animals Article Life Cycle of Edible Jellyfish Acromitus hardenbergi Stiasny, 1934 (Scyphozoa: Rhizostomeae) Inhabiting a Brackish-Water Environment Hiroshi Miyake 1,*, Shiho Honda 1, Jun Nishikawa 2 and Fatimah Md. Yusoff 3 1 School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan; [email protected] 2 Department of Marine Biology, School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka 424-8610, Japan; [email protected] 3 Department of Aquaculture, Faculty of Agriculture, Putra University Malaysia, Selangor Darul Ehsan, Serdang 43400, Malaysia; [email protected] * Correspondence: [email protected]; Tel.: +81-42-778-9132 Simple Summary: The edible jellyfish Acromitus hardenbergi Stiasny, 1934 is an important fishery resource. The aim of the present study was to elucidate the life history of this brackish-water jellyfish in order to conserve the species and develop sustainable jellyfish fisheries. Matured medusae were collected at the mouth of the Perak River. Primary polyps had a long stalk with a small stolon at the base of the calyx. Fully developed polyps were bowl- or goblet-shaped. Asexual reproduction was accomplished only by means of budding. Strobilation was mono-disc type. Polyps of A. hardenbergi expand their population not by podocysts, but by budding as quickly as possible and forming one large ephyra by mono-disc strobilation without the residuum, because the polyp cannot remain Citation: Miyake, H.; Honda, S.; for a long time at its settlement place where there is a sediment-rich environment with drastic Nishikawa, J.; Yusoff, F.M.. Life Cycle salinity change. of Edible Jellyfish Acromitus hardenbergi Stiasny, 1934 (Scyphozoa: Abstract: The edible jellyfish Acromitus hardenbergi Stiasny, 1934 is harvested throughout the year at Rhizostomeae) Inhabiting a the mouth of the Perak River, Malaysia. Although this species is an important fishery resource in Brackish-Water Environment. the local area, limited biological studies have been carried out on it. The aim of the present study Animals 2021, 11, 2138. https:// was to elucidate the life cycle of this unique brackish-water jellyfish in order to conserve the species doi.org/10.3390/ani11072138 and develop sustainable jellyfish fisheries. Mature medusae were collected at the mouth of the Perak River. Embryonic and larval development after fertilization was completed within 24 h until the Academic Editor: Charles Griffiths planula stage and within 48 h until the polyp stage. Primary polyps had a long stalk with a small stolon at the base of the calyx. Fully developed polyps were bowl-or goblet-shaped but became Received: 23 May 2021 Accepted: 8 July 2021 an elongated stalk under starved conditions. Asexual reproduction was accomplished only by means Published: 20 July 2021 of budding, and no podocysts were produced. Strobilation was mono-disc type. These characteristics may be adaptations to the dynamic environmental conditions in the estuary of the Perak River, Publisher’s Note: MDPI stays neutral where salinity fluctuates widely due to strong inflows of highly turbid freshwater coupled with tidal with regard to jurisdictional claims in changes. This study suggests that polyps of A. hardenbergi expand their population not by podocysts, published maps and institutional affil- but by budding as quickly as possible and forming one large ephyra by mono-disc strobilation iations. without the residuum, because the polyp cannot remain for a long time at its settlement place in the sediment-rich environment with drastic salinity change. Keywords: Acromitus hardenbergi; brackish water; budding; life cycle; mono-disc strobilation Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and 1. Introduction conditions of the Creative Commons Jellyfish cuisine is a traditional custom in East Asia. In the 1990s, owing to an increasing Attribution (CC BY) license (https:// demand for jellyfish in Asia, edible jellyfish catches increased to larger than those of scallops or creativecommons.org/licenses/by/ lobsters [1]. Recently, jellyfish demand has drastically increased, leading to expanded jellyfish 4.0/). Animals 2021, 11, 2138. https://doi.org/10.3390/ani11072138 https://www.mdpi.com/journal/animals Animals 2021, 11, x FOR PEER REVIEW 2 of 17 Animals 2021, 11, 2138 2 of 16 expanded jellyfish fisheries worldwide [2–5]. Southeast Asia is the center of jellyfish ex- ports; exportation of edible rhizostomes from this region account for the majority of the fisheriesworld jellyfish worldwide trade [ 2[1,6–9],–5]. Southeast and they Asia are an is theimportant center ofcommodity jellyfish exports; for the fisheries exportation indus- of edibletry in rhizostomes this area. Rhizostome from this region jellyfishes account targ for theeted majority for fisheries of the worldin the jellyfish Southeast trade Asia [1,6– are9], andCrambione they are mastigophora an important Maas, commodity 1903; Crambionella for the fisheries orsini (Vanhöffen, industry in this1888); area. Crambionella Rhizostome an- jellyfishesnandalei Rao, targeted 1931; for Crambionella fisheries in helmbiru the Southeast Nishikawa, Asia are MulyadiCrambione and mastigophora Ohtsuka, 2014;Maas, Lobone- 1903; Crambionellamoides robustus orsini (Vanhöffen,Stiasny, 1920 1888);, RhopilemaCrambionella esculentum annandalei Kishinouye,Rao, 1931; Crambionella 1891; R. helmbiruhispidum Nishikawa,(Vanhöffen, Mulyadi 1888); and and Acromitus Ohtsuka, hardenbergi 2014; Lobonemoides Stiasny, robustus 1934 [6,7,10,11].Stiasny, 1920, JellyfishesRhopilema are escu-used lentumnot onlyKishinouye, for food but 1891; alsoR. for hispidum fishing(Vanhöffen, bait, fish feed, 1888); cosmetics, and Acromitus pharmaceuticals, hardenbergi andStiasny, ma- 1934terial [6 sciences,7,10,11]. [3], Jellyfishes and are also are usedsources not of only collagen for food [12,13]. but also for fishing bait, fish feed, cosmetics,In Malaysia, pharmaceuticals, fisheries andof Rhopilema material sciences esculentum [3],, and Rhopilema are also hispidum sources of, Lobonema collagen [smithii12,13]., and InAcromitus Malaysia, hardenbergi fisheries ofareRhopilema operated esculentumin Bagan Datoh,, Rhopilema Kukup, hispidum and some, Lobonema parts of smithii Sabah, andandAcromitus Sarawak [14]. hardenbergi In general,are operatedjellyfish fisheries in Bagan depend Datoh, on Kukup, the fluctuations and some partsin the oftemporal Sabah andand Sarawak spatial distributions [14]. In general, of medusae. jellyfish fisheries On the dependother hand, on the fisheries fluctuations of A. in hardenbergi the temporal are andoperated spatial all distributions year round in of the medusae. estuary On of Perak the other River, hand, Malaysia. fisheries Acromitus of A. hardenbergi hardenbergiare is operatedone of the all most year important round in the jellyfish estuary species of Perak for River,fisheries Malaysia. in this areaAcromitus [10,14]. hardenbergi The Perakis is onethe ofsecond the most longest important river (402 jellyfish km) in species peninsular for fisheries Malaysia in and this runs area into [10 ,its14]. estuary The Perak located is theat Bagan second Datoh longest to join river the (402 Straits km) of in Malacca peninsular (Figure Malaysia 1). The and river’s runs intolarge its watershed estuary located (14,700 atkm Bagan2) provides Datoh a towide join range the Straitsof salinity of Malacca variations (Figure in its1 estuary). The river’s[15,16]. largeThe Perak watershed estuary (14,700is an important km2) provides area for awide Acromitus range hardenbergi. of salinity variations in its estuary [15,16]. The Perak estuary is an important area for Acromitus hardenbergi. Figure 1. Map of the sampling sites of Perak River in Bagan Datoh, Perak, Malaysia. Black points labelled A–H show CTD castingFigure points.1. Map Mapof the was sampling created sites using of GMTPerak 6.0 River [17 ].in Bagan Datoh, Perak, Malaysia. Black points labelled A–H show CTD casting points. Map was created using GMT 6.0 [17]. Recently, it has been suggested that Acromitus hardenbergi could potentially be used for theRecently, production it has of been nutricosmetics suggested that and Acromitus functional hardenbergi food [12,13 could]. Acromitus potentially hardenbergi be used willfor the be aproduction commercially of nutricosmeti and biologicallycs and important functional species food [12,13]. in Malaysia. Acromitus However, hardenbergi jellyfish will fisheriesbe a commercially in the Perak and River biologically are not regulated.important species Therefore, in Malaysia. overfishing However, of jellyfish jellyfish and fish- the sustainabilityeries in the Perak of its River production are not are regulated. of great Therefore, concern. Thus, overfishing management of jellyfish action and plans the sus- for sustainabletainability fisheriesof its production and conservation are of great of this concern. species Thus, are necessary. management For the action strategic plans plan for to be successful, gaining knowledge of the life cycle of A. hardenbergi is required, and should be the first step in establishing a sustainable management plan. However, other Animals 2021, 11, 2138 3 of 16 than its spatial distribution, limited biological information about A. hardenbergi is now available [10,12,14]. As for the life cycle, within the same family, Catostylidae, the life cycle has been described in only three species, Catostylus mosaicus (Quoy and Gaimard,