Delivery of hatching larvae to estuaries by an amphidromous river shrimp: tests of hypotheses based on larval moulting and distribution

Abstract

1. Amphidromous shrimps live and breed in freshwater rivers and streams, but their larvae require development in sea water. Larvae may hatch upstream and then drift to the sea, although in some species females have been reported to migrate to the coast before larvae are released. Here, we tested the relative importance of larval drift and female migration in Macrobrachium ohione (Decapoda: Palaemonidae) in a distributary of the Mississippi River in Louisiana, U.S.A. 2. Newly hatched (stage-1) larvae are nonfeeding and will not moult to stage 2 (first feeding stage) without encountering salt water. A factorial experiment was conducted in the laboratory to test the effects on moulting to stage 2 of (i) time spent by stage-1 larvae in fresh water before (ii) exposure to and maintenance in water of different salinity. Larvae kept in fresh water for 1 or 3 days before a change to saline water at 6 or 10 ppt showed a greater frequency of moulting than those kept for longer (5 days) in fresh water or changed to less saline water (2 ppt). Non-moulting larvae died or were moribund within 11 days of hatching. 3. The relative abundance of stage-1 larvae was measured with plankton tows at two locations in the river c. 150 km apart, one near the sea and one upstream. Larval abundances near the sea were significantly greater than those upstream. 4. The results indicate that hatched larvae of M. ohione have a limited period in which to drift in fresh water before reaching water sufficiently saline to stimulate moulting to the first feeding stage. Female migrations may play an important role in delivering larvae of amphidromous species from large continental river systems in which distances to the sea are great, while larval drift alone may be sufficient in species living in short streams, like those found in many small mountainous tropical islands.

A test of large-scale reproductive migration in females of the amphidromous shrimp Macrobrachium acanthurus (Caridea : Palaemonidae) from south-eastern Brazil

“…Parental females migrate towards river mouths and/or estuaries to hatch larvae in M. idella (Mohamed and Rao 1971), M. australiense (Lee and Fielder 1979), M. petersi (Read 1985), M. rosenbergii (John 2009) and M. ohione (Bauer and Delahoussaye 2008;Rome et al 2009;Olivier and Bauer 2011). On the other hand, the reproductive behaviour herein reported for M. acanthurus is similar to that observed in several other congeneric species.…”

“…For instance, it is not clear whether females migrate towards estuaries to hatch larvae, as is reported to occur in other congeners (Mohamed and Rao 1971;Lee and Fielder 1979;Read 1985;Bauer and Delahoussaye 2008;John 2009;Rome et al 2009;Olivier and Bauer 2011), or whether females hatch larvae anywhere along the river. Choudhury (1971) demonstrated that larvae of this species have the ability to live in freshwater for ,1 week after hatching.…”

Amphidromy in shrimps: a life cycle between rivers and the sea

“…The proportion of reproductive females with embryos near hatching was much higher in the Atchafalaya Delta (estuary) than 150 km upstream. Rome et al (2009) sampled larvae in the river and found a much greater abundance of hatching (Stage I) larvae within the estuary than at the upstream location, supporting the view that most females are hatching larvae in the estuary. The females of populations of M. ohione, in the lower Mississippi River, have similar migrations as indicated by the upstream-downstream distribution of females bearing embryos near hatching (Olivier & Bauer, 2011).…”

“…Instead, the larvae utilize yolk droplets remaining from embryonic development as a nutritional resource. Such larvae must molt to Stage II (first feeding stage) or sometimes Stage III (Anger & Hayd, 2010) before their food stores are used up or they will starve to death (Rome et al, 2009 and references therein).…”

Crustáceos decápodos de la cuenca del Río Sinú, Córdoba, Colombia

“…Las hembras ovadas de estos camarones utilizan los tributarios y efluentes para realizar sus migraciones hacia las partes más bajas del río, con el fin de liberar sus larvas en condiciones ambientales favorables (Jalihal et al, 1993;Rome et al, 2009). Este proceso de alta conectividad entre la zona alta, media y baja del río Sinú, se debe al mayor volumen de agua durante la época de lluvias; en contraste con la separación que se presenta entre varias localidades del río durante la época seca.…”