The morphological spicules of Acaudina sp. (sea cucumber) from Delta Wulan waters, Demak, Central of Java, Indonesia

This research aims to study the morphological spicules of sea cucumber Acaudina sp. This species is belong to Class Holothuroidea, Order Molpadida, and Family Caudinidae. Samples Acaudina sp. were taken randomly from Delta Wulan Waters, Demak Regency, Central of Java. The sample was preserved by alcohol 70%. NaOCl solution was used for bleaching the samples. According to the result research, most of body part (anterior, posterior, dorsal and ventral) have rod shape, irregular rod shape, straight rod shape, and dumbbell curved.


Introduction
The Delta Wulan waters is located in the Demak waters, the northern part of Central of Java.The area of Delta Wulan is 25 km 2 .Tidal activity affects the development of Delta Wulan, so the mouth of the Wulan Rivers divided into two parts [15].The presence of transport sediments in both branches of the Wulan River causes high productivity in the Delta Wulan Waters.[15].This causes the waters of the Delta Wulan to find many types of benthic and pelagic organisms such as blue crabs, crabs, clams, cockles, gastropod, sea cucumber, and various other types of fish [16].Study on the existence of sea cucumber have been carried out in the Delta Wulan Waters [10].
The existence of Acaudina sp. in the Delta Wulan Waters side by side with Paracaudina sp., Phyllophorus sp., and Phyrella sp., Acaudina sp. was found in clay-sandy subtract, with salinity 28-35ppt, and temperature 28.6-29.9°C[1].Acaudina sp. are found in the Waters of East Asia to Southeast Asia [2], The presence of sea cucumbers Acaudina sp. are located in the Paloh Waters, Sambas Regency, West Kalimantan, Delta Wulan Waters, Kenjeran Waters (Surabaya) [3,10,14], Although in the Delta Wulan Waters, Demak areas, Acaudina sp.do not eaten by the community.Still, in the another area, some peoples eat Acaudina sp in Riau Archipelago.Whereas Acaudina sp. has an important role in the benthic ecosystems such as enhancing redox potential in sediment, increasing mineralization and nutrient cycling in sediment subtrate [4,5,10].Additionally, A. molpadiodes from Paloh Waters, West Kalimantan contains relatively high protein, an essential mineral, and fucoidan [3,17,18] Furthermore, A molpadiodes from Riau Archipelago Waters showed that there was antibacterial activity toward Staphylococcus aureus, and Escherichia coli [13,19].
Taxonomically, the sea cucumber Acaudina sp.grouped into phylum Echinodermata, class Holothuroidea, order Molpadida, family Caudinidae, genera Acaudina sp.[2,6,7,12] Most of sea cucumbers belong to family Caudinidae are very similar in body shape and color.It is very difficult to identify the morphology of family Caudinidae (Caudinid) on the body's external.Some researcher have succeeded in identifying DNA for sea potato (A.molpadiodes) [11].Furthermore the study for completing genome was conducted to identify A. molpadiodes [11].DNA analysis is very expensive to perform, therefore identification of sea cucumber can be done by observing the spicules in the body tissue.During the preservation process, specimen often loses their external characteristic, so preserved species are very dependent on the characteristic of the spiculesound in the sea cucumber body tissue [6,9].
According to research on the Cook Strait, Zew Zealand has successfully identified species from 235 species Holothurian such as genera Acaudina sp., and Paracaudina sp.[6] According to the observation of spicules from body wall tissue of sea cucumber, in the Johor Strait Waters, Malaysia were found Acaudina australis, A. bacilla, A. hualoeides, A. leucoprocta, A. molpadioides, A. pellucida, A. punctata, and A. suspecta [9].This research aims to determine and identify morphologically through the characteristics the spicules of Acaudina sp.

Material and method
Sea cucumbers Acaudina sp. were collected randomly by dreged bottom trawl from Delta Wulan Waters, Demak.This research need some equipment such as; bottles, camera, dissection kit, pipette, object glass, light microscope, alcohol, and NaOCl (Sodium hypochlorite) solution.Samples were preserved with 70% alcohol [20].
In the observing the phenotype of the sea cucumber Acaudina sp., morphological observations were done on the external body and inside of body tissue, namely ossicles (spicules), calcareous rings, tentacle ampullae, polian vesicles, longitudinal muscles, respiratory tree and cloaca.Some stages will be carried out on the observation spicules, such as: (a) body tissue take as much as 1 cm 2 for each body part (dorsal, ventral, anterior, posterior, and tentacles); (b) Put the tissue in beaker glass and then soak it in a beaching solution (NaOCl) during 15 minutes until all the tissue remove; (c) Furthermore, wash the spicules with distilled water as much as 7 times; (d) Spicules samples were put into the object glass and then was examine spicules (e) Spicules samples observed under light microscope with 100 x magnification.

Result and discussion
The body shape of Acaudina sp. is cylindrical with the posterior part having a small shape.The length of this biota can reach 14-15 cm in fresh condition.According to observations, sea cucumber Acaudina sp.do not have tube feet, and smooth body.In fresh condition, the body of this sea cucumber has a transparent orange color and slightly ivory whiteness.This research fit with the morphological study of A. molpadiodes from Kenjeran Surabaya, which showed that this organism has an orange and ivory whiteness color [14].Meanwhile, the anterior part, especially the tentacles, is slightly yellowish in color.According to observation, Acaudina sp has 15 tentacles located anteriorly.This is in accordance with the results of a study which stated that A molpadiodes has 15 tentacles with yellowness [12].Although Acaudina rosettis has the same number of tentacles as A. molpadiodes, A. molpadiodes has different spicules with A rosettis [9].While in the preserved form, the sea cucumber is pale white in color.The body part of the preserved sea cucumber has lost its orange color, but the anterior part is still a pale yellow color.On the fresh sample, there is a fairly longitudinal solid muscle and has orange color (Figure 1).

Calcariuos ring
According to observation, the calcareous ring Acaudina sp. has consisted of 12 radial shape, and 10 inter-radial (Figure 2).This fit with the research result from [9].There are inter-radial shapes between radial shapes and the color of the calcareous ring is ivory white.

Spicules in tissue of Acaudina sp.
According observation in all of tissue on part of anterior, posterior, dorsal and ventral, the Acaudina sp. has ossicles shape predominantly irregular rod, straight rod and dumbbell.(Figure 3).This research fits with [9,12], which showed the presence of short thick smooth rods in straight, irregular or dumbbell of curved form as indicated for small species of Acaudina molpadioides.Based on observations of the anterior, posterior, dorsal and ventral tissues, the types of ossicles found were straight rod, irregular rod, straight curve rod and dumbbell of curved (Figure 3).Comparing with results of others studies, in this study no perforated plate form was found.However, the most common results were straight rod, irregular rod and dumbbell forms [12].Compared with the spicules from Paracaudina australis which have various spicules shapes [1,2], A. molpadioides only found spicules that did not vary.Furthermore, spicules were not found in the tentacle tissue, this fit with research result from [9,12] showed that in the tentacles tissue Caudinid were not detected spicules.

Conclusion
In the body tissue of Acaudina sp, the dominant spicules in the anterior, posterior, dorsal and ventral tissues were straight, irregular, curve, and dumbbell (nut).There are no spicules in the tentacle tissue.Based on the spicules found in body tissues, it can conclude that the type of sea cucumber is A molpadioides.