The occurrence of the alien species Polydora cornuta Bosc, 1802 (Polychaeta: Spionidae) in North Adriatic lagoons: an overlooked presence

Figures & data

Figure 1. Location of the study area: A, Southern part of the Venice lagoon (Val di Brenta); B, Marinetta lagoon; C, Barbamarco lagoon. Dots represent the location of the sampling stations. Dotted lines are the Po riverbed branches. Shaded areas represent the location of ports, harbours and marinas.

Table I. Characterisation of sampling sites where specimens of Polydora cornuta were collected in the three North Adriatic lagoons. The number of individuals is the sum of three replicates. The number of mature females includes the females hatching egg capsules.

								Polydora cornuta
Lagoon	Station	Coordinates (N, E)	Depth (m)	Sediment type	Sampling date	Water temperature (°C)	Salinity (PSU)	Number of individuals	Number of mature individuals (♀/♂)	Number of ♀ hatching egg capsules	Percentage abundance on total macrofauna
Venice (Val di Brenta)	B1	45°11ʹ30“, 12°14ʹ7”	0.9	Sandy mud	6 February 2014	9.0	14
					8 July 2014	25.6	33	2	2/0	1	0.55%
					21 March 2015	12.1	33	2	1/0	0	0.41%
	B2	45°11ʹ6“, 12°15ʹ27”	0.9	Sandy mud	6 February 2014	8.7	11
					8 July 2014	26.5	33
					21 March 2015	12.0	35
	B3	45°11ʹ40“, 12°15ʹ47”	0.6	Mud	6 February 2014	9.6	8
					8 July 2014	25.9	34
					21 March 2015	11.8	36
	B4	45°11ʹ28“, 12°15ʹ43”	0.8	Mud	6 February 2014	8.0	12
					8 July 2014	25.9	33	36	9/7	3	8.29%
					21 March 2015	11.8	35
Marinetta	M1	45°03ʹ13“, 12°22ʹ7”	1.2	Mud	21 March 2014	14.2	10
					23 June 2014	24.7	10
					20 March 2015	10.8	35	59	40/10	12	3.62%
	M2	45°03ʹ11“, 12°22ʹ44”	0.6	Muddy sand	21 March 2014	14.5	25
					23 June 2014	26.4	23	2	1/1	0	0.07%
					20 March 2015	11.7	33	1	0/0	0	0.02%
	M3	45°03ʹ22“, 12°22ʹ30”	1.7	Mud	21 March 2014	14.3	16
					23 June 2014	24.8	25	2	0/1	0	0.10%
					20 March 2015	10.7	35	21	9/11	1	0.98%
	M4	45°03ʹ17“, 12°22ʹ39”	1.5	Muddy sand	21 March 2014	14.5	14				0
					23 June 2014	26.7	22	4	1/1	1	0.13%
					20 March 2015	10.8	35	2	1/0	0	0.08%
Barbamarco	P1	44°58ʹ40“, 12°28ʹ57”	0.9	Silty mud	16 February 2015	8.6	30	35	6/7	1	0.86%
	P2	44°58ʹ43“, 12°28ʹ51”	0.8	Silty mud	16 February 2015	8.6	28	125	29/32	2	3.79%
	P3	44°58ʹ49“, 12°28ʹ55”	1.5	Mud	16 February 2015	8.3	28	1	0/0	0	0.17%
	P4	44°59ʹ4“, 12°29ʹ43”	0.6	Muddy sand	6 February 2014	9.2	35	9	2/0	1	0.36%
	P5	44°59ʹ14“, 12°29ʹ24”	1.1	Muddy sand	8 July 2014	9.0	35	5	1/4	0	0.44%

Figure 2. Polydora cornuta. A, anterior end, dorsal view; a = occipital antenna; B, chaetiger 5 from right side, dorsal view; sp = modified spines; cc = companion chaetae strictly adhering to convex side of the spine; C, chaetae from chaetiger 5: from left to right, unworn posterior spine; unworn posterior companion chaeta; worn anterior companion chaeta on convex (left) and concave (right) side; D, notopodial chaetae from chaetiger 20: s = short capillaries, w = winged capillaries, lc = long capillaries, the square shows the detail of the winged terminal part of the chaeta; E, hooded hook from posterior chaetigers; F, posterior end and pygidium. Scale bars: A = 1.5 mm; B, D = 100 mm; C = 50 mm; E = 30 mm; F = 1 mm.

Figure 3. Polydora cornuta. A, relationship between size of individuals (width of chaetiger 5) and number of spines in the same chaetiger (linear model: y = 3.24 + x·4.01; r = 0.853; P < 0.0001; N = 45); B, relationship between size of individuals (width of chaetiger 5) and maximum number of hooded hooks in posterior segments (linear model: y = 2.46 + x·6.88; r = 0.875; P < 0.0001; N = 41).

Figure 4. Polydora cornuta. A, mud tube with egg capsules attached to inner wall; B, early stage of a three-chaetiger larva extracted from a capsule: yg = yolky globules. Scale bars: A = 1 mm; B = 150 mm.

Figure 5. Polydora cornuta mean densities measured at each sampling station at each sampling time. A, Venice lagoon (Val di Brenta); B, Marinetta lagoon; C, Barbamarco lagoon. Error bars are standard errors (n = 3).