Occurrence and morphological variability of Hydra (Hydroida: Hydridae) in freshwater bodies of Southeast of Buenos Aires Province, Argentina

Maria Irene Deserti; Fabian Horacio Acuña

doi:10.30550/j.azl/2227

Authors

Maria Irene Deserti Laboratorio de Biología de Cnidarios (LABIC), Facultad de Cs. Exactas y Naturales (FCEyN), Universidad Nacional de Mar del Plata (UNMdP) https://orcid.org/0000-0003-4809-3608
Fabian Horacio Acuña Laboratorio de Biología de Cnidarios (LABIC), Facultad de Cs. Exactas y Naturales (FCEyN), Universidad Nacional de Mar del Plata (UNMdP) https://orcid.org/0000-0003-3075-2492

DOI:

https://doi.org/10.30550/j.azl/2227

Keywords:

freshwater cnidarians, intraspecific variation, wetlands

Abstract

Hydra constitutes a monophyletic clade of sessile and solitary polyps
that occur on all continents except Antarctica. Despite its widespread
presence in freshwater habitats, Hydra requires reasonably unpollut-
ed conditions for survival, making its presence a reliable indicator of
good water quality and a certain degree of ecosystem conservation.
Since their discovery, these polyps have become valuable biological
models due to their morphological simplicity, global distribution, and
low maintenance requirements in the laboratory conditions, enabling
experiments on regeneration, reproduction, senescence, cellular differ-
entiation, among other processes. All Hydra species are clustered into
four morphological groups: viridissima (green), vulgaris (common), oli-
gactis (stalked), and braueri (gracile). Species in the viridissima group
are green due to the presence of intracellular symbiotic algae, whereas
the brown hydras (braueri, oligactis, and vulgaris) lack such endosym-
bionts. The oligactis and braueri groups are restricted to the Northern Hemisphere, while the viridissima and vulgaris groups include cosmo-
politan species. To date, only five published records documenting the
presence of Hydra in Argentina are available in the scientific literature.
In the present study, we report six new occurrences from four wetlands
in the southeastern region of Buenos Aires Province: two each for H.
viridissima, H. vulgaris, and H. vulgaris pedunculata. The study includes
a quantitative morphological analysis (body measurements, cnidome,
and reproductive structures) to assess intraspecific variation among pop-
ulations from different freshwater bodies. These findings expand the
known distribution of Hydra in South America and provide reference
data for future ecological and taxonomic studies.

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