Chaetonotus (Hystricochaetonotus) macrochaetus Zelinka, 1889

Kolicka, Małgorzata, Kisielewski, Jacek, Nesteruk, Teresa & Zawierucha, Krzysztof, 2013, Gastrotricha from the Poznań Palm House — one new subgenus and three new species of freshwater Chaetonotida (Gastrotricha), Zootaxa 3717 (2), pp. 231-279 : 266-268

Chaetonotus (Hystricochaetonotus) macrochaetus Zelinka, 1889 ( Table 13)

Locality: Site 3; session I.

Material: 2 specimens (both adult), 1 specimen photographed.

Remarks: Specimens from the Poznań Palm House correspond well with the literature data (Kisielewski 1981, 1997a; Balsamo 1983), with the exception of the insignificantly higher pharynx formula a (30.1% vs 26–28% given), and the shorter terminal spines (16.9 Μm vs 20 Μm). C. (H.) macrochaetus represents a group of very similar species, including Chaetonotus (Hystricochaetonotus) hystrix Mečnikow, 1865 , Chaetonotus (Hystricochaetonotus) euhystrix Schwank, 1990 and Chaetonotus (Hystricochaetonotus) persetosus Zelinka, 1889 .

Distribution: Previously recorded in Austria (Zelinka 1889), Brazil (Kisielewski 1991), Bulgaria (Konsuloff 1913), Canada (Schwank 1990), Denmark (Grilli et al. 2010), Estonia (Järvekülg 1961), Germany (Schwank, 1990), Great Britain (Martin 1981, 1990), Hungary (Varga 1943), Israel (Kisielewski 1999), Italy (e.g. Balsamo 1983), Japan (Sudzuki 1971), Poland (e.g. Kisielewski & Kisielewska 1986; Kisielewska & Kisielewski 1986a, b, c), Romania (Rudescu 1968), Russia (Preobraženskaja 1926), Switzerland (Greuter 1917), Ukraine (Jakubski 1919) and the United States (Robbins 1973).

Character Specimen Body length 104.2 Pharynx length 29.2 Width of anterior pharynx thickening (a) 8.8

Width of pharynx narrowing that follows anterior thickening (n) 5.8

Width of pharynx at its middle length (m) 6.3

Width of posterior pharynx thickening (p) 9.6

Length of cephalic cilia 10.5–19.1 Hypostomium length 5.8

Cephalion length 7.9

Cephalion width 12.8 Diameter of mouth ring 4.6

Furca length 17.0 Length of adhesive tube 10.0 Neck spine length 6.2–10.1 Distance longitudinal denticles from the end of neck spine 1.3–2.3 Neck spines length 16.1–22.7 Distance longitudinal denticles from the end of trunk spine 3.8–5.3 Trunk spine length 16.9 Distance longitudinal denticles from the end of terminal spine 4.6

Neck scale length 3.3–4.8 Neck scale width 3.8–5.1 Trunk scale length 5.6–8.6 Trunk scale width 4.9–6.6 Posterior sensory bristles length 15.6 Number of cephalic cilia in one tuft 5; 5

Number of separated cephalic tufts 4

Number of scales in single longitudinal row 15

Total number of longitudinal alternating rows of scales 14

Pharynx formula a 30.1 Pharynx formula n 19.9 Pharynx formula m 21.6 Pharynx formula p 32.9 Localization of lateral denticle on neck spines 21.0–22.8 Localization of lateral denticle on trunk spines 23.3–23.6 Localization of lateral denticle on terminal spines 27.2 Ratio of scale distribution 93.3 Length ratio of terminal spines 16.2 Width of anterior pharynx thickening (a) 17.1

Width of pharynx narrowing that follows anterior thickening (n) 15.2

Width of pharynx at its middle length (m) 15.7

Width of posterior pharynx thickening (p) 18.2

Length of cephalic cilia 6.6–23.4 Hypostomium length 8.9

Cephalion length 12.6

Cephalion width 26.7

Diameter of mouth ring 10.8

Furca length 34.3

Length of adhesive tube 22.6

Neck spine length 12.9–26.4 Distance longitudinal denticles from the end of neck spine 4.6–11.2 Neck spines length 11.7–62.6 Distance longitudinal denticles from the end of trunk spine 3.4–14.2 Trunk spines length 16.9

Distance longitudinal denticles from the end of terminal spine 5.2

Neck scale length 9.1–10.8 Neck scale width 7.4–9.3 Trunk scale length 11.7–18.1 Trunk scale width 9.8–14.7 Length of ventral terminal spine 26.8

Posterior sensory bristles length 18.6

Number of cephalic cilia in one tuft 2; 3; 4 Number of separated cephalic tufts 6

Number of scales in single longitudinal row 20

Total number of longitudinal alternating rows of scales 12

Pharynx formula a 38.3

Pharynx formula n 34.1

Pharynx formula m 35.2

Pharynx formula p 40.8

Localization of lateral denticle on neck spines 35.7–42.4 Localization of lateral denticle on trunk spines 22.7–29.1 Localization of lateral denticle on terminal spines 30.8

Ratio of scale distribution 60.0

Length ratio of terminal spines 10.3

Subgenus Primochaetus Kisielewski, 1997

Type species: Chaetonotus acanthodes Stokes, 1887 Terra typica : USA

A clearly polyphyletic subgenus in terms of molecular data (Kånneby et al. 2013), encompasses 26 nominal freshwater species. Present in benthic and pheryphytic habitats.