Strong defensive work helped keep Ionians in the game when, even down to 13 men, they managed to hold their hosts at bay and registered a win that keeps them five points clear at the top of the table.
Left-winger Toni Kuku got Ionians off the mark after five minutes and full-back Lewis Minikin converted, and Huddersfield opened their account on the half-hour with prop Harry Whitfield’s try being converted by stand-off Chris Johnson.
The East Yorkshire side edged in front just before the break with centre Callum Smith racing in for a 12-7 lead at the break.
They extended their advantage with forward Ed Falkingham going over on the hour mark to score.
Minikin missed the conversion but added a penalty shortly after to put Ionians 20-7 ahead, but Huddersfield were not done and replacement Thomas Owen dived over almost immediately after the restart.
However, Ionians held firm, winger Stephen Slingsby touching down and Minikin adding the conversion.
Whitfield scored a second try for the hosts and Johnson converted, but with just five minutes left to play it was little more than a consolation.
Otley’s first-half performance against visitors Peterborough Lions was enough to take a 35-5 victory.
They scored all their points before the break with centres Tom De Glanville and Jack Mackie, winger Josh Hall, full-back Ben Magee and scrum-half Joe Rowntree scoring tries.
Wharfedale’s five-match winning run came to an end with a 37-10 defeat at Leicester Lions.
The hosts were 17-0 ahead at half-time before Wharfedale hit back, No 8 Josh Burridge scoring on 44 minutes.
Leicester added a fourth try before the Yorkshire side could score again, with winger Ralph Wellock touching down on 57 minutes. But the Lions roared away to victory with three more tries.
Sheffield Tigers lost 31-17 at Macclesfield, who were securing their first win in eight matches.
Wing-forward Tom Bloor and winger Greg Mellor scored Tigers’ tries and stand-off Mark Ireland kicked the conversions and a penalty. But it was not enough to challenge Macclesfield.
Rotherham Titans lost out 36-24 to promotion-chasing Ampthill in National One.
Centre James Cooke raced in after just five minutes and scrum-half Connor Dever added the conversion, but it was a false dawn for the Titans.
Ampthill responded with three tries before the break to lead 19-7 at half-time.
Rotherham hit back through No 8 Alex Nagle-Taylor on 51 minutes, but the visitors to Clifton Lane extended their lead with two more converted tries to lead 33-12.
Right-winger Daniel Leake had a 65th-minute try converted by Dever as Rotherham reduced the deficit to 33-19 and Leake added a last-minute try.
But it was not enough to challenge for the win and they had to be content with a four-try bonus point.
Leaders Hull were given a hard time by Yorkshire rivals Ilkley in the North Premier league, but still ran out 28-11 winners with a maximum five-point haul.
Harrogate are still in the hunt for promotion, and they also enjoyed a good home win, beating the Vale of Lune 69-14, while Sandal ran in seven tries on their way to a 52-7 win over Kirkby Lonsdale.
Scarborough were 27-22 winners at Driffield in North One East as they maintained their push for promotion, while Morley beat Malton and Norton 31-10.
Huddersfield YMCA were in good form at York and ran in seven tries as they won 39-22, and Cleckheaton were 47-14 winners at Pocklington.