Ceratophysella comosa, Nakamori, Taizo, 2013

Nakamori, Taizo, 2013, A new species of Ceratophysella (Collembola: Hypogastruridae) from Japan, with notes on its DNA barcode and a key to Japanese species in the genus, Zootaxa 3641 (4), pp. 371-378 : 373-376

Ceratophysella comosa sp. nov.

Figs. 1–9

Description.

Body length 0.8–1.3 mm. Colour dark brown to dark grey. Tegumentary granulation coarse on part of the dorsal side of thoracic terga II–abdominal terga VI. Abdominal tergum V with 12–15 tegumentary granules between setae p1. Antennal segment I with seven setae; antennal segment II with 12 setae. Antennal III organ with two sensilla guarded by raised cuticle and two guard sensilla ( Fig. 1 ). Antennal segment III microsensilla present. Antennal segment IV with a simple apical antennal bulb and 5–7 poorly differentiated blunt sensilla ( Fig. 1 ); ventral file with about 40 peg-like setae surrounding a central seta ( Fig. 2 ). Head with 3 + 3 cephalic spines in positions d2, d5, and sd5 ( Fig. 5 ). Eyes 8 + 8. Postantennal organ with four lobes, the posterior two lobes surrounding an accessory boss ( Fig. 3 ). Ocelli area with 3 + 3 setae. Labrum with 5, 5, and 4 setae; labral margin with four tubercles. Maxillary outer lobe with two sublobal hairs. Basolateral field of ventral labium with 4 + 4 setae. Basomedian field of ventral labium with 5 + 5 setae ( Fig. 6 ). Claw with an internal tooth and two lateral teeth ( Fig. 8 ). Empodium with a lamella and a filament reaching the internal tooth of the claw. Ventral tube laterally with 5 + 5 setae (3 + 3 setae located distally and anteriorly to the other 2 + 2 setae; Fig. 4 ). Tenaculum with 4 + 4 teeth ( Fig. 7 ). Dens with seven setae on posterior side ( Fig. 9 ). Mucro curved, with lateral lamella. Dens/mucro ratio = ca. 2. Anal spines long, yellow to brown in colour, situated on basal papillae. Anal spines/inner edge of hind claws ratio = ca. 1.3.

Body setae slender, smooth or slightly serrated and pointed at the apex ( Fig. 5 ). Sensory setae long and weakly differentiated from body setae; those on thoracic tergum II (m7), abdominal tergum II (p7–8), and the lateral aspect of thoracic tergum III (m7) very short and curved. One pair of lateral microsensilla present on thoracic tergum II. Plurichaetosis absent on head thoracic tergum I, and abdominal tergum VI, weak on thoracic terga II–III and abdominal terga I–III and V, more distinct on abdominal tergum IV. Body setae, especially supernumerary setae, often asymmetric in position and number. Head with setae v2 about twice as long as setae v1 or less. Thoracic tergum I with 3 + 3 setae. Thoracic tergum II with setae a2 about twice as long as setae a1 or less, and setae p2 about 1.5 times as long as setae p1. Thoracic terga II–III with sensory setae at the location of p4. Abdominal terga I–III with sensory setae at the location of p7–8. Abdominal tergum I with setae m1. Abdominal tergum IV with setae p2 about 1.5 times as long as setae p1 or less and sensory setae at the location of p5. Abdominal segment II normally with 4 + 4 ventral setae ( Fig. 7 ). Abdominal segment III with 10 + 10 ventral setae. Trochanters I–III with 7, 7, 6 (6–8) setae. Femurs I–III with 14, 13, 12 setae. Tibiotarsi I–III with 19, 19, 18 setae ( Fig. 8 ).

Remarks

Within the genus Ceratophysella , the presence of 3 + 3 cephalic spines and the shape of postantennal organ (the posterior two lobes surrounding an accessory boss) place C. comosa sp. nov. near C. loricata , and C. pilosa . The morphological features of the new species generally fit the original description of C. loricata . Very short sensory setae on thoracic tergum II, abdominal tergum II, and the lateral aspect of thoracic tergum III are also present in types of C. loricata . However, C. comosa sp. nov. has only weak plurichaetosis, whereas plurichaetosis is absent in C. loricata . As a result the apparent locations of sensory setae on abdominal terga I–III differ between these species (p 7–8 in C. comosa sp. nov.; p 5 in C. loricata ). Furthermore, differentiation of macro- and microsetae is weaker in C. comosa sp. nov. than in C. loricata (in types of C. loricata , head with setae v2 about four times as long as v1 or more; thoracic tergum II with setae a2 about three times as long as setae a1 or more, and setae p2 about four times as long as setae p1 or more; abdominal tergum IV with setae p2 about twice as long as setae p1). In addition, tegumentary granules are slightly finer in C. comosa sp. nov. than in C. loricata (the numbers of tegumentary granules between setae p1 on abdominal tergum V are 12–15 in C. comosa sp. nov. and 11–13 in types of C. loricata ). As strong plurichaetosis is seen in C. pilosa , the new species can be easily distinguished from it in having 3 + 3 setae on thoracic tergum I (more setae in C. pilosa ) and from C. loricata by having 5 + 5 setae on ventral tube (4 + 4 in C. loricata ).

Type materials

A holotype male and six paratypes (one male and five females), collected in Nagasaki, Japan (32°46'N, 129°53'E; 360 m above sea level) on 9 April 2011 from ascomata of Ciborinia camellia , have been deposited in the Natural History Museum and Institute, Chiba (the holotype: No. CBM-ZI 146417; the paratypes: Nos. CBM-ZI 146418– 146423). Sequence data for the mitochondrial COI gene for the type specimens were registered in GenBank (the holotype: Accession No. AB740020 ; the paratypes: Nos. AB740021 – AB740026 ).

DNA sequences

The interspecies sequence divergences of the mitochondrial COI gene were larger than intraspecies divergences between C. comosa sp. nov. C. denticulata , C. gibbosa , and C. pilosa individuals examined (Table 2; Fig. 10 ). These results suggest that sequencing the mitochondrial COI gene is useful for discrimination of C. comosa sp. nov. from congeneric species, and supports the applicability of this region for species discrimination as indicated by previous studies on DNA barcoding of Collembola (Hogg and Hebert 2004; Porco et al. 2010). However, a recent study with broader sampling documented cryptic diversity of the mitochondrial COI gene in C. denticulata and distinguished three lineages (Porco et al. 2012). DNA barcoding data are available for only a few of the 142 Ceratophysella species. Further investigations are needed for DNA barcoding of this genus.

See Table 1 for sources of sequence data.

Figures

FIGURE 10. Genetic distance tree of mitochondrial COI gene in Ceratophysella inferred using the Neighbour-Joining method. The bootstrap consensus tree was inferred from 1,000 replicates. The percentages of replicate trees in the bootstrap test are shown next to the branches. The distances were computed using the Kimura 2 - parameter method. Symbols indicate localities from which the specimens were collected: open circle, Japan (Otsu); closed circle, Japan (Nagasaki); open square, Australia; closed square, New Zealand; open triangle, Chile; closed triangle, Argentina; open diamond, France. See Table 1 for sources of sequence data.

FIGURES 1 – 5. Ceratophysella comosa sp. nov.: 1, dorsal view of antennal segments III – IV; 2, ventral view of antennal segments III – IV; 3, ocelli and postantennal organ, right side; 4, lateral view of ventral tube; 5, dorsal chaetotaxy. ms indicate microsensilla; s indicates sensory setae; x indicates supernumerary setae in posterior rows on abdominal terga I – III. Bar 50 μm (Figs. 1 – 4), 100 μm (Fig. 5).

FIGURES 6 – 9. Ceratophysella comosa sp. nov.: 6, ventral view of head; 7, ventral view of abdominal segments II and III; 8, inner view of claw and tibiotarsus III; 9, dens and mucro. Bar 50 μm.