Macrobiotus rawsoni Horning, Schuster & Grigarick, 1978

Kaczmarek, Łukasz & Michalczyk, Łukasz, 2017, A description of Macrobiotus horningi sp. nov. and redescriptions of M. maculatus comb. nov. Iharos, 1973 and M. rawsoni Horning et al., 1978 (Tardigrada: Eutardigrada: Macrobiotidae: hufelandi group), Zootaxa 4363 (1), pp. 79-100 : 92-95

Macrobiotus rawsoni Horning, Schuster & Grigarick, 1978

( Tables 3–4, Figs 9–12 )

Macrobiotus rawsoni n.sp. ( Horning, et al. 1978)

Material examined ( Fig. 9 ). Three paratypes (2 animals and 1 egg) on three slides designated as: 1) Macrobiotus rawsoni Horning et al., 1978 [300], PARATYPE, Rangitira Isl., Triang. Station, Chatham Isl., VIII-25-71, D.S. Horning, NZ-891, National Museum, N.Z.; 2) Macrobiotus rawsoni Horning, Schuster & Grigarick, 1978 [340], PARATYPE, Rangatira Isl., Triang. Station, Chatham Isl., VIII-25-71, D.S. Horning, NZ-891, Museum of New Zealand ; 3) Macrobiotus rawsoni Horning et al., 1978 [egg], Museum of New Zealand, PARATYPE, Rangatira Isl. , Triang. Station, Chatham Isl., VIII-25-71, D.S. Horning, NZ-891, National Museum, N.Z.

Type locality. Original coordinates: 44°17'S, 176°10'W, corrected coordinates: 44°21'S, 176°11'W, ca. 150 m asl: Chatham Islands, Rangatira Island (South East Island), Triangulation Station, 400 m SW of Woolshed, in dense bush, moss ( Porotrichum ramulosum (Mitt.) Mitt. ) from rocks.

Re-description (measurements in Tables 3–4). Animals: Body colour unknown, eyes present ( Fig. 10A ). Entire cuticle covered with round or oval cuticular pores, not arranged in bands ( Fig. 11A ). Obvious granulation only present on legs IV ( Fig. 11 ). Bucco-pharyngeal apparatus of the Macrobiotus type, with ventral lamina and ten peribuccal lamellae ( Fig. 10B–D ). Mouth antero-ventral. The oral cavity armature of the maculatus type (see, Kaczmarek & Michalczyk 2017 for details), with only the third band of teeth visible under LM, composed of three dorsal and three ventral teeth in the shape of transverse ridges ( Fig. 10B–C ). Third band of teeth on dorsal and ventral side composed of small singles teeth arranged irregularly. Pharyngeal bulb spherical with triangular apophyses, two rod-shaped macroplacoids and thin microplacoid. Macroplacoid length configuration 2<1. The first macroplacoid with a central constriction. The second macroplacoid without constrictions, but with latero-terminal globular projections ( Fig. 10D ). Claws of the hufelandi type, stout ( Fig. 11A ). Primary branches with distinct accessory points. Lunules on all legs smooth. Thin bars paired under claws I–III present. Other cuticular thickenings on legs absent.

Eggs: Spherical, ornamented and laid freely ( Fig. 12A ), with the chorion surface of the hufelandi type (reticulated; Fig. 12B ). The reticulum well defined, with only a single peribasal ring (i.e. two lines of mesh between neighbouring egg processes). The mesh size uniform (1.8–2.5 µm in diameter). Process trunks concave, wide at the base, terminated with a concave disc ( Fig. 12C ). Disc edges serrated ( Fig. 12B–C ).

Original measurements according to Horning et al. (1978), including the original terminology: Body length excluding legs IV (456 µm); body length including legs IV (490 µm); body width (160 µm); mouth tube length (43 µm); mouth tube width (6 µm, expanding to 9 µm at base); stylet supports attached 11 µm from base; apophysis length (3 µm); I macroplacoid length (11 µm); II macroplacoid length (6 µm); microplacoid length (3 µm); claw length (18 µm), lunules (ca. 3 µm).

Etymology. Although not specified in the original description, the species was almost certainly dedicated to T.W. Rawson (Botany Division of the Department of Scientific and Industrial Research in Lincoln, New Zealand), who was mentioned in the acknowledgements of Horning et al. (1978) as one of two experts who, “provided the determinations of bryophytes and lichens; material from nearly 2000 samples was identified to species for this study, and their prodigious efforts are gratefully acknowledged”.

Type depositories. Holotype, paratypes and the egg are preserved at the Museum of New Zealand Te Papa Tongarewa, Tory Street, PO Box 467, Wellington , New Zealand.

Remarks. Pilato et al. (2006) partially re-described this species, however, they only provided measurements for a few taxonomic characters, and no eggs measurements; which we are now supplementing. While our measurements are in agreement with those given in Pilato et al. (2006), we came to different conclusions regarding the morphology of the oral cavity armature of M. rawsoni . Namely, Pilato et al. (2006) described the oral cavity armature as, “A band of almost invisible teeth and a system of three dorsal and three ventral thin transverse ridges are present in the posterior portion of the buccal cavity. An anterior band of teeth is not visible”, whereas we did not detect the second band of teeth. Thus, whether the oral cavity armature in M. rawsoni is of the maculatus or patagonicus type (see, Kaczmarek & Michalczyk 2017 for details), will remain open until fresh material is available.

Differential diagnosis. Our observations suggest that Macrobiotus rawsoni is characterised by the oral cavity of the maculatus type and eggs of the hufelandi type, and is therefore most similar to the following five species, but can be distinguished specifically from:

M. almadai Fontoura et al., 2008 , reported from the type locality in the Azores, by: a higher pt of the buccal tube width (13.4–15.5 in M. rawsoni vs. 10.1–11.5 in M. almadai ), a higher pt of the stylet support insertion point (77.0– 77.1 in M. rawsoni vs. 74.0– 76.8 in M. almadai ), and a different parameters of the egg reticulum (one or two lines of mesh between neighbouring processes in M. rawsoni vs. three meshes between neighbouring processes in M. almadai ).

M. humilis Binda & Pilato, 2001 , recorded from the type locality in Sri Lanka, by: the absence of granulation on legs I–III, a higher pt of the buccal tube width (13.4–15.5 in M. rawsoni vs. 11.3–11.8 in M. humilis ), a higher pt of the stylet support insertion point (77.0– 77.1 in M. rawsoni vs. 71.1–71.3 in M. humilis ), higher egg processes (5.2–6.3 µm in M. rawsoni vs. 4.1–5.1 µm in M. humilis ), and a larger diameter of the terminal discs of egg processes (4.9–5.3 µm in M. rawsoni vs. 2.9–3.4 µm in M. humilis ).

M. madegassus Maucci, 1993 , reported from the type locality in Madagascar, by: the absence of teeth on lunules IV, the presence of eyes, a higher pt of the buccal tube width (13.4–15.5 in M. rawsoni vs. 7.0– 11.8 in M. madegassus ), a higher pt of the stylet support insertion point (77.0– 77.1 in M. rawsoni vs. 68.1–71.3 in M. madegassus ), and a lower number of processes on the egg circumference (ca. 26 in M. rawsoni vs. ca. 30–34 in M. madegassus ).

M. martini Bartels et al., 2009 , recorded from the type locality in USA (North Carolina), by: the absence of granulation on legs I–III, the absence of teeth on lunules IV, a higher pt of the buccal tube width (13.4–15.5 in M. rawsoni vs. 12.5–12.9 in M. martini ), a higher pt of the stylet support insertion point (77.0– 77.1 in M. rawsoni vs. 72.9–74.3 in M. martini ), the presence of teeth on the terminal discs of egg processes (smooth discs in M. martini ), and a lower process base/height ratio (96–100% in M. rawsoni vs. 117–157% in M. martini ).

M. modestus Pilato & Lisi, 2009 , reported from the type locality in the Seychelles, by: a higher pt of the buccal tube width (13.4–15.5 in M. rawsoni vs. 7.4–7.9 in M. modestus ), a higher pt of the stylet support insertion point (77.0– 77.1 in M. rawsoni vs. 67.3–69.8 in M. modestus ), the absence of teeth on lunules IV, a lower number of processes on the egg circumference (ca. 26 in M. rawsoni vs. ca. 32–33 µm in M. modestus ), higher egg processes (5.2–6.3 µm in M. rawsoni vs. 4.6–5.1 µm in M. modestus ), wider bases of the egg processes (5.0–6.3 µm in M. rawsoni vs. 4.2–4.9 µm in M. modestus ), and a larger diameter of terminal discs of egg processes (4.9–5.3 µm in M. rawsoni vs. 2.8–3.6 µm in M. modestus ).

SPECIMEN Paratype 300 Paratype 340 CHARACTER µm pt µm pt

Figures

FIGURE 9. Macrobiotus rawsoniHorning et al., 1978—slides constituting part of the type series.

FIGURE 10. Macrobiotus rawsoni Horning et al., 1978 A—habitus (paratype); B–C—oral cavity armature (B—dorsal teeth, C—ventral teeth; arrows indicates the third band of teeth; paratype); D—pharyngeal apophyses and placoids (paratype). Scale bars in µm.

FIGURE 11. Macrobiotus rawsoni Horning et al., 1978 A—claws IV, leg granulation (outlined with a dashed curve) and cuticular pores (arrowhead; paratype); B—cuticular granulation patches above legs IV (outlined with a dashed curve; paratype).Scale bars inµm.

FIGURE 12. Macrobiotus rawsoni Horning et al., 1978 A—egg; B—chorionic reticulum; C—egg processes (midsection). Scale bars in µm.