Among crustaceans, numerous aquatic species are obligate groundwater-dwellers, i.e., stygobionts; their most common adaptations are the absence of eyes and a general depigmentation. Among the most widespread Eurasian stygobionts are the amphipods of the genus Niphargus. They are reported not only from groundwaters but also from groundwater-fed springs, where the abundance of food is higher, but where they also experience the constraint of UV radiation during the day. The aim of this study was to assess if in spring habitats Niphargus amphipods show diel activity, in particular if they are able to exploit the resources during the night. During two consecutive years, we evaluated, with both day and night surveys, the abundance of Niphargus sp. individuals at four springs in NW-Italy. We performed surveys both visually and with dip-nets and we evaluated the relationship between Niphargus sp. abundance and the number of potential predators. We detected a significant difference between day and night in the abundance of Niphargus sp.: during the night the number of individuals was substantially higher. No significant relationship was observed between Niphargus sp. abundance and the abundance of potential invertebrate predators. The broad implication of this study is that the number of active detectable Niphargus in springs is higher at night than during daytime, regardless of the number of potential predator species occurring. This suggests that one of the major constraints for the exploitation of spring habitats by Niphargus amphipods is the UV radiation, and that specific adaptations favouring diel activity in border habitats, like springs, may have evolved in these basically stygobiont species.
Tra i crostacei numerose specie acquatiche dipendono dalle acque sotterranee per il completamento del ciclo vitale, ovvero sono stigobie. Tali specie mostrano spesso adattamenti morfologici e fisiologici quali la mancanza di pigmentazione e l’assenza di occhi. Tra gli stigobi maggiormente diffusi in Eurasia vi sono gli anfipodi del genere Niphargus; essi si rinvengono non solo nelle acque sotterranee propriamente dette, ma anche negli ambienti sorgivi dove le risorse trofiche sono relativamente maggiori, ma dove si trovano ad esperire gli effetti delle radiazioni UV durante il giorno. Lo scopo di questo lavoro è stato di verificare se gli anfipodi del genere Niphargus osservati in ambiente sorgivo mostrino variazioni nell’attività giornaliera con un’abbondanza maggiore di individui attivi durante la notte. Nel corso di due anni consecutivi abbiamo conteggiato sia di notte, sia di giorno l’abbondanza di Niphargus sp. in quattro sorgenti del Nord-Italia. Abbiamo effettuato campionamenti visuali e tramite retino e valutato anche l’effetto dell’abbondanza di potenziali predatori.I risultati ottenuti mostrano che le abbondanze di specie di Niphargus attivi siano significativamente maggiori di notte; al tempo stesso non vi è relazione significativa con il numero di potenziali predatori presenti. Questa ricerca fornisce importanti indicazioni del fatto che in ecotoni acqua superficiale/acqua sotterranea, come nel caso delle sorgenti, le radiazioni UV possano rappresentare uno dei principali fattori che limitano la dispersione dei crostacei stigobi; sottolinea inoltre come, adattamenti quali la capacità di percepire gli stimoli luminosi, potrebbero essere insorti per favorire la colonizzazione di ambienti acquatici superficiali alimentati direttamente dagli acquiferi.
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Among crustaceans, numerous aquatic species are obligate groundwater-dwellers, i.e., stygobionts; their most common adaptations are the absence of eyes and a general depigmentation. Among the most widespread Eurasian stygobionts are the amphipods of the genus Niphargus. They are reported not only from groundwaters but also from groundwater-fed springs, where the abundance of food is higher, but where they also experience the constraint of UV radiation during the day. The aim of this study was to assess if in spring habitats Niphargus amphipods show diel activity, in particular if they are able to exploit the resources during the night. During two consecutive years, we evaluated, with both day and night surveys, the abundance of Niphargus sp. individuals at four springs in NW-Italy. We performed surveys both visually and with dip-nets and we evaluated the relationship between Niphargus sp. abundance and the number of potential predators. We detected a significant difference between day and night in the abundance of Niphargus sp.: during the night the number of individuals was substantially higher. No significant relationship was observed between Niphargus sp. abundance and the abundance of potential invertebrate predators. The broad implication of this study is that the number of active detectable Niphargus in springs is higher at night than during daytime, regardless of the number of potential predator species occurring. This suggests that one of the major constraints for the exploitation of spring habitats by Niphargus amphipods is the UV radiation, and that specific adaptations favouring diel activity in border habitats, like springs, may have evolved in these basically stygobiont species.
Tra i crostacei numerose specie acquatiche dipendono dalle acque sotterranee per il completamento del ciclo vitale, ovvero sono stigobie. Tali specie mostrano spesso adattamenti morfologici e fisiologici quali la mancanza di pigmentazione e l’assenza di occhi. Tra gli stigobi maggiormente diffusi in Eurasia vi sono gli anfipodi del genere Niphargus; essi si rinvengono non solo nelle acque sotterranee propriamente dette, ma anche negli ambienti sorgivi dove le risorse trofiche sono relativamente maggiori, ma dove si trovano ad esperire gli effetti delle radiazioni UV durante il giorno. Lo scopo di questo lavoro è stato di verificare se gli anfipodi del genere Niphargus osservati in ambiente sorgivo mostrino variazioni nell’attività giornaliera con un’abbondanza maggiore di individui attivi durante la notte. Nel corso di due anni consecutivi abbiamo conteggiato sia di notte, sia di giorno l’abbondanza di Niphargus sp. in quattro sorgenti del Nord-Italia. Abbiamo effettuato campionamenti visuali e tramite retino e valutato anche l’effetto dell’abbondanza di potenziali predatori.I risultati ottenuti mostrano che le abbondanze di specie di Niphargus attivi siano significativamente maggiori di notte; al tempo stesso non vi è relazione significativa con il numero di potenziali predatori presenti. Questa ricerca fornisce importanti indicazioni del fatto che in ecotoni acqua superficiale/acqua sotterranea, come nel caso delle sorgenti, le radiazioni UV possano rappresentare uno dei principali fattori che limitano la dispersione dei crostacei stigobi; sottolinea inoltre come, adattamenti quali la capacità di percepire gli stimoli luminosi, potrebbero essere insorti per favorire la colonizzazione di ambienti acquatici superficiali alimentati direttamente dagli acquiferi.
All Time | Past 365 days | Past 30 Days | |
---|---|---|---|
Abstract Views | 423 | 89 | 35 |
Full Text Views | 10 | 0 | 0 |
PDF Views & Downloads | 23 | 0 | 0 |