Limnetica 31

Anaecypris hispanica is the most threatened cyprinid fish in the Iberian Peninsula. The distribution of this Iberian cyprinid is restricted to the Guadiana River drainage and a single tributary in the Guadalquivir River and has been rapidly diminishing over the past thirty years. Several A. hispanica populations have been depleted to a point which individual densities are below a level where adults can be detected, making it necessary to identify A. hispanica larvae to assess populations and to make declarations about local extinctions. This work is the first detailed description of the larval stages of A. hispanica from egg to stage 5 observed from laboratory-reared specimens. The eggs are spherical, adhesive, and transparent, and they measure 1.4 mm (mean diameter). The larvae hatch 72 hours after activation and measure 5.0 mm (mean total length-TL). The notochord flexion occurs at 5.9 mm (mean TL), and larvae have 38-39 total myomeres. Anaecypris hispanica larvae have little cephalic pigmentation with few melanophores anterior to the eyes, although pigmentation intensifies during development. Identifying features are presented here that will enable researchers to distinguish A. hispanica from other sympatric species. This information will allow us to identify larvae and can help to assess whether this species is present at locations where adults are not detected.