INTRODUCTION
Neocaridina denticulata sinensis is an indigenous species of Japan,
Korea, China, Vietnam and Taiwan (Hung et al., 1993).
According to Cai (1996), N. d. sinensis comes
from pond, river, agricultural canals, mountain streams and reservoirs of its
indigenous area. Previously N. d. sinensis from Nuuanu Stream,
Oahu was incorrectly identified as Caridina weberi by Devick
(1991). Unlike the native freshwater atyid shrimp Atyoida bisulcata,
N. d. sinensis does not have an obligate marine phase (Hung
et al., 1993). As they occupy similar habitats, it is possible that
N. d. sinensis can compete with A. bisulcata (Englund
and Cai, 1999). Holthuis (1993) stated that N.
d. sinensis was placed under the genus Caridina before being reclassified
under Neocaridina. This classification was based on the morphological
difference in male, that is the presence of endopod on the first pleopod. While,
Kubo (1938) strengthen it with the appearance of appendix
masculina on its second pleopod.
Many freshwater shrimp from the family Atyidae have been growing in popularity
in the aquarium industry over the past years (Heerbrandt
and Lin, 2006). N. d. sinensis is one of these atyids. It was first
introduced in the aquarium industry in 2003. The bright red colored shrimp looks
great in contrast to green aquatic plant or against dark colored background.
Not only this shrimp enriched the look of the freshwater tank, it is also excellent
maintenance crews in a cleaning the aquatic plants compared to other shrimp,
including the popular Amano shrimp, Caridina japonica (Demas,
2007). According to Niwa and Ohtaka (2006), live
N. d. sinensis imported to Japan from Korea and China were to fulfill
demands in recreational fishing, used as baits for black sea bream, Acanthopagrus
schlegeli and black rockfish, Sebastes inermis. Freshwater shrimp
in Kalimantan, Indonesia were sampled using light trap (Ahmadi,
2012).
In Taiwan, there are 15 species of atyid from 3 genera which include Atyopsis,
Caridina and Neocaridina (Hung et al.,
1993; Shih and Cai, 2007). Similar to palaemonid
shrimps, atyidae demonstrated three types of larval development, normal, abbreviated
and completely suppressed (Shokita, 1981; Shy,
1994). Most of these atyids undergoes the normal type of larval development
and produce relatively small-sized eggs with long planktonic phase. As for abbreviated
type, larval of planktonic phase only takes few days. However, for the completely
suppressed type, eggs were relatively large-sized without planktonic phase since
the larvae hatched in benthic form.
Successful breeding and mass production of this shrimp can provide avenue for
the aquarium industry and contribute to national income. Currently an adult
size N. d. sinensis is priced between MYR 2-3 each. Previous study
by Yang and Ko (2003) provides little information on
the larval development of this shrimp and none on the breeding and complete
life cycle. Thus, this study was conducted with the objective to breed and observed
the life cycle of N. d. sinensis in laboratory condition.
MATERIALS AND METHODS
Experimental works on N. d. sinensis were conducted in the Endocrinology Laboratory, Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
Tank preparation and maintenance: Different sizes of plastic aquarium tank were used for conditioning female broodstock (40x24x30 cm), conditioning male broodstock (35x17x25 cm), breeding (40x24x30 cm), separating ovigerous female (7x7x10 cm), conditioning larvae (26x16x16 cm) and life cycle observation (40x24x30 cm). Throughout this study, PVC pipe (Ø 16 mm) was used as shelter during molting. Aerated tap water was de-chlorinated and used as source of water. Aeration was provided throughout the study period.
Feeding and water quality: Broodstock and larvae were fed ad libitum with commercial shrimp feed containing 40% protein twice a day at 08:00 and 17:00 h. About 50% water change was carried out once a week. Few main water quality parameters measured in this study. The kits or apparatus used were; DO meter (dissolved oxygen and temperature) and API aquarium freshwater test kit (pH, ammonia, nitrite). Measurements were taken twice a week.
Broodstock conditioning: Matured males and females N. d. sinensis were bought from nearby aquarium shops. About 30 females and 30 males used were with average total length of 2.5±0.5 cm and placed into two separated conditioning tanks. Conditioning process takes about one month. Only females with saddle and healthy males were used.
Breeding: Ten pairs of matured male and female N. d. sinensis were placed in breeding tank. Observation was carried until female shrimp become ovigerous.
Larvae: Each of ovigerous females were weighed and moved to individual tank. Female was removed after the larvae hatched. Number of larvae produced by each female was counted and recorded. Larvae produced from the earlier experiment were placed and conditions in tanks for a week. After a week, only healthy larvae were used for the next experiment.
Life cycle: Thirty larvae (one week old) were placed in tank. Observation
was carried out until all the larvae reached first maturity. Life cycle of N.
d. sinensis was presented into illustration form. Total length (TL) of N.
d. sinensis was measured from rostral tip to posteromedian margin of the
telson, excluding posterior setae following Yang and Ko
(2003). Larvae and eggs were observed and measured using ocular micrometer
placed in the microscope eyepiece of Leica DM750, compound microscope with scale
bar. Photographs were taken using Canon S95 digital camera. Ranges of water
quality parameters observed throughout this study were recorded.
RESULTS
N. d. sinensis reached first maturity at around 75 days old with TL 2.3±0.2 cm. Upon reaching maturity, the presence of orange colored ovaries can be seen through the cephalothorax region of the females (Fig. 1). Appendix masculina on the second pleopod (Fig. 2) were observed in males. Mating process usually take place 1-3 day(s) after the introduction of male and female into the same tank. Female molted prior to mating.
Both molting and mating occurred rapidly in less than 10 sec. During mating process male and female of N. d. sinensis will be facing each other and sperm were deposited into the genital opening of female N. d. sinensis using its appendix masculina. The eggs were fertilized when it passed through the sperm on the way to the brood pouch. The pouch was formed by pleopods and overhanging of pleura of the female. A day after mating, female was observed to carry fertilized eggs. The eggs were incubated in the brood pouch until hatch.
Fertilized eggs were oval in shape, vary from greenish to yellowish in color. The egg size was comparatively large, with an average length 1.19 mm. Thin ribbon-like filament binds the eggs in grape-like bunches and attached it to the female's pleopod. The membrane can hardly be distinguished since it is thin, transparent and lying close to the surface.
|
Fig. 1: |
Matured female N. d. sinensis with visible orange colored
ovaries (arrow) in the cephalothorax region |
At 27°C, embryonic development of N. d. sinensis lasted for 15 days.
The eggs became lighter in color and translucent just before hatching. Newly
hatched larvae look like the miniature version of the adult (Fig.
3) with an average TL of 2.3±0.5 mm. Figure 4 showed
the number of larvae produce by females.
|
Fig. 2: |
Appendix masculina (arrow) on the second pleopod of matured
male N. d. sinensis |
|
Fig. 3: |
Newly hatched larvae of N. d. sinensis |
|
Fig. 4: |
Linear regression of fecundity (number of larvae produce)
based on weight of female N. d. sinensis |
It ranged from 21-51 larvae per hatching, increased linearly (R2
= 0.9587) with the size of the female. Larvae reached juvenile stage after 60
days. At this stage, male and female were undifferentiated. Juveniles take 15
days to reach adulthood and first maturity. Complete life cycle of N. d.
sinensis is presented in Fig. 5.
During the study period, it was found that larvae and adult shrimp cultured in freshwater were susceptible to clitellate annelids, Holtodrilus sp. (Fig. 6) resulted in high mortality.
|
Fig. 5: |
Life cycle of N. d. sinensis |
|
Fig. 6(a-c): |
Holtodrilus sp. were distributed all over the body
surface of N. d. sinensis cultured in freshwater, (a) Holtodrilus
sp. attached to the naupliar appendages of larvae, (b) Holtodrilus
sp. elongated (arrow) ready to move and (c) Tooth (arrow) on the jaws
of Holtodrilus sp. |
Table 1: |
Ranges of water quality parameters measured during the study
period |
 |
Holtodrilus sp. with body length 0.5-0.6 mm were found distributed all
over the body surface of the host, with a higher concentration around the appendages.
Culture of this species in slight saline condition between 5-10 ppt can effectively
treat this annelid. Water quality parameters like dissolved oxygen (DO) was
more than 4 mg L-1, temperature 27-28°C, pH 6.5-7.5 and ammonia
and nitrite less than 0.1 mg L-1, respectively (Table
1).
DISCUSSION
In this study, N. d. sinensis was found to be able to reached first
maturity as early as 75 days old, which is similar to those reported by Demas
(2007). Female molted prior to mating, possibly induced by the released
of certain chemical substance into the surrounding water. Somehow, before or
during molting, the release of this substance allows the male to detect gravid
female in the water column. This signaled the male that female is ready to spawn.
Newly hatched larvae of N. d. sinensis look like the miniature version
of adult similar to that observed by Yang and Ko (2003).
Morphological differences were only observed when N. d. sinensis reached
maturity with the appearance of endopod and appendix masculine in males, which
is similar to the report by Englund and Cai (1999). N.
d. sinensis lacked of planktonic larval stage, therefore, it is a completely
suppressed type based on the type categorized by Lai and
Shy (2009). Numbers of egg produced per female of freshwater shrimp is depending
on the size of the female itself. Smaller females produced fewer eggs compared
to larger females (Ketse, 2006). In the present study,
the size (weight) of female N. d. sinensis had a linear and positive
relationship (R2 = 0.959) with number of larvae produced. Similar
observation was reported on Caridina gracilirostris (Heerbrandt
and Lin, 2006).
Female N. d. sinensis was observed to incubate and fan their eggs in
the brood pouch. According to Adiyodi and Adiyodi (1994)
this kind of parental care will results in higher survival rate of larvae produced.
Similar to those reported by Schram (1986), N. d. sinensis
eggs were incubated in brood pouch until hatching.
Infestation by clitellate annelids on N. d. sinensis is quite common.
Similar observation on others freshwater shrimp was reported by Liang
(1963) and Liu (1984). This study suggested it is
better to culture N. d. sinensis larvae in slightly saline water (5-10
ppt) since clitellate annelid, Holtodrilus sp. will not be able to tolerate
saline water. Study by Niwa et al. (2005) stated
that clitellate annelids, Holtodrilus truncatus infestation on freshwater
shrimp can be treated with saline water.
CONCLUSION
Neocaridina denticulata sinensis can successfully breed in laboratory
conditions using a simple experimental setup. This shrimp is able to reach first
sexual maturity earliest at 75 days old. It reproduces throughout the year.
It is recommended to culture newly hatched larvae in slight saline water (5-10
ppt) to avoid infestation and mortality due to clitellate annelid. The findings
of this study can be used as a guideline for culturist interested in the mass
production of this ornamental shrimp for the aquarium industry.
ACKNOWLEDGMENT
Author would like to thank the Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, Serdang, Selangor, Malaysia for providing the materials and facilities for this research.