The genus Pullosquilla Manning, 1978, including P. litoralis, P. thomassini, and P. pardus, has been found in Taiwan for the first time. All three species live in a subtidal sand flat north of the Bitou fishing port within the Kenting National Park, Taiwan. Adult specimens were examined, illustrated, and photographed. The habitat, which all three species share, is described. The implication of such closely related species sharing the same habitat is discussed.

Kenting National Park, Nannosquillidae , new record, Pullosquilla , western Pacific

Among the fourteen genera in the family of Nannosquillidae Manning, 1980, nine have been found in the Indo-West Pacific region (Ahyong 2001). However, only two genera, Acanthosquilla and Bigelowina, are currently known from Taiwan (Ahyong et al. 2008). Located near the center of Indo-West Pacific region, the number of taxa of stomatopod crustaceans found around Taiwan is surprisingly low (Yeh and Hsueh 2010). One possible explanation is that species with small adult size (e.g., smaller than 5 cm) or with deep burrows could have slipped through traditional collecting gears such as trawl nets or shrimp pots. Here, a detailed visual search was conducted on a subtidal sand flat and recorded, for the first time, three species of Pullosquilla Manning, 1978 from Taiwan.

Surveys of sand-dwelling stomatopods were conducted in April 2014, November 2014, and June–July 2017. All specimens were collected in a sand flat north of the Bitou fishing port in the Kenting National Park, Pingtung County, Taiwan. The approximate GPS coordinates are 21°54.69'N, 120°50.76'E. The sampling site, between 5 to 7 m under water, has an undulating white sandy substrate. Specimens were found by visually locating their burrow entrances, usually a pair of circular holes 2–4 mm in diameter. Using a hand net to trawl 1–2 L of sand, the animal was sieved out on the spot. While sieving, special attention was given to avoid a sandy plume rising above the rim of the hand net; shaking the hand net horizontally for a few seconds at a time and looking for the animals above the remaining sand. Once found, individuals or pairs of animals were placed in 20 ml plastic vials with ambient seawater and brought back to laboratory for identification. Collected specimens were measured, photographed, and transferred to 75% alcohol for further analysis. Examined specimens in this study are deposited in National Museum of Nature Science (NMNS), Taichung City, Taiwan and National Chung Kung University (NCKU), Tainan City, Taiwan.

Morphological terminology and abbreviations follow Ahyong (2001). Total length (TL) was measured along the midline from apex of the rostral plate to the apices of the submedian teeth. Abbreviations include:

A1 antennule

A2 antenna

AS abdominal somite

Pullosquilla is a genus of small sand burrowing stomatopods within the superfamily Lysiosquilloidea. Currently, Pullosquilla contains four species: P. litoralis, P. thomassini, P. pardus, and P. malayensis (Ahyong 2001). They grow into one of the smallest adults among spearing stomatopods and are named for their immature appearance (Manning 1978). Similar to many other Lysiosquilloidea, they often live in U-shaped burrows made of a mucus-sand mixture (pers. obs.; Caldwell 1991). However, within the Nannosquillidae, Pullosquilla is the only genus known to form long-term mated pairs sharing the same burrow (Jutte 1997; Wright 2013). As a result of this special monogamous life style, P. litoralis and P. thomassini has been systematically studied with respect to their pairing and biparental care behavior (Jutte 1997; Lindstrom 2003; Wright and Caldwell 2015).

Probably due to the scarcity of specimens, the pairing and breeding systems of P. pardus have rarely been studied. The only report regarding monogamous pairing of P. pardus is speculation on taxonomic samples collected from Timor Sea (Ahyong 2001). In the current study site, more than half of the burrows located belonged to P. pardus. Likewise, monogamous pairs were extracted from single U-shaped burrows, some of which were still caring for their donut-shaped egg clutch. Consequently, monogamous pair bonding and parental care in P. pardus is now confirmed.

In this study, only a tiny portion, approximately 150 m², of a relative large and continuous sandy bottom of more than ten hectares were surveyed. In such a small area, three of the four known Pullosquilla species, P. thomassini, P. litoralis, and P. pardus, were discovered. Although we failed to find P. malayensis, it is interesting to note that this is the first record of the sympatry of more than two Pullosquilla species. The previous records regarding the co-occurrence of Pullosquilla came from Tiahura, Moorea, Society Islands, and Tulear, Madagascar, where only P. litoralis and P. thomassini could be found from the surveyed reef complexes (Manning 1978). However, based on the time, depth, and location of collection it is highly possible that P. malayensis and P. thomassini coexist in Double Reefs, Guam (Ahyong and Erdmann 2003).

The study site is located slightly south of the famous Shell Beach Preservation Zone of the Kenting National Park. While it might appear to be a uniform continuous sandy substrate, there could be some unobserved factors that support the coexistence of these Pullosquilla species. One particular feature of the collection site, which is also the reason for its designation of the Shell Beach Preservation Zone, is the composition of the sand. From the slope of the Shell Beach, it is immediately obvious that the sand grains are very coarse. In conjunction with the nearshore currents, the sandy seabed rarely settles. As a result, there is hardly any coral or algae cover beyond the drop-offs of the nearshore reef flat. The lack of hiding places or food for relatively larger predators in this region could thus be favored by these small sand-dwelling stomatopods.

No research on P. pardus has been done beyond its taxonomic descriptions, probably due to few accessible localities were known for surveys. In Moosa (1991) and Ahyong (2001), among four records of the P. pardus, the holotype of P. pardus and one of the specimens from Australia were both collected at depth over 40 m, while only two other specimens were captured in sand at 6 m. Here, in this survey, more P. pardus were caught than P. litoralis and P. thomassini combined: of the 24 burrows, 17 belonged to P. pardus while only five and two burrows were occupied by P. litoralis and P. thomassini, respectively. Among them, two monogamous pairs were evacuated from two burrows, one of which was occupied by P. pardus and the other belonged to P. litoralis. No triples were found in any of the burrow. During the collection, P. pardus could easily be recognized by its panther-like color pattern and large body size, while other two species needed further examination. Although the sample sizes are too small to have any statistical significance, during the survey it was observed that P. pardus were evenly distributed throughout the subtidal region. They could be caught from near shore sandy substrate at approximately 3 m depth to the sandy plain at 7–9 m depth. On the other hand, the burrows occupied by P. litoralis were usually found on the sandy plain farther away from shore, at depths of 6 to 9 m. They were rarely observed on the near shore sandy substrate at 3-5 m depth. Although our sampling did not cover all seasons, it is suggested that the current location could be a good locality for a detailed study of the behavior of P. pardus. Except for the genus Pullosquilla, several burrows of larger stomatopods were also observed, potentially those of Lysiosquilloidea, on the same sand plain. However, proper collecting tools are required in order to retrieve these larger stomatopods for further examination and identification.

Stomatopod crustaceans are abundant worldwide throughout tropical and temperate waters, where they burrow in coral rock, coral rubble, or sandy benthic substrates (Ahyong et al. 2017). There were 29 genera, and 64 species of stomatopod crustaceans reported from Taiwan (Ahyong et al. 2008; Yeh and Hsueh 2010). In this study, by performing detailed hand surveys throughout the subtidal sand flat, we have successfully found new records from Taiwan, including an additional genus Pullosquilla and three more species of Pullosquilla. Since previous studies obtained specimens mainly by trawling, certain species were inevitably under-represented. For example, the records of Lysiosquilloidea were limited, presumably because larger species typically burrow too deeply while smaller species are too small to be caught in trawl nets. Overall, our findings not only expand the reported distribution of Pullosquilla stomatopods in the western Pacific Ocean but also contribute to the understanding of cohabitation and monogamous behaviors in genus Pullosquilla. Further studies comparing mating and breeding behaviors among these species will likely yield more insight into their unique monogamous system. Based on the diversity of stomatopods found in the Indo-West Pacific region, it is assumed that numerous stomatopod species are yet to be discovered from Taiwan.

We would like to thank scuba instructor Y.P. Lee for his assistance with this work. This research was supported by Ministry of Science and Technology grant to T.H.C. (102-2311-B006-002-MY3). Permits for collecting stomatopods were granted by Kenting National Park, Construction and Planning Agency Ministry of the Interior, Taiwan.