Hatching phenology, life history and population dynamics of the Oriental clam shrimp Eulimnadia indocylindrova Durga Prasad and Simhachalam with notes on phenology patterns in the Spinicaudata

ABSTRACT

We studied the natural history, hatching phenology and egg bank composition of the Oriental spinicaudatan clam shrimp Eulimnadia indocylindrova Durga Prasad and Simhachalam using both field studies and ex situ sediment rehydration. Field observations revealed that hatching began very early (1–2 days) after inundation, and continued for about 5 days. Mature adults could be observed by 10 days, and they survived up to 16 days. The population showed a largely hermaphrodite-biased sex ratio (male:hermaphrodite 1:3) observed over three years, with a decrease in number of males throughout the hydroperiod. Both amphigenic and monogenic hermaphrodites were observed. The total lifetime fecundity recorded was about 300 eggs laid in multiple clutches. The egg bank composition showed a high proportion of intact eggs, indicative of predictable hydrations and low sediment adversity. Hatching began on the first day post-inundation for all successive cyclical hydration treatments, with peak hatching on days 2 and 3. Hatching rate was highest (57% of total hatching in successive cycles) for the first hydration, decreasing subsequently for the further hydrations. Hatching duration decreased with successive hydrations and was the longest (around 7 days) for the first hydration. Maximum hatching (93%) occurred in the first 10 days for the continuous hydration treatment. Overall, the total emergence of nauplii in successive hydrations was larger than that observed for the continuous hydration treatment, indicative of a risk-spreading strategy across hydroperiods. Early and concentrated naupliar emergence, along with decreased hatching durations for successive cycles, was observed for all the hydrations. A survey of literature revealed a general lack of data on hatching phenology of clam shrimps, particularly from tropical and sub-tropical regions. Based on the available data, it appears that hatching patterns, particularly high, early hatching fractions, are commonly observed in Spinicaudata species, and do not seem to differ much across biogeographical regions.

KEYWORDS:

• Spinicaudata
• bet-hedging
• ex situ hydration
• egg banks
• temporary habitats

Acknowledgements

This work was part of the M.Sc. dissertation of NJS at the Dept. of Zoology, Savitribai Phule Pune University, Pune. MRK and SMP thank Dr. Hemant Ghate, Modern College, Pune −05 for his comments, and Mr. Shinde, Dept of Physics, SPPU for help with electron microscopy. MRK and SMP thank the Council for Scientific and Industrial Research (CSIR, India) for research fellowships. KP is supported by the DST- PURSE, DRDP (SPPU/Zoology/2013), UPE-UoP II, UGC-CAS and BCUD grants. All the authors thank the funding agencies for their support, and the reviewers for their constructive comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Council for Scientific and Industrial Research (09/137(0556)/2014-EMR1); Board of College and University Development (BCUD 2014-16/KPai); University with Potential for Excellence – Savitribai Phule Pune University (UPE/SPPU/2016); University Grants Commission – Centre for Advanced Studies (SPPU/Zool/2016); Department of Science and Technology – Promotion of University Research and Scientific Excellence (SPPU/ DST-PURSE/Zool/2012); Departmental Research Development Program (SPPU/DRDP/Zool/2015), (SPPU/Zoology/2013))