# Effect of salinity on the feeding behavior of Cordylophora caspia (Pallas, 1771) (Hydrozoa)

## TL;DR

This study examines how different salinity levels affect the feeding behavior of the invasive hydrozoan Cordylophora caspia on various prey types.

## Contribution

The study provides new insights into the feeding preferences and functional responses of C. caspia across different salinities and prey types.

## Key findings

- C. caspia showed a Type II functional response on all tested prey species.
- Prey consumption and preference were higher for copepods compared to rotifers.
- Higher prey consumption occurred at salinities of 10 and 20 g L−1 compared to 30 g L−1.

## Abstract

Cordylophora caspia, is considered an invasive species in America. We isolated this hydrozoan from the brackish water section of the River Tuxpan (State of Veracruz, Mexico) and cultured it in the laboratory on mixed prey of copepods and rotifers at a salinity of 20 g L−1. C. caspia is tolerant of a wide range of salinities. Most studies on C. caspia report its feeding and population growth on Artemia nauplii. Here we tested the effect of salinity on functional response and prey preference on Brachionus plicatilis (Rotifera), Apocyclops panamensis (Copepoda, Cyclopoida) and Nitokra lacustris (Copepoda, Harpacticoida). Experiments were conducted at 25°C. The hydrozoan killed several prey during functional response studies, which we assumed that it would eventually consume. On all prey test species, C. caspia showed a Type II functional response. Prey consumption, in terms of biomass, and preferences was higher on copepods than on rotifers. Prey consumption was higher at salinities of 10 and 20 g L−1 than of 30 g L−1.