Emerita emeritus

Emerita emeritus (Linnaeus, 1767) (Fig. 2) Cancer emeritus Linnaeus, 1767: 1055 [type locality: Indian Ocean]. Hippa asiatica H. Milne Edwards, 1837: 209 [type locality: “seas of Asia”]. Hippa emerita. —H. Milne Edwards 1837: 209. Material examined. MZB. Cru. 4109, 1 female, Bengkulu Province, 7°42.185'S, 108°39.375'E; IPB Pangandaran 1, 3–5, 4 males, Pangandaran Regency, 7°42.185'S, 108°39.375'E; IPB-Cilacap 11–12, 1 male, 1 female, Cilacap Regency, 7°41.6473'S, 109°11.3026'E, Indonesia. Diagnosis. CL up to 19.0 mm. Carapace anterolateral margin smooth. First pereiopod dactylus with 4 or 5 spines on inner margin (including terminal spine), outer margin usually with 2 spines. Description. Body almost cylindrical. Carapace frontal margin tridentate, all 3 lobes relatively long and slender with horny tips, median lobe triangular, acute; anterolateral margin smooth (Fig. 2A); transverse dorsal rugae carapace crowded and numerous, postfrontal and postgastric furrows carapace well marked, hepatic region strongly grooved; posterolateral margin rounded. Ocular peduncle slender, elongated; length (including cornea) exceeding tip of longest horny spine on second antennal segment. Antennular flagellum of 25–27 articles. Second antennal segment with 3 large spines distally, all with horny tips, median spine longest. Merus of third maxilliped rectangular, length approximately 1.5 times as long as greatest width; outer anterolateral angle tooth-like produced; antero-internal lobe low, triangular, prominent (Fig. 2b). First pereiopod dactylus broadly ovate, length 1.8–2.0 times as long as greatest width (generally less than twice its greatest width), distal margin with one spine, outer margin with 1–3, usually 2 spines, sometimes broken or missing, inner margin typically with 4 spines in distal one-third of lower margin (Fig. 2c). Variation. Specimen MZB.Cru.4109 from Bengkulu, has the first pereiopod dactylus with no spine on the outer margin and only two spines on the inner margin, including the terminal spine (perhaps another spine was broken), and the antennular flagellum consists of 42 articles. Specimen IPB-Pangandaran 1, 3–5 from Pangandaran bears 4 or 5 spines on the inner margin including the terminal spine, 2 s p i n e s on the outer margin, usually, and 25–27 articles on the antennular flagellum. Specimen IPB-Cilacap 11, 12, collected from Cilacap, h a s the first pereiopod dactylus with 1 or 2 spines on the outer margin and 3–5 spines on the inner margin, including the terminal spine, and the antennular flagellum has 30–31 articles. Natural history. Emerita emeritus inhabits sandy beaches, mostly those with coarse sand sediment fractions (Rahmatuloh et al. 2020). This species can produce 419–4572 eggs; the number of eggs increased significantly with size in ovigerous females (Edritanti et al. 2016). Emerita emeritus is distributed on the west coast of India eastwards to Vietnam and southwards to Sumatra and Java, Indonesia (Sankolli 1965). Remarks. The reference specimen of Emerita emeritus used for morphological and molecular identification (MZB.Cru.4109, KR047035) was collected from Bengkulu. The reference specimen’s locality matches that of the specimens from Bengkulu that Schmitt (1937) and Efford (1976) suggested from which one could be chosen as a neotype (no neotype has ever been designated for this species and no type material of Linnaeus is extant). Efford (1976) examined species of Emerita to study their distribution and used specimens from various localities, such as Bengkulu (Sumatra, Indonesia) and Madras (India), to confirm their identity as E. emeritus. Sankolli’s (1965) documentation of the specimen from Madras was used in the current study as our reference in characterizing the morphology of E. emeritus. We conclude that the characters shown in Efford (1976) that look slightly different from our Emerita emeritus specimens (Fig. 2; section dactylus) represent intraspecific variation. This also applies to the presence or absence of spine characters on the outer margin of t h e dactylus of t h e first pereiopod, which Efford (1976) described as variations in E. emeritus originating from Indonesia.