Co-occurrence of free-swimming and quiescent nauplii in a spring hatching of two Chirocephalus diaphanus Prévost, 1803 (Anostraca) populations from mountain pasture pools

Abstract

The anostracan, Chirocephalus diaphanus Prévost, 1803 presents variation in the timing of hatching, since embryos can fall free of the shell and remain in a quiescent state in a small cocoon formed by the hatching membrane. The co-occurrence of free-swimming and quiescent nauplii in a spring hatching was investigated by comparing the cyst behaviour of two local populations colonizing a short-and a long-lived mountain pool. In each pool, a constant number of ovigerous females was collected at the beginning and end of their life cycle. Immediately after deposition, the cysts were removed, counted, and subsequently stored in the laboratory for hatching tests. There were significant differences between the two biotopes in the frequency of pre-hatched nauplii. This confirms the ecological importance of the state of suspended development referred to as quiescence, suggesting that it plays a fundamental role in microevolutionary processes in Anostraca. RIASSUNTOLa specie Chirocephalus diaphanus Prévost, 1803 (Anostraca) produce uova durature (cisti) caratterizzate da una spiccata variabilità di schiusa dovuta alla comparsa ed alla persistenza di embrioni che non schiudono immediatamente ma rimangono all'interno della membrana che li avvolge in uno stato di quiescenza. Tale meccanismo di schiusa ritardata è stato osservato in laboratorio confrontando la reattività delle cisti prodotte da due popolazioni naturali di C. diaphanus d'alta quota caratterizzate da un diverso ciclo idrologico. In ciascun bacino sono state raccolte le covate di un campione costante di femmine mature all'inizio ed al termine del loro ciclo vitale. Immediatamente dopo la deposizione, le cisti sono state raccolte, contate e successivamente sottoposte ai tests di schiusa. Le differenze statisticamente significative rilevate fra le percentuali di embrioni quiescenti osservate nei due biotopi confermano l'importanza adattativa delle prime fasi di schiusa. Le uova durature prodotte dai Crostacei Anostraci giocherebbero infatti un ruolo fondamentale nei processi microevolutivi delle popolazioni locali.

Combined effect of temperature and salinity on hatching characteristics of three fairy shrimp species (Crustacea: Anostraca)

“…This observed delay in cyst hatching is supposed to be an adaptation to overcome unpredictable seasonal changes that could be fatal for the adult life-phase. In this sense, the existence of a marked inter-and intraspecific variation observed in the hatching pattern of fairy shrimps (Merta, 2003;Zarattini, 2004;Zarattini and Mura, 2007), has provided evidence that a different cyst reactiveness exists, and this is related to the degree of environmental unpredictability (Belk and Cole, 1975).…”

Observations on the hatching dynamics and phenology of co-occurring large branchiopods from a small temporary pool in western India usingex situsediment rehydration

“…Sediment rehydration has also been used extensively to study ecological and evolutionary aspects of egg banks (Simovich and Hathaway, 1997;Mura, 2001Mura, , 2004Rossi et al, 2004Rossi et al, , 2012Zarattini, 2004;Zarattini and Mura, 2007) in these Crustacea (see Brendonck and De Meester, 2003 for a review). Only few such studies have been carried out from the Asian region (Saengphan et al, 2005;Wang and Chou, 2015), while most data are available from the temperate zone.…”

Spatial Niche Differentiation of Sympatric Branchiopoda in a Highly Unpredictable Ephemeral Pool

“…Ephemeral pools are unique aquatic habitats characterized by periodic drought and inundation (Williams, 1985;Brendonck, 1996;Simovich and Hathaway, 1997) and usually forms after snowmelt in spring (Daborn, 1975;Mossin, 1986;Saiah and Perrin, 1990;Mura, 2001;Zarattini and Mura, 2007), seasonal river flooding (Eder and Hödl, 2002), artificial irrigation as in rice paddies (Grygier et al, 2002), or heavy rainfall (Huang et al, 2010). Many ephemeral pools are dominated by branchiopods, including fairy shrimps (Anostraca) and clam shrimps (Laevicaudata and Spinicaudata).…”