Emerita pangandaranensis sp. nov., a new sand crab (Anomura: Hippidae) from South Coast of Java, Indonesia

The preprints are preliminary versions of works accessible electronically in advance of publication of the final version. They are not issued for purposes of botanical, mycological or zoological nomenclature and are not effectively/validly published in the meaning of the Codes. Therefore, nomenclatural novelties (new names) or other nomenclatural acts (designations of type, choices of priority between names, choices between orthographic variants, or choices of gender of names) should NOT be posted in preprints. The following provisions in the Codes of Nomenclature define their status:

close resemblance to E. holthuisi (Niazi and Haqub 1970). In Indonesia, only one species of the genus Emerita has been reported (Emerita emeritus). It was reported from the west coast of Sumatera (Padang, Bengkulu) and south coast of Java (Cilacap, Kebumen, Bantul, Purworejo) (Wardiatno and Mashar 2013, Wardiatno Y et al. 2015, Nugaraha et al. 2018. Anomura inhabits the sandy beach, predominantly in the tropical area (Boyko and Harvey 1999). Indonesia is one of the suitable habitats for them that belongs to the second-longest coastline in the world and has a tropical climate. The high activity in coastal areas of Indonesia makes these zones rich in nutrients (Hanim et al. 2021). This situation may influence the occurrence of the sand crab (Anomura). Like the other two genera in the family Hippidae (Hippa and Mastigochirus), Emerita also spends most of their time burrowing into the sand, especially in the swash zone. One of the beaches with high activity is Pangandaran beach, which is located in Pangandaran Regency, West Java.
In this study, we report a new Emerita from Indonesia that was a very close resemblance to E. emeritus. They were distinguished from the species by the spines on the inner margin of the first pereiopod that is sturdy in the new Emerita, but with shallow bases (weak spine) in E. emeritus ( Niazi andHaqub 1970, Sankolli 1962). Another difference is in the outer anterolateral angle of the merus of the third maxilliped which is rectangular and not produced in the new type of Emerita, but with tooth-like produced with a horny tip in E. emeritus (Sankolli 1962). There are at least two previous studies that have suspected the existence of other species besides Emerita emeritus in southern Java (Butet et al. 2019, Nuryanto et al. 2020. This research aims to describe new species of the genus Emerita in Indonesian waters with a morphological and molecular approach.

Materials and methods
Four specimens were captured by hand in the intertidal zone on the South Coast of Java. The specimens were preserved in 70% alcohol for a day, then substituted in 96% alcohol for storage and deposited at the Museum Zoologicum Bogoriense (MZB), Research Center for Biology, Indonesian Institute of Sciences (LIPI), Cibinong, West Java, Indonesia. Specimens were photographed using a Canon camera (PowerShot SX430 IS) and the smaller parts were photographed using Optilab Olympus SZ61, and then illustrated using a Huion tablet (canvas Pro 13).

Description
Body is almost cylindrical; the frontal margin of the carapace is tridentate (with three lobes). All three lobes sharply triangular (horny tips), the median lobe is shorter than the lateral lobes, separated by the U-shaped sinus (Fig. 1a). The U-shaped sinus on each side is greater in width than the breath of the median lobe at the base. The dorsal surface of the carapace is covered with quite prominent transverse rugae, in the area between the cardiac region and the frontal lobes. The lateral border of the carapace is serrulate in its anterior half. The serrulate appearance formed by the minutely setose pit. Posterolateral carapace margin rounded.
Eyes with slender, elongated peduncles, length (including cornea) exceeding the tip of the longest horny spine on the second antennal segment (Fig. 1a). Antennular flagellum with 27 articles. The second antennal segment with three large spines distally, all with horny tips, median spine is the longest (Fig. 1b).
Merus of the third maxilliped rectangular, the length approximately 1.63 times as long as greatest width. The outer anterolateral angle of the merus of the third maxilliped is rectangular, not produced. The antero-internal lobe is blunt, distally rounded, but prominent (high) (Fig. 1c).
Dactylus of the first pereiopod elongated, 1.85 times as long as greatest width, distally with one spine, lower margin with five distinct horny spines, no spine on the upper margin (Fig. 1d).

Diagnosis
The spines in dactyls of the first pereiopod contain five distinct spines on the inner margin. The spine on the terminal or apical spine and the last spine is relatively shorter than the three others, with no one on the upper margin.

Etymology
The name of the new species has been taken from the name of the area where the holotype was found.

Distribution
Pangandaran and Cilacap (South Coast of Java, Indonesia)

Discussion
For several characters such as the spines in dactyls of the first legs, this species is most similar to E. karachiensis and E. holthuisi that have spines about four until six on the inner margin of dactyls of the first pereiopod and have no spine on the outer margin. For merus of the third maxilliped, this species has a close resemblance to E. holthuisi which both of them have the outer anterolateral angle of the external margin of the merus of the third maxilliped is rectangular and not produced (Table 1). Emerita holthuisi was from India and E. karachiensis was from Pakistan.
These Emerita were found in Pangandaran beach and the same kinds were also found in Cilacap. These two locations were one coastline (south coast of Java), and face directly to the Indian Ocean. According to the previous studies as was mentioned in the preface, where E. emeritus was also found in Cilacap, it means both species were sympatric.
In the course of our research on sand crabs, we usually find the presence of this group on beaches close to river mouths. Like this study, we found it on Pangandaran beach which is close to the mouth of the Citunjong river. Perhaps the link between the existence of this species and the river mouth is about the availability of abundant food because the presence of the river indicates the existence of human settlements which indirectly contribute to the improvement of the food chain. In this case, the remnants of human food distributed to the estuary can be utilized by sand crabs, one of which acts as a detritivore.  The dactylus of the first leg, in length, is either double or more than double of its breadth and usually terminates in a distal spine but sometimes in two or even three distal spines The dactylus of the first leg, in length, is more than twice its width and terminates in a spine distally.
The dactylus of the first leg is broadly ovate, less than twice its greatest width.

It terminates in a spine
It terminates in a spine distally The dactylus is more length than width,1.85 times as long as the greatest width Table 1.
Morphological differences between Emerita spp.

Shape of carapace
The carapace is more or less cylindrical

The body subcylindrical
The body is oblong-oval and comparatively narrow The body is more or less cylindrical The body is almost cylindrical