new record of thalassina spinosa (crustacea: decapoda...

Key words: distribution, Gebiidea, Indo-West Pacific, Panay Island, Philippines, Thalassina

New record of Thalassina spinosa (Crustacea: Decapoda: Gebiidea: Thalassinidae) from the Philippines

1Camp John Hay, Baguio City, Philippines2Zoological Society of London - Philippines, La Paz, Iloilo City, Philippines

*Corresponding author: [email protected]

Agatha Maxine B. Bedi1,* and Jurgenne H. Primavera2

The mud lobster Thalassina spinosa Ngoc-Ho and de Saint Laurent, 2009 is reported for the first time in the Philippines based on material collected from a mangrove swamp of Ibajay, Aklan in Panay Island. It is the third species of the genus Thalassina recorded from the country. Although burrowing activities of the Thalassina species create volcano-like mounds that are commonly seen in coastal areas, their species are very little known in the country. Four plots, each measuring 10 m x 10 m, were laid out in the 44-ha Katunggan It Ibajay Eco-Park (KII) which is situated inside a 70-ha mangrove patch with 27 mangrove species in the villages of Naisud and Bugtong-Bato. Juvenile specimens of T. spinosa and T. anomala specimens were obtained from the same plot located in a mixed forest along the banks of the main tidal creek. The mud lobsters’ mounds ranged from 2 cm to 30 cm in height and 4 cm to 15 cm in width. All T. spinosa specimens showed a spinose carapace and an armed cervical groove. Diagnostic characters and geographical distribution of T. spinosa are briefly discussed.

Philippine Journal of Science147 (3): 357-361, September 2018ISSN 0031 - 7683Date Received: 15 Jun 2017

INTRODUCTIONAmong decapod crustaceans, the family Thalassinidae is classified in the infraorder Gebiidea. Thalassina Latreille, 1806 is the sole genus belonging to the family and commonly called mud lobsters. It contains ten species from the Indo-West Pacific region (Lin et al. 2016): T. anomala Herbst, 1804; T. australiensis Sakai and Türkey, 2012; T. gracilis Dana, 1852; T. kelanang Moh and Chong, 2009; T. krempfi Ngoc-Ho and de Saint Laurent, 2009; T. pratas Lin, Komai & Chan, 2016; T. saetichelis Sakai and Türkey, 2012; T. spinirostris Ngoc-Ho and de Saint Laurent, 2009; T. spinosa Ngoc-Ho and de Saint Laurent, 2009 and T. squamifera De Man, 1915.

Species of Thalassina are shy and inhabit in burrows found in littoral and infra-littoral zones (Holthius 1991),

but their large mounds can be easily recognized. The mounds are often associated with mangrove swamps or mangrove forests (Sankolli 1963). Ng and Kang (1988) noted that T. anomala seemed to develop a tolerance to the noxious anaerobic mangrove mud. Their constant digging and burrowing activities, however, aerate the mangrove soil, bring fresh mud to the surface, and thus play a role in the recycling of nutrients in the mangrove ecosystem.

Only two mud lobster species – T. anomala and T. squamifera, widely distributed across the Indo-West Pacific – have been reported from the Philippines (Ngoc-Ho & de Saint Laurent 2009). During a recent field research in Panay Island, the researchers found Thalassina spinosa as a new record and the third species of the genus from the Philippines. The present paper provides new information on T. spinosa based on the collected material.

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Figure 1. A biotope map of KII indicating the position of the creeks and sampling plots. Retrieved and modified from “Baseline assessment of fisheries for three species of mud crabs (Scylla spp.) in the mangroves of Ibajay, Aklan, Philippines” (Lebata et al. 2007).

MATERIALS AND METHODS Study Area

Thalassina specimens examined in this study were collected from Katunggan It Ibajay Eco-Park (KII), Ibajay, Panay Island in 2016. KII is situated in a 70-ha mangrove patch that has high plant species diversity, with mature (at least a century-old) and young (less than a century-old) mangrove trees. Natural mangroves cover 50 ha and the remaining area comprises plantations of Nypa fruticans, settlements and cleared areas (Lebata et al. 2012).

The total area has three creeks (Fig.1); the main creek forms Naisud River towards the sea and turns into a creek as it moves landward. Two other creeks are Paraw creek and a shorter creek that ends in a mature forest of Avicennia rumphiana and Avicennia officinalis.

Four sampling plots were designated in KII (Fig.1): plot A (Ceriops decandra patch), plot B (mixed species community), plot C (mature forest of A. rumphiana and A. officinalis), and plot D (Nypa plantation). Sampling plots of 10 m x 10 m were measured with a transect tape, demarcated with sticks and tied with yellow ribbons for visibility.

MethodFor capturing mud lobsters, two bamboo snare traps used by fishermen to capture crabs were inserted into their burrows. The cylindrical trap (31 cm long by 3.7 cm in diameter) contained two holes: one for the trigger and the other for a paddle-like piece of wood to slip in and block the trap entrance if triggered by the movement

of the animal. Mounds with moist and black mud were partially excavated to place the trap securely in the hole, in the late afternoon around 17:00 h and retrieved the next morning at 08:00 h. However, individuals were also caught by directly picking from the entrance of their mounds when the water level rose due to high tide or rainfall. They were then washed, and the total length (from the tip of the rostrum to the tip of the telson) and carapace width were measured with a vernier caliper. Specimens were labelled and stored in 70% ethanol for preservation. The morphological features used in the description follow the terminology used in Ngoc-Ho and de Saint Laurent (2009).

Architectural (width and height of mounds), physicochemical (salinity and pH), and environmental parameters (fauna and flora) were measured and identified in the plots. A tape was used to measure the mound dimensions. A pH meter and a refractometer were used to measure pH and salinity of the water, respectively, inside the mounds.

RESULTSJuvenile individuals of T. spinosa and T. anomala were collected by hand-picks and some of them excavated from their mounds during high tide or rainfall in plot B.Adult T. anomala individuals were caught during 12 snare trap trials. The 67% snare failure rate was mainly due to the ability of the mud lobster to sidestep the trap (Fig. 2) by making a new exit hole or exiting from one of tunnels.

Philippine Journal of ScienceVol. 147 No. 3, September 2018

Bedi & Primavera.: New Record of Thalassina spinosa from the Philippines

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Table 1. Mud lobster samples collected from each plot.

Plots Number of individuals

A 2 T . a n o m a l a

B 4 T . s p i n o s a4 T . a n o m a l a

C 2 T . a n o m a l a

D 0

Figure 2. Snare trap that was outsmarted by a mud lobster.

Two mature Avicennia rumphiana and Avicennia alba trees bordered plot B. Small mounds were dominant, ranging from 2 cm to 30 cm in height and 4 cm to 15 cm in widest diameter. The mounds of T. spinosa individuals were constructed from clayish and sandy soils. Each primary mound contained one straight tunnel, measuring less than one meter and leading into the ground. Mounds were separated from each other and significantly smaller in size compared to bigger mounds found in other plots, particularly in plot C where adult T. anomala individuals were collected. Plot C was located at the edges of creek 3,400 m into the mature forest of A. rumphiana/A. officinalis. The mounds ranged from 1 m to 2 m in height and diameter. The mounds were stacked vertically or horizontally on other mounds and formed island-like connections or ‘condominiums’ that ranged from 6 m to 24 m in diameter.

Thalassina spinosa Ngoc-Ho and de Saint Laurent, 2009Material examined. PHILIPPINES, PANAY ISLAND, AKLAN PROVINCE, Ibajay, Katunggan It Ibajay Eco-Park, mangrove swamp, 11°45’6.7"N, 122°11’9.4"E, Collector: A.M. Bedi, Jun 2016, four females.

The total length (TL) and carapace width (CW) of the four female specimens are as follows: 1st specimen: 101.6 mm TL, 15 mm CW; 2nd: 101.6 mm TL, 12 mm CW; 3rd: 76.2 mm TL, 12 mm CW; and 4th: 100 mm TL, 15 mm CW.

The specimens were initially deposited in several areas. However, only one specimen (76.2 mm TL, 12 mm CW) has been maintained by the science club of Bugtong-Bato high school.

Description. The rostrum has an obtuse tip and a lateral border with seven to ten round tubercles. The carapace including the dorsal and branchial regions bears numerous spines and a long posteromedian process (Fig. 3A and 3C). The cervical groove is armed with eight to ten large median spines posteriorly and three lateral spines. The abdominal pleura are rounded and bordered by prominent tubercles; the abdominal sternites have two to five median tubercles. The pereopods are armed with numerous spines. The pereopods 1 are unequal or subequal in size; the merus has two to five large proximal spines; the propodus is armed with conspicuous round tubercles on the dorsal and median carinas of the lateral surface, extending in full length, the lateral ventral carina bears round and elongated tubercles. The pereopod 2 ischium is armed with four or five ventral spines; the merus is armed with six to nine dorsal spines; the carpus has two or three dorsal spines; the propodus is unarmed, without or with small discontinuous tufts of setae near the dorsal border of the mesial surface, a discontinuous curved row of setae is found near the ventral border and at the base of the fixed finger, respectively.

Distribution. India, Indonesia, Papua New Guinea (Ngoc-Ho & de Saint Laurent 2009), Philippines (this study), and Japan (Sakai & Türkay 2012).

Remarks. The specimens examined agree well with the description of T. spinosa by Ngoc-Ho and de Saint Laurent (2009) in having the species diagnostic characters. T. spinosa can be differentiated from other congeners by the presence of numerous spines on the carapace and pereopods, the armed cervical grooves, and the rounded abdominal pleuras bordered with large or pointed tubercles. Furthermore, the spinose cervical groove and the presence of tubercles and spines in the branchial region agree with the key characters of T. spinosa given by Sakai and Türkay (2012).



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Figure 3. A) Entire view of T. spinosa, left 2nd-4th pereopods and right 4th pereopod missing (TL: 101.6 mm, CW: 15 mm). B & C) Dorsal view of the gastric region of T. anomala with the right 2nd pereopod and left 2nd and 4th- 5

th pereopods missing compared to C) the dorsal view of the gastric region of T. spinosa (TL: 100 mm, CW: 15 mm) with the right and left 2nd-5th pereopods missing, with an armed cervical groove (4), a spinose posterior carapace and branchial region (5), and a long posteromedian process (6).

DISCUSSIONAll T. spinosa individuals were collected from the same homogeneous plot, which seemed to overlap with the open and muddy habitat of T. anomala. In the present study, plots were designated according to habitat type and accessibility. The main creek, where plot B is designated, contains a mixture of mature and immature mangroves with rich species diversity. Plot B was in a natural dock temporarily used to transport building materials into the forest. Small mud lobster mounds in the plot were completely submerged during high tide. During low tide, much of the water was drained out of the creek except in lower areas where pools of water remained, making the muddy soil in plot B waterlogged. The mounds were frequently trampled down by construction workers and rolled over by heavy materials such as wood and sacks of cement. They were poked out from their tunnels with twigs from nearby trees by collecters. The openings of the small mud lobster mounds can be easily mistaken as crab holes but can be distinguished by the presence of mud caps that plugged the mound openings.

Due to the mysterious life of Thalassina species, they have been rarely studied in the Philippines. Although T. spinosa was known from neighboring Indonesia (Ngoc-Ho & de Saint Laurent 2009), the species has been never known from the Philippines until the present report. Further studies are required to cover different mangrove habitats and other estuarine areas in order to gain new information on the diversity and species of mud lobsters in the Philippines.

ACKNOWLEDGMENTSThe authors wish to thank the Zoological Society of London - Philippines for providing the opportunity to study mud lobsters. The study was made possible with the financial aid and personal assistance of the Bedi family and the field assistance of Elizabeth and Garrett Villoria and the locals of Ibajay. Lastly, the authors are grateful to Mr. Marc Philippe for providing critical comments to improve the manuscript.



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