The Effects of Eyestalk Ablation on the Reproductive and Immune Function of Female Macrobrachium americanum

Abstract

Eyestalk ablation is the most common procedure used to induce crustacean reproduction in commercial hatcheries. However, other physiological and metabolic processes are affected by the removal of the X-organ sinus gland complex located in the eyestalk. In this study, the effect of unilateral eyestalk ablation on the concentration of several hemolymph metabolites, reproduction and immune function in female Macrobrachium americanum was investigated. Molting cycle time was not significantly (P=0.17) shortened in eyestalk-ablated females. However, an increased number of molts was observed in the eyestalk-ablated group because survival was significantly higher due to increased passivity and lowered aggression. As M. americanum has closed thelyca, reproduction was not accelerated after eyestalk ablation compared to control prawns. Food intake (P=0.007) and oxygen consumption (P=0.047) were both higher in eyestalk-ablated females. Concentrations of protein and glucose in hemolymph were not affected (P=0.54 and P=0.19, respectively), indicating that the demand for these metabolites was met. Glucose was metabolized by aerobic metabolism as shown by the lower lactate concentration (P=0.02) and higher respiration rate after ablation. Protein was metabolized for growth as revealed by the 100% higher growth rate in eyestalkablated females (P=0.017). Triglycerides were more highly concentrated (P=0.02) in eyestalk-ablated females. This difference was most likely due to being transported from the digestive gland to the gonad.By analyzing the immune system it was observed that only the total hemocyte count was higher (P=0.002) in eyestalk-ablated females. The protein content in hemocytes, the prophenol oxidase system and the coagulation time were not affected. In conclusion, the eyestalk ablation procedure did not cause female M. americanum to have more reproductive events over time. Despite this failure to accelerate reproduction, eyestalk ablation reduced aggression, and thus increased survival, and promoted superior growth. This result suggests that eyestalk ablation is promising for the cultivation of M. americanum.

Unilateral eyestalk ablation improves molting frequency and reproduction in Macrobrachium amazonicum females

“…In this current study, unilateral eyestalk ablation led to a 30% increase in the number of ovigerous females and a 13% increase in the number of molts. However, in species such as M. americanum, which has asynchronous molting and reproduction, these effects have been shown not to occur (Asusena et al 2012). In the present study, unilateral eyestalk ablation reduced the intermolt period in M. amazonicum females by approximately 6 days.…”

“…In general, the length of the crustacean molting cycle increases as growth occurs (Asusena et al 2012;Lobão, Rojas, and Valenti 1986;Santos and Pinheiro 2000). Reproduction (consisting of copulation and spawning) in Macrobrachium species and other caridean prawns is preceded by molting.…”

“…In some cases, mortality occurs immediately after ablation owing to the loss of hemolymph or presence of infection (Santos and Pinheiro 2000). In some species such as P. monodon (Vicente, Valdez, and Valdez 1979), P. plebejus (Kelemec and Smith 1980), and M. americanum (Asusena et al 2012), ablation does not influence survival. Other probable causes of mortality in females include nutritional deficiency, environmental stresses, spawning, handling (Primavera 1985;Pudadera, Primavera, and Young 1980), and the presence of pathogens in the culture (Chen and Chen 2003).…”

“…The eyestalk ablation has been used to induce gonadal maturation, stimulate the ovigerous state, increase the spawning frequency, and reduce the intermolt period in Macrobrachium species (Asusena et al 2012;Cunha and Oshiro 2010;Pervaiz, Jhon, and Sikdar-Bar 2011;Santos and Pinheiro 2000). To the best of our knowledge, however, there are no previous studies regarding the use of eyestalk ablation in M. amazonicum.…”

Exploring the molecular basis of adaptive evolution in hydrothermal vent crab Austinograea alayseae by transcriptome analysis

“…In hepatopancreas, the typical immune organ of crustacean, hemocyanin and serine proteinase were abundant as expected, while in the muscle, genes related to muscle formation were highly expressed, such as skeletal muscle actin 1 , troponin and myosin heavy chain . It was noted that in the eyestalk, immune related genes, ferritin , metallothionein ( MT ) and hemocyanin were highly expressed, indicating the eyestalk might be involved in the vent crab immune responses as revealed in other decapod species [ 31 – 33 ]. The gill also displayed the character of resistance to stress, with an anti-lipopolysaccharide factor ( ALF ) gene and a heat shock protein ( HSP ) gene over expressed.…”