Proximate composition of marine invertebrates from tropical coastal waters, with emphasis on the relationship between nitrogen and protein contents

Ninety-nine percent of all animal species on the globe are invertebrate species. People do not currently consider them when they hear about animals (Mather 833). Mammals are thought to make up less than 1% of animals at the moment, but they are the subject of research investigations, grabbing the public's attention (Mather 833). Notably, the majority of the marine ecosystem's population consists of invertebrates. Therefore, understanding how aquatic invertebrates are formed chemically greatly aids in understanding these creatures. Additionally, analyses of elements such as lipids, carbohydrates, and proteins, likewise entire phosphorous and nitrogen are significant, considering the fact that they are the main components of living matter (Diniz, Barbarino and Oiano-Neto 333). Importantly, the study of proteins in marine invertebrates has vast applications, for instance, data obtained provide vital information regarding physiological mechanisms in cells, nutritional significance of animals, and resource utilization in commercial and biotechnological actions (Diniz, Barbarino and Oiano-Neto 333).
EXPERIMENTAL DESIGN
Sampling
In the study, twelve species of aquatic invertebrates spread in 5 distinct phyla were studied (Diniz, Barbarino and Oiano-Neto 334). In addition, identification of the organisms was done under expert supervision. The invertebrates were chosen according to their ecological significance and availability in the area of study. For instance, Echinometra lucunter, Bunodosoma caissarum, Lytechinus variegatus and Eledone massyae were gathered from Arraial do Cabo. Additionally, Echinaster brasilliensis, Desmapsamma anchorata andPhallusia nigra were gathered from Angra dos Reis. Aplysia brasiliana was obtained from Armacao dos Buzios; Hymeniacidon heliophilia, Holothuria grisea and Isognomon bicolor came from Niteroi, while Renilla muelleri was gathered from Rio de Janeiro. The sampling stations were based in Rio de Janeiro, southern Brazil. Furthermore, the specimens were packaged in plastics and stored in ice-cold till they arrived at the lab, based in Niteroi. Distilled water was used to wash the animals that were then treated with respect to their distinct features. Additionally, samples were taken randomly from for investigations, ice-cold at -18 oC and afterwards wilted in a Terroni Fauvel machine (Diniz, Barbarino and Oiano-Neto 335).
Chemical analysis
In the chemical investigation, 4 specimens were investigated, n=4, considering nitrogen, carbohydrate, phosphorous, lipids and proteins (Diniz, Barbarino and Oiano-Neto 335). However, three duplicates were investigated for individual species due to the lofty cost of amino acids investigation. For the evaluation of hydrosoluble protein, The Lowry approach was employed. In addition, spectrophotometric decisions were carried out at 750 nanometers, 35 minutes after the commencement of the chemical reactions (Diniz, Barbarino and Oiano-Neto 335). On the other hand, the entire carbohydrate was obtained with 80% sulphuric acid. Its concentration was regulated spectrophotometrically at 485 nm, half an hour after the beginning of the reaction, applying the phenol-sulfuric approach. Furthermore, the entire lipid was obtained using the Forch approach and regulated gravimetrically after evaporating the solvent. Also, the absolute phosphorous and nitrogen was regulated in the specimens after digestion of peroxymonosulphuric acid, with the aid of a Hach Digester. Absolute amino acid was decided by high working liquid chromatography alongside pre-column derivatization amidst AccQ Fluor indicator. Importantly, the nitrogen ratio present in individual amino acid was applied in the calculation of nitrogen retrieved from the investigation of amino acid. Consequently, the N-prot aspects were completed for individual species by the proportion of amino acid leftovers. Lastly, the outcomes were inferred by one-way interpretation of the variance, amidst significance level of 0.05, alongside Turkey's multiple relation trials (Diniz, Barbarino and Oiano-Neto 336).
Results
The entire nitrogen percent revealed broad fluctuations within the individual species, changing in the octocoral R. muelleri from 2.02% of the dry weight, dw, to 12.7% dry weight in E. massyae (Diniz, Barbarino and Oiano-Neto 336). Poriferans revealed identical concentrations of nitrogen, around 3.6% dry weight. However, a meaningful difference was established in nitrogen composition of a pair of C. nidarians, B. caissarum revealed a greater nitrogen concentration (9.71% dw) contrasted to R. muelleri (2.02%) (Diniz, Barbarino and Oiano-Neto 336). Sea urchins, L. variegatus and E. lucunter revealed analogous concentrations (5.09% dw and 5.42% dw correspondingly) while H. grisea (sea cucumber) had the least, 3.66% dw and the E. brasilliensis showed the greatest TN value among the entire echinoderms analyzed (Diniz, Barbarino and Oiano-Neto 336).On the other hand, P. nigra nitrogen concentration was in-between (4.70%) when contrasted with the rest of the species.
Phosphorous shifted broadly, with least concentration being noticed in R. muelleri, 0.24% dw and the maximum in E. massyae, 1.16% dw (Diniz, Barbarino and Oiano-Neto 336). Notably, Poriferans revealed no important variations in their phosphorous composition, with values of around 0.43% dw. An important variation was noticed in C. nidarians, P ˂ 0.001. The greatest concentration was observed in B. caissarum (anemone) with 1.0% dw contrasted to R. muelleri, 0.24% dw. Moreover, E. massyae revealed the greatest phosphorous concentration among molluscs, with 1.16% dw. In echinoderms, H. grisea had the least concentration, with 0.54% dw (Diniz, Barbarino and Oiano-Neto 336).
Total carbohydrates results pointed out chiefly small concentrations in the aquatic invertebrates examined. First, 10 out of 12 species revealed outcomes below 7.5% dw of carbohydrates, although A. brasiliana showed 18.4% dry weight of the entire carbohydrates.

Table1 Gross chemical content of 12 species of aquatic invertebrates examined in the tropical areas of Brazil
The values are given as a percentage of the dry weight and serve as the average of 4 duplicates± standard deviation (n=4). The analysis was carried out among taxonomic classes. Similar superscript letters (a, a;b,b) or non appearance of the letters showed that the average outcomes were not significantly distinct (Diniz, Barbarino and Oiano-Neto 337).

Interpretation of results
Chemical formation of aquatic animals can be affected by a variety of factors comprising of the life cycle, physiological features, habitat and chemical pollutants (Chiarelli and Roccheri 94). Also, it is influenced by environmental and oceanographic conditions. Consequently, majority of the animals examined revealed high concentrations of nitrogen, more than 4% dw (Diniz, Barbarino and Oiano-Neto 338). The concentration is attributed to the high amounts of proteins present in aquatic organisms. On the contrary, high TN concentrations are attributed to the trimethylamine nitrogen oxide, largely present in the aquatic organisms (Pechenik 55). On the other hand, concentrations of carbohydrates in the animals was low, less than 7.5% dw- this was influenced by the use of mantle for the examination. High concentration is attributed to the possibility that the organisms reserve their energy majorly in glycogen form. The present study focused on aquatic animals from Brazil, which was also the central point on animals from the same habitat. Considering organisms from different habitats across the globe can reveal a variation from what was yielded in this study.
Future research
With the rising agricultural and industrial activities, a study should be carried out to investigate the effects of heavy metal pollutants on the chemical composition of marine invertebrates. With increasing cases of overfishing, there has been physical destruction of corals where the animals' food grows. Therefore, a study should be carried out to assess the effects of overfishing and determine the species at risk.

References
Chiarelli, Roberto, Maria Roccheri. "Scientific Research." Marine Invertebrates as Bioindicators of Heavy Metal pollution (2014): 93-106. print.
Diniz, Graciela, Elisabete Barbarino and João Oiano-Neto. "Research Article." Proximate composition of marine invertebrates from tropical coastal waters, with emphasis on the relationship between nitrogen and protein contents (2014): 332-352. print.
Mather, Jennifer. "Biology." Marine Invertebrates: Communities at Risk (2013): 832-840. print.
Pechenik, Jan A. Biology of the Invertebrates. New York: Mc Graw Hill, 2010. print.