per week for the period until April 26,1981, and $825 in arrears of temporary alimony of $75 per week for the period from April 26, 1981 until entry of the judgment appealed from. Special Term further provided for the equitable distribution of the parties’ assets pursuant to part B of section
236 of the Domestic Relations Law. “[T]he determinative time for applicability of part B of section
236 of the Domestic Relations Law is not when [the] claim was interposed but when the action in which it was interposed was commenced” (see
Valladares v Valladares, 55 NY2d 388 , 392). Accordingly, it is irrelevant whether the cause of action for adultery is asserted by a supplemented, rather than an amended complaint. The crucial fact is that this action was commenced prior to the effective date of part B of section
236 of the Domestic Relations Law. The fact that the wife could be deprived of the benefits of part B does not, as a matter of law, constitute grounds to deny the husband leave to supplement or amend his pleadings (see
Tucker v Tucker, 55 NY2d 378 , 386, n 3). However, in the instant case the wife suffered cognizable prejudice. Because the husband’s motion for leave to interpose a cause of action for a divorce on the ground of the wife’s adultery was made during the course of the trial itself, the wife was deprived of an opportunity to plead, prepare and prove any of the defenses set forth in section
171 of the Domestic Relations Law, was unable to exercise her right to a trial by jury (see Domestic Relations Law, §
173), and was unable to challenge the sufficiency of the husband’s proof. Motions for leave to amend the pleadings and motions for leave to supplement the pleadings are generally governed by the same standards (see CPLR 3025, subd [b]; Siegel, Practice Commentaries, McKinney’s Cons Laws of NY, Book 7B, CPLR 3025.9) and should not be granted if the opposing party can show prejudice. Therefore, we find that Special Term improvidently exercised its discretion when it granted the husband leave to supplement his complaint by adding a new cause of action for divorce on the ground of adultery (see
De Angelis v DeAngelis, 54 AD2d 1088 ;
James-Smith v Rottenberg, 32 AD2d 792 ). Since the parties failed to establish causes of action for divorce on the grounds asserted in their original complaints, that portion of the judgment which decrees that the marriage between the parties is dissolved must be vacated, along with the relief incidential thereto which was granted pursuant to part B of section
236 of the Domestic Relations Law, namely the distribution of the parties’ assets. Our modification is without prejudice to the institution of a new action for divorce on the ground of the wife’s adultery, if the husband be so advised. Although the grounds for divorce asserted in the complaints were not established, Special Term still could determine questions of child custody (see Domestic Relations Law, §
240;
Caldwell v Caldwell, 298 NY 146 ;
Miller v Miller, 10 AD2d 796 ), award one spouse exclusive possession of the marital residence (see Domestic Relations Law, §
234;
Waksenbaum v Waksenbaum, 53 AD2d 890 ), and direct either spouse to provide suitably for the support of the other (see Domestic Relations Law, §
236, part A). Special Term’s determinations with respect to child custody and visitation were a proper exercise of its discretion. Since the husband has custody of the children, he was properly awarded exclusive possession of the marital residence. Further, the award to the wife of support of $125 per week, and health insurance coverage was reasonable, considering the length of the marriage, the ability of each spouse to be self-supporting, and the circumstances of the instant case. The arrears of temporary alimony of $75 per week for the 14-week period from April 26,1981, until entry of the judgment, were miscalculated as $825. The amount should be $1,050. We have considered the parties’ remaining contentions and find them to be without merit. Mollen, P. J., Damiani, Titone and Weinstein, JJ., concur.