), Zootaxa 4878 (2), pp. 267-286 : 276-282

Family: Doryphoribiidae Gąsiorek, Stec, Morek & Michalczyk, 2019

Genus: Doryphoribius Pilato, 1969

Doryphoribius cephalogibbosus sp. nov.

( Figures 5–9 ; Table 3 )

Material examined: holotype (adult), six adult paratypes and four exuvia in polyvinyl lactophenol mounting media. All specimens were found in samples of lichens, on sidewalk tree trunks.

Type locality: Salta city (24°27´– 25°47´S, 64°55´– 65°40´W), 1150 m asl, Salta province, Republic of Argentina .

Type repositories: the holotype ( MNCS Tar. 000020-2) and two paratypes ( MNCS Tar. 000022-1 & 3) are deposited in the Museum of Natural Sciences , National University of Salta, Argentina . Three paratypes (slide number: 5861) are deposited in the Pilato and Binda collection, Museum of Animal Biology, University of Catania, Italy . One paratype (UNLPam 727) and four exuvia (UNLPam 726-1-2, UNLPam 728-1-2) are housed in Rocha and Doma collection in the Department of Natural Sciences at the National University of La Pampa, Argentina .

Species description: Body ( Fig. 5 ) orange in vivo (still visible in some specimens after slide mounting); body length 168–438 µm, eye spots present in all examined specimens. Ventral cuticle smooth, dorsal and lateral cuticle sculptured with an evident reticular design which appears rather rough showing a certain degree of variability regarding the mesh size and shape, as well as the thickness of the ridges delimiting the mesh ( Fig. 5 , 6 A, B ); smallest mesh about 0.6 µm, largest about 4.6 µm, but the majority of the mesh has a more limited range, about 1–3 µm. Flat tubercles are formed at some reticular nodes ( Fig. 6 B , arrows). Dorsal cuticle with 20 transverse undulations and 44 gibbosities arranged in ten transverse rows, with a gibbosity on each leg I–III ( Fig. 5 , 7 ), gibbosity formula X:2-4-6- 6-6-6-6-4-2-2+2[L I–III]. Rows III, V and VII placed in line with legs I, II and III respectively. Row I: quite flattened, small, oval gibbosities, not visible in all specimens ( Fig. 5 , arrows, Fig. 7 ); row II–VIII: hemispheric gibbosities; row IX–X: elongated gibbosities. All gibbosities show the reticular sculpture, but on average with smaller mesh.

Bucco-pharyngeal apparatus ( Fig. 8 A, B ) of the Doryphoribius type, mouth antero-ventral. Oral cavity armature composed of seven-eight sparse teeth on the dorsal wall ( Fig. 8 A, B , black arrows), while ventrally teeth are absent and two typical lateral ridges are present. Buccal tube rigid with anterior bend. Stylet furcae of the Hypsibius type. Rounded pharyngeal bulb with pyramidal apophyses and two rod-shaped macroplacoids; the first macroplacoid longer and with slight central constriction not always visible, second shorter and without constriction. Microplacoid and septulum absent.

Claws ( Fig. 9 A–D) stout, well developed, of the Isohypsibius type, only moderately different in shape and size on each leg. Accessory points usually attached to the main branches along their entire length; only in some exuvia, claws with very short and thin free accessory points have been observed ( Fig. 9 D , arrow). External claws I–III and posterior claws IV slightly larger and with wider bases than internal claws I–III and anterior IV, respectively. Smooth pseudolunulae present under all claws ( Fig. 9 A, C , arrows), quite narrow on legs I–III, better developed on legs IV. Cuticular bars absent on all legs.

The measurements of the taxonomically important structures, with relative indices, of the holotype and ranges within the population are reported in Table 3 .

Smooth, oval, orange eggs laid in exuvium. Four exuvia containing 1– 6 eggs found, in some cases with the fully developed embryos.

Etymology: The name “ cephalogibbosus ” (compounded word with cephalon = head and gibbosus = with gibbosities) refers to the presence of cephalic gibbosities, never reported until now.

Taxonomic remarks: The paratypes showed the same qualitative characters of the holotype, with only moderate variability of the quantitative ones (see Tab. 3 ), though this may arise, at least partially, from the difficulty in measuring structures and from different preparation results. As usual in eutardigrades with gibbosities, the complete configuration was determined after comparing several specimens; the holotype is the specimens which best show it, in addition to the other characters of the species. Comments on the presence of cephalic gibbosities and attached accessory points are provided in the Differential diagnosis and in the Discussion.

Differential diagnosis: Doryphoribius cephalogibbosus sp. nov. belongs to the flavus group sensu Gąsiorek et al. (2019) by the presence of two macroplacoids and gibbosities, and living in terrestrial environments, but differs from all the members of the group in having 10 rows of trunk gibbosities. In particular, the peculiar character exclusive of the new species consists in the presence of the two cephalic gibbosities, never reported for other Doryphoribius species before.

However, considering that such gibbosities are not always well visible, and we cannot exclude that in some species described earlier they may be present but have passed unnoticed, we here compare D. cephalogibbosus sp. nov. with the species of the flavus group with nine rows of gibbosities (such rows of gibbosities perfectly correspond to the rows II–X of the new species), excluding species with a lower number of rows, or without dorsal gibbosities, and D. monstruosus ( Maucci, 1991) which has conical gibbosities. Without considering the cephalic gibbosities, D. cephalogibbosus sp. nov., would have formula IX:4-6-6-6-6-6-4-2-2+2[L I–III], which still keeps the new species clearly distinct from all the others, as it can be seen from the following list of those species with nine rows of gibbosities:

D. zyxiglobus ( Horning, Schuster & Grigarick, 1978) , amended by Claxton et al. (2010), IX:4-6-4-6-4-6-4-4-2.

D. huangguoshuensis Wang, Wang & Li, 2007 , IX:4-4-4-4-4-4-4-2-2.

D. dawkinsi Michalczyk & Kaczmarek, 2010 , IX:6-6-4-6-4-6-4-4-2+2[L IV].

D. niedbalai Zawierucha, Michalczyk & Kaczmarek, 2012 , IX:4-6-5-6-5-6-4-2-2.

D. barbarae Beasley & Miller, 2012 , IX:2-4-4-4-4-6-4-4-2.

D. maasaimarensis Fontoura, Lisi & Pilato, 2013 , IX:4-6-4-6-4-6-4-4-2.

D. mcinnesae Meng, Sun & X. Li, 2014 , IX:2-3-1-3-1-3-3-2-2 according to Daza et al. (2017) (see discus sion).

D. rosanae Daza, Caicedo, Lisi & Quiroga, 2017 , IX:4-6-2-6-2-6-4-2-2.

In addition, the new species differs from these eight species also in having a gibbosity on each foreleg. Other, more detailed differences are as follows:

• D. cephalogibbosus sp. nov. differs from D. zyxiglobus , known from New Zealand, also in having: a shorter ventral lamina (pt 53.4–55.8 vs 58.2–62.5), a wider buccal tube (pt external width 12.6–15.2 vs about 10 from Fontoura et al. 2013), in having cuticular reticular sculpture and teeth in the oral cavity (lacking in D. zyxiglobus ), and typically in having accessory points attached to the primary branch on their entire length (tips of accessory points always detached from the primary branch in D. zyxiglobus ).

• The new species differs from D. huangguoshuensis , known from China, also in having: a wider buccal tube (pt external width 12.6–15.2 vs about 8–9 in D. huangguoshuensis ), eyes and cuticular tubercles (lacking in D. huangguoshuensis ), shorter posterior primary branches (pt 28.4–35.6 vs about 41.0– 44.5 in D. huangguoshuensis ) and typically in having accessory points attached to the primary branch on their entire length (tips of accessory points always detached from the primary branch in D. huangguoshuensis ).

• D. cephalogibbosus sp. nov. differs from D. dawkinsi , known from Costa Rica, also in having: a wider buccal tube (pt external width 12.6–15.2 vs 8.0– 11.1 in D. dawkinsi ) and has eyespots, reticular sculpture and pseudolunulae (all lacking in D. dawkinsi ).

• The new species differs from D. niedbalai , known from Zambia, also in having: shorter ventral lamina (pt 53.4–55.8 vs 56.5–60.3 in D. niedbalai ), shorter claws of legs IV, eyes spots (lacking in D. niedbalai ) and dorsal instead of ventral teeth in the oral cavity.

• D. cephalogibbosus sp. nov. differs from D. barbarae , known from China, also in having: a wider buccal tube (pt external width 12.6–15.2 vs in 9.3–11.6 in D. barbarae ), eyes, reticular sculpture, and teeth in the oral cavity (all lacking in D. barbarae ).

• The new species differs from D. maasaimarensis , known from Kenia, also in having: wider buccal tube (pt external width 12.6–15.2 vs 8.5–9.5 in D. maasaimarensis ), several teeth in the oral cavity (only one tooth in D. maasaimarensis ), shorter ventral lamina (pt 53.4–55.8 vs 66.3–69.9) and typically in having accessory points attached to the primary branch on their entire length (tips of accessory points always detached from the primary branch D. maasaimarensis ).

• D. cephalogibbosus sp. nov. differs from D. mcinnesae , known from China, also in having: dorsal (instead of ventral) teeth in the oral cavity, wider buccal tube (pt 12.6–15.2 vs 8.7–9.5 in D. mcinnesae ), typically in having accessory points attached to the primary branch on their entire length (tips of accessory points always detached from the primary branch D. mcinnesae ) and pseudolunulae (lacking in D. mcinnesae ).

• The new species differs from D. rosanae , known from Colombia, also in having: less regular reticular sculpture with various width of the ridges (always narrow in D. rosanae ), and only dorsal teeth in the oral cavity (also ventral in D. rosanae ).

Figures

FIGURE 5. A. Habitus of the holotype of Doryphoribius cephalogibbosus sp. nov. showing the dorsal cuticle with gibbosities and reticular ornamentation. The arrows indicate the cephalic gibbosities typical of this species. B. Magnification of the anterior portion of the body, in dorsal view, showing better the cephalic gibbosities (arrows). Scale bars are 20 µm.

FIGURE 6. Details of the reticular cuticular ornamentation of the holotype of Doryphoribius cephalogibbosus sp. nov. A. On the anterior portion of the body. B. On a more posterior portion of the body; the arrows indicate some tubercles. Scale bars are 10 µm.

FIGURE 7. Schematic drawing showing the entire gibbosity arrangement of Doryphoribius cephalogibbosus sp. nov.

FIGURE 8. Bucco-pharyngeal apparatus of Doryphoribius cephalogibbosus sp. nov. A. Holotype; the arrow indicates the buccal teeth. B. A paratype (UNLPam 727-2); the black arrows indicate the buccal teeth; the white arrows indicate the eyespots. Scale bars are 10 µm.

FIGURE 9. Claws and their details of Doryphoribius cephalogibbosus sp. nov. A. Claws of legs II of the holotype; the arrow indicates a pseudolunula. B. Claws of legs II of a paratype (MNCS Tar. 000020-1). C. Claws of legs IV of the same paratype (MNCS Tar. 000020-1); the arrows indicate the pseudolunulae. D. Claws of legs IV of an exuvium (UNLPam 726-2) showing a free accessory point (arrow). All scale bars are 10 µm.