Regional Studies in Marine Science 40 (2020) 101500 Contents lists available at ScienceDirect Regional Studies in Marine Science journal homepage: www.elsevier.com/locate/rsma Feeding ecology of deep-water Arabian red shrimp, Aristeus alcocki Ramadan, 1938 (Decapoda: Penaeoidea: Aristeidae) from southwestern India (Arabian Sea) ∗ Purushothaman Paramasivam a,b ,1 , Rekha Devi Chakraborty a , ,1 , Kuberan Ganesan a,b , Maheswarudu Gidda a a b Crustacean Fisheries Division, Central Marine Fisheries Research Institute, Ernakulam North P.O., Post Box No. 1603, Cochin - 682018, Kerala, India Department of Biosciences, Mangalore University, Mangalagangothri - 574199, Karnataka, India article info Article history: Received 4 August 2019 Received in revised form 2 June 2020 Accepted 10 October 2020 Available online 13 October 2020 Keywords: Arabian sea Feeding behaviour Amundsen Crustaceans Diversity index a b s t r a c t The Arabian red shrimp, Aristeus alcocki Ramadan, 1938 constitutes a commercially important decapod in the southern coast of India with an annual average catch of greater than 2,122 tons. The diet contents in connection to the sex, maturity, season and size group of this species were investigated using an aggregate number of 634 samples collected from the south-west coast of India. The diet components of A. alcocki were deduced to consist of 71 prey categories, which belonged to smaller crustaceans (e.g. amphipods, decapods, euphausiids), foraminiferans (Rotaliida, and Miliolida), molluscs (bivalves, gastropods, and cephalopods), polychaetes, and bryozoans. Feeding pattern of the studied species was examined using Amundsen graphical method, which recognized that A. alcocki exhibited different degrees of generalization and specialization with various preys. The marginal seasonal variation related to major prey items could be attributed to the environmental fluctuations of the deep waters and other biological processes. Considering stomach fullness and food quality, the females of A. alcocki were found to be the effective predators than males. The parameters, such as population characteristics, somatic and gonadal development might be attributed to this variation. Notably, the larger-sized animal have good swimming ability, which could help in an effective selection of prey, while the smaller individuals depend on the epibenthic organisms for their food. This study comprises the first report on the feeding biology of A. alcocki in the Arabian Sea. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Arabian red shrimp, Aristeus alcocki (Ramadan, 1938) forms an economically important crustacean resource in the southwestern and southeastern coast of India (Suseelan et al., 1989a; Madhusoodana Kurup et al., 2008). This decapod is broadly distributed in the continental slope region (200 to 3200 m depth) of the Gulf of Aden to the islands of Lakshadweep in the southwestern coast and Andaman Sea through Bay of Bengal (Alcock, 1901; Holthuis, 1980; Menon and Pillai, 1996; Pérez Farfante and Kensley, 1997; Suseelan, 1985; Suseelan et al., 1989b). In India, the Arabian red shrimp , which was developed as a major targeting species from multiday bottom trawl fisheries, has been exploited commercially. This species formed a beneficial fishery from the ∗ Corresponding author at: Crustacean Fisheries Division, Central Marine Fisheries Research Institute, Ernakulam North P.O., Post Box No. 1603, Cochin - 682018, Kerala, India. E-mail address: rekhadevi7674@gmail.com (R.D. Chakraborty). 1 These authors contributed equally. https://doi.org/10.1016/j.rsma.2020.101500 2352-4855/© 2020 Elsevier B.V. All rights reserved. Southern coast of India with a profitability ratio ranging from 0.35 to 0.38 (Rajan et al., 2001; Shanis et al., 2014). Previous reports of literature described that more than 2122 tons were fished annually since 2011–2016 (CMFRI, 2012, 2013, 2014, 2015, 2016). Many aspects of biology, such as taxonomy (Alcock, 1901; Suseelan et al., 1989a; Chakraborty et al., 2015), bathymetric distribution and abundance (Suseelan, 1985; Jayaprakash et al., 2006; Madhusoodana Kurup et al., 2008; Radhika Rajasree, 2011), population structure (Purushothaman et al., 2018a, 2020), reproductive biology (Suseelan, 1985; Purushothaman et al., 2018b) and population dynamics (Chakraborty et al., 2018) have been studied from the southern coast of India. Despite its enormous biological importance in the Indian coast, no study has been conducted on the ecology (such as diet composition, seasonal, ontogeny variations, etc.) of the species. Knowledge on the dietary habits forms an important aspect to understand growth, nutritional requirements, breeding and migration patterns of marine species (Cartes et al., 2010), which are vital for fisheries management. The consumed prey spectrum would define the fundamental niche (Hutchinson, 1957), along P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 with the vertical and horizontal movements (Cartes, 1995) and feeding characters of the fish species, and also helps to evaluate the trophic relationships with the marine food cycle (Potier et al., 2007). Therefore, it is significant to examine the food and feeding behaviour for commercially important species on a regional basis to manage the sustainable fishery. Aristeids are one of the megabenthic predators, and their diet components constitute a variety of species ranging from benthic and smaller crustaceans, molluscs, polychaetes, echinoderms, and fishes, which occupy a vital position in the trophic food chain of the deep-water communities (Cartes and Carrassón, 2004; Kapiris et al., 2010). Many deepsea species showed different feeding patterns, which were found to vary with the seasonal and temporal distribution of the prey species (Kapiris, 2012; Karuppasamy and Menon, 2004; Maynou and Cartes, 1997; Gartner et al., 1997). The present study constitutes the first report on the feeding biology of A. alcocki in the Arabian Sea. This study envisaged to evaluate the feeding strategies of A. alcocki based on the seasonal variation and to ascribe the relationship between sex and different size groups with regard to the feeding habits. whereas the CL and body weight ranged between 13–51 mm and 2.0–28.1 g for female and 11–29 mm and 2.2–8.1 g for male, respectively. The lowest level of taxonomic identification and counting of prey items were carried out with the stereomicroscope (Nikon SMZ1270, Japan). The smaller crustaceans were characterized by the presences of broken fragments (e.g. rostra, carapace, antennae, chela, and telson), whereas the unidentified foraminiferans, crustaceans, natantians, reptantians, brachyurans, and molluscs were referred separately. Foraminifera were identified with the guide of Debenay (2012). Fish remains and polychaetes were noted as odd prey items owing to the inability to count the particular number of items in the stomach contents. Further, the molluscs were separated by class. Algae and green items were noted as a plant, whereas the detritus and sand were listed separately. Flesh pieces and digested prey items, which were not in a condition to identify, were separated as the unknown components in the list of food contents. To explore the importance of various prey items, two percentage indices were used (Hyslop, 1980). FI % = (No. of stomachs having a particular prey item/ total No. of non-empty stomachs) ∗ 100. NI % = (No. of prey items of a particular prey in all non-empty stomachs/ the total No. of food items from all stomachs) ∗ 100 Where, FI — Frequency of occurrence, NI — is an abundance of food contents. The feeding strategy was studied using specific prey abundance (Pi ) and frequency of occurrence (FI %) data. The preyspecific abundance is 2. Material and methods 2.1. Sample collection During March 2014 to February 2015, a total of 1519 specimens of A. alcocki were collected from the commercial landing centre. The exploitation was carried out off the southwestern coast of India in depth of 170–800 by deep-water bottom trawlers (cod-end mesh size of 20–26 mm) (Fig. 1). The collected specimens were transported into the laboratory under fresh condition, and the specimens were fixed in 10% neutral formalin solution for further studies. Morphological characterization of the specimens was carried out by following the taxonomic literatures of Ramadan (1938), Crosnier (1978) and Suseelan et al. (1989a). Pi = (Σ Si/Σ Sti) ∗ 100 where Pi - the prey-specific abundance of prey type ‘i’, Si - total stomach contents (number) with prey ‘i’, and Sti – the total stomach content in particularly those occurred with prey item ‘i’ in the stomach. Amundsen et al. (1996) described the methodology to understand the importance of prey items, feeding approaches and niche size of the predator, which could be deduced by analysing the distributions of axes points in the plot. The plot indicates the feeding strategy of A. alcocki, and also to attribute the generalized or prey-specific predator trait. The presence of points in upper left or lower right in plot could indicates the specialized (high specific abundance and low occurrence of the prey) or generalized (lower abundance and higher occurrence of prey) behaviour of the predator, respectively. For cluster analysis, we have selected many important preys to find out the relative abundance between the seasons and sexes, where the mean value of relative abundance of prey was used. Bray–Curtis model was used to find out relative abundance of the given prey items in both sexes. Further, Kruskal–Wallis analysis was used to find out the relative abundance of the prey between the seasons. To examine the possibility of variation in feeding habits related to size class of A. alcocki, females were classified into three size categories, such as ‘‘small size’’ (<30 mm of CL), ‘‘medium size’’ (30–40 mm of CL), and ‘‘large size’’ (>40 mm of CL) and males into two size groups such as ‘‘small size’’ (<25 mm of CL) and ‘‘large size’’ (>25 mm of CL), based on their length at maturity (Purushothaman et al., 2018b). 2.2. Laboratory analysis The specimen size (carapace length CL: the posterior margin of orbit to the outer end of carapace) was measured with vernier calipers, and body weight (BW) was recorded with an weighing balance (0.0001 g). Female and male individuals were segregated with the presence of thelycum and petasma, respectively. Maturation stage of the specimens was determined by following the method of Purushothaman et al. (2018b) as the presence (mature) or absence (immature) of sperm in testes for male, and spermatophores in thelycum for female. In order to understand the general effectiveness of feeding intensity of A. alcocki and relation with sex, season, and reproductive stages: the stomach fullness, repletion, vacuity indexes were calculated. The stomach fullness of each specimen was identified optically and segregated in four classes with percentages: class 1 (empty stomach or <10% of stomach fullness), class 2 (11%– 25% of stomach fullness), class 3 (26%–75% of stomach fullness) and class 4 (>75% of stomach fullness). The repletion index (RI) (Kapiris, 2004) and vacuity index (VI) (Hyslop, 1980) were estimated using the following formulae. RI = (SC/BW) ∗ 100 2.3. Diversity index (H′ ) where, SC-stomach contents (g) and BW-Body weight The dietary niche size in both the sexes, size categories, and different seasons were examined using the Shannon and Weaver (1963) model. The formula is VI = (ES/TS) ∗ 100 where, ES — Number of empty stomach, TS — Total number of stomachs examined To understand the diet components, stomach contents of 634 specimens (356 females, 278 males) were diluted with water, H′ = − s ∑ i=1 2 Pi log(Pi ) P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 1. Location of study areas of Aristeus alcocki along the south-west coast of India. where Pi is proportion of prey item i in the total of all food items. Evenness (E) was calculated by Pielou’s formula (1975). sexes (Mann–Whitney, P < 0.001). The stomach content weight of females ranged from 0.01–0.48 g which showed significantly higher difference (Kruskal–Wallis, P < 0.001) from that of males (0.012–0.13 g). Although, the statistical significant differences between sex, season, maturity stages and CL on stomach fullness were observed (Kruskal–Wallis, P < 0.001) empty stomachs were noticed in all the seasons and the highest proportion was observed during winter monsoon in both sexes. While the lesser number of empty stomachs and higher number of non-empty stomachs were observed in period of pre-monsoon in males and it was in summer monsoon in case of females. The average seasonal VI for the whole study period was 27.9% (15.3–50.7) for females and 38.5% (16.6– 52.3) for males. In maturation stage, stomach fullness was found to be declining condition from immature to mature for both the sex (Fig. 2). In specimens with different CLs categories compared, the stomach fullness was fewer in smaller group individuals (<20 mm of CL) than in larger individuals (>30 mm of CL), where the average of VI values for females was 17.0 and male was 8.5 (Fig. 2). Regarding the Repletion index, significant statistical differences were found between the season and sex (Fig. 3) (Kruskal– Wallis, P < 0.001). The mean value of RI for a female was 1.15 (Ranges: 0.11 – 3.570) which was significantly higher than the value in male 0.97 (0.09 – 2.96). The mean of seasonal RI in females ranged from 0.71 – 1.50 and in males, it ranged from 0.82 – 1.23 while the mean of RI values in matured females ranged between 0.97 – 1.3 and 0.96–1.15 in males. However, insignificant E = H′ /log(S) where, H′ is Shannon–Wiener Index; ‘S’ is total number of prey items in the sample. 2.4. Overlapping index (η) The test of food items’ overlapping among sex, size groups and seasons were estimated using the percentage of similarity (Schoener, 1970). ∑ η = 1 − 0.5( |PAi − PBi |) where, PAi and PBi are the real probability density of the food items i for the two size groups in the seasons A and B. The significant overlapping between the groups were assumed by the observation of the overlapping index of more than 0.6 (Macpherson, 1981). Hence, the values are equal to 1.0 signified that the similar food items were consumed by both group of the predator. All the analysis was done with the help of PRIMER 5.0 and SPSS STATISTICS 24.0. 3. Results 3.1. Feeding activity The weight of stomach contents of the specimens falling in median size class were found to differ significantly between the 3 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 2. The differences occurred in the percentage of stomach fullness of Aristeus alcocki according to seasons (A, Female; B, Male), Carapace length (C, Female; D, Male), maturity (E), and sexes (F). 1 (stomach empty, <10%), 2 (stomach fullness 11%–25%), 3 (stomach fullness 26%–75%) and 4 (stomach fullness >75%). FM, female; M, male; PM, pre-monsoon; SM, summer monsoon; FM, fall intermonsoon, WM, winter monsoon; F-IM, female immature; F-M, female mature; M-IM, male immature; M-M, male mature. 35 belonged to foraminifera (includes Lagenida, Rotaliida, and Miliolida), 15 belonged to smaller crustacean (contains decapods, euphausiids, amphipods, cumaceans, tanaids and copepods), 5 belonged to molluscs (includes bivalves, gastropods, scaphopods and cephalopods), polychaetes, and bryozoans. The crustacean and foraminiferans were the most important categories of prey items for both the sexes based on values of both FI% and NI%. Molluscs was the next most dominant food items, with 10% of abundance and other items (Mud/sand, plants, plastics, and unknown) form noticed more than 20% of abundance. difference was observed with maturity in both sex (Kruskal– Wallis, P > 0.001). In different CL groups: small, medium, and large size, RI values exhibited insignificant differences (Mann– Whitney, P > 0.001) with values of 0.89, 1.14, 1.07 and 0.67, 0.72, 0.78 for females and males, respectively. 3.2. Diet composition The diet compositions in both the sexes of A. alcocki during all the sampling seasons are summarized in Table 1. Totally 71 prey categories were observed in both sexes (Figs. 4, 5) with 4 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 3. The differences occurred in the percentage of repletion index (RI%) of Aristeus alcocki according to seasons (a, Female; b, Male), Size (c, Female; d, Male), maturity (e), and sexes (f). PM, pre-monsoon; SM, summer monsoon; FM, fall intermonsoon, WM, winter monsoon; F-IM, female immature; F-M, female mature; M-IM, male immature; M-M, male mature; F-Sl, female small, F-Md, female medium, F-Lg, female large; M-Sl, male small, M-Lg, male large. Also, the other food items such as unidentified flesh, mud/sand, plastics and unidentified items were the most abundant prey categories of this species (Fig. 6, Table 1). The Kruskal–Wallis test showed that the relative abundance of the prey (NI %) in both the sex differed significantly with seasonality (P < 0.001). Different relationship of the diet contents in both sexes were studied consecutively on seasonal basis (PM, pre-monsoon (March to June); SM, summer monsoon (July to September); FM, fall inter-monsoon (October); WM, winter monsoon (November to February)). The feeding behaviour of female differed significantly among the seasons. Rotaliids, crustacean, molluscs were predominated in pre-monsoon and also observed in all the seasons (35%–52%). ‘Others’ items were noticed to be in a higher abundance during PM and FM (25%–32%) and lesser in SM and WM (5%–10%). Lagenida, Miliolida, polychaetes and fishes were consumed in lower abundance throughout the study period (Fig. 6) with the 3.3. Seasonal difference in diet compositions Based on the Amundsen et al. (1996) diagrams, A. alcocki exbhited a mixed feeding strategy: specialization and generalization in both the sexes. Lower frequency of occurrence was observed in the prey species with higher abundance of particular prey in the diet component, which notes that Arabian red shrimps are specialized predators with different prey species. Whereas, a few number of preys were observed with less frequency of abundance and occurrence, indicating the species having generalized feeding strategy. The females pointed towards an opportunistic feeding strategy with higher phenotype components in comparison with males and occasionally consuming the larger prey items (e.g. cephalopod and fishes). The points for Rotaliida, Crustacea, and Mollusca were found in the lower left corner and increasing with the diagonally to the upper right corner of the diagrams which states, most important prey in both males and females. 5 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 4. Diet compositions of Aristeus alcocki, Major foraminiferans: Vaginulinidae: 1–2, Amphicoryna spp. ; 3, Vaginulinopsis spp. , Nodosariidae: 4, 6–10, Laevidentalina spp. ; 5, Grigelis spp.; Planulinidae: 11–15, Hyalinea spp., 16,17, Planulina spp., 18–20, Nonionidae: Pseudononion spp., Epistomariidae: 21-23, Pseudoeponides spp.; Amphisteginidae: 24, 25, Amphistegina spp., 26–28, Ammoniidae: Ammonia spp. Bolivinidae: 29–36, Bolivina spp.; Buliminidae: 37-42 Bulimina spp. Uvigerinidae : 43–49, Uvigerina spp.; Spiroloculinidae: 50–55, Spiroloculina spp. increased feeding activity (lowest VI, highest fullness) during SM. Similar to females, increased feeding activity was observed during SM in males. The diet majorly constituted of crustaceans, foraminiferans (Rotaliida: Globigernidae, Globborotliidae, Bolivinidae, Buliminidae and Uvigernidae) gastropods, bivalves, polychaetes, and bryozoans, in all the seasons. The dominant prey item was crustacean, mostly natantians, euphausids, and 6 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 5. Diet compositions of Aristeus alcocki; foraminiferans: Globorotaliidae: 1–3, Globorotalia spp.; Globigerinidae: 4, Turborotalita spp., 5–7, Globigerinella spp, 8–11, Globorotaloides spp, 12–14, Globoturborotalita spp.; 15, Ophidiidae; 16, Euphausid; 17, Sergestes sp. amphipods (Fig. 6). During FM and WM the feeding activity was reduced (increased VI, decreased fullness) (Fig. 2) however, a few specimens were noticed with higher occurrence of mollusc (e.g. bivalves and gastropods), natantians and polychaetes (Fig. 6) in their diet. to be high and the estimated diversity value for the entire sample of the female population was slightly lesser (3.71) than the male population (3.8). The highest value of dietary diversity was observed during WM for females (4.0) and PM for males (3.8) which indicate that A. alcocki consumed the high intensity of prey during WM and PM. Evenness (E) showed a decreased value in both the sexes with the increasing average intensity of prey items. To a large extent diversity was noticed to be decreasing along with mean prey items with increasing overlap. 3.4. Feeding habits in relation with size class The comparison among the prey diversity of different size class showed a significant difference in both the sex (Fig. 7). For larger females >60% was accounted by foraminifera (Globigernidae, Globborotliidae, Bolivinidae, Buliminidae and Uvigernidae, Hauerinidae) and crustacean (Brachyura, Amphipods, and Euphausids). Even diet of medium size class specimens was similar to that of large size class. But in smaller females prey consumed majorly constituted of ‘others’ items such as flesh, mud/sand, plastics, plants and unknown. In the case of males, smaller individuals consumed more of molluscs (gastropods and bivalves) and polychaetes whereas larger group of individuals exhibited more diversity in the prey consumed with other items, crustaceans and foraminiferans. The trophic level overlap was observed between the individuals of the smaller and larger males which recorded relatively less value (0.74). While, the individuals of females in different size class showed dietary overlapping with high intensity (0.81– 0.89) (Table 2) with the greatest overlap value observed between medium–larger individuals. Overall, the dietary overlapping analysis inferred higher values (0.67–0.80) in both the sex in all the seasons. However, the maximum dietary overlap was observed in winter monsoon and minimum during pre-monsoon. Between the sex the seasonal overlap values were found to be very high which ranged from 0.67 (summer monsoon) to 0.80 (winter monsoon) as indicated in Table 2 (see Table 3). The diversity values for various seasons were differed slightly with significant variations between size classes and sex (Mann– Whitney, P < 0.001) (Figs. 8 & 9). Generally, diversity observed 4. Discussion The present study provided the first information on the feeding biology of the deep-water shrimp, Aristeus alcocki in India complementing the studies on taxonomic (Suseelan et al., 1989a), distributional (Madhusoodana Kurup et al., 2008; Radhika Rajasree, 2011), economics importance (Shanis et al., 2014), length weight and molecular identification (Chakraborty et al., 2015), molecular phylogenetic (Chan et al., 2017; Purushothaman et al., 2019), reproductive biology, stock structure and population dynamics (Purushothaman et al., 2018a,b, 2020; Chakraborty et al., 2018) from southwest coast. In present study both extrinsic (seasonal) and intrinsic (sex, maturity) factors were found to affect the feeding intensity (stomach fullness) of A. alcocki in the Arabian water. The highest feeding intensity was noted in SM and FM period, where the shrimp grows faster with the beginning of gonad development and lower intensity was observed in WM season when the peak breeding period of the species coincides. Females with fully matured ovary or spent showed decreased feeding intensity, the reasons may be: (1) generally ovigerous decapods were not able to involve in moulting process till the eggs are released into the water, which reduces the interest for feeding activity (Hartnoll, 1985), (2) the space for stomach expansion was constrained by the huge size of the matured ovaries (Dall et al., 1990; Haefner and Spaargaren, 1993; Spaargaren and Haefner, 1998). With respect to 7 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Table 1 Seasonal dietary composition (%NI, %FI) for female and male of Aristeus alcocki in the Arabian Sea. Pre monsoon FM(76) M(78) Summer monsoon Fall inter monsoon Winter monsoon FM(92) FM(84) FM(104) M(60) M(66) M(74) %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI Foraminifera Unid. Foraminifera 43.59 11.99 43.90 15.61 51.43 11.63 40.38 10.36 31.82 9.64 13.79 4.93 54.35 10.36 31.82 9.64 1. Order: Lagenida Vaginulinidae Amphicoryna spp. Vaginulinopsis spp. Nodosariidae Laevidentalina spp. 15.38 12.82 12.82 5.13 5.13 0.19 0.12 0.35 0.09 0.05 11.43 0.43 11.36 1.12 0.1 0.13 0.8 1.12 0.1 0.37 0.02 0.29 0.09 0.02 11.36 3.45 11.5 1.92 5.76 5.76 1.92 0.43 0.3 0.27 0.31 3.45 3.45 6.9 4.55 5.71 2.86 8.57 0.37 0.02 0.29 0.09 0.02 0.43 0.04 0.29 11.54 1.92 5.77 5.77 1.92 4.55 2.44 2.44 17.95 0.41 4.88 0.53 11.43 0.22 17.31 1.76 4.55 0.42 6.9 0.05 6.52 1.76 4.55 0.42 10.26 12.82 25.64 0.18 0.35 2.02 2.44 4.88 29.27 0.22 0.98 6.9 5.71 5.71 31.43 0.09 0.20 3.69 11.54 9.62 26.92 0.69 0.91 3.80 6.82 4.55 13.64 0.42 0.62 2.88 6.52 6.52 21.74 0.69 0.91 3.80 6.82 4.55 13.64 0.42 0.62 2.88 10.26 20.51 10.26 12.82 5.13 30.77 10.26 28.21 25.64 20.51 25.64 12.82 12.82 5.13 23.08 20.51 5.13 7.69 20.51 0.33 1.47 0.63 0.48 0.36 2.26 0.55 1.77 1.11 0.85 0.89 0.33 0.32 0.18 1.36 0.91 0.16 0.18 0.69 9.76 17.07 7.32 25.00 2.44 29.27 9.76 9.76 7.32 4.88 4.88 0.00 2.44 2.44 7.32 7.32 1.18 1.94 1.05 0.27 0.18 4.67 1.16 1.56 1.07 0.67 0.71 0.00 0.18 0.04 0.62 1.45 0.86 0.46 0.96 0.28 0.07 1.73 0.6 1.46 1.40 1.85 2.14 0.28 1.00 0.24 0.58 1.12 9.00 6.82 9.09 2.27 1.49 0.48 0.74 0.50 15.22 15.22 2.17 10.87 9.00 6.82 9.09 2.27 1.49 0.48 0.74 0.50 11.76 1.54 11.76 1.54 4.55 6.38 4.00 6.82 11.36 4.55 0.81 0.39 0.65 0.60 1.11 0.21 4.55 6.38 4.00 6.82 11.36 4.55 0.81 0.39 0.65 0.60 1.11 0.21 4.55 0.57 4.55 0.57 0.11 0.31 1.49 0.32 0.27 0.48 1.33 2.09 0.76 2.20 2.46 1.22 0.93 1.24 0.42 0.02 1.55 1.30 0.03 0.22 11.54 11.54 13.46 3.85 3.85 17.31 5.77 15.38 13.46 15.38 23.08 3.85 13.46 5.77 7.69 17.31 2.44 2.44 25.71 5.71 11.43 11.43 2.86 25.71 8.57 20.00 25.71 17.14 20.00 22.86 11.43 2.86 11.43 17.14 2.86 5.71 3.85 5.77 0.04 0.35 2.27 0.28 2.27 0.28 5.13 0.09 2.44 0.13 2.85 0.06 7.69 0.15 17.95 0.57 4.88 0.42 8.57 0.31 9.62 0.46 13.64 1.04 10.26 0.12 2.44 0.04 11.43 0.27 7.69 0.38 6.82 5.13 0.18 9.76 0.24 5.71 0.18 1.92 0.11 12.82 0.27 14.29 0.30 3.85 10.26 0.26 2.44 0.29 5.71 0.19 35.9 7.75 7.32 1.02 28.57 38.46 12.82 10.26 7.25 0.70 0.74 21.95 2.44 7.32 10.79 1.07 2.96 2.56 2.56 0.16 0.49 10.26 15.38 5.13 10.26 15.38 0.39 1.43 1.95 1.21 3.92 2.56 0.01 25.64 2.93 Order: Rotaliida 1. Planulinidae Planulina spp. Hyalineaspp. 1. Globigerinidae Globigerina spp. Globigerinella spp. Globorotaloides spp. Globoturborotalita spp. Turborotalita spp. Globorotaliidae Globorotalia spp. Neogloboquadrina spp. Bolivinidae Bolivina spp. Buliminidae Bulimina spp. Globobulimina spp. Nonionidae Uvigerinidae Uvigerina spp. Bolivinitidae Neocassidulina spp. 3.45 3.45 3.45 0.31 0.39 0.31 10.34 6.9 1.16 0.31 6.9 10.34 3.45 3.45 6.90 1.08 1.9 0.39 0.31 0.21 32.61 23.91 10.87 4.35 6.52 19.57 15.22 13.04 3.45 3.45 0.13 0.41 8.7 6.52 0.86 0.46 0.96 0.28 0.07 1.73 0.6 1.46 1.40 1.85 2.14 0.28 1.00 0.24 0.58 1.12 4.35 2.17 0.04 0.35 1. Ammoniidae 0.15 Ammonia spp. 3.45 0.18 6.52 0.46 13.64 1.04 0.46 10.87 0.38 6.82 0.46 6.82 0.39 8.70 0.11 6.82 0.39 0.17 4.55 0.07 0.17 4.55 0.07 7.69 0.25 4.55 0.28 0.25 4.55 0.28 7.18 15.38 4.32 9.09 1.91 17.24 3.55 4.35 4.32 9.09 1.91 40.00 8.57 17.14 12.37 1.16 2.6 32.69 1.92 5.77 10.42 0.37 2.99 38.64 14.92 41.38 12.34 26.09 38.64 14.92 9.09 4.23 10.34 1.90 4.35 4.35 10.42 0.37 2.99 9.09 4.23 2.86 0.74 1.92 0.61 2.27 0.99 2.17 0.61 2.27 0.99 2.27 0.02 2.27 0.02 3.85 9.62 9.62 7.69 1.92 1.15 3.55 2.51 4.41 0.47 1.15 3.55 2.51 4.41 0.47 9.09 4.55 2.27 3.15 3.11 0.39 9.15 27.27 6.58 Epistomariidae 1. Order: Miliolida Hauerinidae Spirosigmoilina spp. 6.90 0.28 Spiroloculinidae Spiroloculina spp. Bryozoa Crustacea Unid. Crustacea Order: Decapoda Unid. Natantia Pasiphaea sp. Sergestes sp. Sergia sp. Plesionika sp. Acanthephyra sp. Unid. Reptantia Unid. Brachyoura Order: Euphausiacea Order: Amphipoda Order: Cumacea Order: Tanaidacea Order: Copepoda Mollusca Unid. Mollusca 2.44 7.32 2.44 9.76 4.88 2.44 19.51 0.98 5.49 1.16 6.76 1.76 1.05 6.76 2.86 8.57 2.86 0.13 1.24 1.46 2.6 2.82 2.86 0.11 28.57 2.69 26.92 9.15 9.09 4.55 2.27 27.27 3.15 3.11 0.39 6.58 10.34 2.49 3.45 3.45 1.03 0.82 6.52 8.7 10.87 8.70 10.34 10.34 0.00 24.14 5.60 8.70 (continued on next page) 8 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Table 1 (continued). Pre monsoon FM(76) Class: Bivalvia Class: Gastropoda Class: Scaphopoda Class: Cephalopoda Egg Polychaeta Fishes Ophidiidae Mud/sand Plastics Plants Unknown Summer monsoon M(78) FM(92) M(60) Fall inter monsoon Winter monsoon FM(84) FM(104) M(66) M(74) %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI %FI %NI 30.77 25.64 12.82 2.56 5.13 25.64 3.07 2.13 0.12 1.54 0.03 0.07 19.51 17.07 2.07 2.74 17.14 31.43 11.23 1.98 2.11 0.1 2.28 0.64 20.69 3.45 4.09 0.31 4.35 2.17 2.28 0.64 4.55 1.84 0.00 0.00 4.55 1.84 11.36 3.25 3.25 0.72 8.41 0.07 6.75 15.31 2.44 31.71 0.02 6.36 0.4 4.14 13.46 42.31 0.75 6.26 4.60 10.7 0.04 0.18 13.28 47.82 4.88 19.51 9.09 68.18 4.55 15.91 43.18 9.02 0.39 0.13 15.78 11.36 5.13 64.10 23.08 48.72 58.97 20.69 10.34 3.45 44.83 4.35 4.35 17.39 2.71 1.08 0.02 0.5 0.02 6.85 0.02 1.42 4.94 22.73 9.09 1.02 0.24 0.09 2.71 1.08 0.02 0.5 0.02 6.85 0.02 1.42 4.94 22.73 9.09 2.44 7.32 9.76 28.85 13.46 1.92 1.92 1.92 11.54 3.85 3.85 48.08 27.59 37.93 4.99 13.39 26.09 30.43 0.75 6.26 9.09 68.18 4.55 15.91 43.18 4.60 10.7 0.04 0.18 13.28 8.57 1.15 8.57 51.43 20.0 28.57 48.57 1.94 5.77 0.11 0.72 10.79 the feeding intensity, female shows higher feeding intensity than males because of increased growth rates. Arabian red shrimps mostly feeds in the night times at few metres above from the bottom substratum. The greater catchability and feeding activity has been noticed during night time for this species (Shanis et al., 2014) which strongly corroborates with the reports of other aristeid shrimps from many parts of the world oceans (Aristeus antennatus and Aristaeomorpha foliacea: Cartes and Sardà, 1989; Cartes, 1994; Kapiris, 2004; Kapiris and Thessalou-Legaki, 2011, and Aristaeopsis edwardsiana: Rezende et al., 2014) which can be described by the highest metabolic demand during the early stages of ova development (Maynou and Cartes, 1997; Cartes et al., 2008a,b; Kapiris et al., 2010). The present study specifies that the deep-sea shrimp A. alcocki has the highly diversified diet in the Arabian Sea. The diverse diet component mostly consists of benthic communities and these are divided into three categories (1) endobenthic invertebrates-lives fully or burrowing or partially buried in the sediment (foraminifera, polychaetes, bivalves, etc.) (2) epibenthic invertebrates–lives on or in the sediments (e.g. amphipods, euphausiids, gastropods, etc.) and (3) bathypelagic organisms and including decapods and fish. There are few individuals with the highest abundance of amphipods, gastropods in the stomachs which probably reflect availability in the benthic environment. Also, few more individuals of A. alcocki have the greater mean number of prey species in the stomach which indicates that is a megabenthic predator. Generally, fishes, cephalopods, and few crustacean groups have great swimming capacity, and the presence of these prey items in the stomach of A. alcocki indcates it as an effective predator. The present study confirms that A. alcocki is an active predator which is similar to A. antennatus (Cartes and Sardà, 1989; Kapiris et al., 2010; Kapiris and Thessalou-Legaki, 2011), A. foliacea (Cartes, 1995; Kapiris et al., 1999) and Aristaeopsis edwardsiana (Rezende et al., 2014). Also, the diet diversity of Arabian red shrimp showed considerable similarity with the diet of other deep-water shrimps, Heterocarpus chani (Earlier H. gibbosus) and Heterocarpus woodmasoni and Oplophorus typus found in the same area (Karuppasamy and Menon, 2004; Radhika and Kurup, 2011). Studies on the diet of Solenocera choprai in these waters indicated that crustaceans, polychaetes, foraminiferans and molluscs are the important food items (Aravindakshan and Karbari, 1994; Dineshbabu and Manissery, 2009). The results of this study probably confirms to the corresponding resemblance in the faunal assemblages of the macro-benthic communities persisting in the continental slopes of the region. Table 2 Overlap index values between the seasons of Aristeus Alcocki in the Arabian Sea. PM, pre-monsoon; SM, summer monsoon; FM, fall intermonsoon, WM, winter monsoon. Female Seasons PM SM FM WM PM SM FM WM – 0.75 0.78 0.79 – 0.80 0.78 – 0.80 – – 0.61 0.64 0.65 – 0.79 0.71 – 0.73 – Male PM SM FM WM Table 3 Overlap index values between the size groups of Aristeus Alcocki in the Arabian Sea. PM, pre-monsoon; SM, summer monsoon; FM, fall intermonsoon, WM, winter monsoon. Female Seasons F-Sl F-Md F-Lg F-Sl F-Md F-Lg M-Sl M-Lg – 0.86 0.81 – 0.89 – M-Sl M-Lg 0.75 0.75 – between sexes. The male individuals showed less quantity of fullness, diversity indices than female individuals while the latter showed higher abundance, occurrence and diversity in the diet than males. These results indicate females being active predators which might also be the reason to sexual dimorphism in this species. The reports of the earlier studies (Cartes, 1994, 1995) suggested the deep-water species have the seasonal rhythms in the feeding behaviour which can be attributed to the seasonal variations in the abundance of prey species, the deep water current pattern, the seabed, the depth, bottom nature, the submarine canyons, the horizontal and vertical migrations of the species etc. Comparably, the seasonal variations in stomach intensity of A. alcocki might be possibly associated with the oceanographic and biological processes in the environment. There were slight seasonal and diet shifts in the relative abundance of major prey species changes in the diet components of this shrimp in the Arabian Sea, which may be in relation to the existence of environmental fluctuations in the deep waters and their biological processes such as mating and reproduction in the species. The increased food quality indices and diversity were noted in spring inter–summer monsoon and lower 4.1. Sex and seasonal variations According to the diet composition and feeding activity of A. alcocki, slight variations were noticed in the feeding behaviour 9 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 6. Feeding strategy graph for Aristeus alcocki, by sex and season in the Arabian Sea. PM, pre-monsoon; SM, summer monsoon; FM, fall intermonsoon, WM, winter monsoon; 1, Lagenida; 2, Rotaliida; 3, Miliolida; 4, Crustacea; 5, Mollusca; 6, Polychaetes; 7, Fishes; 8, Bryozoa; 9, Others. which appears to be more intense in summer. Hence, this kind of energetic diet can be stimulus to the increased mating and gonad development process, which was observed in this period (Purushothaman et al., 2018b). During winter both sexes of A. alcocki in the Arabian Sea, 2+, 3+ age class of this species was vacuity index (VI) values found in summer seasons. Considerable increase in prey species such as foraminiferans (Bolivinidae, Uvigernidae, Globigernidae and Ammoniidae) amphipods, and scaphopods were noticed in the stomach content of predator, A. alcocki suggests that the species having rooting behaviour 10 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 Fig. 7. Importance of prey by size group of Aristeus alcocki, by sex in the Arabian Sea. 1, Lagenida; 2, Rotaliida; 3, Miliolida; 4, Crustacea; 5, Mollusca; 6, Polychaetes; 7, Fishes; 8, Bryozoa; 9, Others. observed in higher level and these groups are more active predators than juveniles (Chakraborty et al., 2018), which consume an increased number of prey items, resulting in the highest stomach fullness. This phenomenon could be related to the growth and gonad development which takes place this season (Purushothaman et al., 2018b). Next, the possible explanations for these seasonal changes in diet are food availability and migrations of the species; which may be the important factor for A. alcocki in the Arabian Sea and the high consumption of prey items in summer may be linked to the oceanographic process. During the process of upwelling prevailing in the southwest coast, summer monsoons are characterized by phenomena of vertical mixing and cascading flow of upper dense water layers enriching the deepwaters with organic nutrients notably with phytoplanktonic and zooplanktonic swarms (Madhupratap et al., 1990). Similarly, the results of the present study also showed the fluctuations in the diet of A. alcocki based on food availability. 4.2. Ontogenetic variations Studying the influence of size-related diet content variability is particularly important for determining the ecological relationship of species. The presence of notable ontogenetic variation in a generalist predator group, where smaller groups target smaller or lower trophic level prey species than adults (Graeb et al., 2005). It is commonly observed that the increase in predator size with the increase in the size of prey item (Dall et al., 1990). Also, many reports on the diet content of decapods highlighted on the ontogenetic variations in the diet of predators influenced by the biotic components (Freire and Gonzalez-Gurriaran, 1995). Similarly, dietary diversity and feeding activity of A. alcocki differed significantly in the Arabian Sea. In both sex, medium and large size individuals were found to consume an increased level of brachyurans, amphipods, and euphausids forming effective predators due to their good swimming capability and had bigger size mandibles. Also, foraminifer’s percentages were steadily 11 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 increased along with the increase in the size of the animal in both the sex while small size individuals consumed smaller size prey which was mostly epibenthic organisms. The possible trend was observed between the diet and females’ size groups, where larger females consumed the larger prey items (decapods, fish). These differences formed due to morphological and population features of the different size groups, sexes (Burukovsky, 1972) and somatic growth moreover, gonad developments can induce different feeding behaviour. Similar kind of ontogenic size-related diet variation was observed in H. gibbosus and H. woodmasoni where the major food items reported to be smaller crustaceans (Amphipods, euphausids), foraminiferans (Radhika and Kurup, 2011). 5. Conclusions The findings of the present study forms the first report on the feeding ecology of the deep-water shrimp, A.alcocki from the Arabian Sea. Gut content analysis revealed that the species consumes highly diversified diet and feeds largely on invertebrates like crustaceans (Amphipods, euphausiids), foraminiferans, molluscs from the benthic substrate and to a lesser extent on mesopelagic species having seasonal fluctuations. Females are found to be effective feeders (feeding intensity and fullness) in comparison with males. Major factors that drive the seasonal variation in the feeding behaviour of this species, due to the increased energy requirements related to the availability of food in the marine habitat, ontogenetic and sexual developments. The bigger size of the animal with good swimming capability helps in the selection of prey, while the smaller individuals depend on the epibenthic organisms for their food. The result of the present study provides the quantifiable criteria to determine the major prey group which consecutively explains the need to develop geo-spatial management plans for this species. Fig. 8. Diversity and evenness values and mean prey items of Aristeus alcocki per sex and season. CRediT authorship contribution statement Purushothaman Paramasivam: Sample collection, Methodology, Software, Writing - original draft. Rekha Devi Chakraborty: Concept development, Project acquisition, Planning, Draft editing, Investigation, Supervision. Kuberan Ganesan: Sample collection. Maheswarudu Gidda: Over all Guidance. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements Authors express thanks to the Science and Engineering Research Board (SERB) (grant number SR/FT/LS-73/2012) of Department of Science and Technology, New Delhi, India. The authors thank the Director, Indian Council of Agricultural ResearchCentral Marine Fisheries Research Institute (ICAR-CMFRI) for the facilities provided. We also thank the anonymous Reviewers for their critical comments and valuable suggestions to improve the manuscript. Fig. 9. Diversity and evenness values and mean prey items of Aristeus alcocki per sex and size groups. 12 P. Paramasivam, R.D. Chakraborty, K. Ganesan et al. Regional Studies in Marine Science 40 (2020) 101500 References Hartnoll, R.G., 1985. Growth. In: Abele, L.G. (Ed.), The Biology of Crustacea, Vol. 2. Academic Press, New York, pp. 111–196. Holthuis, L.B., 1980. Annotated catalogue of species of interest to fisheries – Shrimps and prawns of the world. FAO Species Catal. 1, 147–153. Hutchinson, G.E., 1957. Concluding remarks. In: Cold Spring Harbour Symposium on Quantitative Biology, Vol. 22. pp. 415–427. Hyslop, E.J., 1980. Stomach contents analysis – a review of methods and their application. Fish Biol. 17, 411–429. 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