Helicops boitata, Moraes-Da-Silva, Cecilia Amaro, Sales-Nunes, Strussmann, Teixeira, Andrade, Sudre, Recoder, Rodrigues, Curcio, 2019, Moraes-Da-Silva, Cecilia Amaro, Sales-Nunes, Strussmann, Teixeira, Andrade, Sudre, Recoder, Rodrigues, Curcio, 2019
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publication ID |
https://doi.org/10.11646/zootaxa.5477.3.5 |
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publication LSID |
lsid:zoobank.org:pub:8D0112B5-7D0D-47BD-8920-97CDC032F839 |
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DOI |
https://doi.org/10.5281/zenodo.17543908 |
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persistent identifier |
https://treatment.plazi.org/id/A273879E-FFA2-F809-90DC-FBE1A621720D |
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treatment provided by |
Plazi |
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scientific name |
Helicops boitata |
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Data on variation in size (total length and tail length), scale counts (dorsals, ventrals, subcaudals, labials, and temporals), tooth counts, and the condition of cloacal plate and nasal scale of the five new specimens and the holotype (reexamined herein) appear in Table 1 View TABLE 1 . The most relevant information from the expanded series refers to the polymorphic condition of the cloacal plate and nasal scale. The holotype had both scales undivided, but the new individuals revealed variations of these features, with the divided condition representing the more frequent character state in both structures (cloacal and nasal scales divided in four and in three individuals, respectively). Asymmetric labial counts (more often infralabials) occur in five out of the six specimens. Nonetheless, the counts of supralabials (10/10) and infralabials (13/12) in the holotype comprise the upper limit of both parameters in the whole sample. Temporal counts exhibit not only individual variations, but also general asymmetry since none of the five new specimens had the same temporal formula on both sides of the head.
The same dorsal counts of the holotype (25/25/21) occur in four out of the five new specimens, while one individual (UFMT-R 12506) has reduction of two rows near the neck (23/25/21). The only female of which we were able to count ventrals (UFMT-R 12505) has three more scales than the male with the higher ventral counts (118 vs. 115, respectively), while the male with fewer subcaudals has 10 scales more than the female with the higher subcaudal counts (66 vs. 56). Similarly, the range of tail length/total length ratio is higher in males (0.29–0.32, n = 4, holotype included) than in females (0.22–0.25, n = 2). The same tooth counts of the holotype (20+2) occur in three more individuals, while the remaining ones have 19+2 maxillary teeth. The divided first ventral scales near the neck region of the holotype occur in all five new specimens.
In the field and during the three days that preceded the euthanasia of the three specimens (kept alive already in the terrarium), we recorded particular aspects of behavior and habitat use that deserve notice. The first and most contrasting behavioral feature compared with other congeners (already observed in the holotype) refers to the complete lack of aggressiveness during manipulation exhibited by all the three individuals collected alive (S1). Immediately after collection (and at all times when handled) none of the snakes expressed any mentions of biting or reacting with cloacal discharge, corroborating the previous assumptions of a general harmless behavior reported in the original description ( Moraes-da-Silva et al. 2019).
After removed from its shelter by the bulldozer, one of the specimens attempted to escape by digging the revolved soil as efficiently as some typical fossorial snake species (S2). In the terrarium, the three snakes remained inactive and completely entangled in the peat fragments for prolonged periods of the day. Apart from a few appearances outside the peat between the morning and early afternoon (8:00 AM–2:00 PM), all individuals started to become active at dusk (6:00–7:00 PM), slowly coming out from the peat snout-up, with nearly one-half of the fore trunk positioned in an almost perpendicular posture. Then, the snakes slowly left the peat and dove into the water to swim freely and explore the water column and roots of macrophytes (S3).
The uncommon display of the 90º-elevated trunk represented a position in which the specimens remained still for extended periods of time (up to 60 minutes). In the water, we recorded the specimens exhibiting this display usually anchored on water plants, but also dismissing any supporting substrate ( Fig. 4 View FIGURE 4 ). While active, the three specimens also dug galleries in the sand, remaining almost entirely buried with only a small part of the head exposed at the surface level ( Fig. 4 View FIGURE 4 ).
The period of activity (aquatic and terrestrial) lasted nearly 60 minutes; then, one by one, the snakes started returning to the peat, hiding completely, and ceasing to move. In the next morning (6:00 AM), the three individuals remained motionless and inactive in the small peat fragment. A very similar repertoire occurred repeatedly in the next two days, with activities starting around 6:30 PM, although only one of the individuals explored the water for a distinctly reduced period of time (only 10 minutes).
Discussion
The recent discovery of Helicops boitata by Moraes-da-Silva et al. (2019) reignites discussions on the long-held view of the Pantanal as an area with abundant—but few diverse—reptile species ( Junk et al. 2006; Stŗssmann et al. 2007, 2010). Nonetheless, despite the strong evidence supporting the validity of the species (including genetic data), virtually all information on its morphology, general distribution, behavior, and natural history relied strictly on the holotype. In this context, our new data not only improve the primary knowledge on strict biological features (e.g., morphological variations, behavior, and habitat use), but also shed some light on the first speculations about local abundance and spatial restrictions of a potential Pantanal endemic.
Morphological variations revealed by our five additional specimens demonstrated that some of the features assumed as unique to Helicops boitata are actually polymorphic, with the holotype exhibiting the less common condition regarding the nasal scale (entire vs. semi-divided in the five new specimens) and cloacal (undivided vs. divided in four out of five new specimens) plate. In contrast, the color pattern (especially of the venter), head shape, and the divided condition of the foremost ventral shields represent conserved and unique attributes of the species ( Moraes-da-Silva et al. 2019, 2021).
Regarding behavior, our sparse ex-situ observations suggest that Helicops boitata has predominantly nocturnal habits—in contrast with the holotype, found active in open water during the day; see Moraes-da-Silva et al. (2019) — and confirm the general harmlessness alluded in the original description, in a sharp contrast with other Helicops species ( Marques et al. 2005). Besides this odd behavioral distinction, the unique slender skull with a distinctive acuminate snout might reflect diet adaptations unrevealed by our sparse and short-term observations in life.
The fact that the species had never been detected until 2016 (date of collection of the holotype) suggested rather low local abundance rates in comparison with other conspicuously common snake species, some of which often associated with water environments [e.g., Erythrolamprus poecilogyrus (Wied-Neuwied, 1824) , Helicops leopardinus and Dryophylax chaquensis (Bergna & Álvarez, 1993) ]. Nonetheless, the finding of five individuals in the same area does not imply that previous impressions of rarity were false. Since the collection site comprised a small spot of humidity in the dry season of the Pantanal, it apparently served as shelter to several aquatic species with low dispersal capacity, preventing (or delaying) the severe physiological consequences of water stress. The high number of individuals of Helicops leopardinus found in the same area supports such an assumption, suggesting that local aggregations on sparse spots of humidity might reflect a general spatial pattern at least for small aquatic reptiles during the dry seasons in the Pantanal.
Although we concede that our field data are still far from conclusive, we must notice that the general microhabitat of the collection points of the Helicops boitata individuals differed in plant coverage and soil structure from the close site in which we found all the specimens of H. leopardinus . While the latter occupied a more humid habitat, mostly associated with the roots of water plants immersed in dense mud, the five H. boitata specimens occurred in an area mostly covered by grass and a thick peat layer, representing a relatively drier environment probably more linked to the margins of ponds. Such a substrate consistence favors the odd digging behavior detected in the field and in the terrarium, possibly indicating that H. boitata has less water affinities than other fully aquatic congeners. In fact, such micro-habitat specificities might help explain the late discovery of the species amongst other more generalist aquatic reptiles in the Pantanal basin. More conclusive data on behavior and spatial restrictions of H. boitata depend on long term monitoring studies, still scarce or totally lacking with respect to reptile species.
Finally, one could not avoid mentioning the evident conservation unfolding linked to the potential endemism of Helicops boitata to the Pantanal wetlands. The Pantanal occupies a central position in recent discussions regarding seasonal megafires that consumed large extensions of natural environments, particularly pronounced in the dry seasons of 2020 and 2021 ( Tomas et al. 2021). While a huge number of reptile specimens perished in these fires, the populations affected included mostly widespread species, abundantly represented throughout the floodplain and surrounding domains. However, the confirmed existence of a small population of a watersnake possibly restricted to specific habitats of the Pantanal requires attention and directed efforts that must be encouraged in the future.
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