Short Communication |
Corresponding author: André R. S. Garraffoni ( arsg@unicamp.br ) Academic editor: M. Antonio Todaro
© 2018 Axell K. Minowa, André R. S. Garraffoni.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Minowa AK, Garraffoni ARS (2018) Redescription of the dasydytid gastrotrich Haltidytes ooëides (Brunson, 1950) based on type material. ZooKeys 785: 41-48. https://doi.org/10.3897/zookeys.785.28382
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The semi-pelagic gastrotrich species Haltidytes ooëides (Brunson, 1950) is redescribed based on original type material deposited at the Smithsonian National Museum of Natural History. Herein we present a new diagnosis and figures of the species, detailing the insertion position of the lateral spines, misinterpreted in the original description. Furthermore, we reassess the taxonomic key for the genus Haltidytes Remane, 1936 based on our new findings.
Chaetonotida , Dasydytidae , Gastrotricha , Haltidytes , USA
While most gastrotrichs are epibenthic, periphytic, or interstitial, some species belonging to the family Dasydytidae Daday, 1905 present a semi-pelagic lifestyle (
While preparing a forthcoming study incorporating phylogenetic analyses of all valid Dasydytidae species based on morphology (Minowa and Garraffoni, in preparation), we came across the possible type specimen of Haltidytes ooëides (Brunson, 1950), originally described as Dasydytes ooëides (USNM W 26869S). Although
Herein we redescribe Haltidytes ooëides based upon a single type material deposited at the Smithsonian National Museum of Natural History. External morphology was observed using an Olympus BX63F compound fluorescence microscope with a digital DP80 camera and cellSens software (Olympus, Philadelphia, USA). Videos were prepared using the open-source platform Fiji (
The observed specimen has a compact, bowling pin-shaped body, measuring 88 μm in total body length, 184 μm with spines included. Conical head with convex sides (24 μm wide), pentalobate, dorsally with a middle furrow (Figure
Cephalic spines or rear spines not observed. On the anterior half of the trunk four paired groups of 2-2-2-1 curved simple spines (ta1-2, tb1-2, tc1-2, td) respectively, inserted directly on the cuticle without scales (Figs
Trunk locomotory ciliation divided into 2-paired ventral tufts at 15U and 93U on the ventral side of at the neck and posterior trunk, respectively (Figure
Mouth ring is terminal (3 μm in diameter). Pharynx (33 μm in length) increases in width uniformly from 9 μm anteriorly to 11 μm at the posterior end) (Figure
Light micrographs (DIC) of Haltidytes ooëides (Brunson, 1950). A dorsal view, B–C ventral view showing the insertion of trunk spines D dorsal view of the head E–F ventral view of the head. Asterisks (*) indicate the body cuticle. Scales bars: A–C 50 µm, D–F 25 µm. Abbreviations: alt anterior lateral ciliary tuft att anterior locomotory ciliation tuft ce cephalion, hy: hypostomion mf middle furrow mlt mediolateral ciliary tuft mo mouth plb posterior lateral ciliary band ptt posterior locomotory ciliation tuft tb1-2 trunk spines tc1-2 trunk spines td trunk spines.
Usually, the trunk width is given as the maximum trunk widthwhich is at the midgut level. In this case, the type specimen H. ooëides is 42 μm wide. However,
Differences in spines length between the original description and the present one (Table
Additionally, the original description mentions a pair of caudal bristles (Figure
As previously mentioned, the description of some morphological characters of H. ooëides were misinterpreted by
Light micrographs (DIC) and redrawing of the schematic drawing of Haltidytes ooëides (Brunson, 1950). A whole animal view B redrawing of the schematic drawing of the original description C the same image of A in which the arrangement of the trunk spines is highlighted D schematic drawing of the dorsal view E schematic drawing of the ventral view. Scales bars: 50 µm. Abbreviations: alt anterior lateral ciliary tuft att anterior locomotory ciliation tuft cd caudal bristle ce cephalion hy: hypostomion mlt mediolateral ciliary tuft mo mouth ph pharynx plb posterior lateral ciliary band ptt: posterior locomotory ciliation tuft ta1-2 trunk spines tb1-2 trunk spines tc1-2 trunk spines td trunk spines.
Morphometric features of Haltidytes ooëides (Brunson, 1950): measures are expressed in µm; the relative positions of morphological structures along the body are expressed in percentage unities (U) in relation to the total body length.
Feature type | Measure (μm) |
---|---|
Total body length, spines excluded | 88 |
Total body length, spines included | 184 |
Maximum head width) (U17) | 24 |
Minimum neck width (µm) (U30) | 17 |
Maximum trunk width (µm) (U65) | 42 |
Trunk length (µm) | 60 |
Pharynx length (µm) | 33 |
Anterior pharynx width (µm) | 9 |
Posterior pharynx width (µm) | 11 |
Diameter of mouth ring (µm) | 3 |
Kephalion length (µm) | 9 |
Kephalion width (µm) | 13 |
Hypostomion length (µm) | 5 |
Hypostomion width (µm) | 8 |
Spine ta1-2 length (µm) | 100, 90 |
Spine tb1-2 length (µm) | 75, 90 |
Spine tc1-2 length (µm) | 82, 80 |
Spine td length (µm) | 140 |
Ventral spine ta1-2 insertion | U32, U35 |
Ventral spine tb1-2 insertion | U38, U40 |
Ventral spine tc1-2 insertion | U46, U50 |
Ventral spine td insertion (U) | U60 |
Cephalic ciliary tufts insertion (U) | U1, U4, U8 |
Ventral trunk ciliary tufts insertion (U) | U15, U93 |
1 | Seven pairs of spines with ventral insertion besides td (saltatorial spines) | 2 |
– | Six or fewer pairs of spines with ventral insertion besides td (saltatorial spines) | 4 |
2 | Dorsal trunk totally or partially covered with rhombic scales arranged sparsely or aggregate | 3 |
– | Dorsal trunk without scales | H. festinans |
3 | Dorsal scales arranged sparsely; dorsal trunk covered with rhombic scales with a short median keel or smooth; ventral trunk covered with small smooth scales | H. squamosus |
– | Dorsal scales aggregate; median and rear dorsal trunk covered with smooth, rhombic scales; ventral trunk without scales | H. pseudosquamosus |
4 | Anterior spines (ta) cross each other above dorsal trunk | H. saltitans |
– | Anterior spines (ta) do not cross each other above dorsal portion of the trunk | 5 |
5 | Ventral ciliature consisting of 2 tufts; 3 pairs of spines arrive to the dorsum while 3 other spines remain ventral besides td group | H. ooëides |
– | Ventral ciliature consisting of 2 longitudinal bands; all 5 pairs of spines arrive to the dorsum; only td group remain on venter | H. crassus |
We are grateful to Fundação Amparo à Pesquisa do Estado de São Paulo − FAPESP (grant numbers: 2014/23856-0; 2017/20312-8) for financial support; Freya Goetz (Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology) for assistance with micrographs and videos of the type specimen; to Brett Christopher Gonzalez for editing the English text; an anonymous referee for offering suggestions that greatly improved the paper.