Columbianum major, Read & Enghoff, 2018
Read, Helen J. & Enghoff, Henrik, 2018, Siphonophoridae from Brazilian Amazonia Part 1 - The genus Columbianum Verhoeff, 1941 (Diplopoda, Siphonophorida), European Journal of Taxonomy 477, pp. 1-23: 10-13
treatment provided by
Columbianum major sp. nov.
Large, dark, robust species. Rostrum abruptly set off from head when seen in dorsal view but head not domed. With narrow ridge-like metazonites anteriorly. Metatergites with a dense and even cover of setae and tubercles all over. Limbus crenulated, and probably the hind edge of the pleurites, too. Simple claws and accessory claws. Posterior and anterior gonopods composed of several clear segments but no large projections or forks on either.
Comparative adjective relating to the relatively large overall size of this species.
Material studied (2 ♂♂, 3 ♀♀)
BRAZIL: ♂, Amazonas Province , Reserva Flor.A. Duche, Terra Firma, 2°55´S, 59°59´W, 14 Feb. 1996, primary upland forest, not inundated, Adis et al. leg. ( INPA).GoogleMaps
BRAZIL: 1 ♂, same data as for the holotype, 17 Apr. 1996, ZFII 3, soil emergence trap (ZMUM); 2 ♀♀, same data as for the preceding, 20 Feb. 1992, standing crop samples (ZMUM, INPA); 1 ♀ (smaller paler specimen), same data as for the preceding, 8 Dec. 1982, K12 RD4, Kempson extractor (INPA).
MEASUREMENTS. Body length ♂: 18–39 mm, ♀: 22–43 mm. Body width ♂: 1.8–2.5 mm, ♀: 1.9–3.1 mm. Number of podous tergites: ♂: 66–87, ♀: 78–94. Number of apodous tergites: 1.
COLOUR. Deep brown (except smallest specimen which is pale); generally darker at anterior end, to rings 15–20. Head and legs variable but paler, antennae dark or pale.
BODY SHAPE ( Fig. 2A View Fig ). More or less parallel sided, attenuated posteriorly.
HEAD ( Fig. 2 View Fig B–C). Pilose, width (between antennal sockets) 0.7–0.8 mm. Sharp transition from head to rostrum when seen from above, more gradual from the side, head not domed. Length of rostrum from tip to antennal base: 0.6–0.8 mm. Rostrum appearing relatively short in relation to body size (but relative length difficult to evaluate as head is tucked under collum so very little is showing from dorsal view). Rostrum more or less horizontal in lateral view, with short setae along the entire length and a few longer ones at the base, these setae reaching almost to tip of rostrum.
ANTENNAE. Slightly shorter than body width (1:0.85), much longer than rostrum and surpassing it by over 150% of rostrum length. Length:width ratio of antennomeres 1–8: 1–broken, 1.73, 1.03, 0.95, 0.83, 1.8, 7–heavily sclerotised and difficult to see, sensory cones not measured. Sensory pits present on antennomeres 5 and 6, with numerous sensory organs in each.
COLLUM. Densely pilose; anterior margin appearing very deeply V-shaped under light microscope but with a thin membrane across the apparent incision, anterior margin actually only smoothly curved posteriorly. Tergite 2 half the length of the collum or less.
MIDBODY RINGS. When plotted this species forms a group with a larger body width for a similar number of segments, relative to the other species ( Fig. 1 View Fig ). No obvious paranota but a slight angle to the body shape in cross section in mid to posterior part of trunk with the angle where the repugnatorial glands occur. Metazonites standing slightly proud of prozonites and appearing as a ridge on anterior segments, smoother outline posteriorly. Relative width of pro- and metazonites approximately 0.89. Anterior margin of tergites smooth at midpoint, with dense and even cover of setae, tuberculate all over. Channel between pro- and metazonites with clear line of setae. Length of longest metazonital setae 0.06–0.14 × body width. Limbus crenulate ( Fig. 2D View Fig ). Pleurites densely pilose, hind edge possibly serrate, ventral margin with sharp notch for the coxae and curved posterior edge ( Fig. 2 View Fig E–F). Ozopores present from tergite 6 to penultimate tergite, very round in shape, situated in the middle of the ridge formed by the metazonite anteriorly, moving to the posterior edge of the ridge more posteriorly.
LEGS. Length 0.54 of the body width. Length: width ratio of podomeres (prefemur to claw): 1.19, 1.57, 1.35, 1.73, 3.12, 2.83. Coxae covered in tubercles and with obvious pores. Tarsus very long and narrow. Claw with ventral groove, slightly thickened. Accessory claw approximately 50% of the claw length, strong and arising from base of anterior side; visible using light microscope in anterior legs of females (difficult to see in males due to poor preservation) ( Fig. 3A View Fig ). Overall appearance of claw + accessory claw almost like a double claw.
TELSON. Length width ratio: 1.7–2.9.
MALE ANTERIOR LEGS (pairs 1–8). Without modifications.
ANTERIOR GONOPODS ( Fig. 3 View Fig ). Apparently with six ‘segments’ (including coxa) but poorly preserved. Distally coming to a gradual point with a hyaline projection at tip but hidden in abundant setae. Third segment with small posterior lobe on the mesal side. Several prominent setae on inside and outside of the ‘knee’.
POSTERIOR GONOPODS ( Fig. 3 View Fig ). Apparently with five ‘segments’ (including coxa). Distal segment long and thin, coming to simple point. A small ‘nick’ near base of terminal part. As specimens are poorly preserved other projections or spines may have been broken.
Comments on ecology
Columbianum major sp. nov. was found only in the primary upland forest.
These specimens appear to have been hand-collected (in contrast to other specimens) so the colour is perhaps more similar to live colour, however the state of preservation of most of them is poor, and many of the appendages are damaged or broken and so difficult to measure accurately. Due to the relatively few specimens scanning electron mounts were only made of midbody segments.
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