Predation and feeding behavior of corallimorpharian Paracorynactis hoplites (: Anthozoa) on Acanthaster planci in Sogod Bay, Southern Leyte, Philippines

Homer Hermes Y. de Dios Journal of Science, Engineering and Technology Vol. 3:46- 54(2015)

Abstract

Paracorynactis hoplites is one of the natural predators of Acanthaster planci. Hence, this study offers a new knowledge on the and feeding behavior of P.hoplites on A. planci in Sogod Bay, Southern Leyte, Philippines. Three different individuals of P.hoplites located in the crevices of the fringing reef of Balong-balong, Pintuyan, So. Leyte were fed in situ with adult size A. planci (diameter in cm: 23.75±0.44, mean±SE) in the morning and in the afternoon for the months of Mar 2015 and Jun 2015. The feeding behavior and predation of polyps P. hopliteson A. planci were observed using SCUBA and were video/photo documented for less than 40 minutes using the underwater camera. The P. hoplites extended to reach the prey and pulled A. planci towards the mouth, swallowed and ingested completely. It took about 17.378 to 29.382 min(95% CI) to complete ingestion in the morning and 17.582 to 37.991 min(95% CI) in the afternoon and showed no significant difference using paired t-test (t=0.337; p=0.308). However, the time to complete the ingestion of A. planci by P. hoplites in day one was significantly different from day two (t=0.167; p=0.041) showing that the predator was satiated with its prey but still capable of capturing/ killing its prey. Ingestion on day one took 18.603 to 25.862 min(95% CI) and 23.434 to 31.683 min (95% CI) for day two. In the afternoon of the second day, the undigested parts of A. planci composed of spines and skeleton/test were regurgitated into the sand near the polyp.

Keywords: Ingestion, predator, prey, regurgitate

1.0 Introduction represents one of the most significant threats to reef Crown-of-thorns biodiversity and a major (Acanthaster planci) is one of the management problem of tropical well-studied in coral coral reefs in the Indo-Pacific reefs. A. planci population outbreak regions (Birkeland & Lucas 1990, ______Southern Leyte State University, Bontoc, Southern Leyte 47 Homer Hermes Y. de Dios Journal of Science, Engineering and Technology Vol. 3:46- 54(2015) Moran & De’ath 1992, Pratchett Strait near Papua New Guinea by 2005, Pratchett 2010, Tokeshi & Haddon & Shackleton in 1893 and Daud 2011, Grand et al. 2014).The had been long considered to belong absence of A. planci outbreak, coral to the genus Pseudocorynactis (Bos cover in Indo-Pacific region could et al. 2011). Ecologically P. hoplites increase 0.89%/y (De’ath et al. can be found at depths between 1–28 2012). m and preferred to settle under reef A. planci outbreak have crevices (Bos et al. 2008a, de Dios et occurred across the Philippine al. 2014). Paracorynactic hoplites archipelago such as in Inopacan, was first published feeding on A. Leyte (Benliro et al. 1999), in Apo planci in Davao Gulf, Philippines Reef and Puerto Galera of Mindoro, (Bos et al. 2008b, Bos et al. 2011) in Tubbataha reefs of Sulu Sea (Bos and was also observed to prey on 2010), in Samal Island, Davao del large asteroids like Protoreaster Norte (Bos et al. 2011; Bos et al. nodosus and Linckia laevigata (Bos 2013) and in Southern Leyte (de et al. 2008a, Bos et al. 2011). It was Dios et al. 2014, de Dios et al. reported that P. hoplites helped 2015). A. planci outbreak has reduce A. planci population outbreak become a regular menace to in Lungsodaan Marine Sanctuary, Philippine coral reefs hence the Southern Leyte, Philippines (de Dios attention to controlling their et al. 2014). Furthermore, Bos et al. population outbreak should be (2008a) described how a polyp P. immediate. A. planci population hoplites extends when attacking outbreaks remain a very poorly starfish and how the prey is ingested. understood phenomenon. Predator In feeding experiments for seven removal due to overfishing is one of weeks, a P. hoplites in a cage can the hypotheses on the causes of the consumed 29.5, 19.0 and 25.0 g/day A. planci outbreak (Vine 1973, of A. planci, Linckia laevigata, and Endean 1973, Sweatman 2008). Protoreaster nodosus, respectively Since then, some COTS natural (Bos et al. 2011). However, there is predators have been listed by Rivera no study about predation of A. -Posada et al. (2014) which include planci by P. hoplites based on the , gastropods, crustaceans and rate of ingestion in the morning and corallimorpharian, Pseudocorynactis afternoon for two consecutive days. sp. It aimed to know how fast a predator Corallimorpharian P. hoplites (P. hoplites) can capture, swallow was first recorded in the Torres and ingest its prey (A.planci) and its ______Southern Leyte State University, Bontoc, Southern Leyte 48 Homer Hermes Y. de Dios Journal of Science, Engineering and Technology Vol. 3:46- 54(2015) feeding behavior in an open system. hoplites. Instead the starfish were fed directly to the P. hoplites. The 2.0 Methodology feeding was done in the morning between 9:00am to 10:00am and in The predation and feeding the afternoon between 2:00pm to behavior of three different 3:00pm for two consecutive days for individual polyps of Paracorynactis the month of March 2015 and hoplites on A. planci were studied in another two consecutive days for Balong-balong, Pintuyan, Southern June 2015. The predation of A. Leyte, Philippines during the months planci by P. hoplites was observed of March and June 2015. Predation for less than 40 min and the time can be defined as interaction (minutes) to complete the ingestion between predator and prey in which of A. planci by P. hoplites was a predator (P. hoplites) feeds or kills recorded. However, only seventy- its prey (A. planci). Predation can five (75%) to eighty-three percent be expressed using the time to ingest (83%) of the total collected A. completely the prey (A. planci) by planci were ingested by P. hoplites. its predator (P.hoplites). Ingestion is The mean time of ingestion of A. defined as the taking of food into the planci by P. hoplites in the morning body by mouth. Three individual and afternoon was compared using polyps were observed 2-4 m apart paired T-test and the statistical test hiding inside the reef crevices at a was also used to compare the mean depth of 12 m in Balong-balong. time of ingestion during the first and Predation and behavior of the three second day of in situ experiment. individual polyps were observed by SCUBA diving and were video/ photo documented for at least 40 3.0 Results and Discussion minutes. A total of twenty-four adult size A. planci (diameter in cm: Polyps of Paracorynactis 23.75±0.44, mean±SE) were hoplites (predator) were found collected nearby the reef of Balong- hidden in reef crevices in Balong- balong and were fed to P. hoplites in balong, Pintuyan, Southern Leyte situ. while waiting to capture potential Each A. planci was placed prey (A. planci) (Fig. 1a). When A. approximately 10 cm near the polyp planci was introduced to P. hoplites, P. hoplites. Not all of the adult A. the polyp began to move slowly by planci moved towards the P. extending its body and tentacles in ______Southern Leyte State University, Bontoc, Southern Leyte 49 Homer Hermes Y. de Dios Journal of Science, Engineering and Technology Vol. 3:46- 54(2015) an effort to detect a potential prey significant difference (t=0.337; (Fig. 1b). As the acrospheres, the end p=0.308). However, the time to part of tentacles (sticky balls covered complete the ingestion of A. planci with nematocyst-stinging cells) come by P. hoplites for two consecutive in contact with A. planci, days differs significantly (t=0.167; immediately it stuck into its test and p=0.041). Day one took 18.603 to the polyp extended (3-5 times its 25.862 min (95% CI) and 23.434 to normal body length) towards the 31.683 min (95% CI) for day two prey, bringing all the other remaining (Fig. 4). A day after feeding, the acrospheres towards A. planci until it undigested parts of A. planci was completely trapped (Fig. 1d-f). consisting of spines and calcium The polyp then slowly pulled the carbonate skeleton/test were prey towards its mouth, and regurgitated by some of the P. swallowed and ingested it. (Fig. 1g). hoplites into the sand near the polyp It was observed that A. planci (Fig. 1h-i). In the afternoon of the (diameter in cm: 23.75±0.44, second day of the in situ experiment, mean±SE) was ingested by P. some of the P. hoplites regurgitated hoplites at a rate of 17.378 to 29.382 the whole , but became minutes (95% CI) in the morning and immobile and the color changed into 17.582 to 37.991 min (95% CI) in white ash (Fig. 2). the afternoon (Fig. 3) and showed no

a b c

d e f

g h i

Figure 1. Feeding behavior of Paracorynactis hoplites on Acanthaster planci ______(Photos: H.H.Y. de Dios). Southern Leyte State University, Bontoc, Southern Leyte 50 Homer Hermes Y. de Dios Journal of Science, Engineering and Technologyy Vol. 3:46- 54(2015)

Figure 2. P. hoplites regurgitated the whole A. planci after being ingested. (Photos: H.H.Y. de Dios).

Figure 3. Mean time (95% Confidence Interval) to complete the ingestion of Acanthaster planci by Paracorynactis hoplites in the morning and afternoon.

Figure 4. Mean time (95% Confidence Interval) to complete the ingestion of Acanthaster planci by Paracorynactis hopiletes for two consecutive days. ______Southern Leyte State University, Bontoc, Southern Leyte 51 Homer Hermes Y. de Dios Journal of Science, Engineering and Technologyy Vol. 3:46- 54(2015) COTS population outbreak is 23.75±0.44, mean±SE) at a rate of considered as the second major more or less 30 min in the morning cause of the decline of the world’s and afternoon. However, in the coral cover (Dea’th et al. 2011). afternoon in day two, some of the P. Crown-of-thorns starfish hoplites regurgitated the whole A. (Acanthaster planci), a natural planci after ingestion which became predator of hermatypic , less mobile and turned some part of appear to be a potential prey by the prey into white ash color as a corallimorpharian, Paracorynactis sign of initial digestion. This hoplites. The had long been indicates that P. hoplites can capture considered to belong to food and kill its prey when they are Pseudocorynactis (Bos et al. 2011) not hungry or satiated. under Phylum Cnidaria, Class Other studies showed that A. Anthozoa, . planci can escape from the pull of P.hoplites is known to feed on the tentacles of P. hoplites due to different species of asteroids and their stiff skeleton, or the predator is echinoids such as Linckia laevigata, satiated and it will cease to feed due Protreaster nodusos and to the reduction of adhesiveness of Echinometra mathaei excluding long acrosphere. (Bos et al. 2011). -spined sea urchins (Bos et al. 2011). Although many cnidarians are P. hoplites preyed on relatively short known to ingest almost any spines which allows the acrospheres like zooplankton as well as a dead to attach to the soft tissue of the prey organic matter that falls into their such as A. planci. Aside from P. oral disks (Fabricius & Metzner, hoplites, other species of teleost fish, 2004). crustacean, mollusk were listed as It is indeed fascinating that P. predators to A. planci (Rivera- hoplites may have a special trait or Posada et al. 2014). ability to ingest A. planci without Bos et al. (2011) reported being adversely affected; even the that P. hoplites in cage can consume prey is considered toxic to humans 29.5g/d of A. planci in a seven-week and other marine organisms as study while Charonia tritonis can reported by Moran (1990) Sato et al. consume 0.7/wk of A. planci (2008) and Watanabe et al.(2009). (Pearson and Endean, 1969) when Thus, P. hoplites and maybe other given unlimited supply. This study, predators in Balong-balong are P. hoplites can ingest a single adult responsible for the low density of A. A. planci (diameter in cm: planci. The towns of Lungsodaan ______Southern Leyte State University, Bontoc, Southern Leyte 52 Homer Hermes Y. de Dios Journal of Science, Engineering and Technology Vol. 3:46-54(2015) and Padre Burgos in Southern Leyte Benliro IMP, Bothe CII, Sonder K, showed that the presence of P. Szinicz G, Cesar SA, hoplites helped reduce the density of Schoppe S. 1999. Status of A. planci (de Dios et al. 2014). shallow reefs around Apid However, it is recommended that the Island, Inopacan, Leyte, number of observations will be Philippines. Annals of increased into ten consecutive days Tropical Research. 21: 54- that include gut content analysis of 56. P. hoplites and nocturnal feeding behavior of P. hoplites. Bos AR. 2010. Crown-of-thorns outbreak in the Tubbataha Reefs. UNESCO World 4.0 Acknowledgement Heritage Site. Zoological Studies. 49, 124 p. The author is grateful to the Commission on Higher Commission Bos AR. Gumanao GS, Salac FN. for research funds; the implementing 2008a. A newly discovered agency, Southern Leyte State predator of Crow-of-thorns University (SLSU) through the sea stars. Coral Reefs. 27 support of President Dr. Prose Ivy (3):58 Yepes and VP-RDE Dr. Francis Ann Sy; and the staff and researchers of Bos AR, Gumanao GS, Mueller B. SLSU-Bontoc Campus headed by 2011. Feeding biology and Dr. Dewoowoogen P. Baclayon. symbiotic relationships of the This study was part of the Marine corallimorpharian Biodiversity Management of Sogod Paracorynactis hoplites Bay research program. (Anthozoa: Hexacorallia). The Raffles Bulletin . 59(2): 245-250.

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