Skeletal Anomalies in Senegalese Sole (Solea senegalensis, Kaup) Fed with Different Commercial Enriched Artemia: A Study in Postlarvae and Juveniles

Abstract

The high incidence of skeletal anomalies in Senegalese sole (Solea senegalensis) still constitutes a bottleneck constraining its production. There are diverse commercially available products for the enrichment of live preys, but few reports of their influence on skeletogenesis in Senegalese sole. This study evaluated the presence of vertebral anomalies in postlarvae and juvenile Senegalese sole fed with Artemia spp. metanauplii enriched with four commercial products (EA, EB, EC, and ED) in a fish farm. The most frequent alterations consisted of deformations of the neural/haemal arches and spines and fusions and deformations of hypurals, epural, or parhypural. The correspondence analysis ordered fish from each age in separated semiaxis, indicating the presence of different anomaly patterns for the two sampled stages. The results showed only very light changes in the frequency of vertebral abnormalities among tested enrichment products, i.e., individuals from EC and EA lots displayed less vertebral body anomalies and/or vertebral column deviations at 31 and 105 days after hatching, respectively. The existence of a large shared malformation pattern in all the experimental groups leads to impute to the rearing conditions as the main driving factor of the onset of such group of anomalies, probably masking some dietary effect.

Keywords: Senegalese sole (Solea senegalensis); enrichment products; rearing conditions; skeletal anomalies.

Figure 1

Survival rate (%) for each replicate (EA-1, EA-2, EB-1, EB-2, EC-1, EC-2, ED-1, ED-2) from 15 to 105 days after hatching.

Figure 2

More common anomalies in 31 days after hatching (dah) (a–c) and 105 dah (d–g) Senegalese sole (Solea senegalensis). Double staining technique with alcian blue and alizarin red. (a) Severe deformations affecting both abdominal and caudal vertebrae exhibiting evident flattening of centra and irregularity of vertebral surface and central fusion among the affected elements (asterisk); slight deformities in abdominal neural spines and first caudal haemal spine (black arrowheads); note also the two short neural spines with absence of the neural arch of the first abdominal vertebra (white arrowhead); (b) Fusion between the second and third caudal vertebrae with shortening of the first vertebral body (asterisk); incomplete arch (white arrowhead) and alteration of the insertion (short arrow) of the caudal haemal arches; twisted haemal spines (black arrowheads), with a thin layer of bone and slight torsion at the tip of the haemal spine (black arrow); (c) Fusion between preurals with fusion of neural and haemal arches (white arrowheads), the union has the appearance of one elongated vertebra; alterations of the shape of epural and hypural 5; fusion among hypurals (white star); (d) Overview of the caudal complex in 105 dah Senegalese sole; (e) Vertebral fusion between preurals and the last caudal centra, displaying also fusion of preural neural arches (white arrowhead); deformities of hypural 5 and parhypural, denote the thin layer of bony tissue in epural reshaping the element (black arrow); (f) Fusions among caudal vertebrae exhibiting an altered orientation of the central structure in opposite directions (asterisks); (g) Lordosis in the transition area between abdominal and caudal regions (L); the affected vertebrae are also shorter and deformed, highlights the central vertebra which shows a trapezoidal shape (asterisk). Bars = 500 μm.

Figure 3

Relative frequency (%) of individuals with at least one anomaly for each group (31 EA, 31 EB, 31 EC-1, 31 EC-2, 31 ED-1, 31 ED-2, 105 EA, 105 EB, 105 EC, 105 ED-1, 105 ED-2) regarding the anatomical regions. (a) 31 days after hatching (dah). Haemal caudal elements and the structures of the caudal complex were the most affected; (b) 105 dah. The caudal complex region presented the highest frequency of anomalies. A-D: abdominal (A) deformation; A-F: A fusion; A-K: A kyphosis; A-L: A lordosis; A-N: A neural elements; A-S: A scoliosis; CC-D: caudal complex (CC) deformation; CC-F: CC fusion; CC-H: CC haemal elements; CC-K: CC kyphosis; CC-L: CC lordosis; CC-N: CC neural elements; CC-S: CC scoliosis; C-D: caudal (C) deformation; C-F: C fusion; C-H: C haemal elements; C-K: C kyphosis; C-L: C lordosis; C-N: C neural elements; C-S: C scoliosis; HYE: hypurals, epural, parhypural; PP: parapophysis.

Figure 4

Correspondence analysis results on the frequency matrix (FM) at 31 and 105 days after hatching: ordination model of diet-tank groups (31 EA, 31 EB, 31 EC-1, 31 EC-2, 31 ED-1, 31 ED-2, 105 EA, 105 EB, 105 EC, 105 ED-1, 105 ED-2) (a) and descriptor points (b) in axis 1 and axis 2. Note the overlapping anomaly categories CC-F, CC-D, CC-N, and HYE (b). A-D: abdominal (A) deformation; A-F: A fusion; A-K: A kyphosis; A-L: A lordosis; A-N: A neural elements; A-S: A scoliosis; ABS: absence of anomalies; CC-D: caudal complex (CC) deformation; CC-F: CC fusion; CC-H: CC haemal elements; CC-K: CC kyphosis; CC-L: CC lordosis; CC-N: CC neural elements; CC-S: CC scoliosis; C-D: caudal (C) deformation; C-F: C fusion; C-H: C haemal elements; C-K: C kyphosis; C-L: C lordosis; C-N: C neural elements; C-S: C scoliosis; HYE: hypurals, epural, parhypural; PP: parapophysis.

Figure 5

Anomaly index (number of anomalies per malformed specimen) in each group (31 EA, 31 EB, 31 EC-1, 31 EC-2, 31 ED-1, 31 ED-2, 105 EA, 105 EB, 105 EC, 105 ED-1, 105 ED-2). Graphs display median values, maximums, and minimums (a) 31 days after hatching (dah). (b) 105 dah. A-D: abdominal (A) deformation; A-F: A fusion; A-K: A kyphosis; A-L: A lordosis; A-N: A neural elements; A-S: A scoliosis; CC-D: caudal complex (CC) deformation; CC-F: CC fusion; CC-H: CC haemal elements; CC-K: CC kyphosis; CC-L: CC lordosis; CC-N: CC neural elements; CC-S: CC scoliosis; C-D: caudal (C) deformation; C-F: C fusion; C-H: C haemal elements; C-K: C kyphosis; C-L: C lordosis; C-N: C neural elements; C-S: C scoliosis; HYE: hypurals, epural, parhypural; PP: parapophysis.