Dataset: RNA:DNA Ratios and Total lipids – experiment data

Mnemiopsis leidyi and juvenile Callinectes similis were collected in March – April 2022, and Beroe ovata was collected in November 2022, using a plankton net (50 cm diameter, 500 μm mesh) from Aransas Pass inlet at Port Aransas (27.8396° N, 97.0726° W). Palaemon pugio was collected using a plankton net from Corpus Christi Bay  (27.8035° N, 97.0898° W) in Port Aransas in July 2021. Opisthonema oglinum and Lagodon rhomboides were collected using a seine (6.4 m wide by 1.2 m high with 5 mm square mesh) from Aransas Pass inlet at Port Aransas (27.8396° N, 97.0726° W) in August 2021 and Redfish Bay at Aransas Pass (27.8611° N, 97.07632° W) in May 2022, respectively.

The live animals of each species were divided into two treatments (control and experimental). Both treatments were fed a common diet of either live Artemia sp. nauplii (enriched with Alga-Mac 3050; Aquafauna Bio-Marine, Inc.) or commercial fish food, Otohime (EP1, Reed Mariculture, Inc.) during the acclimation period of 10 – 45 days. After acclimation (Day 0), both treatments received a common diet of Artemia or Otohime, and the diet of experimental treatments was supplemented with red drum eggs for a period of 10 – 94 days. Controls did not receive eggs. Three to eight tanks of study species were sampled at the end of acclimation (day 0). Three to eight replicate tanks were sampled from each treatment 24 h and 2 – 10 days after the experimental treatment received eggs.

Mnemiopsis leidyi, B. ovata, and C. similis were held in rectangular tanks (26.7 cm long x 16.5 cm high x 16.5 cm wide), and P. pugio and fishes were held in circular tanks (12 cm in diameter, 6.4 cm deep) with recirculating filtered water. Within each rectangular tank, individuals of C. similis were held separately in round plastic containers (106.7 cm in diameter, 43.2 cm deep) with perforated lids to prevent aggressive contact. For the same reason, individuals of L. rhomboides were kept in separate perforated cylindrical enclosures (30 cm in diameter, 45 cm high) within each circular tank. Excess food and solid waste were siphoned daily from all tanks, and complete water changes were performed in rectangular tanks every 2 – 4 days. Environmental conditions were measured daily and were constant throughout the experiment (temperature: 21 – 24°C, salinity: 28 – 35 ppt, and photoperiod: 12-h light and 12-h dark).

Invertebrates removed from both treatments on sampling days were kept in clean sea water overnight to evacuate their guts and were sacrificed the following morning. For taxa with low dry weight, i.e., ctenophores, 3 – 4 individuals from each tank were pooled together to make a replicate. A single individual per tank of C. similis, and three individuals of P. pugio (subsamples, n=3) per tank were removed at each sampling day. Invertebrates were analyzed whole, except for C. similis, for which the exoskeleton was excluded. On each sampling day, one fish per tank was removed and immediately euthanized with tricaine methanesulfonate (MS-222). Euthanized fish were placed on ice where a fillet of dorsal white muscle tissue, liver and muscle plug were collected.  All samples were rinsed twice in distilled water and frozen at -80°C until analysis.

For total lipids, each sample was lyophilized, homogenized, and weighed. Total lipid was measured by the phosphosulphovanillin method (Barnes and Blackstock, 1973). Briefly, lipids were cold extracted from lyophilized and homogenized samples with 2:1 chloroform: methanol (v/v). A calibration curve was prepared by performing 1:2 serial dilutions on a cholesterol standard (Millipore-Sigma, Burlington, MA, USA) dissolved in 2:1 chloroform:methanol (v/v). Blank, standards, and extracted lipid samples were reacted with concentrated sulphuric acid and vanillin (vanillin in 4:1 85% phosphoric acid: water v/v) and were run in duplicate. Absorbance was measured using a Spectramax 190 Microplate Reader (Molecular Devices, San Jose, CA, USA) at a wavelength of 520 nm. Total lipids were expressed as mg g−1 dry weight.

Measurements of RNA:DNA were made on individuals. DNA and RNA were measured using the ethidium bromide (EB) fluorometric technique (Westerman and Holt 1988) based on aliquots (10 µL) of homogenates. Calculations were based upon comparisons with DNA-EB and RNA-EB calibration curves from calf thymus DNA and yeast RNA (Type 111) standards. RNA:DNA ratios were normalized using a standardization factor based on the common RNA:DNA slope ratio procedure described by Caldarone et al. (2006). Results of the analysis were reported as the ratio of RNA content to DNA content. Measurements of RNA:DNA were unsuccessfully attempted for invertebrates.

Laboratory experiments took place at the Fisheries and Mariculture Laboratory of the University of Texas Marine Science Institute from July 2021 to November 2022.