Pemilihan Pakan Alami Untuk Mendukung Pemeliharaan Ikan Capungan Banggai (Pterapogon kauderni) Di Lini Aquaculture Training Center (Latc) Bali

Tujuan dari penelitian ini adalah untuk mendapatkan jenis pakan alami yang tepat dan dosis pemberian pakan yang optimal untuk mendukung pemeliharan ikan capungan banggai. Penelitian dilakukan dengan Rancangan Acak Lengkap (RAL), dan dilaksanakan pada bulan September-Desember 2016. Pakan yang diujikan yaitu ikan rucah, abalon (Haliotis glabra) dan cumi-cumi (Loligo pealei). Setelah ditemukan pakan yang paling disukai, kemudian dilakukan pengujian dosis pakan pilihan dengan dosis 10%, 20% dan 30% dari berat bobot ikan. Sampel ikan yang digunakan memiliki rerata panjang 3 cm dan berat 0,47 g sebanyak 45 ekor. Akuarium yang digunakan berukuran 95 cm x 45 cm x 35 cm. Pemberian pakan dilakukan tiga kali sehari. Hasil penelitian menunjukkan bahwa pakan abalon lebih disukai dibandingkan dengan kedua pakan lainnya dengan konsumsi sebesar 0,11 g/ekor per hari. Hasil pengujian dosis pakan abalon menunjukkan pertumbuhan tertinggi dihasilkan pada dosis perlakuan 30% yaitu panjang 2,07 cm dan berat 0,34 g dan dosis 20% yang menghasilkan panjang 2,07 cm dan berat 0,33 g. Hasil uji statistik (LSD) menunjukkan perlakuan dosis 30% dan 20% tidak berbeda nyata (P>0,05). Berdasarkan penelitian ini dapat disimpulkan bahwa abalon adalah pakan alami yang disukai untuk mendukung pemeliharaan ikan capungan banggai dengan pemberian dosis optimal sebesar 20% dari berat bobot sampel per hari. Kata Kunci : Ikan capungan banggai, Pakan alami, Lini Aquacultur Training Center.

Sodium Flux Ratio in Na/K Pump-Channels Opened by Palytoxin

Palytoxin binds to Na+/K+ pumps in the plasma membrane of animal cells and opens an electrodiffusive cation pathway through the pumps. We investigated properties of the palytoxin-opened channels by recording macroscopic and microscopic currents in cell bodies of neurons from the giant fiber lobe, and by simultaneously measuring net current and 22Na+ efflux in voltage-clamped, internally dialyzed giant axons of the squid Loligo pealei. The conductance of single palytoxin-bound “pump-channels” in outside-out patches was ∼7 pS in symmetrical 500 mM [Na+], comparable to findings in other cells. In these high-[Na+], K+-free solutions, with 5 mM cytoplasmic [ATP], the K0.5 for palytoxin action was ∼70 pM. The pump-channels were ∼40–50 times less permeable to N-methyl-d-glucamine (NMG+) than to Na+. The reversal potential of palytoxin-elicited current under biionic conditions, with the same concentration of a different permeant cation on each side of the membrane, was independent of the concentration of those ions over the range 55–550 mM. In giant axons, the Ussing flux ratio exponent (n') for Na+ movements through palytoxin-bound pump-channels, over a 100–400 mM range of external [Na+] and 0 to −40 mV range of membrane potentials, averaged 1.05 ± 0.02 (n = 28). These findings are consistent with occupancy of palytoxin-bound Na+/K+ pump-channels either by a single Na+ ion or by two Na+ ions as might be anticipated from other work; idiosyncratic constraints are needed if the two Na+ ions occupy a single-file pore, but not if they occupy side-by-side binding sites, as observed in related structures, and if only one of the sites is readily accessible from both sides of the membrane.

Cloning of a Na+-driven Cl/HCO3 exchanger from squid giant fiber lobe

We extracted RNA from the giant fiber lobe (GFL) of the squid Loligo pealei and performed PCR with degenerate primers that were based on highly conserved regions of Na+-coupled HCO3- transporters. This approach yielded a novel, 290-bp sequence related to the bicarbonate transporter superfamily. Using an L. opalescens library, we extended the initial fragment in the 3′ and 5′ directions by a combination of library screening and PCR and obtained the full-length clone (1,198 amino acids) by PCR from L. pealei GFL. The amino acid sequence is 46% identical to mammalian electrogenic and electroneutral Na-HCO3 cotransporters and 33% identical to the anion exchanger AE1. Northern blot analysis showed strong signals in L. pealei GFL, optic lobe, and heart and weaker signals in gill and stellate ganglion. To assess function, we injected in vitro-transcribed cRNA into Xenopus oocytes and subsequently used microelectrodes to monitor intracellular pH (pHi) and membrane voltage ( Vm). Superfusing these oocytes with 5% CO2-33 mM HCO3- caused a CO2-induced fall in pHi, followed by a slow recovery. The absence of a rapid HCO3--induced hyperpolarization indicates that the pHi recovery mechanism is electroneutral. Ion substitutions showed that Na+ and Cl- are required on opposite sides of the membrane. Transport was blocked by 50 μM 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS). The characteristics of our novel clone fit those of a Na+-driven Cl/HCO3 exchanger (NDCBE).

Embryonic development of southern calamary (Sepioteuthis australis) within the constraints of an aggregated egg mass

A post-cleavage embryological scheme was established for southern calamary Sepioteuthis australis. Using this developmental scheme, intra- and interspecific comparisons were made. Sepioteuthis australis development most closely resembled that of its tropical congeneric species, S. lessoniana, with only a few subtle heterochronies. The greatest developmental difference was observed when comparisons were made with Loligo pealei. These differences were attributed to developmental duration and respective egg sizes. Within S. australis, variation in developmental rates among embryos was associated with the size of the egg mass, with less variation evident in smaller egg masses. Embryos located on the periphery of the egg mass and at the distal or unattached end of an individual egg strand developed significantly faster than those located deep within the egg mass. On average, embryos in small egg masses, consisting of five individual egg strands, developed significantly faster than those in dense aggregations (>100 strands).