Scyllarides squammosus H. Milne Edwards 1837

Scyllarides squammosus (H. Milne Edwards, 1837) Stage VI (NHMUK 2015.3279) Measurements (Fig. 2 A). TL = 11.7 mm; CW = 6.3 mm; CL = 9.0 mm. Cephalic shield (Fig. 2 A). Spindle-shaped, longer than wide (CL/CW = 1.42), maximum width located to mid length. Antennule (Fig. 2 B). Peduncle 3-segmented, each segment with similar length. Distal segment biflagellated, accesory flagellum half the length of primary flagellum. Primary flagellum with 7 rows of aesthetascs on inner margin. Antenna (Fig. 2 B). Biramous, endopod 2-segmented. The inner ramus reaching the anterior end of first antennular segment. Maxillule (Fig. 2 C). Uniramous, palp (endopod) absent. Coxal endite with 4 setae (three strong terminal cuspidate setae). Basal endite with 4 setae (three long strong terminal cuspidate setae). Maxilla (Fig. 2 D). Rudimentary bud with small elongation at distal end. Triangular shape. Endites, endopod and scaphognathite not differentiated. First maxilliped (Fig. 2 D). Undeveloped, present as small conical protuberance. Third maxilliped (Fig. 2 A). Uniramous. Five segmented (ischio-merus fused to basis). Without ventral coxal spine. Pereiopods (Fig. 2 A). Biramous, without coxal or subexopodal spines. Exopods of pereiopods 1���4 flagellated distally with ~12���14 annulations, each annulation bears a pair of plumose natatory setae. Pereiopod 5 underdeveloped, small single segment with conical shape. Distal end nearly reaching the telson. Pleon (Fig. 2 E). Unsegmented. Pleopods or uropods absent. Stage VII (NHMUK 2015.3280) Measurements (Fig. 3 A). TL = 14.9 mm; CW = 8.2 mm; CL = 12.0 mm. Cephalic shield (Fig. 3 A). Pear-shaped, longer than wide (CL/CW = 1.46), maximum width located to mid length. Antennule (Fig. 3 B). Primary flagellum with 8 rows of aesthetascs on inner margin. Antenna (Fig. 3 B). Longer than first antennular segment. Endopod 2-segmented, reaching the middle of the second antennular segment. Exopod retracts and widens, becoming triangular-shaped. Maxillula (Fig. 3 C). Coxal endite with 6 setae, 4 located in apical position and 2 in basal position. Basal endite with 6 setae (3 terminal, elongated, with strong structure and serrated laterally). Maxilla (Fig. 3 D). Small tapered elongation becomes less evident, reduced in length. Triangular shape. First maxilliped (Fig. 3 D). Unchanged. Third maxilliped (Fig. 3 A). Unchanged. Pereiopods (Fig. 3 E). Exopods of pereiopods 1���4 distally flagellated with 15���17 annulations. Pereiopod 5 underdeveloped, with conical base at thorax. Distal end reaches beyond telson. Pleon (Fig. 3 E). Pleon non-segmented, uropods present as small uniramous buds. Telson more developed, longer than previous stage. Stage VIII (NHMUK 2015.3 281) Measurements (Fig. 4 A). TL = 19.5 mm; CW = 10.6 mm; CL = 15.5 mm. Cephalic shield (Fig. 4 A). Pear-shaped, longer than wide (CL/CW = 1.46), maximum width located to mid length. Antennule (Fig. 4 B). Accessary flagellum reaches middle length of primary flagellum. Primary flagellum with 8���9 rows of aesthetascs on inner margin. Antenna (Fig. 4 B). Reaches proximal end of third antennular segment. Endopod now 3-segmented. Significant increase in length of second segment. Triangular outer ramus becomes shorter and stouter. Maxillule (Fig. 4 C). Coxal endite with 6 setae, 4 located at distal portion and 2 located in basal position. Basal endite with 7 setae (3 terminal, elongated). Maxilla (Fig. 4 D). Still underdeveloped, but wider than in previous stages. First maxilliped (Fig. 4 D). Present as a minute protuberance. Diameter of conical base significantly larger than previous stages. Pereiopods (Fig. 4 E). Exopods of pereiopods 1���4 distally flagellated with 16���18 annulations. Pereiopod 5 now 2-segmented, and reaching beyond telson. Pleon (Fig. 4 E). Somite divisions incomplete. Uropods are biramous. Stage IX (NHMUK 2015.3282) Measurements (Fig. 5 A). TL = 23.6 mm; CW = 13.8 mm; CL = 19.0 mm. Cephalic shield (Fig. 5 A). Pear-shaped, longer than wide (CL/CW = 1.37). Slightly narrower than thorax. Antennule (Fig. 5 B). Primary flagellum with 9���10 rows of aesthetascs on inner margin. Antenna (Fig. 5 B). Exceeds second antennular segment. Four segments remain but the exopod now reduced to small tip. Maxillule (Fig. 5 C). Coxal endite with 7 setae (3 longer setae in distal portion). Basal endite with 9 setae (3 terminal, long and serrated). Maxilla (Fig. 5 D). Similar to previous stages, but scaphognathite acquires rudimentary rectangular shape. First maxilliped (Fig. 5 D). Adopting more tubular form with length significantly larger than previous stages. Pereiopods (Fig. 5 A, E). Exopods of pereiopods 1���4 distally flagellated. Pereiopod 5 now 3-segmented and reaching beyond telson. Pleon (Fig. 5 E). Divisions of somites becomes evident. Pleopods present, underdeveloped and biramous. Uropods biramous, length of internal lobe half than outer lobe. Telson unchanged. Stage X (NHMUK 2015.3283) Measurements (Fig. 6 A). TL = 31.0 mm; CW = 18.5 mm; CL = 24.0 mm. Cephalic shield (Fig. 6 A). Pear-shaped, longer than wide (CL/CW = 1.29), but relatively wider than previous stages. Antennule (Fig. 6 B). Accessory flagellum longer than half length of primary flagellum. Primary flagellum with 10���12 rows of aesthetascs on inner margin. Antenna (Fig. 6 B). Five-segmented and reaching beyond third antennular segment. Second antennal segment develops a lateral extension (lateral process) while first segment becomes cylindrical. Maxillule (Fig. 6 C). Coxal endite with 13 setae. Basal endite with 9 setae (3 long, strong and serrated). Maxilla. (Fig. 6 D). Scaphognathite slightly differentiated, without setae, flattened and reduced in size. First maxilliped (Fig. 6 D). Like previous stage. Second maxilliped (Fig. 6 A). Five-segmented, with rudimentary and unarmed minute exopod bud present. Third maxilliped (Fig. 6 A, F). Uniramous. Five segmented (ischio-merus fused to basis). Without ventral coxal spine. Distal part of propodus and dactylus densely setose. Pereiopods (Fig. 6 E, G). Pereiopods 1���4 biramous, without coxal or subexopodal spines. Exopods of pereiopods 1���4 flagellated distally with 17���19 annulations, each annulation bears a pair of plumose natatory setae. Pereiopod 5 with four-segmented endopod, without setae. Distal end reaches beyond telson. Pleon (Fig. 6 E). Five-segmented (five somites plus telson, somite 1 not differentiated). Pleonites 2���5 with a pair of biramous pleopods, unsegmented and unarmed. Uropods biramous and incipiently segmented, but not outreaching posterior margin of telson. Telson rounded posteriorly, without processes or teeth. Stage XI (NHMUK 2015.3284) Measurements (Fig. 7A). TL = 39.0 mm; CW = 23.1 mm; CL = 29.0 mm. Cephalic shield (Fig. 7A). Pear-shaped, longer than wide (CL/CW = 1.26), maximum width located to mid length. Antennule (Fig. 7B). Primary flagellum with 12���14 rows of aesthetascs on inner margin. Antenna (Fig. 7B). Almost equal in length to antennule. Lateral expansion on the second segment widens while segment 4 gets narrower. Maxillule (Fig. 7C). Coxal endite with 14 setae (2 terminal setae considerably longer and stronger). Basal endite with 9 setae (3 long, strong and serrated). Maxilla (Fig. 7D). Similar to previous stage, but scaphognathite more differentiated, without setae, flattened and slightly expanded anteriorly and posteriorly. First maxilliped (Fig. 7D). Further developed. Pereiopods (Fig. 7E). Biramous, without coxal or subexopodal spines. Exopods of pereiopods 1���4 flagellated distally with>18 annulations, each annulation bears a pair of plumose natatory setae. Pereiopod 5 with 5 segments present, segment 2 with rudimentary exopod. Pleon (Fig. 7E, F). Segmented, with six pleonites plus telson. Pleonites 2���5 with a pair of biramous and unsegmented pleopods each, without appendix interna. Presence of two dorsal spines on pleonites 3���4. Biramous uropods outreaching posterior margin of telson. Stage XII (NHMUK 2015.3285) Measurements (Fig. 8 A). TL = 51.0 mm; CW = 26.5 mm; CL = 36.0 mm Cephalic shield (Fig. 8 A). Pear-shaped, longer than wide (CL/CW = 1.35), but proportionally longer than previous stage. Antennule (Fig. 8 B). Accessory flagellum extended, equal in length to primary flagellum. Primary flagellum with 13���15 rows of aesthetascs on inner margin. Antenna (Fig. 8 B). Longer than antennule. Segments fully developed. Lateral expansion on second segment directed anteriorly (more developed than previous stage). Last antennal segment leaf-shaped. Maxillule (Fig. 8 C). Coxal endite with 14 setae (2 terminal setae considerably longer and stronger). Basal endite with 11 setae (3 long, strong and serrated). Maxilla (Fig. 8 D). Fully developed, scaphognathite considerably expanded anteriorly and posteriorly. Endopod becomes triangular. First maxilliped (Fig. 8 D). Fully developed and markedly biramous. Second maxilliped (Fig. 8 A). Exopod bud elongated. Third maxilliped (Fig. 8 A). Gill buds present, with one pleurobranch, one arthrobranch and epipod with podobranch. Pereiopods (Fig. 8 E). Pereiopod 1 with one pleurobranch, one arthrobranch and epipod with podobranch. Pereiopods 2���4 with two pleurobranchs, one arthrobranch and epipod with podobranch. Pereiopod 5 with one pleurobranch. Pereiopod 5 now 6-segmented. Basis with exopod bud and ischium and merus are fused. Pleon (Fig. 8 E, F). Fully segmented with 4 pairs of segmented pleopods. Posterolateral margin of the pleura of somites 2, 3, 4 and 6 ended with acute spine. Dorsally, somites 4 and 5 bear a strong median spine. Pleopods biramous, segmented and without setae, endopod with appendix interna. Biramous uropods outreaching posterior margin of telson. Morphometric analyses showed that total length of the larvae follows an exponential growth in late stages of development (see Table 2). The ratio of cephalic width over the total length increased during phyllosoma development up to a maximum value of CW/TL = 0.61 at around 30 mm TL (see Fig. 9) and then decreased again in the sub-final and final stages (CW/ TL = 0.43 + 0.011 TL���0.00018 TL2; r2 = 0.999). The relative growth of CL and CW during larval development in phyllosoma larvae assigned to Scyllarides squammosus was found to follow a power law equation (CW = 0.84 CL0.96), with a high correlation coefficient (r2 = 0.996). However, the confidence interval for the exponent parameter comprised the value b = 1 (0.91���1.01), which indicates that the growth of CW does not show a significantly allometric pattern. Stage = Stage of development; N = Sample size; Range = range of lengths per stage; Mean = Average total length per stage. Total length (TL) measured from the anterior margin of the cephalic shield between the eyes to the posterior margin of the telson.
Published as part of Palero, Ferran, Genis-Armero, Rebeca, Hall, Michael R. & Clark, Paul F., 2016, DNA barcoding the phyllosoma of Scyllarides squammosus (H. Milne Edwards, 1837) (Decapoda: Achelata: Scyllaridae), pp. 481-498 in Zootaxa 4139 (4) on pages 487-495, DOI: 10.11646/zootaxa.4139.4.2, http://zenodo.org/record/264222