PENGAYAAN PAKAN BENIH RAJUNGAN (Portunus Pelagicus) STADIA MEGALOPA MELALUI PEMBERIAN BETA KAROTEN

Penelitian ini bertujuan untuk meningkatkan nilai nutrisi pakan alami rotifer dan artemia melalui penambahan beta karoten yang bersumber dari wortel. Penelitian ini dilaksanakan pada bulan Mei 2020 di unit pembenihan kepiting dan rajungan Balai Pe-rikanan Budidaya Air Payau (BPBAP) Takalar. Rancangan penelitian yang digunakan adalah rancangan acak lengkap (RAL) sebanyak 4 perlakuan dan 3 ulangan. Hewan uji yang digunakan adalah larva rajungan (Portunus Pelagicus) stadia megalopa yang ditebar dengan kepadatan 5 ekor/l dan dipelihara sampai memasuki stadia crab. Luaran penelitian yang ditargetkan adalah teknologi pengayaan pakan alami rotifer dan artemia menggunakan beta karoten yang berasal dari wortel. Hasil penelitian menunjukkan bahwa Pemberian frekwensi pakan yang tepat setelah dikayakan dengan beta caroten akan meningkatkan sintasan dan pertumbuhan pada larva rajungan. Frekwensi pakan yang tepat diberikan pada larva rajungan yang terbaik untuk kelang-sungan hidup larva rajungan adalah pemberian pakan 3 kali/hari. This study aims to increase the nutritional value of natural rotifer and artemia feed by adding beta carotene from carrots. This research was conducted in May 2020 at the hatchery unit of the Brackish Water Cultivation Fishery Center (BPBAP) Takalar. The research design used was a completely randomized design (CRD) with 4 treatments and 3 replications. The experimental animals used were small crab larvae (Portunus pelagicus) in the megalopa stage which were stocked with a density of 5 individuals/l and they were kept until entering the crab stage. The target output of this research is natural feed enrichment technology for rotifer and artemia using beta carotene derived from carrots. The results showed that giving the right frequency of feed after being enriched with beta carotene would increase survival and growth in small crab larvae. The best frequency of feed given to small crab larvae for the survival of small crab larvae is feeding 3 times/day.

Description of the first juvenile stage of the fiddler crab Minuca mordax (Smith, 1870) (Crustacea, Decapoda, Ocypodidae)

The first stage of the fiddler crab Minuca mordax is described here. Zoea larvae obtained from four ovigerous female were reared in the laboratory until the development of the first crab stage. The development from zoea I to the first juvenile instar lasted 35 days after hatching. The first crab stage of Minuca mordax can be morphologically distinguished from those of Minuca burgersi and Leptuca cumulanta by a 2‑segmented antennule endopod (3‑segmented in M. burgersi, unsegmented in L. cumulanta), an unsegmented maxillule endopod (2‑segmented in M. burgersi and L. cumulanta), and a 4‑segmented first and second maxilliped endopod (respectively unsegmented and 5‑segmented in M. burgersi and L. cumulanta). The three species have the following characters in common: segmented peduncle of antennule 2; endopod of antennule unsegmented; presence of aesthetascs on the antennule; peduncle of antenna 3‑segmented; flagellum of antenna 6‑segmented; mandible 3‑segmented; maxilla with coxal and basal endite bilobed; first, second and third maxillae with exopod 2‑segmented and abdomen with six somites that are wider than long.

The effect of temperature and salinity on the larval development of Stenorhynchus seticornis (Brachyura: Inachidae) reared in the laboratory

Larvae of Stenorhynchus seticornis were reared in the laboratory in a factorial experiment employing three temperatures (22, 25 and 28°C) and three salinities (30, 35 and 40‰) to determine the effects of these variables on the survival and duration of the larval stages. Larvae from five females were subdivided in six groups of 10 and reared in glass bowls containing 125 ml filtered and UV-irradiated seawater at different temperature–salinity combinations. Larvae were transferred daily to clean bowls with newly hatched Artemia nauplii, and the number of moults and mortality within each bowl was recorded. Complete larval development of S. seticornis occurred under all experimental conditions, except at temperature 28°C and salinity 35‰. Salinity affected percentage survival of the two zoeal stages, but not that of the megalopa. Survival of the second zoeal stage, the megalopa, and the complete development to the first crab was affected by temperature, with the greatest survival occurring at 25°C. Duration of the two zoeal stages, the megalopa, and development to the first crab stage showed a gradual reduction with increasing temperature. Development from hatching to the first crab stage required 17 to 31 days and was inversely related to temperature, averaging 26.9 days at 22°C, 21.0 days at 25°C and 19.7 days at 28°C. Salinity affected the duration of the first zoeal stage only.

Influence of natural settlement cues on the metamorphosis of fiddler crab megalopae, Uca vocator (Decapoda: Ocypodidae)

Megalopae of many decapod crab species accelerate their development time to metamorphosis (TTM) when exposed to natural physical and/or chemical cues characteristic of the parental habitat. In the present study, the influence of natural settlement cues on the moulting rates and development TTM in megalopae of the fiddler crab Uca vocator was investigated. The effects of mud from different habitats (including well-preserved and degraded-polluted mangrove habitats) and conspecific adult 'odours' (seawater conditioned with crabs) on the induction of metamorphosis were compared with filtered pure seawater (control). 95 to 100% of the megalopae successfully metamorphosed to first juvenile crab stage in all treatments, including the control. However, the development TTM differed significantly among treatments. Settlement cues significantly shortened development, while moulting was delayed in their absence. The fact that megalopae responded to metamorphosis-stimulating cues originating from both adult and non-adult benthic habitats demonstrates that settlement in this species may occur in a wider range of habitats within the mangrove ecosystem, including impacted areas.

First record of an early pea crab stage on Tonicia chilensis (Frembly, 1827) (Mollusca, Polyplacophora)

Pea crabs, or pinnotherids (Crustacea, Decapoda), known since Aristoteles from mussels like Pinna nobilis Linnaeus, 1758, can be found in association with various marine evertebrates, such as tunicates, tube worms, sea urchins and others. Among molluscs, they are not only found in bivalves, but also in several gastropods (see Geiger & Martin 1999). However, there is only one report to date of a pea crab-polyplacophoran association, that of Opisthopus transversus Rathbun, 1893 and Cryptochiton stelleri (von Middendorff, 1847) from the Californian coast (Webster 1968).

Development of juvenile Australian giant crabs, (Pseudocarcinus gigas Lamarck, 1818) (Decapoda : Oziidae), reared in the laboratory

Juvenile giant crabs (Pseudocarcinus gigas), sourced from laboratory-reared larvae, were ongrown through to the 7th crab stage over 2 years to allow identification of specimens collected for ecological studies. Morphological development through these stages is described. Each stage up to Crab 5 can be distinguished by changes in morphology of the appendages, primarily the 3rd maxilliped and antennule. Growth of juveniles under laboratory conditions was also recorded, with mean size of juveniles reaching 24.5 mm carapace length, 737 days after hatch.